Patient-Adapted and Improved Articular Implants, Designs and Related Guide Tools

[0001] This application is a continuation of U.S. Ser. No. 13/397,457, entitled “Patient-Adapted and Improved Articular Implants, Designs and Related Guide Tools,” filed Feb. 15, 2012, which in turn claims the benefit of U.S. Provisional Patent Application Ser. No. 61/443,155, entitled “Patient-Adapted and Improved Articular Implants, Designs and Related Guide Tools,” filed Feb. 15, 2011, each of which is hereby incorporated herein by reference in its entirety.

[0002] U.S. Ser. No. 13/397,457 is also a continuation-in-part of the following applications: U.S. Ser. No. 12/799,641, filed Apr. 28, 2010; U.S. Ser. No. 12/799,355, filed Apr. 22, 2010; U.S. Ser. No. 12/799,299, filed Apr. 21, 2010; U.S. Ser. No. 12/821,301, filed Jun. 23, 2010; U.S. Ser. No. 13/044,413, filed Mar. 9, 2011, and U.S. Ser. No. 12/660,529, filed Feb. 25, 2010.

[0003] U.S. Ser. No. 13/044,413 also claims the benefit of U.S. Ser. No. 61/339,766, entitled “Patient-adapted and Improved Orthopedic Implants, Designs, and Related Tools, filed Mar. 9, 2010.

[0004] U.S. Ser. No. 12/660,529 also claims the benefit of: U.S. Ser. No. 61/155,362, entitled “Patient-Specific Orthopedic Implants And Models,” filed Feb. 25, 2009; U.S. Ser. No. 61/269,405, entitled “Patient-Specific Orthopedic Implants And Models,” filed Jun. 24, 2009; U.S. Ser. No. 61/273,216, entitled “Patient-Specific Orthopedic Implants And Models,” filed Jul. 31, 2009; U.S. Ser. No. 61/275,174, entitled “Patient-Specific Orthopedic Implants And Models,” filed Aug. 26, 2009; U.S. Ser. No. 61/280,493, entitled “Patient-Adapted and Improved Orthopedic Implants, Designs and Related Tools,” filed Nov. 4, 2009; U.S. Ser. No. 61/284,458, entitled “Patient-Adapted And Improved Orthopedic Implants, Designs And Related Tools,” filed Dec. 18, 2009; U.S. Ser. No. 61/155,359, entitled “Patient Selectable Joint Arthroplasty Devices and Surgical Tools,” filed Feb. 25, 2009; and U.S. Ser. No. 61/220,726, entitled “Patient-Specific Orthopedic Implants And Models,” filed Jun. 26, 2009.

[0005] U.S. Ser. No. 13/397,457 is also a continuation-in-part of U.S. Ser. No. 12/965,493, filed Dec. 10, 2010, which claims the benefit of U.S. Ser. No. 61/284,022, filed Dec. 11, 2009.

[0006] U.S. Ser. No. 13/397,457 is also a continuation-in-part of U.S. Ser. No. 12/712,072, entitled “Automated Systems For Manufacturing Patient-Specific Orthopedic Implants And Instrumentation” filed Feb. 24, 2010, which claims the benefit of U.S. Ser. No. 61/208,440, entitled “Automated Systems for Manufacturing Patient-Specific Orthopedic Implants and Instrumentation” filed Feb. 24, 2009, and U.S. Ser. No. 61/208,444, entitled “Automated Systems for Manufacturing Patient-Specific Orthopedic Implants and Instrumentation” filed Feb. 24, 2009.

[0007] U.S. Ser. No. 13/397,457 is also a continuation-in-part of U.S. Ser. No. 13/157,857, entitled “Implant Device and Method for Manufacture” filed Jun. 10, 2011, which claims the benefit of U.S. Ser. No. 61/353,386, filed on Jun. 10, 2010.

[0008] The invention relates to improved and/or patient-adapted (e.g., patient-specific and/or patient-engineered) orthopedic implants and guide tools, as well as related methods, designs and models.

[0009] Generally, a diseased, injured or defective joint, such as, for example, a joint exhibiting osteoarthritis, has been repaired using standard off-the-shelf implants and other surgical devices. Specific off-the-shelf implant designs have been altered over the years to address particular issues. For example, several existing designs include implant components having rotating parts to enhance joint motion. Ries et al. describes design changes to the distal or posterior condyles of a femoral implant component to enhance axial rotation of the implant component during flexion. See U.S. Pat. Nos. 5,549,688 and 5,824,105. Andriacchi et al. describes a design change to the heights of the posterior condyles to enhance high flexion motion. See U.S. Pat. No. 6,770,099. However, in altering a design to address a particular issue, historical design changes frequently have created one or more additional issues for future designs to address. Collectively, many of these issues have arisen from one or more differences between a patient's existing or healthy joint anatomy and the corresponding features of an implant component.

[0010] Historically, joint implants have employed a one-size-fits-all (or a few-sizes-fit-all) approach to implant design that has resulted in significant differences between a patient's existing or healthy biological structures and the resulting implant component features in the patient's joint. Accordingly, advanced implant designs and related devices and methods that address the needs of individual patient's are needed.

[0011] The embodiments described herein include advancements in or that out of the area of patient-adapted articular implants that are tailored to address the needs of individual, single patients. Such patient-adapted articular implants offer advantages over the traditional one-size-fits-all approach, or a few-sizes-fit-all approach. The advantages include, for example, better fit, more natural movement of the joint, reduction in the amount of bone removed during surgery and a less invasive procedure. Such patient-adapted articular implants can be created from images of the patient's joint. Based on the images, patient-adapted implant components can be selected and/or designed to include features (e.g., surface contours, curvatures, widths, lengths, thicknesses, and other features) that match existing features in the single, individual patient's joint as well as features that approximate an ideal and/or healthy feature that may not exist in the patient prior to a procedure. Moreover, by altering the design approach to address several design implant issues, several non-traditional design approaches have been identified that offer improvements over traditional implant designs.

[0012] Patient-adapted features can include patient-specific and/or patient-engineered. Patient-specific (or patient-matched) implant component or guide tool features can include features adapted to match one or more of the patient's biological features, for example, one or more biological/anatomical structures, alignments, kinematics, and/or soft tissue features. Patient-engineered (or patient-derived) features of an implant component can be designed and/or manufactured (e.g., preoperatively designed and manufactured) based on patient-specific data to substantially enhance or improve one or more of the patient's anatomical and/or biological features.

[0013] The patient-adapted (e.g., patient-specific and/or patient-engineered) implant components and guide tools described herein can be selected (e.g., from a library), designed (e.g., preoperatively designed including, optionally, manufacturing the components or tools), and/or selected and designed (e.g., by selecting a blank component or tool having certain blank features and then altering the blank features to be patient-adapted). Moreover, related methods, such as designs and strategies for resectioning a patient's biological structure also can be selected and/or designed. For example, an implant component bone-facing surface and a resectioning strategy for the corresponding bone-facing surface can be selected and/or designed together so that an implant component's bone-facing surface matches the resected surface. In addition, one or more guide tools optionally can be selected and/or designed to facilitate the resection cuts that are predetermined in accordance with resectioning strategy and implant component selection and/or design.

[0014] In certain embodiments, patient-adapted features of an implant component, guide tool or related method can be achieved by analyzing imaging test data and selecting and/or designing (e.g., preoperatively selecting from a library and/or designing) an implant component, a guide tool, and/or a procedure having a feature that is matched and/or optimized for the particular patient's biology. The imaging test data can include data from the patient's joint, for example, data generated from an image of the joint such as x-ray imaging, cone beam CT, digital tomosynthesis, and ultrasound, a MRI or CT scan or a PET or SPECT scan, is processed to generate a varied or corrected version of the joint or of portions of the joint or of surfaces within the joint. Certain embodiments provide method and devices to create a desired model of a joint or of portions or surfaces of a joint based on data derived from the existing joint. For example, the data can also be used to create a model that can be used to analyze the patient's joint and to devise and evaluate a course of corrective action. The data and/or model also can be used to design an implant component having one or more patient-specific features, such as a surface or curvature.

[0015] In one aspect, embodiments described herein provide a pre-primary articular implant component that includes (a) an outer, joint-facing surface and an inner, bone-facing surface. The outer, joint-facing surface can include a bearing surface. The inner joint facing surface can include one or more patient-engineered bone cuts selected and/or designed from patient-specific data. In certain embodiments, the patient-engineered bone cuts can be selected and/or designed from patient-specific data to minimize the amount of bone resected in one or more corresponding predetermined resection cuts. In certain embodiments, the patient-engineered bone cuts substantially negatively-match one or more predetermined resection cuts. The predetermined resection cuts can be made at a first depth that allows, in a subsequent procedure, removal of additional bone to a second depth required for a traditional primary implant component. In addition, the pre-primary articular implant component can be a knee joint implant component, a hip joint implant component, a shoulder joint implant component, or a spinal implant component. For example, the pre-primary articular implant component can be a knee joint implant component, such as a femoral implant component. Moreover, the pre-primary articular implant component can include six or more (e.g., six, seven, eight, nine, ten, eleven, twelve, thirteen, or more) patient-engineered bone cuts on its bone facing surface.

[0016] In certain embodiments, the pre-primary articular implant component can include an implant component thickness in one or more regions that is selected and/or designed from patient-specific data to minimize the amount of bone resected. The one or more regions comprises the implant component thickness perpendicular to a planar bone cut and between the planar bone cut and the joint-surface of the implant component.

[0017] In another aspect, embodiments described herein provide methods for minimizing resected bone from, and/or methods for making an articular implant for, a single patient in need of an articular implant replacement procedure. These methods can include (a) identifying unwanted tissue from one or more images of the patient's joint; (b) identifying a combination of resection cuts and implant component features that remove the unwanted tissue and also provide maximum bone preservation; and (c) selecting and/or designing for the patient a combination of resection cuts and implant component features that provide removal of the unwanted tissue and maximum bone preservation. In certain embodiments, the unwanted tissue is diseased tissue or deformed tissue.

[0018] In certain embodiments, step (c) can include designing for the single patient a combination of resection cuts and implant component features that provide removal of the unwanted tissue and maximum bone preservation. Designing can include manufacturing. Moreover, the implant component features in step (c) can include one or more of the features selected from the group consisting of implant thickness, bone cut number, bone cut angles, and/or bone cut orientations.

[0019] In certain embodiments, a measure of bone preservation can include total volume of bone resected, volume of bone resected from one or more resection cuts, volume of bone resected to fit one or more implant component bone cuts, average thickness of bone resected, average thickness of bone resected from one or more resection cuts, average thickness of bone resected to fit one or more implant component bone cuts, maximum thickness of bone resected, maximum thickness of bone resected from one or more resection cuts, maximum thickness of bone resected to fit one or more implant component bone cuts.

[0020] In certain embodiments, a minimum implant component also can be established. For example, step (a) also can include identifying a minimum implant component thickness for the single patient. Step (b) also can include identifying a combination of resection cuts and/or implant component features that provide a minimum implant thickness determined for the single patient. Step (c) also can include selecting and/or designing the combination of resection cuts and/or implant component features that provides at least a minimum implant thickness for the single patient. The minimum implant component thickness is based on one or more of femur and/or condyle size or patient weight.

[0021] The articular implant component can be a knee joint implant component, a hip joint implant component, a shoulder joint implant component, or a spinal implant component. For example, the pre-primary articular implant component can be a knee joint implant component, such as a femoral implant component.

[0022] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising six or more bone cuts.

[0023] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising a distal bone cut having two or more planar facets or portions that are non-coplanar with each other. In certain embodiments, the two or more facets or portions are non-parallel with each other. The first of the two or more facets or portions can be on a lateral condyle bone-facing surface and the second can be on a medial condyle bone-facing surface.

[0024] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising an anterior bone cut having two or more planar facets or portions that are non-coplanar with each other. In certain embodiments, the two or more planar facets or portions are non-parallel with each other.

[0025] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising a posterior bone cut having two or more facets or portions that are non-parallel with each other. In certain embodiments, the first of the two or more facets or portions can be on a lateral condyle bone-facing surface and the second can be on a medial condyle bone-facing surface.

[0026] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising an anterior chamfer bone cut having two or more planar facets or portions that are non-coplanar with each other. In certain embodiments, the two or more planar facets or portions are non-parallel with each other. The first of the two or more facets or portions can be on a lateral condyle bone-facing surface and the second can be on a medial condyle bone-facing surface.

[0027] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising a bearing surface portion, and (b) a bone-facing surface comprising a posterior chamfer bone cut having two or more facets or portions that are non-parallel with each other. In certain embodiments, the first of the two or more facets or portions can be on a lateral condyle bone-facing surface and the second can be on a medial condyle bone-facing surface.

[0028] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a joint-facing surface comprising lateral and medial condylar surface portions, and (b) a bone-facing surface comprising an anterior bone cut, wherein the distance between the anterior bone cut and the lateral condylar surface portion is different from the distance between the anterior bone cut and the medial condylar surface portion. In certain embodiments, the two or more facets or portions are substantially non-parallel.

[0029] In another aspect, embodiments described herein provide a femoral implant component that includes (a) a lateral and medial condylar portions, and (b) a bone-facing surface comprising a distal bone cut facet that is asymmetric about its center line in a sagittal plane. In certain embodiments, the asymmetric distal bone cut facet lies on the bone-facing surface of the lateral condyle. In certain embodiments, the femoral implant component can accommodate asymmetric distal bone cut facets on the bone-facing surface of the medial condyle.

[0030] In another aspect, embodiments described herein provide a femoral implant component that includes a femoral implant component having a bone-facing surface comprising one or more bone cuts, wherein at least one of the one or more bone cuts comprises two planar bone cut facets separated by at least one step cut. In certain embodiments, the step cut is substantially perpendicular to at least one of the bone cut facets. In certain embodiments, the step cut can rise or fall at about 30 degrees or more from at least one of the bone cut facet planes.

[0031] In another aspect, embodiments described herein provide implant components having an inner, bone-facing surface designed to negatively-match a bone surface that was cut, for example based on pre-determined geometries or based on patient-specific geometries. In certain embodiments, an outer joint-facing surface includes at least in a portion that substantially negatively-matches a feature of the patient's anatomy and/or an opposing outer joint-facing surface of a second implant component. In certain embodiments, by creating negatively-matching component surfaces at a joint interface, the opposing surfaces may not have an anatomic or near-anatomic shape, but instead may be negatively-matching or near-negatively-matching to each other. This can have various advantages, such as reducing implant and joint wear and providing more predictable joint movement.

[0032] In another aspect, some embodiments provide implant components having one or more patient-specific curvatures or radii of curvature in one dimension, and one or more standard or engineered curvatures or radii of curvature in a second dimension.

[0033] In another aspect, some embodiments provide methods of designing, selecting, manufacturing, and implanting the patient-adapted implant components.

[0034] It is to be understood that the features of the various embodiments described herein are not mutually exclusive and may exist in various combinations and permutations.

[0239] Additional figure descriptions are included in the text below. Unless otherwise denoted in the description for each figure, “M” and “L” in certain figures indicate medial and lateral sides of the view; “A” and “P” in certain figures indicate anterior and posterior sides of the view, and “S” and “I” in certain figures indicate superior and inferior sides of the view.

[0240] 1. Introduction

[0241] When a surgeon uses a traditional off-the-shelf implant to replace a patient's joint, for example, a knee joint, hip joint, or shoulder joint, certain features of the implant typically do not match the particular patient's biological features. These mismatches can cause various complications during and after surgery. For example, surgeons may need to extend the surgery time and apply estimates and rules of thumb during surgery to address the mismatches. For the patient, complications associated with these mismatches can include pain, discomfort, soft tissue impingement, and an unnatural feeling of the joint during motion, e.g., so-called mid-flexion instability, as well as an altered range of movement and an increased likelihood of implant failure. In order to fit a traditional implant component to a patient's articular bone, surgeons typically remove substantially more of the patient's bone than is necessary to merely clear diseased bone from the site. This removal of substantial portions of the patient's bone frequently diminishes the patient's bone stock to the point that only one subsequent revision implant is possible.

[0242] Certain embodiments of the implants, guide tools, and related methods of designing (e.g., designing and making), and using the implants and guide tools described herein can be applied to any joint including, without limitation, a spine, spinal articulations, an intervertebral disk, a facet joint, a shoulder, an elbow, a wrist, a hand, a finger, a hip, a knee, an ankle, a foot, or a toe joint. Furthermore, various embodiments described herein can apply to methods and procedures, and the design of methods and procedures, for resectioning the patient's anatomy in order to implant the implant components described herein and/or to using the guide tools described herein.

[0243] 1.1 Patient-Adapted Features

[0244] Certain embodiments relate to patient-adapted implants, guide tools, and related methods. Patient-adapted features of an implant component, guide tool or related implantation method can be achieved by analyzing imaging test data and selecting and/or designing (e.g., preoperatively selecting from a library and/or preoperatively designing) an implant component, a guide tool, and/or a procedure having a feature that is matched and/or optimized for the particular patient's anatomy and/or biology. Accordingly, the patient-adapted implant components, guide tools, and/or methods include one or more patient-adapted features. Patient-adapted features can include patient-specific features and/or patient-engineered features.

[0245] Certain embodiments relate to patient-specific implants, guide tools, and related methods. For example, some embodiments relate to articular implant components having one or more patient-specific features adapted to match one or more of the patient's biological features, such as one or more of biological/anatomical structures, alignments, kinematics, and/or soft tissue impingements. Accordingly, the one or more patient-specific features of an implant component can include, but are not limited to, one or more implant component surfaces, such as surface contours or angles, and one or more implant component dimensions such as thickness, width, depth, or length. The patient-specific feature(s) of an implant component can be designed based on patient-specific data to substantially match one or more of the patient's biological features (i.e., anatomical and/or biological features). In various embodiments described herein, the act of designing an implant component can include manufacturing the implant component having the related design features. For example, designing an implant component can include preoperatively establishing a design of one or more features of an implant component, for example, using a CAD computer program on a computer system specialized operated for such use and having one or more user interfaces, and instructing the transfer of that design data, for example, from a CAD computer program or computer system to a CAM (computer-aided manufacturing) computer program or computer system. Optionally, in certain embodiments, designing the implant can further include instructing the initiation of manufacturing the physical implant and/or manufacturing the implant.

[0246] Alternatively, patient-specific feature(s) of an implant component or guide tool can be achieved by analyzing imaging test data and selecting (e.g., preoperatively selecting from a library of implant components) the implant component that best fits one or more pre-determined patient-specific parameters that are derived from the imaging test.

[0247] Moreover, an implant component or guide tool can include a patient-specific feature that is both selected and designed. For example, an implant component initially can be selected (e.g., preoperatively selected from a library of implants) to have a feature with a standard or blank dimension, or with a larger or smaller dimension than the predetermined patient-specific dimension. Then, the implant component can be machined (if selected from an actual library of implant components) or manufactured (if selected from a virtual library of implant components) so that the standard dimension or blank dimension or larger-dimensioned or smaller-dimensioned implant feature is altered to have the patient-specific dimension.

[0248] In addition or alternatively, certain embodiments relate to patient-engineered implants, guide tools, and related methods. Some embodiments relate to articular implant components having one or more patient-engineered features optimized from patient-specific data to meet one or more parameters to enhance one or more of the patient's biological features, such as one or more biological/anatomical structures, alignments, kinematics, and/or soft tissue impingements. Accordingly, the one or more patient-engineered features of an implant component can include, but are not limited to, one or more implant component surfaces, such as surface contours, angles or bone cuts, and dimensions such as thickness, width, depth, or length of one or more aspects of the implant component. The patient-engineered feature(s) of an implant component can be designed and/or manufactured (e.g., preoperatively designed and manufactured) based on patient-specific data to substantially enhance or improve one or more of the patient's anatomical and/or biological features. Methods for preparing certain patient-engineered features are described, for example, in U.S. Ser. No. 12/712,072, entitled “Automated Systems For Manufacturing Patient-Specific Orthopedic Implants And Instrumentation” filed Feb. 24, 2010, the disclosure of which is incorporated herein by reference.

[0249] As with the patient-specific feature(s) of an implant component or guide tool, the patient-engineered features of an implant component or guide tool can be designed (e.g., preoperatively designed and manufactured) or they can be selected, for example, by selecting an implant component that best meets the one or more predetermined parameters that enhance one or more features of the patient's biology.

[0250] Moreover, an implant component or guide tool can include a patient-engineered feature that is both selected and designed. For example, an implant component initially can be selected (e.g., preoperatively selected from a library of implants) to have a feature with a larger or smaller dimension than the desired patient-engineered dimension. Then, the implant component can be machined (if selected from an actual library of implant components) or manufactured (if selected from a virtual library of implant components) so that the larger-dimensioned or smaller-dimensioned implant feature is altered to have the desired patient-engineered dimension.

[0251] 1.2 Combinations of Patient-Adapted and Standard Features

[0252] A single implant component, guide tool, and/or related method can include one or more patient-specific features, one or more patient-engineered features, and/or one or more standard (e.g., off-the-shelf features). The standard, off-the-shelf features can be selected to best fit with one or more of the patient-specific and/or patient-engineered features. For example, in a knee joint, a metal backed tibial component can include a standard locking mechanism and a patient-adapted (i.e., patient-specific or patient-engineered) perimeter of the tibial component. A patient-specific perimeter of the tibial component can be achieved, for example, by cutting the perimeter of a selected tibial component to match the patient's cortical bone perimeter in one or more dimensions of one more sections. Similarly, a polyethylene insert can be chosen that includes a standard locking mechanism, while the perimeter is adapted for better support to the patient's tibial bone perimeter or the perimeter of the metal backing.

[0253] In certain aspects, an implant, guide tool, and/or related method can include one or more patient-adapted features and one or more standard features. For example, the joint-facing surface of an implant component can include a patient-specific feature (e.g., curvature) in the axis or axes of motion and one or more standard features in other axes. Using a curvature in the direction of motion that is matched to the patient's curvature (patient-specific) or that is optimized based on the patient's curvature (patient-engineered) can help to maintain and/or improve the biomechanical aspects of the patient's joint.

[0254] As one illustrative example, in certain embodiments, the joint-facing surface of a condylar portion of a femoral implant component and/or a corresponding groove in the bearing surface of a tibial implant component can include a patient-specific sagittal curvature (e.g., having one or more patient-specific radii of curvature) and a standard coronal curvature or radii of curvature. Coronal radii of curvature also can be patient-derived, but an average or an optimum can be derived across the articular surface that is constant along the extent of the articular surface in the coronal plane. The patient-specific sagittal curvature or radii of curvature can be designed from patient-specific data to match an existing feature of the patient's biology or it can be patient-engineered from patient-specific data to improve an existing feature of the patient's biology.

[0255] In certain embodiments, implant components and/or related methods described herein can include a combination of patient-specific and patient-engineered features. For example, patient-specific data collected preoperatively can be used to engineer one or more optimized surgical cuts to the patient's bone and to design or select a corresponding implant component having or more bone-facing surfaces or facets (i.e., “bone cuts”) that specifically match one or more of the patient's resected bone surfaces. The surgical cuts to the patient's bone can be optimized (i.e., patient-engineered) to enhance one or more parameters, such as: (1) deformity correction and limb alignment (2) maximizing preservation of bone, cartilage, or ligaments, (3) maximizing preservation and/or optimization of other features of the patient's anatomy, such as trochlea and trochlear shape, (4) restoration and/or optimization of joint kinematics or biomechanics, (5) restoration or optimization of joint-line location and/or joint gap width, (6) and/or addressing one or more other parameters. Based on the optimized surgical cuts and, optionally, on other desired features of the implant component, the implant component's bone-facing surface can be designed or selected to, at least in part, negatively-match the shape of the patient's resected bone surface.

[0256] Optionally, the implant component can include other patient-adapted features. For example, the joint-facing surface can be designed to, at least in part, substantially negatively-match an opposing surface at the joint cavity (e.g., the surface of the patient's biological structure, native or resected, or the surface of an opposing implant component). In certain embodiments, the joint-facing surface of the implant component can include patient-adapted features such as a patient-specific sagittal curvature and a patient-engineered coronal curvature, or a patient-specific sagittal curvature and a patient-specific coronal curvature. These curvatures can be patient-specific in at least a portion or the entire joint-facing surface of the implant. Alternatively or in addition, one or more of these curvatures can be patient-adapted in one condyle, but not patient-adapted in the other condyle. Moreover, the shape (e.g., curvature) of a first condyle can be used, for example, to generate a shape (e.g., curvature) for the second condyle.

[0257] For example, some portion or all of the j-curve of a medial condyle can be used to derive a shape of at least portions of a lateral condyle. In one embodiment, a linear or non-linear scaling factor or a mathematical formula or algorithm can be applied to the medial femoral condyle J-curve or radii associated with it. This can be done along some portion of the lateral condyle, along a posterior portion of the lateral condyle only, along a posterior and central portion, or along the entire condyle. The resultant shape of the lateral condyle portion of the femoral implant can have dimensions similar to the uncut lateral condyle, for example, now corrected for arthritic deformity, it can be smaller in one or more dimensions than the uncut lateral condyle, it can have a similar size than the uncut lateral femoral condyle, or it can be larger in one or more aspects and/or dimensions than the uncut lateral condyle. The same concept can be applied to a medial condyle, using lateral condyle shape or J-curve information. Similarly, a coronal curvature of a lateral condyle can be derived based on a medial condyle, with the optional application of some scaling factors or formulas or algorithms. A coronal curvature of a medial condyle can be derived based on a lateral condyle, with the optional application of some scaling factors or formulas or algorithms. In a similar fashion, the shape information of a medial or lateral condyle of the opposing leg can be used to assist in deriving or designing anatomical features of a targeted medial or lateral condyle.

[0258] While it is described with regards to a knee joint, the various embodiments described herein can be applied to various other joints or joint surfaces in the body, e.g., a knee, hip, ankle, foot, toe, shoulder, elbow, wrist, hand, and a spine or spinal joints.

[0259] 1.3 Implant Systems

[0260] An implant (i.e., an implant system) can include one or more implant components, which, as described above, can each include one or more patient-specific features, one or more patient-engineered features, and one or more standard (e.g., off-the-shelf) features. Moreover, an implant system can include one or more patient-adapted (e.g., patient-specific and/or patient-engineered) implant components and one or more standard implant components.

[0261] For example, a knee implant can include a femoral implant component having one or more patient-adapted and standard features, and an off-the-shelf tibial implant component having only standard features. In this example, the entire tibial implant component can be off-the-shelf. Alternatively, a metal-backed implant component (or portion of an implant component) can be patient-specific, e.g., matched in the A-P dimension or the M-L dimension to the patient's tibial cortical bone, while the corresponding plastic insert implant component (or corresponding portion of the implant component) can include a standard off-the-shelf configuration.

[0262] Off-the-shelf configuration can mean that the tibial insert has fixed, standard dimensions to fit, for example, into a standard tibial tray. Off-the-shelf configuration also can mean that the tibial insert has a fixed, standard dimension or distance between two tibial dishes or curvatures to accommodate the femoral bearing surface. The latter configuration is particularly applicable in an implant system that uses a femoral implant component that is patient-specifically matched in the M-L dimension to the distal femur of the patient's bone, but uses a standardized intercondylar notch width on the femoral component to achieve optimal mating with a corresponding tibial insert. For example, FIGS. 1A and 1B show schematic representations in a coronal plane of a patient's distal femur (FIG. 1A) and a femoral implant component (FIG. 1B). As shown in the figures, the implant component M-L dimension 100 (e.g. epicondylar M-L dimension) patient-specifically matches the corresponding M-L dimension of the patient's femur 102. However, the intercondylar M-L dimension (i.e., notch width) of the implant component, 104, can be standard, which in this figure is shorter than the patient's intercondylar M-L dimension 106. In this way, the epicondylar M-L dimension of the implant component is patient-specific, while the intercondylar M-L dimension (i.e., notch width) is designed to be a standard length, for example, so that is can properly engage during joint motion a tibial insert having a standard distance between its dishes or curvatures that engage the condyles of the femoral implant component.

[0263] 1.4 Improved Implants, Guide Tools and Related Methods

[0264] Certain embodiments are directed to implants, guide tools, and/or related methods that can be used to provide to a patient a pre-primary procedure and/or a pre-primary implant such that a subsequent, replacement implant can be performed with a second (and, optionally, a third, and optionally, a fourth) patient-adapted pre-primary implant or with a traditional primary implant. In certain embodiments, the pre-primary implant procedure can include 3, 4, 5, 6, 7, or more resection or surgical cuts to the patient's bone and the pre-primary implant can include on its corresponding bone-facing surface a matching number and orientation of bone-cut facets or surfaces.

[0265] In one illustrative embodiment, a first pre-primary joint-replacement procedure includes a patient-adapted implant component, guide tool, and/or related method. The patient-adapted implant component, guide tool, and/or related method can be preoperatively selected and/or designed from patient-specific data, such as one or more images of the patient's joint, to include one or more features that are patient-specific or patient-engineered. The features (e.g., dimensions, shape, surface contours) of the first pre-primary implant and, optionally, patient-specific data (e.g., features of the patient's resected bone surfaces and features of the patient's contralateral joint) can be stored in a database. When the first pre-primary implant fails, for example, due to bone loss or osteolysis or aseptic loosening at a later point in time (e.g., 15 years after the original implantation) a second implant can be implanted. For the second implant procedure, the amount of diseased bone can be assessed. If the amount of diseased bone to be resected is minimal, the patient-specific data can be used to select and/or design a second pre-primary procedure and/or a pre-primary implant. If the amount of diseased bone to be resected is substantial, a traditional primary procedure and a traditional implant can be employed.

[0266] Alternatively, certain embodiments are directed to implants, guide tools, and/or related methods that can be used to provide to a patient a primary procedure and/or a primary implant such that a subsequent replacement implant can be used as part of a traditional revision procedure. Certain embodiments are directed to implants, guide tools, and/or related methods that can be used to provide a patient-adapted revision implant. For example, following a traditional implant, a subsequent revision can include a patient-adapted procedure and/or a patient-adapted implant component as described herein.

[0267] FIG. 2 is a flow chart illustrating a process that includes selecting and/or designing a first patient-adapted implant, for example, a pre-primary implant. First, using the techniques described herein or those suitable and known in the art, measurements of the target joint are obtained 210. This step can be repeated multiple times, as desired. Optionally, a virtual model of the joint can be generated, for example, to determine proper joint alignment and the corresponding resection cuts and implant component features based on the determined proper alignment. This information can be collected and stored 212 in a database 213. Once measurements of the target joint are obtained and analyzed to determine resection cuts and patient-adapted implant features, the patient-adapted implant components can be selected 214 (e.g., selected from a virtual library and optionally manufactured without further design alteration 215, or selected from a physical library of implant components). Alternatively, or in addition, one or more implant components with best-fitting and/or optimized features can be selected 214 (e.g., from a library) and then further designed (e.g., designed and manufactured) 216. Alternatively or in addition, one or more implant components with best-fitting and/or optimized features can be designed (e.g., designed and manufactured) 218, 216 without an initial selection from a library. Using a virtual model to assess the selected or designed implant component(s), this process also can be repeated as desired (e.g., before one or more physical components are selected and/or generated). The information regarding the selected and/or designed implant component(s) can be collected and stored 220, 222 in a database 213. Once a desired first patient-adapted implant component or set of implant components is obtained, a surgeon can prepare the implantation site and install the first implant 224. The information regarding preparation of the implantation site and implant installation can be collected and stored 226 in a database 213. In this way, the information associated with the first pre-primary implant component is available for use by a surgeon for subsequent implantation of a second pre-primary or a primary implant.

[0268] FIG. 3 is a flow chart illustrating a process that includes selecting and/or designing a second implant. In certain embodiments, the second implant can be a traditional primary implant. Alternatively, the second implant can be a patient-adapted implant, which optionally can be used as second pre-primary implant that allows for a subsequent (i.e., third) primary implant using a traditional implant.

[0269] The steps described in FIG. 3 are similar to those described above for a first pre-primary implant (see FIG. 2); however, in the second implant process, the database information 213 collected and stored in the first implant process can be used as part of the process for the second implant. In addition to the database information from the first implant process 213, additional measurements of the target joint optionally can be obtained 310 and used together with the database information 213 from the first implant process as a basis for selecting and/or designing a second implant. This step can be repeated multiple times, as desired. Optionally, a virtual model of the joint can be generated (with our without a model of the first implant), for example, to determine proper joint alignment, corresponding resection cuts and, optionally, patient-adapted implant component features based on the determined proper alignment. This information can be collected and stored 312 as new or additional database information 313. Once the database information from the first implant process and optionally new measurements of the target joint and first implant are obtained and analyzed, the implant component(s) for the second implant can be selected 314 (e.g., selected from a virtual library and optionally manufactured without further design alteration 315, or selected from a physical library of implant components, or selected from among traditional implant components). Alternatively or in addition, one or more implant components with best-fitting and/or optimized features can be selected 314 (e.g., from a library) and then further designed (e.g., designed and manufactured) 316. Alternatively or in addition, one or more implant components with best-fitting and/or optimized features can be designed (e.g., designed and manufactured) 038 without an initial selection from a library. Using a virtual model to assess the selected or designed implant component, this process also can be repeated as desired (e.g., before one or more physical components are selected and/or generated). The information regarding the selected and/or designed implant components for the second implant can be collected and stored 320, 322 in a database 313. Once a desired implant component or set of implant components is obtained for the second implant, a surgeon can prepare the implantation site, including removing the first implant, and install the second implant 324. The information regarding preparation of the implantation site and second implant installation can be collected and stored 326 in a database 313.

[0270] The second implant can have standard attachment mechanisms, e.g., a stem and or pegs or other attachment means known in the art. Alternatively, the attachment mechanisms can be patient-specific by deriving shape information on the residual bone, e.g., of a femur and acetabulum or of a femur and a tibia or of a humerus and a glenoid, using image data, e.g., CT or MRI data. One or more dimensions or shapes or joint-facing surfaces of the second implant can be adapted to include, at least in part, information reflective of the corresponding dimension(s) or shape(s) or joint-facing surface(s) of the first implant. In this manner, a better functional result can be achieved with the revision implant by maintaining patient-specific shapes and/or geometry in the revision implant by accessing data in the patient database.

[0271] Accordingly, certain embodiments described herein are directed to implants, implant components, guide tools, and related methods that address many of the problems associated with traditional implants, such as mismatches between an implant component and a patient's biological features (e.g., a feature of a biological structure, a distance or space between two biological structures, and/or a feature associated with anatomical function) and substantial bone removal that limits subsequent revisions following a traditional primary implant.

[0272] 2. Exemplary Implant Systems and Patient-Adapted Features

[0273] The concepts described herein can be embodied in various types of articular implants including, but not limited to, knee-joint implants, hip-joint implants, shoulder-joint implants, and spinal implants (e.g., intervertebral implants and facet joint implants), as well as related surgical tools (e.g., guide tools) and methods. Exemplary traditional implants are illustrated in FIGS. 4A-4M. In particular, FIGS. 4A and 4B illustrate exemplary traditional knee-joint implants as described, for example, in U.S. Pat. Nos. 5,824,105 and 5,133,758, respectively; FIGS. 4C-4G illustrate traditional hip-joint implants, including Austin Moore-type, Thompson-type, and Bipolar hip-type prostheses; FIGS. 4H-4J illustrate traditional shoulder-joint implants as described, for example, in U.S. Pat. No. 7,175,663; and FIGS. 4K-4M illustrate traditional spinal implants, as described, for example, in U.S. Pat. No. 7,166,129 and at the web site, www.facetsolutions.com/AFRSproduct.html.

[0274] In certain embodiments described herein, an implant or implant system can include one, two, three, four or more components having one or more patient-specific features that substantially match one or more of the patient's biological features, for example, one or more dimensions and/or measurements of an anatomical/biological structure, such as bone, cartilage, tendon, or muscle; a distance or space between two or more aspects of a biological structure and/or between two or more different biological structures; and a biomechanical or kinematic quality or measurement of the patient's biology. In addition or alternatively, an implant component can include one or more features that are engineered to optimize or enhance one or more of the patient's biological features, for example, (1) deformity correction and limb alignment (2) preserving bone, cartilage, and/or ligaments, (3) preserving and/or optimizing other features of the patient's anatomy, such as trochlea and trochlear shape, (4) restoring and/or optimizing joint kinematics or biomechanics, and/or (5) restoring and/or optimizing joint-line location and/or joint gap width. In addition, an implant component can be designed and/or manufactured to include one or more standard (i.e., non-patient-adapted) features.

[0275] Exemplary patient-adapted (i.e., patient-specific and/or patient-engineered) features of the implant components described herein are identified in Table 1. One or more of these implant component features can be selected and/or designed based on patient-specific data, such as image data.

TABLE 1
Exemplary implant features that can be patient-adapted based on
patient-specific measurements
Category	Exemplary feature
Implant or	One or more portions of, or all of, an external implant
implant or	component curvature
component	One or more portions of, or all of, an internal implant
(applies knee,	dimension
shoulder, hip,	One or more portions of, or all of, an internal or
ankle, or other	external implant angle
implant or	Portions or all of one or more of the ML, AP, SI
implant	dimension of the internal and external component and
component)	component features
	An locking mechanism dimension between a plastic
	or non-metallic insert and a metal backing component
	in one or more dimensions
	Component height
	Component profile
	Component 2D or 3D shape
	Component volume
	Composite implant height
	Insert width
	Insert shape
	Insert length
	Insert height
	Insert profile
	Insert curvature
	Insert angle
	Distance between two curvatures or concavities
	Polyethylene or plastic width
	Polyethylene or plastic shape
	Polyethylene or plastic length
	Polyethylene or plastic height
	Polyethylene or plastic profile
	Polyethylene or plastic curvature
	Polyethylene or plastic angle
	Component stem width
	Component stem shape
	Component stem length
	Component stem height
	Component stem profile
	Component stem curvature
	Component stem position
	Component stem thickness
	Component stem angle
	Component peg width
	Component peg shape
	Component peg length
	Component peg height
	Component peg profile
	Component peg curvature
	Component peg position
	Component peg thickness
	Component peg angle
	Slope of an implant surface
	Number of sections, facets, or cuts on an implant
	surface
Femoral implant	Condylar distance of a femoral component, e.g.,
or implant	between femoral condyles
component	A condylar coronal radius of a femoral component
	A condylar sagittal radius of a femoral component
Tibial implant or	Slope of an implant surface
implant	Condylar distance, e.g., between tibial joint-facing
component	surface concavities that engage femoral condyles
	Coronal curvature (e.g., one or more radii of curvature
	in the coronal plane) of one or both joint-facing
	surface concavities that engage each femoral condyle
	Sagittal curvature (e.g., one or more radii of curvature
	in the sagittal plane) of one or both joint-facing
	surface concavities that engage each femoral condyle

[0276] The patient-adapted features described in Table 1 also can be applied to patient-adapted guide tools described herein.

[0277] The patient-adapted implant components and guide tools described herein can include any number of patient-specific features, patient-engineered features, and/or standard features. Illustrative combinations of patient-specific, patient-engineered, and standard features of an implant component are provided in Table 2. Specifically, the table illustrates an implant or implant component having at least thirteen different features. Each feature can be patient-specific (P), patient-engineered (PE), or standard (St). As shown, there are 105 unique combinations in which each of thirteen is either patient-specific, patient-engineered, or standard features.

TABLE 2
Exemplary combinations of patient-specific (P), patient-engineered
(PE), and standard (St) features1 in an implant
Implant
system	Implant feature number2
number	1	2	3	4	6	6	7	8	9	10	11	12	13
1	P	P	P	P	P	P	P	P	P	P	P	P	P
2	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE
3	St	St	St	St	St	St	St	St	St	St	St	St	St
4	P	St	St	St	St	St	St	St	St	St	St	St	St
5	P	P	St	St	St	St	St	St	St	St	St	St	St
6	P	P	P	St	St	St	St	St	St	St	St	St	St
7	P	P	P	P	St	St	St	St	St	St	St	St	St
8	P	P	P	P	P	St	St	St	St	St	St	St	St
9	P	P	P	P	P	P	St	St	St	St	St	St	St
10	P	P	P	P	P	P	P	St	St	St	St	St	St
11	P	P	P	P	P	P	P	P	St	St	St	St	St
12	P	P	P	P	P	P	P	P	P	St	St	St	St
13	P	P	P	P	P	P	P	P	P	P	St	St	St
14	P	P	P	P	P	P	P	P	P	P	P	St	St
15	P	P	P	P	P	P	P	P	P	P	P	P	St
16	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE
17	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE
18	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE
19	P	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE
20	P	P	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE
21	P	P	P	P	P	P	PE	PE	PE	PE	PE	PE	PE
22	P	P	P	P	P	P	P	PE	PE	PE	PE	PE	PE
23	P	P	P	P	P	P	P	P	PE	PE	PE	PE	PE
24	P	P	P	P	P	P	P	P	P	PE	PE	PE	PE
25	P	P	P	P	P	P	P	P	P	P	PE	PE	PE
26	P	P	P	P	P	P	P	P	P	P	P	PE	PE
27	P	P	P	P	P	P	P	P	P	P	P	P	PE
28	PE	St	St	St	St	St	St	St	St	St	St	St	St
29	PE	PE	St	St	St	St	St	St	St	St	St	St	St
30	PE	PE	PE	St	St	St	St	St	St	St	St	St	St
31	PE	PE	PE	PE	St	St	St	St	St	St	St	St	St
32	PE	PE	PE	PE	PE	St	St	St	St	St	St	St	St
33	PE	PE	PE	PE	PE	PE	St	St	St	St	St	St	St
34	PE	PE	PE	PE	PE	PE	PE	St	St	St	St	St	St
35	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St	St	St
36	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St	St
37	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St
38	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St
39	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St
40	P	PE	St	St	St	St	St	St	St	St	St	St	St
41	P	PE	PE	St	St	St	St	St	St	St	St	St	St
42	P	PE	PE	PE	St	St	St	St	St	St	St	St	St
43	P	PE	PE	PE	PE	St	St	St	St	St	St	St	St
44	P	PE	PE	PE	PE	PE	St	St	St	St	St	St	St
45	P	PE	PE	PE	PE	PE	PE	St	St	St	St	St	St
46	P	PE	PE	PE	PE	PE	PE	PE	St	St	St	St	St
47	P	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St	St
48	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St
49	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St
50	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St
51	P	P	PE	St	St	St	St	St	St	St	St	St	St
52	P	P	PE	PE	St	St	St	St	St	St	St	St	St
53	P	P	PE	PE	PE	St	St	St	St	St	St	St	St
54	P	P	PE	PE	PE	PE	St	St	St	St	St	St	St
55	P	P	PE	PE	PE	PE	PE	St	St	St	St	St	St
56	P	P	PE	PE	PE	PE	PE	PE	St	St	St	St	St
57	P	P	PE	PE	PE	PE	PE	PE	PE	St	St	St	St
58	P	P	PE	PE	PE	PE	PE	PE	PE	PE	St	St	St
59	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	St	St
60	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	PE	St
61	P	P	P	PE	St	St	St	St	St	St	St	St	St
62	P	P	P	PE	PE	St	St	St	St	St	St	St	St
63	P	P	P	PE	PE	PE	St	St	St	St	St	St	St
64	P	P	P	PE	PE	PE	PE	St	St	St	St	St	St
65	P	P	P	PE	PE	PE	PE	PE	St	St	St	St	St
66	P	P	P	PE	PE	PE	PE	PE	PE	St	St	St	St
67	P	P	P	PE	PE	PE	PE	PE	PE	PE	St	St	St
68	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE	St	St
69	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE	PE	St
70	P	P	P	P	PE	St	St	St	St	St	St	St	St
71	P	P	P	P	PE	PE	St	St	St	St	St	St	St
72	P	P	P	P	PE	PE	PE	St	St	St	St	St	St
73	P	P	P	P	PE	PE	PE	PE	St	St	St	St	St
74	P	P	P	P	PE	PE	PE	PE	PE	St	St	St	St
75	P	P	P	P	PE	PE	PE	PE	PE	PE	St	St	St
76	P	P	P	P	PE	PE	PE	PE	PE	PE	PE	St	St
77	P	P	P	P	PE	PE	PE	PE	PE	PE	PE	PE	St
78	P	P	P	P	P	PE	St	St	St	St	St	St	St
79	P	P	P	P	P	PE	PE	St	St	St	St	St	St
80	P	P	P	P	P	PE	PE	PE	St	St	St	St	St
81	P	P	P	P	P	PE	PE	PE	PE	St	St	St	St
82	P	P	P	P	P	PE	PE	PE	PE	PE	St	St	St
83	P	P	P	P	P	PE	PE	PE	PE	PE	PE	St	St
84	P	P	P	P	P	PE	PE	PE	PE	PE	PE	PE	St
85	P	P	P	P	P	P	PE	St	St	St	St	St	St
86	P	P	P	P	P	P	PE	PE	St	St	St	St	St
87	P	P	P	P	P	P	PE	PE	PE	St	St	St	St
88	P	P	P	P	P	P	PE	PE	PE	PE	St	St	St
89	P	P	P	P	P	P	PE	PE	PE	PE	PE	St	St
90	P	P	P	P	P	P	PE	PE	PE	PE	PE	PE	St
91	P	P	P	P	P	P	P	PE	St	St	St	St	St
92	P	P	P	P	P	P	P	PE	PE	St	St	St	St
93	P	P	P	P	P	P	P	PE	PE	PE	St	St	St
94	P	P	P	P	P	P	P	PE	PE	PE	PE	St	St
95	P	P	P	P	P	P	P	PE	PE	PE	PE	PE	St
96	P	P	P	P	P	P	P	P	PE	St	St	St	St
97	P	P	P	P	P	P	P	P	PE	PE	St	St	St
98	P	P	P	P	P	P	P	P	PE	PE	PE	St	St
99	P	P	P	P	P	P	P	P	PE	PE	PE	PE	St
100	P	P	P	P	P	P	P	P	P	PE	St	St	St
101	P	P	P	P	P	P	P	P	P	PE	PE	St	St
102	P	P	P	P	P	P	P	P	P	PE	PE	PE	St
103	P	P	P	P	P	P	P	P	P	P	PE	St	St
104	P	P	P	P	P	P	P	P	P	P	PE	PE	St
105	P	P	P	P	P	P	P	P	P	P	P	PE	St
1S = standard, off-the-shelf, P = patient-specific, PE = patient-engineered (e.g., constant coronal curvature, derived from the patient's coronal curvatures along articular surface)
2Each of the thirteen numbered implant features represents a different exemplary implant feature, for example, for a knee implant the thirteen features can include: (1) femoral implant component M-L dimension, (2) femoral implant component A-P dimension, (3) femoral implant component bone cut, (4) femoral implant component sagittal curvature, (5) femoral implant component coronal curvature, (6) femoral implant component inter-condylar distance, (7) femoral implant component notch location/geometry, (8) tibial implant component M-L dimension, (9) tibial implant component A-P dimension, (10) tibial implant component insert inter-condylar distance, (11) tibial implant component insert lock, (12) tibial implant component metal backing lock, and (13) tibial implant component metal backing perimeter.

[0278] The term “implant component” as used herein can include: (i) one of two or more devices that work together in an implant or implant system, or (ii) a complete implant or implant system, for example, in embodiments in which an implant is a single, unitary device. The term “match” as used herein is envisioned to include one or both of a negative-match, as a convex surface fits a concave surface, and a positive-match, as one surface is identical to another surface.

[0279] Three illustrative embodiments of implants and/or implant components are schematically represented in FIGS. 5A-5C. In FIG. 5A, the illustrative implant component 500 includes an inner, bone-facing surface 502 and an outer, joint-facing surface 504. The inner bone-facing surface 502 engages a first articular surface 510 of a first biological structure 512, such as bone or cartilage, at a first interface 514. The articular surface 510 can be a native surface, a resected surface, or a combination of the two. The outer, joint-facing surface 504 opposes a second articular surface 520 of a second biological structure 522 at a joint interface 524. The dashed line across each figure illustrates a patient's joint-line. In certain embodiments, one or more features of the implant component, for example, an M-L, A-P, or S-I dimension, a feature of the inner, bone-facing surface 502, and/or a feature of the outer, joint-facing surface 504, are patient-adapted (i.e., include one or more patient-specific and/or patient-engineered features).

[0280] The illustrative embodiment shown in FIG. 5B includes two implant components 500, 500′. Each implant component 500, 500′ includes an inner, bone-facing surface 502, 502′ and an outer, joint-facing surface 504, 504′. The first inner, bone-facing surface 502 engages a first articular surface 510 of a first biological structure 512 (e.g., bone or cartilage) at a first interface 514. The first articular surface 510 can be a native surface, a cut surface, or a combination of the two. The second bone-facing surface 502′ engages a second articular surface 520 of a second biological structure 522 at a second interface 514′. The second articular surface 520 can be a native surface, a resected surface, or a combination of the two. In addition, an outer, joint-facing surface 504 on the first component 500 opposes a second, outer joint-facing surface 504′ on the second component 500′ at the joint interface 524. In certain embodiments, one or more features of the implant component, for example, one or both of the inner, bone-facing surfaces 502, 502′ and/or one or both of the outer, joint-facing surfaces 504, 504′, are patient-adapted (i.e., include one or more patient-specific and/or patient-engineered features).

[0281] The illustrative embodiment represented in FIG. 5C includes the two implant components 500, 500′, the two biological structures 512, 522, the two interfaces 514, 514′, and the joint interface 524, as well as the corresponding surfaces, as described for the embodiment illustrated in FIG. 5B. However, FIG. 5C also includes structure 550, which can be an implant component in certain embodiments or a biological structure in certain embodiments. Accordingly, the presence of a third structural 550 surface in the joint creates a second joint interface 524′, and possibly a third 524″, in addition to joint interface 524. Alternatively or in addition to the patient-adapted features described above for components 500 and 500′, the components 500, 500′ can include one or more features, such as surface features at the additional joint interface(s) 524, 524″, as well as other dimensions (e.g., height, width, depth, contours, and other dimensions) that are patient-adapted, in whole or in part. Moreover, structure 550, when it is an implant component, also can have one or more patient-adapted features, such as one or more patient-adapted surfaces and dimensions.

[0282] Traditional implants and implant components can have surfaces and dimensions that are a poor match to a particular patient's biological feature(s). The patient-adapted implants, guide tools, and related methods described herein improve upon these deficiencies. The following two subsections describe two particular improvements, with respect to the bone-facing surface and the joint-facing surface of an implant component; however, the principles described herein are applicable to any aspect of an implant component.

[0283] 2.1 Bone-Facing Surface of an Implant Component

[0284] In certain embodiments, the bone-facing surface of an implant can be designed to substantially negatively-match one more bone surfaces. For example, in certain embodiments at least a portion of the bone-facing surface of a patient-adapted implant component can be designed to substantially negatively-match the shape of subchondral bone, cortical bone, endosteal bone, and/or bone marrow. A portion of the implant also can be designed for resurfacing, for example, by negatively-matching portions of a bone-facing surface of the implant component to the subchondral bone or cartilage. Accordingly, in certain embodiments, the bone-facing surface of an implant component can include one or more portions designed to engage resurfaced bone, for example, by having a surface that negatively-matches uncut subchondral bone or cartilage, and one or more portions designed to engage cut bone, for example, by having a surface that negatively-matches a cut subchondral bone.

[0285] In certain embodiments, the bone-facing surface of an implant component includes multiple surfaces, also referred to herein as bone cuts. One or more of the bone cuts on the bone-facing surface of the implant component can be selected and/or designed to substantially negatively-match one or more surfaces of the patient's bone. The surface(s) of the patient's bone can include bone, cartilage, or other biological surfaces. For example, in certain embodiments, one or more of the bone cuts on the bone-facing surface of the implant component can be designed to substantially negatively-match (e.g., the number, depth, and/or angles of cut) one or more resected surfaces of the patient's bone. The bone-facing surface of the implant component can include any number of bone cuts, for example, two, three, four, less than five, five, more than five, six, seven, eight, nine or more bone cuts. In certain embodiments, the bone cuts of the implant component and/or the resection cuts to the patient's bone can include one or more facets on corresponding portions of an implant component. For example, the facets can be separated by a space or by a step cut connecting two corresponding facets that reside on parallel or non-parallel planes. These bone-facing surface features can be applied to various joint implants, including knee, hip, spine, and shoulder joint implants.

[0286] FIG. 6A illustrates an exemplary femoral implant component 600 having six bone cuts. FIG. 6B illustrates a femoral implant component 600 having seven bone cuts. In FIG. 6A and FIG. 6B, the six or seven respective bone cuts are identified by arrows on the inner, bone-facing surface 602 of the implant component 600. The bone cuts can include, for example, an anterior bone cut A, a distal bone cut D, and a posterior bone cut P, as well as one or more anterior chamfer bone cuts between the anterior bone cut A and distal bone cut D, and/or one or more posterior chamfer bone cuts between the distal posterior bone cut P and the distal bone cut D. The implant component depicted in FIG. 6A includes one anterior chamfer bone cut and two posterior chamfer bone cuts, in addition to anterior, posterior and distal bone cuts. The implant component depicted in FIG. 6B includes two anterior chamfer bone cuts and two posterior chamfer bone cuts, in addition to anterior, posterior and distal bone cuts.

[0287] Any one or more bone cuts can include one or more facets. For example, the implant components exemplified in FIG. 6A and FIG. 6B depict corresponding condylar facets for each of the distal bone cut, posterior bone cut, first posterior chamfer bone cut and second posterior chamfer bone cut. In FIG. 6A, distal bone cut facets on lateral and medial condyles are identified by 604 and 606, respectively. Facets of a bone cut can be separated by a space between corresponding regions of an implant component, as exemplified by the condylar facets separated by the intercondylar space 608 in FIG. 6A and FIG. 6B. Alternatively or in addition, facets of a bone cut can be separated by a step cut, for example, a vertical or angled cut connecting two non-coplanar or non facets of a bone cut. As shown by the implant components exemplified in each of FIG. 6A and FIG. 6B, each bone cut and/or bone cut facet can be substantially planar. Two substantially planar facets of the same bone cut can be non-coplanar (i.e., not lying in the same cut plane) and/or non-parallel (i.e., not lying in the same cut plane and not lying in a substantially parallel cut plane).

[0288] In certain embodiments, one or more bone cut facets, bone cuts, and/or the entire bone-facing surface of an implant can be non-planar, for example, substantially curvilinear. FIG. 6C illustrates a femoral implant component 610 having two planar bone cuts 612 and one curvilinear bone cut 614. In the figure, the femoral implant component 610 is shown attached to resected surfaces 616 of a femur 618.

[0289] In certain embodiments, corresponding sections of an implant component can include different thicknesses (i.e., distance between the component's bone-facing surface and joint-facing surface), surface features, bone cut features, section volumes, and/or other features. For example, as shown in FIG. 6A, the corresponding distal lateral and medial sections of the implant, identified by 604 and 606 on their respective bone cut facets, include different thicknesses, section volumes, bone cut angles, and bone cut surface areas. As this example illustrates, one or more of the thicknesses, section volumes, bone cut angles, bone cut surface areas, bone cut curvatures, numbers of bone cuts, peg placements, peg angles, and other features may vary between two or more sections (e.g., corresponding sections on lateral and medial condyles) of an implant component. Alternatively or in addition, one, more, or all of these features can be the same in corresponding sections of an implant component. An implant design that allows for independent features on different sections of an implant allows various options for achieving one or more goals, including, for example, (1) deformity correction and limb alignment (2) preserving bone, cartilage, and/or ligaments, (3) preserving and/or optimizing other features of the patient's anatomy, such as trochlea and trochlear shape, (4) restoring and/or optimizing joint kinematics or biomechanics, and/or (5) restoring and/or optimizing joint-line location and/or joint gap width.

[0290] In certain embodiments, it can be advantageous to maintain certain features across different portions of an implant component, while varying certain other features. For example, two or more corresponding sections of an implant component can include the same implant thickness(es). As a specific example, with a femoral implant component, corresponding medial and lateral sections of the implant's condyles (e.g., distal medial and lateral condyle and/or posterior medial and lateral condyles) can be designed to include the same thickness or at least a threshold thickness, particularly the bone cut intersections. Alternatively or in addition, every section on the medial and lateral condyles can be designed to include the same thickness or at least a threshold thickness. This approach is particularly useful when the corresponding implant sections are exposed to similar stress forces and therefore require similar minimum thicknesses in response to those stresses. Alternatively or in addition, an implant design can include a rule, such that a quantifiable feature of one section is always greater than, greater than or equal to, less than, or less than or equal to the same feature of another section of the implant component. For example, in certain embodiments, an implant design can include a lateral distal and/or posterior condylar portion that is thicker than or equal in thickness to the corresponding medial distal and/or posterior condylar portion. Similarly, in certain embodiments, an implant design can include a lateral distal posterior condyle height that is higher than or equal to the corresponding medial posterior condylar height.

[0291] In certain embodiments, one or more of an implant component's bone cut or bone cut facet features (e.g., thickness, section volume, cut angle, surface area, and/or other features) can be patient-adapted. For example, as described more fully below, patient-specific data, such as imaging data of a patient's joint, can be used to select and/or design an implant component (and, optionally, a corresponding surgical procedure and/or surgical tool) that matches a patient's anatomy and/or optimizes a parameter of that patient's anatomy. Alternatively or in addition, one or more aspects of an implant component, for example, one or more bone cuts, can be selected and/or designed to match predetermined resection cuts. Predetermined as used herein includes, for example, preoperatively determined (e.g., preoperatively selected and/or designed). For example, predetermined resection cuts can include resection cuts determined preoperatively, optionally as part of the selection and/or design of one or more implant components and/or one or more guide tools. Similarly, a surgical guide tool can be selected and/or designed to guide the predetermined resection cuts. For example, the resection cuts and matching component bone cuts (and, optionally, a guide tool) can be selected and/or designed, for example, to remove diseased or malformed tissue and/or to optimize a desired anatomical and/or kinematic parameter, such as maximizing bone preservation, correcting a joint and/or alignment deformity, enhancing joint kinematics, enhancing or preserving joint-line location, and/or other parameter(s) described herein.

[0292] 2.2 Joint-Facing Surface of an Implant Component

[0293] In various embodiments described herein, the outer, joint-facing surface of an implant component includes one or more patient-adapted (e.g., patient-specific and/or patient-engineered features). For example, in certain embodiments, the joint-facing surface of an implant component can be designed to match the shape of the patient's biological structure. The joint-facing surface can include, for example, the bearing surface portion of the implant component that engages an opposing biological structure or implant component in the joint to facilitate typical movement of the joint. The patient's biological structure can include, for example, cartilage, bone, and/or one or more other biological structures.

[0294] For example, in certain embodiments, the joint-facing surface of an implant component is designed to match the shape of the patient's articular cartilage. For example, the joint-facing surface can substantially positively-match one or more features of the patient's existing cartilage surface and/or healthy cartilage surface and/or a calculated cartilage surface, on the articular surface that the component replaces. Alternatively, it can substantially negatively-match one or more features of the patient's existing cartilage surface and/or healthy cartilage surface and/or a calculated cartilage surface, on the opposing articular surface in the joint. As described below, corrections can be performed to the shape of diseased cartilage by designing surgical steps (and, optionally, patient-adapted surgical tools) to re-establish a normal or near normal cartilage shape that can then be incorporated into the shape of the joint-facing surface of the component. These corrections can be implemented and, optionally, tested in virtual two-dimensional and three-dimensional models. The corrections and testing can include kinematic analysis and/or surgical steps.

[0295] In certain embodiments, the joint-facing surface of an implant component can be designed to positively-match the shape of subchondral bone. For example, the joint-facing surface of an implant component can substantially positively-match one or more features of the patient's existing subchondral bone surface and/or healthy subchondral bone surface and/or a calculated subchondral bone surface, on the articular surface that the component attaches to on its bone-facing surface. Alternatively, it can substantially negatively-match one or more features of the patient's existing subchondral bone surface and/or healthy subchondral bone surface and/or a calculated subchondral bone surface, on the opposing articular surface in the joint. Corrections can be performed to the shape of subchondral bone to re-establish a normal or near normal articular shape that can be incorporated into the shape of the component's joint-facing surface. A standard thickness can be added to the joint-facing surface, for example, to reflect an average cartilage thickness. Alternatively, a variable thickness can be applied to the component. The variable thickness can be selected to reflect a patient's actual or healthy cartilage thickness, for example, as measured in the individual patient or selected from a standard reference database.

[0296] In certain embodiments, the joint-facing surface of an implant component can include one or more standard features. The standard shape of the joint-facing surface of the component can reflect, at least in part, the shape of typical healthy subchondral bone or cartilage. For example, the joint-facing surface of an implant component can include a curvature having standard radii or curvature of in one or more directions. Alternatively or in addition, an implant component can have a standard thickness or a standard minimum thickness in select areas. Standard thickness(es) can be added to one or more sections of the joint-facing surface of the component or, alternatively, a variable thickness can be applied to the implant component.

[0297] Certain embodiments, such as those illustrated by FIGS. 5B and 5C, include, in addition to a first implant component, a second implant component having an opposing joint-facing surface. The second implant component's bone-facing surface and/or joint-facing surface can be designed as described above. Moreover, in certain embodiments, the joint-facing surface of the second component can be designed, at least in part, to match (e.g., substantially negatively-match) the joint-facing surface of the first component. Designing the joint-facing surface of the second component to complement the joint-facing surface of the first component can help reduce implant wear and optimize kinematics. Thus, in certain embodiments, the joint-facing surfaces of the first and second implant components can include features that do not match the patient's existing anatomy, but instead negatively-match or nearly negatively-match the joint-facing surface of the opposing implant component.

[0298] However, when a first implant component's joint-facing surface includes a feature adapted to a patient's biological feature, a second implant component having a feature designed to match that feature of the first implant component also is adapted to the patient's same biological feature. By way of illustration, when a joint-facing surface of a first component is adapted to a portion of the patient's cartilage shape, the opposing joint-facing surface of the second component designed to match that feature of the first implant component also is adapted to the patient's cartilage shape. When the joint-facing surface of the first component is adapted to a portion of a patient's subchondral bone shape, the opposing joint-facing surface of the second component designed to match that feature of the first implant component also is adapted to the patient's subchondral bone shape. When the joint-facing surface of the first component is adapted to a portion of a patient's cortical bone, the joint-facing surface of the second component designed to match that feature of the first implant component also is adapted to the patient's cortical bone shape. When the joint-facing surface of the first component is adapted to a portion of a patient's endosteal bone shape, the opposing joint-facing surface of the second component designed to match that feature of the first implant component also is adapted to the patient's endosteal bone shape. When the joint-facing surface of the first component is adapted to a portion of a patient's bone marrow shape, the opposing joint-facing surface of the second component designed to match that feature of the first implant component also is adapted to the patient's bone marrow shape.

[0299] The opposing joint-facing surface of a second component can substantially negatively-match the joint-facing surface of the first component in one plane or dimension, in two planes or dimensions, in three planes or dimensions, or in several planes or dimensions. For example, the opposing joint-facing surface of the second component can substantially negatively-match the joint-facing surface of the first component in the coronal plane only, in the sagittal plane only, or in both the coronal and sagittal planes.

[0300] In creating a substantially negatively-matching contour on an opposing joint-facing surface of a second component, geometric considerations can improve wear between the first and second components. For example, the radii of a concave curvature on the opposing joint-facing surface of the second component can be selected to match or to be slightly larger in one or more dimensions than the radii of a convex curvature on the joint-facing surface of the first component. Similarly, the radii of a convex curvature on the opposing joint-facing surface of the second component can be selected to match or to be slightly smaller in one or more dimensions than the radii of a concave curvature on the joint-facing surface of the first component. In this way, contact surface area can be maximized between articulating convex and concave curvatures on the respective surfaces of first and second implant components.

[0301] The bone-facing surface of the second component can be designed to negatively-match, at least in part, the shape of articular cartilage, subchondral bone, cortical bone, endosteal bone or bone marrow (e.g., surface contour, angle, or perimeter shape of a resected or native biological structure). It can have any of the features described above for the bone-facing surface of the first component, such as having one or more patient-adapted bone cuts to match one or more predetermined resection cuts.

[0302] Many combinations of first component and second component bone-facing surfaces and joint-facing surfaces are possible. Table 3 provides illustrative combinations that may be employed.

TABLE 3
Illustrative Combinations of Implant Components
1st	1st	1st		2nd
component	component	component	2nd	component	2nd
bone-facing	joint-facing	bone	component joint	bone facing	component
surface	surface	cut(s)	facing surface	surface	bone cuts
Example:	Example:	Example:	Example: Tibia	Example:	Example:
Femur	Femur	Femur		Tibia	Tibia
At least one	Cartilage	Yes	Negative-match of 1st	At least one	Yes
bone cut			component joint-facing	bone cut
			(opposing cartilage)
At least one	Cartilage	Yes	Negative-match of 1st	Subchondral	Optional
bone cut			component joint-facing	bone
			(opposing cartilage)
At least one	Cartilage	Yes	Negative-match of 1st	Cartilage	Optional
bone cut			component joint-facing	(same side,
			(opposing cartilage)	e.g. tibia)
At least one	Subchondral	Yes	Negative-match of 1st	At least one	Yes
bone cut	bone		component joint-facing	bone cut
			(opposing subchondral
			bone)
At least one	Subchondral	Yes	Negative-match of 1st	Subchondral	Optional
bone cut	bone		component joint-facing	bone
			(opposing subchondral
			bone)
At least one	Subchondral	Yes	Negative-match of 1st	Cartilage	Optional
bone cut	bone		component joint-facing	(same side,
			(opposing subchondral	e.g. tibia)
			bone)
Subchondral	Cartilage	Optional	Negative-match of 1st	At least one	Yes
bone			component joint-facing	bone cut
			(opposing cartilage)
Subchondral	Cartilage	Optional	Negative-match of 1st	Subchondral	Optional
bone			component joint-facing	bone
			(opposing cartilage)
Subchondral	Cartilage	Optional	Negative-match of 1st	Cartilage	Optional
bone			component joint-facing	(same side,
			(opposing cartilage)	e.g. tibia)
Subchondral	Subchondral	Optional	Negative-match of 1st	At least one	Yes
bone	bone		component joint-facing	bone cut
			(opposing subchondral
			bone)
Subchondral	Subchondral	Optional	Negative-match of 1st	Subchondral	Optional
bone	bone		component joint-facing	bone
			(opposing subchondral
			bone)
Subchondral	Subchondral	Optional	Negative-match of 1st	Cartilage	Optional
bone	bone		component joint-facing	same side,
			(opposing subchondral	e.g. tibia)
			bone)
Subchondral	Standard/	Optional	Negative-match of 1st	At least one	Yes
bone	Model		component joint-facing	bone cut
			standard
Subchondral	Standard/	Optional	Negative-match of 1st	Subchondral	Optional
bone	Model		component joint-facing	bone
			standard
Subchondral	Standard/	Optional	Negative-match of 1st	Cartilage	Optional
bone	Model		component joint-facing	(same side,
			standard	e.g. tibia)
Subchondral	Subchondral	Optional	Non-matching standard	At least one	Yes
bone	bone		surface	bone cut
Subchondral	Cartilage	Optional	Non-matching standard	At least one	Yes
bone			surface	bone cut

[0303] 2.3 Multi-Component Implants and Implant Systems

[0304] The implants and implant systems described herein include any number of patient-adapted implant components and any number of non-patient-adapted implant components. An illustrative implant or implant system is depicted in FIGS. 7A-7C. Specifically, FIG. 7A shows a photograph of a patient-adapted knee replacement implant system that includes a patient-specific bicompartmental implant component 700 and patient-specific unicompartmental implant component 710. Both components are patient-specific on both their bone-facing surfaces and on their joint-facing surfaces. FIGS. 7B and 7C show x-ray images showing the implant of FIG. 7A in the coronal plane (FIG. 7B) and the sagittal plane (FIG. 7C).

[0305] In certain embodiments, the implants and implant systems described herein can include a combination of implant components, such as a traditional unicompartmental device with a patient-specific bicompartmental device or a combination of a patient-specific unicompartmental device with standard bicompartmental device. Such implant combinations allow for a flexible design of an implant or implant system that includes both standard and patient-specific features and components. This flexibility and level of patient-specificity allows for various engineered optimizations, such as retention of alignments, maximization of bone preservation, and/or restoration of normal or near-normal patient kinematics.

[0306] In certain embodiments, an implant component is designed and installed as one or more pieces. For example, FIGS. 8A-8E illustrates a femoral implant component that can be installed in two pieces.

[0307] Embodiments described herein can be applied to partial or total joint replacement systems. Bone cuts or changes to an implant component dimension described herein can be applied to a portion of the dimension, or to the entire dimension.

[0308] 3. Collecting and Modeling Patient-Specific Data

[0309] As mentioned above, certain embodiments include implant components designed and made using patient-specific data that is collected preoperatively. The patient-specific data can include points, surfaces, and/or landmarks, collectively referred to herein as “reference points.” In certain embodiments, the reference points can be selected and used to derive a varied or altered surface, such as, without limitation, an ideal surface or structure. For example, the reference points can be used to create a model of the patient's relevant biological feature(s) and/or one or more patient-adapted surgical steps, tools, and implant components. For example the reference points can be used to design a patient-adapted implant component having at least one patient-specific or patient-engineered feature, such as a surface, dimension, or other feature.

[0310] Sets of reference points can be grouped to form reference structures used to create a model of a joint and/or an implant design. Designed implant surfaces can be derived from single reference points, triangles, polygons, or more complex surfaces, such as parametric or subdivision surfaces, or models of joint material, such as, for example, articular cartilage, subchondral bone, cortical bone, endosteal bone or bone marrow. Various reference points and reference structures can be selected and manipulated to derive a varied or altered surface, such as, without limitation, an ideal surface or structure.

[0311] The reference points can be located on or in the joint that will receive the patient-specific implant. For example, the reference points can include weight-bearing surfaces or locations in or on the joint, a cortex in the joint, and/or an endosteal surface of the joint. The reference points also can include surfaces or locations outside of but related to the joint. Specifically, reference points can include surfaces or locations functionally related to the joint. For example, in embodiments directed to the knee joint, reference points can include one or more locations ranging from the hip down to the ankle or foot. The reference points also can include surfaces or locations homologous to the joint receiving the implant. For example, in embodiments directed to a knee, a hip, or a shoulder joint, reference points can include one or more surfaces or locations from the contralateral knee, hip, or shoulder joint.

[0312] 3.1 Measuring Biological Features

[0313] Reference points and/or data for obtaining measurements of a patient's joint, for example, relative-position measurements, length or distance measurements, curvature measurements, surface contour measurements, thickness measurements (in one location or across a surface), volume measurements (filled or empty volume), density measurements, and other measurements, can be obtained using any suitable technique. For example, one dimensional, two-dimensional, and/or three-dimensional measurements can be obtained using data collected from mechanical means, laser devices, electromagnetic or optical tracking systems, molds, materials applied to the articular surface that harden as a negative match of the surface contour, and/or one or more imaging techniques described above and/or known in the art. Data and measurements can be obtained non-invasively and/or preoperatively. Alternatively, measurements can be obtained intraoperatively, for example, using a probe or other surgical device during surgery.

[0314] In certain embodiments, an imaging data collected from the patient, for example, imaging data from one or more of x-ray imaging, digital tomosynthesis, cone beam CT, non-spiral or spiral CT, non-isotropic or isotropic MRI, SPECT, PET, ultrasound, laser imaging, photo-acoustic imaging, is used to qualitatively and/or quantitatively measure one or more of a patient's biological features, one or more of normal cartilage, diseased cartilage, a cartilage defect, an area of denuded cartilage, subchondral bone, cortical bone, endosteal bone, bone marrow, a ligament, a ligament attachment or origin, menisci, labrum, a joint capsule, articular structures, and/or voids or spaces between or within any of these structures. The qualitatively and/or quantitatively measured biological features can include, but are not limited to, one or more of length, width, height, depth and/or thickness; curvature, for example, curvature in two dimensions (e.g., curvature in or projected onto a plane), curvature in three dimensions, and/or a radius or radii of curvature; shape, for example, two-dimensional shape or three-dimensional shape; area, for example, surface area and/or surface contour; perimeter shape; and/or volume of, for example, the patient's cartilage, bone (subchondral bone, cortical bone, endosteal bone, and/or other bone), ligament, and/or voids or spaces between them.

[0315] In certain embodiments, measurements of biological features can include any one or more of the illustrative measurements identified in Table 4.

TABLE 4
Exemplary patient-specific measurements of biological features that
can be used in the creation of a model and/or in the selection and/or
design of an implant component
Anatomical feature	Exemplary measurement
Joint-line, joint gap	Location relative to proximal reference point
	Location relative to distal reference point
	Angle
	Gap distance between opposing surfaces in one or
	more locations
	Location, angle, and/or distance relative to
	contralateral joint
Soft tissue tension	Joint gap distance
and/or balance	Joint gap differential, e.g., medial to lateral
Medullary cavity	Shape in one or more dimensions
	Shape in one or more locations
	Diameter of cavity
	Volume of cavity
Subchondral bone	Shape in one or more dimensions
	Shape in one or more locations
	Thickness in one or more dimensions
	Thickness in one or more locations
	Angle, e.g., resection cut angle
Cortical bone	Shape in one or more dimensions
	Shape in one or more locations
	Thickness in one or more dimensions
	Thickness in one or more locations
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
Endosteal bone	Shape in one or more dimensions
	Shape in one or more locations
	Thickness in one or more dimensions
	Thickness in one or more locations
	Angle, e.g., resection cut angle
Cartilage	Shape in one or more dimensions
	Shape in one or more locations
	Thickness in one or more dimensions
	Thickness in one or more locations
	Angle, e.g., resection cut angle
Intercondylar notch	Shape in one or more dimensions
	Location
	Height in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Angle, e.g., resection cut angle
Medial condyle	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Lateral condyle	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Trochlea	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Groove location in one or more locations
	Trochlear angle, e.g. groove angle in one or more
	locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Medial trochlea	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Central trochlea	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Groove location in one or more locations
	Trochlear angle, e.g. groove angle in one or more
	locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Lateral trochlea	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Entire tibia	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	(e.g. medial and/or lateral)
	Angle, e.g., resection cut angle
	Axes, e.g., A-P and/or M-L axes
	Osteophytes
	Plateau slope(s), e.g., relative slopes medial and
	lateral
	Plateau heights(s), e.g., relative heights medial and
	lateral
	Bearing surface radii, e.g., e.g., relative radii medial
	and lateral
	Perimeter profile
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Medial tibia	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness or height in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Perimeter profile
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Lateral tibia	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness/height in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Perimeter profile
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Entire patella	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Perimeter profile
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Medial patella	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or direction
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Central patella	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Lateral patella	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Femoral head	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Portions or all of bone perimeter at an intended
	resection level
	Resection surface at an intended resection level
Femoral neck	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Angle in one or more locations
	Neck axis in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Leg length
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Femoral shaft	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Angle in one or more locations
	Shaft axis in one or more locations
	Curvature in one or more locations
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Leg length
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Acetabulum	2D and/or 3D shape of a portion or all.
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Glenoid	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Humeral head	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Humeral neck	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Angle in one or more locations
	Neck axis in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Arm length
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Humeral shaft	2D and/or 3D shape of a portion or all
	Height in one ormore locations
	Length in one ormore locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Angle in one or more locations
	Shaft axis in one ormore locations
	Curvature in one or more locations
	Angle, e.g., resection cut angle
	Anteversion or retroversion
	Arm length
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Ankle joint	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Elbow	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more location
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more location
	Curvature in one or more locations
	Slope in one or more locations and/or direction
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter of an
	intended resection level
	Resection surface at an intended resection level
Wrist	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Hand	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or direction
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Finger	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Spine	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle
	Portions or all of cortical bone perimeter at an
	intended resection level
	Resection surface at an intended resection level
Spinal facet joint	2D and/or 3D shape of a portion or all
	Height in one or more locations
	Length in one or more locations
	Width in one or more locations
	Depth in one or more locations
	Thickness in one or more locations
	Curvature in one or more locations
	Slope in one or more locations and/or directions
	Angle, e.g., resection cut angle

[0316] Depending on the clinical application, a single or any combination or all of the measurements described in Table 4 and/or known in the art can be used. Additional patient-specific measurements and information that be used in the evaluation can include, for example, joint kinematic measurements, bone density measurements, bone porosity measurements, identification of damaged or deformed tissues or structures, and patient information, such as patient age, weight, gender, ethnicity, activity level, and overall health status. Moreover, the patient-specific measurements may be compared, analyzed of otherwise modified based on one or more “normalized” patient model or models, or by reference to a desired database of anatomical features of interest. For example, a series of patient-specific femoral measurements may be compiled and compared to one or more exemplary femoral or tibial measurements from a library or other database of “normal” femur measurements. Comparisons and analysis thereof may concern, but is not limited to one, more or any combination of the following dimensions: femoral shape, length, width, height, of one or both condyles, intercondylar shapes and dimensions, trochlea shape and dimensions, coronal curvature, sagittal curvature, cortical/cancellous bone volume and/or quality, etc., and a series of recommendations and/or modifications may be accomplished. Any parameter mentioned in the specification and in the various Tables throughout the specification including anatomic, biomechanical and kinematic parameters can be utilized, not only in the knee, but also in the hip, shoulder, ankle, elbow, wrist, spine and other joints. Such analysis may include modification of one or more patient-specific features and/or design criteria for the implant to account for any underlying deformity reflected in the patient-specific measurements. If desired, the modified data may then be utilized to choose or design an appropriate implant to match the modified features, and a final verification operation may be accomplished to ensure the chosen implant is acceptable and appropriate to the original unmodified patient-specific measurements (i.e., the chosen implant will ultimately “fit” the original patient anatomy). In alternative embodiments, the various anatomical features may be differently “weighted” during the comparison process (utilizing various formulaic weightings and/or mathematical algorithms), based on their relative importance or other criteria chosen by the designer/programmer and/or physician.

[0317] In a similar manner, the various anatomical features of the tibia (i.e, anterior-posterior and/or medial-lateral dimensions, perimeters, medial/lateral slope, shape, tibial spine height, and other features) can be measured, modeled, and then compared to and/or modified based on a database of one or more “normal” or “healthy” tibial measurement and/or models, with the resulting information used to choose or design a desired implant shape, size and placement. Of course, similar verification of implant appropriateness to the original measured parameters may be accomplished as well.

[0318] In a similar manner, the various anatomical features of any joint can be measured and then compared/modified based on a database of “healthy” or otherwise appropriate measurements of appropriate joints, including those of the medial condyle, a lateral condyle, a trochlea, a medial tibia, a lateral tibia, the entire tibia, a medial patella, a lateral patella, an entire patella, a medial trochlea, a central trochlea, a lateral trochlea, a portion of a femoral head, an entire femoral head, a portion of an acetabulum, an entire acetabulum, a portion of a glenoid, an entire glenoid, a portion of a humeral head, an entire humeral head, a portion of an ankle joint, an entire ankle joint, and/or a portion or an entire elbow, wrist, hand, finger, spine, or facet joint.

[0319] The patient-specific measurements selected for the evaluation then can be used to select (e.g., from a library), to design, or to select and design an implant component having one or more measurements corresponding to or derived from the one or more of the assessed patient-specific measurements. For example, the implant component can include one or more patient-specific measurements and/or one or more patient-engineered measurements. Optionally, one or more patient-specific models, one or more patient-adapted surgical steps, and/or one or more patient-adapted surgical guide tools also can be selected and/or designed to include one or more measurements corresponding to or derived from the one or more of these patient-specific measurements.

[0320] In addition to (or if place of) the above-mentioned measurements, it may be desirable to obtain measurements of the targeted joint (as well as surrounding anatomical areas and or other joints of the patient's anatomy) in a load-bearing or otherwise “real-world” condition. Such measurements can potentially yield extremely useful data on the alignment and/or movement of the joint and surrounding structures (as well as the loading conditions of the various joint components)—information which may be difficult to obtain or model from standard imaging techniques (i.e., sitting or lying X-rays, CT-scans and/or MRI imaging). Such load-bearing measurements can include imaging of the patient standing, walking and/or carrying loads of varying sizes and/or weights.

[0321] It may also be desirable to model various of the patient measurements (especially non-load-bearing measurements as described above) to simulate the targeted joint and surrounding anatomy virtually. Such simulations can include virtually modeling the alignment and load bearing condition of the joint and surrounding anatomical structures for the patient standing and/or moving (i.e., walking, running, jumping, squatting, kneeling, walking up and down stairs or inclines/declines, picking up objects, etc.). Such simulations can be used to obtain valuable anatomical, biomechanical and kinematic data including the loaded condition of various joint components, component positions, component movement, joint and/or surrounding tissue anatomical or biomechanical constraints or limitations, as well as estimated mechanical axes in one or more directions (i.e., coronal, sagittal or combinations thereof). This information could then be utilized (alone or in combination with other data described herein) to design various features of a joint resurfacing/replacement implant. This method can be incorporated in the various embodiments described herein as additional patient measurement and anatomical/joint modeling and design data. This analysis is applicable to many different joints, including those of the medial condyle, a lateral condyle, a trochlea, a medial tibia, a lateral tibia, the entire tibia, a medial patella, a lateral patella, an entire patella, a medial trochlea, a central trochlea, a lateral trochlea, a portion of a femoral head, an entire femoral head, a portion of an acetabulum, an entire acetabulum, a portion of a glenoid, an entire glenoid, a portion of a humeral head, an entire humeral head, a portion of an ankle joint, an entire ankle joint, and/or a portion or an entire elbow, wrist, hand, finger, spine, or facet joint.

[0322] 3.2 Generating a Model of a Joint

[0323] In certain embodiments, one or more models of at least a portion of a patient's joint can be generated. Specifically, the patient-specific data and/or measurements described above can be used to generate a model that includes at least a portion of the patient's joint. Optionally, one or more patient-engineered resection cuts, one or more drill holes, one or more patient-adapted guide tools, and/or one or more patient-adapted implant components can be included in a model. In certain embodiments, a model of at least part of a patient's joint can be used to directly generate a patient-engineered resection cut strategy, a patient-adapted guide tool design, and/or a patient-adapted implant component design for a surgical procedure (i.e., without the model itself including one or more resection cuts, one or more drill holes, one or more guide tools, and/or one or more implant components). In certain embodiments, the model that includes at least a portion of the patient's joint also can include or display, as part of the model, one or more resection cuts, one or more drill holes, (e.g., on a model of the patient's femur), one or more guide tools, and/or one or more implant components that have been designed for the particular patient using the model. Moreover, one or more resection cuts, one or more drill holes, one or more guide tools, and/or one or more implant components can be modeled and selected and/or designed separate from a model of a particular patient's biological feature.

[0324] Various methods can be used to generate a model. As illustrated in FIG. 9, in certain embodiments the method of generating a model of a patient's joint (and/or a resection cut, drill hole, guide tool, and/or implant component) or other biological feature (and/or a patient-specific feature of a guide tool or implant component) can include one or more of the steps of obtaining image data of a patient's biological structure 910; segmenting the image data 930; combining the segmented data 940; and presenting the data as part of a model 950.

[0325] Image data can be obtained 910 from near or within the patient's biological structure of interest. For example, pixel or voxel data from one or more radiographic or tomographic images of a patient's joint can be obtained, for example, using computed or magnetic resonance tomography. Other imaging modalities known in the art such as ultrasound, laser imaging, PET, SPECT, radiography including digital radiography, digital tomosynthesis, cone beam CT, and contrast enhanced imaging can be used. In this or a subsequent step, one or more of the pixels or voxels can be converted into one or a set of values. For example, a single pixel/voxel or a group of pixel/voxels can be converted to coordinate values, e.g., a point in a 2D or 3D coordinate system. The set of values also can include a value corresponding to the pixel/voxel intensity or relative grayscale color. Moreover, the set of values can include information about neighboring pixels or voxels, for example, information corresponding to relative intensity or grayscale color and or information corresponding to relative position.

[0326] Then, the image data can be segmented 930 to identify those data corresponding to a particular biological feature of interest. For example, as shown in FIG. 188A, image data can be used to identify the edges of a biological structure, in this case, the surface outline for each of the patient's femur and tibia. As shown, the distinctive transition in color intensity or grayscale 19000 at the surface of the structure can be used to identify pixels, voxels, corresponding data points, a continuous line, and/or surface data representing the surface of the biological structure. This step can be performed automatically (for example, by a computer program operator function) or manually (for example, by a clinician or technician), or by a combination of the two.

[0327] Optionally, the segmented data can be combined 940. For example, in a single image segmented and selected reference points (e.g., derived from pixels or voxels) and/or other data can be combined to create a line representing the surface outline of a biological structure. Moreover, as shown in FIG. 188B, the segmented and selected data from multiple images can be combined to create a 3D representation of the biological structure. Alternatively, the images can be combined to form a 3D data set, from which the 3D representation of the biological structure can be derived directly using a 3D segmentation technique, for example an active surface or active shape model algorithm or other model based or surface fitting algorithm.

[0328] Optionally, the 3D representation of the biological structure can be generated or manipulated, for example, smoothed or corrected, for example, by employing a 3D polygon surface, a subdivision surface or parametric surface, for example, a non-uniform rational B-spline (NURBS) surface. For a description of various parametric surface representations see, for example Foley, J. D. et al., Computer Graphics: Principles and Practice in C; Addison-Wesley, 2nd edition (1995). Various methods are available for creating a parametric surface. For example, the 3D representation can be converted directly into a parametric surface, for example, by connecting data points to create a surface of polygons and applying rules for polygon curvatures, surface curvatures, and other features. Alternatively, a parametric surface can be best-fit to the 3D representation, for example, using publicly available software such as Geomagic® software (Research Triangle Park, N.C.).

[0329] Then, the data can be presented as part of a model 950, for example, a patient-specific virtual model that includes the biological feature of interest. Optionally, the data associated with one or more biological features can be transferred to one or more resection cuts, drill holes, guide tools, and/or implant components, which also can be included as part of the same model or in a different model. The virtual model(s) can be used to generate one or more patient-adapted guide tools and/or implant components for surgical use, for example, using computer-aided design (CAD) software and/or one or more of the several manufacturing techniques described below, optionally in conjunction with computer-aided manufacturing (CAM) software.

[0330] As will be appreciated by those of skill in the art, one or more of these steps 910, 930, 940, 950 can be repeated 911, 931, 941, 951 as often as desired to achieve the desired result. Moreover, the steps can be repeated reiteratively 932, 933, 934. Moreover, the practitioner can proceed directly 933 from the step of segmenting image data 930 to presenting the data as part of a model 950. Data, models and/or any related guide tools or implant components can be collected in one or more libraries for subsequent use for the same patient or for a different patient (e.g., a different patient with similar data).

[0331] In certain embodiments, individual images of a patient's biological structure can be segmented individually and then, in a later step, the segmentation data from each image can be combined. The images that are segmented individually can be one of a series of images, for example, a series of coronal tomographic slices (e.g., front to back) and/or a series of sagittal tomographic slices (e.g., side to side) and/or a series of axial tomographic slices (e.g., top to bottom) of the patient's joint. Segmenting each image individually can create noise in the combined segmented data. As an illustrative example, in an independent segmentation process, an alteration in the segmentation of a single image does not alter the segmentation in contiguous images in a series. Accordingly, an individual image can be segmented to show data that appears discontinuous with data from contiguous images. To address this issue, certain embodiments include a method for generating a model from a collection of images, for example, simultaneously, rather than from individually segmented images. One such method is referred to as deformable segmentation.

[0332] In the deformable segmentation method, a template model having a surface data representation, such as for example a parametric surface, a subdivision surface or a meshed surface, is deformed to fit a collection of multiple images. By fitting the template model to a collection of images, alterations to one location in the template model can be carried across the model and, therefore, connect information corresponding to various images in the collection, thus preserving continuity and smoothness of the surface model. For example, in certain embodiments, a template model includes a parametric surface that includes multiple patches or sections. During deformation, the patches can maintain a set of properties, such as continuity, curvature, and/or other properties within each patch and/or across patch boundaries with neighboring patches. These properties also can be reinforced during deformation so that the integrity of the model is maintained.

[0333] FIG. 189 shows a flowchart of steps in certain embodiments of a deformable segmentation method. The steps include one or more of collecting multiple images of a patient's biological structure 19460; optionally approximating a biological feature of interest 19464; applying a template model to the approximate biological feature of interest 19468; optionally roughly fitting the template model to the approximate biological feature 19472; and precisely fitting the template model to the collection of multiple images 19476. Similar to the method described above, one or more of these steps 19460, 19464, 19468, 19472, 19476 can be repeated 19461, 19465, 19469, 19473, 19477 as often as desired to achieve the desired result. Moreover, the steps can be repeated reiteratively 19462, 19466, 19470, 19474, 19478. FIGS. 190A-190O show exemplary images from a computer program that applies an embodiment of the deformable segmentation method.

[0334] In one step 19460, multiple images can be collected for processing together, for example, the images can be processed together in a single event rather than individually. As illustrated in FIG. 190A, a computer program can be used to load and view the multiple images as one or more views into one or more 3D image data stacks, for example coronal, sagittal or axial views. In the figure, a series of coronal image slices 19480 and a series of sagittal image slices 19482 can be viewed as separate stacks or decks of 2D images. These stacks of images can result from separate image scans or can be different views of the same scan(s). In addition, any two or more images can be combined 19484 to provide a 3D image.

[0335] In another step 19464, a biological feature of interest is approximated from the multiple images. FIG. 190B illustrates the approximated biological features of a femoral surface 19486 and a tibial surface 19488. The approximated surface can be provided by the method described above, for example, by detecting edges in each image based on relative grayscale or intensity changes, and then combining the image data. This step is optional.

[0336] In another step 19468, a template model is applied to the approximate biological feature or directly to the combined image data stack. FIG. 190C illustrates a femoral template model 19490 applied to the approximate femoral surface 19486. In applying a template model, the operator or user or the software can select one or more initial best fit template models. Template models can be available, for example, from a library of models, for example, collected from one or more previous assessments.

[0337] As shown by the template outline 19492 in the 2D images, the femoral template 19490 initially is not a substantial match for the approximate femoral surface 19486. This match can be improved by making global and local adjustments. Global adjustments align the template by performing operations such as rotating, translating or scaling. Local adjustments deform the surface representation of the template in certain subregions. In an optional step 19472, an operator or a user or the software can roughly fit the template model to the biological feature of interest or directly to the image data stack. FIG. 190D-190G illustrate the femoral template model 19490 being roughly adjusted to best-fit the approximate femoral surface 19486. As shown in the figures, a user can perform the adjustments using a control panel 19494. Adjustments can include, for example, adjusting the location of the template in one or more dimensions; adjusting the scale (e.g., size) of the template in one or more dimensions; and adjusting the rotation of the template in one or more dimensions. As shown in the control panel 19494 as position changes to the user-controlled knobs relative to their initial center positions, FIG. 190D illustrates a user adjustment to the location of the template model in the x axis (e.g., in the M-L direction); FIG. 190E illustrates a user adjustment to the location of the template model in the z axis (e.g., in the proximal-distal direction); FIG. 190F illustrates a user adjustment to the scale (i.e., size) of the template model in the x axis; and FIG. 190G illustrates a user adjustment to rotation of the template model about the z-axis (the axis perpendicular to the view). These adjustments can be performed in any order and repeated as desired to achieve the best rough fit of the template with the approximate biological feature. In other embodiments, the software can automatically determine the initial best fit of the template model to the biological feature of interest or the image data. This can be achieved by finding the scaling, rotation and translation parameters that result in the closest fit of the template to the structure of interest, for example using a multidimensional optimization algorithm. FIG. 190H illustrates the rough fit of the template to the approximate surface following these adjustments.

[0338] In another step 19476, the model template can be precisely fit to the collection of multiple images (rather than, in the method described above, independently processing each image). As shown in FIG. 190I, the surface quadrangles or “patches” of surface data representation of the femoral template 19490 can be deformed to match the surface(s) across the entire collection of images. In certain embodiments, the template patches can be deformed to directly fit the radiographic or tomographic image data (e.g., voxel data) rather than any subsequently processed data, for example, data points representing multiple voxels or data compatible with a computer monitor. Currently, radiographic or tomographic images can include much higher gray value resolution (e.g., can assign one of a much greater number of unique shades of gray to each pixel or voxel) than data compatible with a computer monitor. Accordingly, by deforming the template to directly fit the radiographic images, a high degree of resolution can be maintained, which can provide a highly precise model.

[0339] The points or dots shown in association with the template outline 19492 represent control points that can be used by a technician to manually alter the outline and surface of the template. By moving a control point, the user can manually alter and deform adjacent sections of the surface data representation of the template, and the resulting alterations and deformations appear in both the 2D outline view and in the 3D view of the template. In another embodiment, the software can optimize the position of the control points and thus the fit of the surface automatically using various criteria, for example gray values or gray value gradients in the image data or smoothness and continuity constraints in the surface data representation.

[0340] FIG. 190I illustrates the femur template model 19490 being deformed to fit the edges of the femur in the collection of radiographic images. As shown in the 2D images, the model surface 19492 fits precisely with the outline of the femur in the images shown. As indicated by FIG. 190J, the model surface 19492 can be viewed and/or visually checked across any of the 2D image slices. The precision of the model can be enhanced further by adding additional surface detail (e.g., additional parametric surface quadrangles or patches) to the model and repeating the deforming step. This process can be reiterated, as indicated by the increasing number of polygon surfaces in FIGS. 190K and 190L, to provide a highly precise patient-specific model. As shown in FIGS. 190M-190O, control points can be hidden and the patient-specific model can be viewed in 2D comparison to any of the images, or in 3D 19490.

[0341] The patient-specific model and/or model data then can be used for selection and/or design of resection cuts, guide tools, and/or implant components, which can be included in the same model or in a different model. For example, the model and/or model data can be exported to a CAD program, for example, SolidWorks, to design one or more patient-engineered resection cuts, patient-specific guide tools, and/or patient-adapted implant components. Alternatively or in addition, the model and/or model data can be exported to a library, for example, to be included in the library as a template model for future assessments and/or for selecting from the library one or more resection cut strategies, guide tools, and/or implant components.

[0342] In another embodiment, the virtual model includes, in addition to or instead of the surface model representation, a template for one or more implants and/or guide tools, including the position and shape of bearing surfaces as well as the location and direction of bone cuts and/or drill holes needed to position the implants. Similar to the way the surface data representation is adjusted using global transformations and local deformations as described above to match the individual patient's anatomy, the shape of the implants and/or guide tools can be adjusted accordingly, i.e. the software applies the same global transformations and local deformations applied to the surface model to the implants and/or guide tools as well. During this process, the position and shape of the bearing surfaces as well as the position and direction of bone cuts and/or drill holes can be adjusted as well based on the transformations and deformations of the virtual shape model. Adjusting the position and shape of bearing surfaces and the position and direction of bone cuts and/or drill holes can be performed automatically by the software or based on user or operator input or a combination thereof.

[0343] In another embodiment, the global transformations and local deformations of the surface model as well as the implant, guide tool, bearing surface, bone cut and drill hole information are determined to not only match the surface of the patient's biological structure of interest, but also taking into account anatomical landmarks of the patient's individual anatomy. This can include, for example and without limitation, the femoral sulcus line, the femoral notch, the femoral trochlea, the cruciate ligaments, the medial and/or lateral tibial spine, the anterior or posterior femoral shaft cortex, the medial or lateral margin of the patella, the anterior or posterior margin of the medial or lateral tibial plateau or the margin of the femoral or tibial articular surface. The shape of the patient's anatomy, for example the shape of one or more articular surfaces, can also be used.

[0344] In another embodiment, the position and/or direction of the implant, guide tool and/or bone cuts and drill holes is determined, at least in part, based on axis information of the patient's individual anatomy, for example an anatomical or a mechanical axis of the patient's knee.

[0345] In another embodiment, the global transformations and local deformations are determined by the software, at least in part, based on external design constraints pertinent to a particular implant design. This can include, for example, specific surface curvature radii, minimum distance between structures such as anchoring elements and/or minimum or maximum thickness or length or width dimensions of the implant or parts thereof. The transformations can also be optimized to minimize bone cuts.

[0346] In a further embodiment, the model or template of the implants and/or guide tools can be fit to the patient's anatomy after the axis alignment of the joint, for example the anatomical or biomechanical axis, has been corrected. The fitting, optimization or deformation of the model or template can then be performed taking the corrected axis into account. Alternatively, the axis alignment is corrected after the model has been fitted. The model can then undergo further adjustments as the alignment correction is performed. Thus, the position or shape of the bearing surfaces and the position and/or direction of the implant, guide tool and/or bone cuts and drill holes is determined based on the corrected axis information.

[0347] In another embodiment, the virtual model includes, in addition to or instead of the surface model representation, one or more geometric reference structures. This can include, for example, planes, axes, curves or surfaces that are used as construction parameters for one or more implants and/or guide tools. The geometric reference structures can be used to define the position and shape of bearing surfaces as well as the location and direction of bone cuts and/or drill holes needed to position the implants. Similar to the way the surface data representation is adjusted using global transformations and local deformations as described above to match the individual patient's anatomy, the position, direction, scale and/or shape of the geometric reference structures can be adjusted accordingly, i.e. the software applies the same global transformations and local deformations applied to the surface model to the geometric reference structures as well. During this process, the position, direction, scale and/or shape of the geometric reference structures can be adjusted as well based on the transformations and deformations of the virtual shape model. Adjusting the position, direction, scale and shape of the geometric reference structures can be performed automatically by the software or based on user or operator input or a combination thereof.

[0348] Once the adjustment of the geometric reference structures is complete, they can be used as construction parameters for the implants and/or guide tool. For example, reference planes can be used to define bone cuts of the implant and associated cut guides. Reference axes can serve to define the direction of anchoring pegs and the holes that need to be drilled. Reference curves can define the outer margin of an implant. Reference surfaces can define the bearing surface of an implant.

[0349] 3.3 Modeling and Addressing Joint Defects

[0350] In certain embodiments, the reference points and/or measurements described above can be processed using mathematical functions to derive virtual, corrected features, which may represent a restored, ideal or desired feature from which a patient-adapted implant component can be designed. For example, one or more features, such as surfaces or dimensions of a biological structure can be modeled, altered, added to, changed, deformed, eliminated, corrected and/or otherwise manipulated (collectively referred to herein as “variation” of an existing surface or structure within the joint). While it is described in the knee, these embodiments can be applied to any joint or joint surface in the body, e.g. a knee, hip, ankle, foot, toe, shoulder, elbow, wrist, hand, and a spine or spinal joints.

[0351] Variation of the joint or portions of the joint can include, without limitation, variation of one or more external surfaces, internal surfaces, joint-facing surfaces, uncut surfaces, cut surfaces, altered surfaces, and/or partial surfaces as well as osteophytes, subchondral cysts, geodes or areas of eburnation, joint flattening, contour irregularity, and loss of normal shape. The surface or structure can be or reflect any surface or structure in the joint, including, without limitation, bone surfaces, ridges, plateaus, cartilage surfaces, ligament surfaces, or other surfaces or structures. The surface or structure derived can be an approximation of a healthy joint surface or structure or can be another variation. The surface or structure can be made to include pathological alterations of the joint. The surface or structure also can be made whereby the pathological joint changes are virtually removed in whole or in part.

[0352] Once one or more reference points, measurements, structures, surfaces, models, or combinations thereof have been selected or derived, the resultant shape can be varied, deformed or corrected. In certain embodiments, the variation can be used to select and/or design an implant component having an ideal or optimized feature or shape, e.g., corresponding to the deformed or corrected joint feature or shape. For example, in one application of this embodiment, the ideal or optimized implant shape reflects the shape of the patient's joint before he or she developed arthritis.

[0353] Alternatively or in addition, the variation can be used to select and/or design a patient-adapted surgical procedure to address the deformity or abnormality. For example, the variation can include surgical alterations to the joint, such as virtual resection cuts, virtual drill holes, virtual removal of osteophytes, and/or virtual building of structural support in the joint deemed necessary or beneficial to a desired final outcome for a patient.

[0354] Corrections can be used to address osteophytes, subchondral voids, and other patient-specific defects or abnormalities. In the case of osteophytes, a design for the bone or joint facing surface of an implant component or guide tool can be selected and/or designed after the osteophyte has been virtually removed. Alternatively, the osteophyte can be integrated into the shape of the bone or joint facing surface of the implant component or guide tool. FIGS. 10A-10D are exemplary drawings of an end of a femur 1010 having an osteophyte 1020. In the selection and/or design of an implant component for a particular patient, an image or model of the patient's bone that includes the osteophyte can be transformed such that the osteophyte 1020 is virtually removed, as shown in FIG. 10B at removed osteophyte 1030, to produce, as shown in FIG. 10C, an implant component 1040 based on a smooth surface at the end of femur 1010. Alternatively, as shown in FIG. 10D, an implant component 1050 can be selected and/or designed to conform to the shape of the osteophyte 1020. In the case of building additional or improved structure, additional features of the implant component then can be derived after bone-facing surface correction is modeled. Optionally, a surgical strategy and/or one or more guide tools can be selected and/or designed to reflect the correction and correspond to the implant component.

[0355] For example, a tibial component can be designed either before or after virtual removal of various features of the tibial bone have been accomplished. In one embodiment, the initial design and placement of the tibial tray and associated components can be planned and accomplished utilizing information directly taken from the patient's natural anatomy. In various other embodiments, the design and placement of the tibial components can be planned and accomplished after virtual removal of various bone portions, including the removal of one or more cut planes (to accommodate the tibial implant) as well as the virtual removal of various potentially-interfering structures (i.e., overhanging osteophytes, etc.) and/or the virtual filling of voids, etc. Prior virtual removal/filling of such structures can facilitate and improve the design, planning and placement of tibial components, and prevent anatomic distortion from significantly affecting the final design and placement of the tibial components. For example, once one or more tibial cut planes has been virtually removed, the size, shape and rotation angle of a tibial implant component can be more accurately determined from the virtually surface, as compared to determining the size, shape and/or tibial rotation angle of an implant from the natural tibial anatomy prior to such cuts. In a similar manner, structures such as overhanging osteophytes can be virtually removed (either alone or in addition to virtual removal of the tibial cut plane(s)), with the tibial implant structure and placement (i.e., tibial implant size, shape and/or tibial rotation, etc.) subsequently planned. Of course, virtually any undesirable anatomical features or deformity, including (but not limited to) altered bone axes, flattening, potholes, cysts, scar tissue, osteophytes, tumors and/or bone spurs may be similarly virtually removed and then implant design and placement can be planned.

[0356] Similarly, to address a subchondral void, a selection and/or design for the bone-facing surface of an implant component can be derived after the void has been virtually removed (e.g., filled). Alternatively, the subchondral void can be integrated into the shape of the bone-facing surface of the implant component. FIGS. 11A-11D are exemplary drawings of an end of a femur 1110 having a subchondral void 1120. During development of an implant, an image or model of the patient's bone that includes the void can be transformed such that the void 1120 is virtually removed, as shown in FIG. 11B at removed void 1130, to produce, as shown in FIG. 11C, an implant component 1140 based on a smooth surface at the end of femur 1110. Alternatively, implant 1110 can be selected and/or designed to conform to the shape of void 1120, as shown in FIG. 11D. Note that, while virtually conforming to void 1120, implant 1150 may not practically be able to be inserted into the void. Therefore, in an certain embodiments, the implant may only partially protrude into a void in the bone. Optionally, a surgical strategy and/or one or more guide tools can be selected and/or designed to reflect the correction and correspond to the implant component.

[0357] In addition to osteophytes and subchondral voids, the methods, surgical strategies, guide tools, and implant components described herein can be used to address various other patient-specific joint defects or phenomena. In certain embodiments, correction can include the virtual removal of tissue, for example, to address an articular defect, to remove subchondral cysts, and/or to remove diseased or damaged tissue (e.g., cartilage, bone, or other types of tissue), such as osteochondritic tissue, necrotic tissue, and/or torn tissue. In such embodiments, the correction can include the virtual removal of the tissue (e.g., the tissue corresponding to the defect, cyst, disease, or damage) and the bone-facing surface of the implant component can be derived after the tissue has been virtually removed. In certain embodiments, the implant component can be selected and/or designed to include a thickness or other features that substantially matches the removed tissue and/or optimizes one or more parameters of the joint. Optionally, a surgical strategy and/or one or more guide tools can be selected and/or designed to reflect the correction and correspond to the implant component.

[0358] Various methods of more accurately modeling a target anatomical site can be utilized prior to designing and placing an implant component. For example, in the case of designing and placing a tibial implant, it may be desirous to incorporate additional virtual criteria into the virtual anatomic model of the targeted anatomy prior to designing and placing the tibial implant component. (One or more of the following, in any combination, may be incorporated with varying results.)

• • [0359] Tibial plateau (leave uncut or virtually cut along one or more planes in model)
  • [0360] Osteophytes (leave intact or virtually remove in model)
  • [0361] Voids (leave intact or virtually fill in model)
  • [0362] Tibial tubercle (incorporate in virtual model or ignore this anatomy)
  • [0363] Femoral anatomic landmarks (incorporate in virtual model or ignore)
  • [0364] Anatomic or biomechanical axes (incorporate in virtual model or ignore)
  • [0365] Femoral component orientation (incorporate in virtual model or ignore)

[0366] After creation of the virtual anatomic model, incorporating one or more of the previous virtual variations in various combinations, the design and placement of the tibial implant (i.e., size, shape, thickness and/or tibial tray rotation angle and orientation) can be more accurately determined. Similarly, the design and placement of a femoral implant (i.e., size, shape, thickness and/or femoral component rotation angle and orientation) can be more accurately determined. Likewise, the design and placement of a other implant components (i.e., size, shape, thickness and/or component rotation angle and orientation), e.g. for acetabular or femoral head resurfacing or replacement, glenoid or humeral head resurfacing or replacement, elbow resurfacing or replacement, wrist resurfacing or replacement, hand resurfacing or replacement, ankle resurfacing or replacement, for resurfacing or replacement can be more accurately determined.

[0367] In certain embodiments, a correction can include the virtual addition of tissue or material, for example, to address an articular defect, loss of ligament stability, and/or a bone stock deficiency, such as a flattened articular surface that should be round. In certain embodiments, the additional material may be virtually added (and optionally then added in surgery) using filler materials such as bone cement, bone graft material, and/or other bone fillers. Alternatively or in addition, the additional material may be virtually added as part of the implant component, for example, by using a bone-facing surface and/or component thickness that match the correction or by otherwise integrating the correction into the shape of the implant component. Then, the joint-facing and/or other features of the implant can be derived. This correction can be designed to re-establish a near normal shape for the patient. Alternatively, the correction can be designed to establish a standardized shape or surface for the patient.

[0368] In certain embodiments, the patient's abnormal or flattened articular surface can be integrated into the shape of the implant component, for example, the bone-facing surface of the implant component can be designed to substantially negatively-match the abnormal or flattened surface, at least in part, and the thickness of the implant can be designed to establish the patient's healthy or an optimum position of the patient's structure in the joint. Moreover, the joint-facing surface of the implant component also can be designed to re-establish a near normal anatomic shape reflecting, for example, at least in part the shape of normal cartilage or subchondral bone. Alternatively, it can be designed to establish a standardized shape.

[0369] In certain embodiments, models can be generated to show defects of interest in a patient's joint. For example, a model or set of models of a patient's joint can be generated showing defects of interest and, optionally, another model or set of models can be generated showing no defects (e.g., as defect and reference, or before and after models). Alternatively, or in addition, the same or additional models can be generated with and/or without resection cuts, guide tools, and/or implant components positioned in the model. Moreover, the same or additional models can be generated to show defects of interest that interfere with one or more resection cuts, guide tools, and/or implant components. Such models, showing defects of interest, resection cuts, guide tools, implant components, and/or interfering defects of interest, can be particularly useful as a reference or guide to a surgeon or clinician prior to and/or during surgery, for example, in identifying proper placement of a guide tool or implant component at one or more steps in a surgery, and/or in identifying features of a patient's anatomy that he or she may want to alter during one or more steps in a surgery. Accordingly, such models that provide, for example, patient-specific renderings of implant assemblies and defects of interest (e.g., osteophyte structures) together with bone models, are useful in aiding surgeons and clinicians in surgery planning and/or during surgery.

[0370] In certain embodiments, a model or set of models of a patient's biological structure are obtained and/or generated to show one or more defects of interest, one or more resection cuts, one or more guide tools, one or more implant components, and/or a combination of any of these. For models that include defects of interest, the defects can be categorized and differentiated into various groups and displayed on the model or set of models in any way that conveys the appropriate information to a surgeon or clinician. For example, two or more defects can be differentiated into categories based on defect type, defect location, severity of the defect, potential interference with a guide tool or implant component, and/or any one or more other useful categories.

[0371] In certain embodiments, one or more additional models or set of models of the patient's biological structure also can be generated and conveyed to the surgeon or clinician to show an additional presence, or absence, of one or more defects of interest, one or more resection cuts, one or more guide tools, and/or one or more implant components, or any combination of these. FIGS. 12A and 12B illustrate models for one particular patient receiving a single compartment knee implant having both femoral and tibial implant components. In a first set of models, illustrated in FIG. 12A, the top panel shows two perspectives of a patient's distal femur and the bottom panel shows two images of the patient's proximal tibia, without (left image) and with (right image) a patient-adapted guide tool. In both the top and bottom panels, defects, osteophytes in this example, can be categorized and differentiated into two colors or shades of grey, beige (lighter shade) and red (darker shade). The light-colored osteophytes 1210 depict osteophytes that do not interfere with placement of the guide tools or implant components. The dark-colored osteophytes 1220 depict osteophytes that will interfere with placement of a guide tool or an implant component. Accordingly, the categorization of the osteophytes serve as a guide or reference to the surgeon or clinician in determining which osteophytes should be removed prior to placement of the guide tools or implant components.

[0372] In a second set of models, illustrated in FIG. 12B, the top panel shows two images of a patient's distal femur with a patient-adapted guide tool (left image) and with a patient-adapted unicompartmental femoral implant component (right image). The bottom panel shows two images of the patient's proximal tibia, with a patient-adapted guide tool (left image) and with a patient-adapted unicompartmental tibial implant component (right image). Images in this figure show no osteophytes. Instead, these images show how each guide tool and implant component engages the patient's biological structure. In addition, the images showing the guide tools also show corresponding resection planes 1230 and the patient's tibial mechanical axis 1240. Accordingly, these images can serve as a guide or reference to the surgeon or clinician in planning and/or determining the surgical placement of the guide tools, implant components, and related resection cuts.

[0373] FIGS. 13A and 13B illustrate models for a different patient receiving a bicompartmental knee implant having both femoral and tibial implant components. The features in FIGS. 13A and 13B are similar to those described above for FIGS. 12A and 12B. In comparing the models for the two different individuals, it is clear that the individual receiving the unicompartmental knee implant (FIGS. 12A and 12B) has substantially more osteophyte coverage than the individual receiving the bicompartmental knee implant (FIGS. 13A and 13B).

[0374] Computer software programs to generate models of patient-specific renderings of implant assembly and defects (e.g., osteophyte structures), together with bone models, to aid in surgery planning can be developed using various publicly available programming environments and languages, for example, Matlab 7.3 and Matlab Compiler 4.5, C++ or Java. In certain embodiments, the computer software program can have a user interface that includes one or more of the components identified in FIG. 14. Alternatively, one or more off-the-shelf applications can be used to generate the models, such as SolidWorks, Rhinoceros, 3D Slicer or Amira.

[0375] An illustrative flow chart of the high level processes of an exemplary computer software program is shown in FIG. 15. Briefly, a data path associated with one or more patient folders that include data files, for example, patient-specific CT images, solid models, and segmentation images, is selected. The data files associated with the data path can be checked, for example, using file filters, to confirm that all data files are present. For example, in generating models for a knee implant, a data path can confirm the presence of one, several, or all coronal CT data files, sagittal CT data files, a femoral solid model data file, a tibial solid model data file, a femoral guide tool model, a tibial guide tool model, a femoral coronal segmentation model, a femoral sagittal segmentation model, a tibial coronal segmentation model, and a tibial sagittal segmentation model. If the filter check identifies a missing file, the user can be notified. In certain instances, for example, if a tibial or femoral guide tool model file is unavailable, the user may elect to continue the process without certain steps, for example, without guide tool—defect (e.g., osteophyte) interference analysis.

[0376] Next, a patient-specific bone-surface model is obtained and/or rendered. The bone surface model provides basic patient-specific features of the patient's biological structure and serves as a reference for comparison against a model or value that includes the defect(s) of interest. As an illustrative example, previously generated patient-specific files, for example, STL files exported from “SOLID” IGES files in SolidWorks, can be loaded, for example, as triangulation points with sequence indices and normal vectors. The triangles then can be rendered (e.g., using Matlab TRISURF function) to supply or generate the bone-surface model. The bone surface model can include corrections of defects, such as osteophytes removed from the bone. In a similar fashion, one or more guide tool models can be obtained and/or rendered.

[0377] Next, a patient-specific model or values of the patient's biological feature that include the defect of interest can be obtained and/or rendered. For example, patient-specific defects, such as osteophytes, can be identified from analysis of the patient's segmentation images and corresponding CT scan images. The transformation matrix of scanner coordinate space to image matrix space can be calculated from image slice positions (e.g., the first and last image slice positions). Then, patient-specific segmentation images for the corresponding scan direction can be assessed, along with CT image slices that correspond to the loaded segmentation images. Images can be processed slice by slice and, using selected threshold values (e.g., intensity thresholds, Hounsfield unit thresholds, or neighboring pixel/voxel value thresholds), pixels and/or voxels corresponding to the defects of interest (e.g., osteophytes) can be identified. The identified voxels can provide a binary bone surface volume that includes the defects of interest as part of the surface of the patient's biological structure. Various masks can be employed to mask out features that are not of interest, for example, an adjacent biological surface. In some instances, masking can generate apparent unattached portions of an osteophyte defect, for example, when a mask covers a portion of an osteophyte extension.

[0378] Next, the defects of interest are isolated by comparing the model that does not include the defects of interest (e.g., bone-surface model) with the model or value that does include the defects of interest (e.g., the binary bone surface volume). For example, the triangulation points of the bone surface model can be transformed onto an image volume space to obtain a binary representation of the model. This volume binary can be dilated and thinned to obtain a binary bone model. The binary bone model then can serve as a mask to the binary bone surface volume to identify defect volume separate from the binary bone surface volume. For example, for osteophyte detection, the osteophyte volume (e.g., osteophyte binary volume), as well as the osteophyte position and attachment surface area, can be distinguished from the patient's biological structure using this comparative analysis. Various thresholds and filters can be applied to remove noise and/or enhance defect detection in this step. For example, structures that have less than a minimum voxel volume (e.g., less than 100 voxels) can be removed. Alternatively, or in addition, rules can be added to “reattach” any portion of an osteophyte defect that appears unattached, e.g., due to a masking step.

[0379] In an alternative approach, surface data can be used instead of voxel or volume data when comparing the bone surface model with corrected defects and the patient's actual bone surface. The bone surface model, for example, can be loaded as a mesh surface (e.g. in an STL file) or a parametric surface (e.g. in an IGES file) without conversion to volumetric voxel data. The patient's natural bone surface can be derived from the medical image data (e.g. CT data) using, for example, a marching cubes or isosurface algorithm, resulting in a second surface data set. The bone surface model and the natural bone surface can be compared, for example, by calculating intersection between the two surfaces.

[0380] Next, optionally, the models can be used to detect interference between any defect volume and the placement of one or more guide tools and/or implant components. For example, guide tool model triangulation points can be transformed onto an image volume space to obtain a binary representation of the guide tool. The binary structure then can be manipulated (e.g., dilated and eroded using voxel balls having pre-set diameters) to obtain a solid field mask. The solid field mask can be compared against the defect volume, for example, the osteophyte binary volume, to identify interfering defect volume, for example, interfering osteophyte binary volume. In this way, interfering defect volume and non-interfering defect volume can be determined (e.g., using Matlab ISOSURFACE function), for example, using representative colors or some other distinguishing features in a model. See, e.g., FIGS. 12A and 13A. The resulting model image can be rendered on a virtual rendering canvas (e.g., using Matlab GETFRAME function) and saved onto a computer-readable medium.

[0381] Finally, optionally, as exemplified by FIGS. 12A-B and 13A-B, one or more combinations of model features can be combined into one or models or sets of models that convey desired information to the surgeon or clinician. For example, patient-specific bone models can be combined with any number of defects or defect types, any number of resection cuts, any number of drill holes, any number of axes, any number of guide tools, and/or any number of implant components to convey as much information as desired to the surgeon or clinician. The patient-specific bone model can model any biological structure, for example, any one or more (or portion of) a femoral head and/or an acetabulum; a distal femur, one or both femoral condyle(s), and/or a tibial plateau; a trochlea and/or a patella; a glenoid and/or a humeral head; a talar dome and/or a tibial plafond; a distal humerus, a radial head, and/or an ulna; and a radius and/or a scaphoid. Defects that can be combined with a patient-specific bone model can include, for example, osteophytes, voids, subchondral cysts, articular shape defects (e.g., rounded or flattened articular surfaces or surface portions), varus or valgus deformities, or any other deformities known to those in the art.

[0382] The models can include virtual corrections reflecting a surgical plan, such as one or more of removed osteophytes, cut planes, drill holes, realignments of mechanical or anatomical axes. The models can include comparison views demonstrating the anatomical situation before and after applying the planned correction. The individual steps of the surgical plan can also be illustrated in a series of step-by-step images wherein each image shows a different step of the surgical procedure.

[0383] The models can be presented to the surgeon as a printed or digital set of images. In another embodiment, the models are transmitted to the surgeon as a digital file, which the surgeon can display on a local computer. The digital file can contain image renderings of the models. Alternatively, the models can be displayed in an animation or video. The models can also be presented as a 3D model that is interactively rendered on the surgeon's computer. The models can, for example, be rotated to be viewed from different angles. Different components of the models, such as bone surfaces, defects, resection cuts, axes, guide tools or implants, can be turned on and off collectively or individually to illustrate or simulate the individual patient's surgical plan. The 3D model can be transmitted to the surgeon in a variety of formats, for example in Adobe 3D PDF or as a SolidWorks eDrawing.

[0384] 3.4 Modeling Proper Limb Alignment

[0385] Proper joint and limb function depend on correct limb alignment. For example, in repairing a knee joint with one or more knee implant components, optimal functioning of the new knee depends on the correct alignment of the anatomical and/or mechanical axes of the lower extremity. Accordingly, an important consideration in designing and/or replacing a natural joint with one or more implant components is proper limb alignment or, when the malfunctioning joint contributes to a misalignment, proper realignment of the limb.

[0386] Certain embodiments described herein include collecting and using data from imaging tests to virtually determine in one or more planes one or more of an anatomic axis and a mechanical axis and the related misalignment of a patient's limb. The misalignment of a limb joint relative to the axis can identify the degree of deformity, for example, varus or valgus deformity in the coronal plane or genu antecurvatum or recurvatum deformity in the sagittal plane. Then, one or more of the patient-specific implant components and/or the implant procedure steps, such as bone resection, can be designed to help correct the misalignment.

[0387] The imaging tests that can be used to virtually determine a patient's axis and misalignment can include one or more of such as x-ray imaging, digital tomosynthesis, cone beam CT, non-spiral or spiral CT, non-isotropic or isotropic MRI, SPECT, PET, ultrasound, laser imaging, and photoacoustic imaging, including studies utilizing contrast agents. Data from these tests can be used to determine anatomic reference points or limb alignment, including alignment angles within the same and between different joints or to simulate normal limb alignment. Any anatomic features related to the misalignment can be selected and imaged. For example, in certain embodiments, such as for a knee or hip implant, the imaging test can include data from at least one of, or several of, a hip joint, knee joint and ankle joint. The imaging test can be obtained in lying, prone, supine or standing position. The imaging test can include only the target joint, or both the target joint and also selected data through one or more adjoining joints.

[0388] Using the image data, one or more mechanical or anatomical axes, angles, planes or combinations thereof can be determined. In certain embodiments, such axes, angles, and/or planes can include, or be derived from, one or more of a Whiteside's line, Blumensaat's line, transepicondylar line, femoral shaft axis, femoral neck axis, acetabular angle, lines tangent to the superior and inferior acetabular margin, lines tangent to the anterior or posterior acetabular margin, femoral shaft axis, tibial shaft axis, transmalleolar axis, posterior condylar line, tangent(s) to the trochlea of the knee joint, tangents to the medial or lateral patellar facet, lines tangent or perpendicular to the medial and lateral posterior condyles, lines tangent or perpendicular to a central weight-bearing zone of the medial and lateral femoral condyles, lines transecting the medial and lateral posterior condyles, for example through their respective centerpoints, lines tangent or perpendicular to the tibial tuberosity, lines vertical or at an angle to any of the aforementioned lines, and/or lines tangent to or intersecting the cortical bone of any bone adjacent to or enclosed in a joint. Moreover, estimating a mechanical axis, an angle, or plane also can be performed using image data obtained through two or more joints, such as the knee and ankle joint, for example, by using the femoral shaft axis and a centerpoint or other point in the ankle, such as a point between the malleoli.

[0389] As one example, if surgery of the knee or hip is contemplated, the imaging test can include acquiring data through at least one of, or several of, a hip joint, knee joint or ankle joint. As another example, if surgery of the knee joint is contemplated, a mechanical axis can be determined. For example, the centerpoint of the hip knee and ankle can be determined. By connecting the centerpoint of the hip with that of the ankle, a mechanical axis can be determined in the coronal plane. The position of the knee relative to said mechanical axis can be a reflection of the degree of varus or valgus deformity. The same determinations can be made in the sagittal plane, for example to determine the degree of genu antecurvatum or recurvatum. Similarly, any of these determinations can be made in any other desired planes, in two or three dimensions.

[0390] Exemplary methods for virtually aligning a patient's lower extremity are described below in Example 9. In particular, Example 9 illustrates methods for determining a patient's tibial mechanical axis, femoral mechanical axis, and the sagittal and coronal planes for each axis. However, any current and future method for determining limb alignment and simulating normal knee alignment can be used.

[0391] Once the proper alignment of the patient's extremity has been determined virtually, one or more surgical steps (e.g., resection cuts) may be planned and/or accomplished, which may include the use of surgical tools (e.g., tools to guide the resection cuts), and/or implant components (e.g., components having variable thicknesses to address misalignment).

[0392] 3.5 Modeling Articular Cartilage

[0393] Cartilage loss in one compartment can lead to progressive joint deformity. For example, cartilage loss in a medial compartment of the knee can lead to varus deformity. In certain embodiments, cartilage loss can be estimated in the affected compartments. The estimation of cartilage loss can be done using an ultrasound MRI or CT scan or other imaging modality, optionally with intravenous or intra-articular contrast. The estimation of cartilage loss can be as simple as measuring or estimating the amount of joint space loss seen on x-rays. For the latter, typically standing x-rays are preferred. If cartilage loss is measured from x-rays using joint space loss, cartilage loss on one or two opposing articular surfaces can be estimated by, for example, dividing the measured or estimated joint space loss by two to reflect the cartilage loss on one articular surface. Other ratios or calculations are applicable depending on the joint or the location within the joint. Subsequently, a normal cartilage thickness can be virtually established on one or more articular surfaces by simulating normal cartilage thickness. In this manner, a normal or near normal cartilage surface can be derived. Normal cartilage thickness can be virtually simulated using a computer, for example, based on computer models, for example using the thickness of adjacent normal cartilage, cartilage in a contralateral joint, or other anatomic information including subchondral bone shape or other articular geometries. Cartilage models and estimates of cartilage thickness can also be derived from anatomic reference databases that can be matched, for example, to a patient's weight, sex, height, race, gender, or articular geometry(ies).

[0394] In certain embodiments, a patient's limb alignment can be virtually corrected by realigning the knee after establishing a normal cartilage thickness or shape in the affected compartment by moving the joint bodies, for example, femur and tibia, so that the opposing cartilage surfaces including any augmented or derived or virtual cartilage surface touch each other, typically in the preferred contact areas. These contact areas can be simulated for various degrees of flexion or extension.

[0395] 4. Parameters for Selecting and/or Designing a Patient-Adapted Implant

[0396] The patient-adapted implants (e.g., implants having one or more patient-specific and/or patient-engineered features) of certain embodiments can be designed based on patient-specific data to optimize one or more parameters including, but not limited to: (1) deformity correction and limb alignment (2) maximum preservation of bone, cartilage, or ligaments, (3) preservation and/or optimization of features of the patient's biology, such as trochlea and trochlear shape, (4) restoration and/or optimization of joint kinematics, and (5) restoration or optimization of joint-line location and/or joint gap width. Various features of an implant component that can be designed or engineered based on the patient-specific data to help meet any number of user-defined thresholds for these parameters. The features of an implant that can be designed and/or engineered patient-specifically can include, but are not limited to, (a) implant shape, external and internal, (b) implant size, (c) and implant thickness.

[0397] There are several advantages that a patient-specific implant designed and/or engineered to meet or improve one of more of these parameters can have over a traditional implant. These advantages can include, for example: improved mechanical stability of the extremity; opportunity for a pre-primary or additional revision implant; improved fit with existing or modified biological features; improved motion and kinematics, and other advantages.

[0398] 4.1 Deformity Correction and Optimizing Limb Alignment

[0399] Information regarding the misalignment and the proper mechanical alignment of a patient's limb, for example, as illustrated in Example 9, can be used to preoperatively design and/or select one or more features of a joint implant and/or implant procedure. For example, based on the difference between the patient's misalignment and the proper mechanical axis, a knee implant and implant procedure can be designed and/or selected preoperatively to include implant and/or resection dimensions that substantially realign the patient's limb to correct or improve a patient's alignment deformity. In addition, the process can include selecting and/or designing one or more surgical tools (e.g., guide tools or cutting jigs) to direct the clinician in resectioning the patient's bone in accordance with the preoperatively designed and/or selected resection dimensions.

[0400] In certain embodiments, the degree of deformity correction that is necessary to establish a desired limb alignment is calculated based on information from the alignment of a virtual model of a patient's limb. The virtual model can be generated from patient-specific data, such 2D and/or 3D imaging data of the patient's limb. The deformity correction can correct varus or valgus alignment or antecurvatum or recurvatum alignment. In a preferred embodiment, the desired deformity correction returns the leg to normal alignment, for example, a zero degree biomechanical axis in the coronal plane and absence of genu antecurvatum and recurvatum in the sagittal plane.

[0401] The preoperatively designed and/or selected implant or implant component, resection dimension(s), and/or cutting jig(s) can be employed to correct a patient's alignment deformity in a single plane, for example, in the coronal plane or in the sagittal plane, in multiple planes, for example, in the coronal and sagittal planes, and/or in three dimensions. For example, Example 9 describes a virtual model of a patient's misaligned lower limb and virtually corrected limb. In particular, the patient's lower limb is misaligned in the coronal plane, for example, a valgus or varus deformity. The deformity correction can be achieved by designing and/or selecting one or more of a resection dimension, an implant component thickness, and an implant component surface curvature that adjusts the mechanical axis or axes into alignment in one or more planes. For example, a lower limb misalignment can be corrected in a knee replacement by designing or selecting one or more of a femoral resection dimension, a femoral implant component thickness, a femoral implant component surface curvature, a tibial resection dimension, a tibial implant component thickness, a tibial implant component insert thickness, and a tibial implant component surface curvature to adjust the femoral mechanical axis and tibial mechanical axis into alignment in the coronal plane.

[0402] FIG. 16 illustrates a coronal plane of the knee with exemplary resection cuts that can be used to correct lower limb alignment in a knee replacement. As shown in the figure, the selected and/or designed resection cuts can include different cuts on different portions of a patient's biological structure. For example, resection cut facets on medial and lateral femoral condyles can be non-coplanar and parallel 1602, 1602′, angled 1604, 1604′, or non-coplanar and non-parallel, for example, cuts 1602 and 1604′ or cuts 1602′ and 1604. Similar, resection cut facets on medial and lateral portions of the tibia can be non-coplanar and parallel 1606, 1606′, angled and parallel 1608, 1608′, or non-coplanar and non-parallel, for example, cuts 1606 and 1608′ or cuts 1606′ and 1608. Non-coplanar facets of resection cuts can include a step-cut 1610 to connect the non-coplanar resection facet surfaces. Selected and/or designed resection dimensions can be achieved using or more selected and/or designed guide tools (e.g., cutting jigs) that guide resectioning (e.g., guide cutting tools) of the patient's biological structure to yield the predetermined resection surface dimensions (e.g., resection surface(s), angles, and/or orientation(s). In certain embodiments, the bone-facing surfaces of the implant components can be designed to include one or more features (e.g., bone cut surface areas, perimeters, angles, and/or orientations) that substantially match one or more of the resection cut or cut facets that were predetermined to enhance the patient's alignment. As shown in FIG. 16, certain combinations of resection cuts can aid in bringing the femoral mechanical axis 1612 and tibial mechanical axis 1614 into alignment 1616.

[0403] Alternatively, or in addition, certain implant features, such as different implant thicknesses and/or surface curvatures across two different sides of the plane in which the mechanical axes 1612, 1614 are misaligned also can aid correcting limb alignment. For example, FIG. 17 depicts a coronal plane of the knee shown with femoral implant medial and lateral condyles 1702, 1702′ having different thicknesses to help to correct limb alignment. These features can be used in combination with any of the resection cut 1704, 1704′ described above and/or in combination with different thicknesses on the corresponding portions of the tibial component. As described more fully below, independent tibial implant components and/or independent tibial inserts on medial and lateral sides of the tibial implant component can be used enhance alignment at a patient's knee joint. An implant component can include constant yet different thicknesses in two or more portions of the implant (e.g., a constant medial condyle thickness different from a constant lateral condyle thickness), a gradually increasing thickness across the implant or a portion of the implant, or a combination of constant and gradually increasing thicknesses.

[0404] FIG. 18 illustrates a virtual model of a patient's limb that is misaligned in the sagittal plane, for example, a genu antecurvatum deformity, and the virtually corrected limb. The deformity correction can be achieved using a similar design approach as described above for a coronal plane deformity. However, the selection and/or design of one or more femoral resection dimensions, femoral implant component thicknesses, femoral implant component surface curvatures, tibial resection dimensions, tibial implant component thicknesses, tibial implant component insert thicknesses, and/or tibial implant component surface curvatures can be used to adjust the femoral mechanical axis and tibial mechanical axis into alignment in the sagittal plane (e.g., by altering corresponding features across the sagittal plane, for example, by altering anterior features relative to corresponding posterior features). Alignment deformities in both the coronal and sagittal planes, or in multiple planes about the mechanical axes, can be addressed by designing and/or selecting one or more resection dimensions, one or more implant component thicknesses, and/or one or more implant component surface curvatures.

[0405] In certain embodiments, an implant component that is preoperatively designed and/or selected to correct a patient's alignment also can be designed or selected to include additional patient-specific or patient-engineered features. For example, the bone-facing surface of an implant or implant component can be designed and/or selected to substantially negatively-match the resected bone surface. As depicted in FIG. 19A, the perimeters and areas 1910 of two bone surface areas is different for two different bone resection cut depths 1920. Similarly, FIG. 19B depicts a distal view of the femur in which two different resection cuts are applied. As shown, the resected perimeters and surface areas for two distal facet resection depths are different for each of the medial condyle distal cut facet 1930 and the lateral condyle distal cut facet 1940.

[0406] If resection dimensions are angled, for example, in the coronal plane and/or in the sagittal plane, various features of the implant component, for example, the component bone-facing surface, can be designed and/or selected based on an angled orientation into the joint rather than on a perpendicular orientation For example, the perimeter of tibial implant or implant component that substantially positively-matches the perimeter of the patient's cut tibial bone has a different shape depending on the angle of the cut. Similarly, with a femoral implant component, the depth or angle of the distal condyle resection on the medial and/or lateral condyle can be designed and/or selected to correct a patient alignment deformity. However, in so doing, one or more of the implant or implant component condyle width, length, curvature, and angle of impact against the tibia can be altered. Accordingly in certain embodiments, one or more implant or implant component features, such as implant perimeter, condyle length, condyle width, curvature, and angle is designed and/or selected relative to the a sloping and/or non-coplanar resection cut.

[0407] 4.2 Preserving Bone, Cartilage or Ligament

[0408] Traditional orthopedic implants incorporate bone cuts. These bone cuts achieve two objectives: they establish a shape of the bone that is adapted to the implant and they help achieve a normal or near normal axis alignment. For example, bone cuts can be used with a knee implant to correct an underlying varus of valgus deformity and to shape the articular surface of the bone to fit a standard, bone-facing surface of a traditional implant component. With a traditional implant, multiple bone cuts are placed. However, since traditional implants are manufactured off-the-shelf without use of patient-specific information, these bone cuts are pre-set for a given implant without taking into consideration the unique shape of the patient. Thus, by cutting the patient's bone to fit the traditional implant, more bone is discarded than is necessary with an implant designed to address the particularly patient's structures and deficiencies.

[0409] In certain embodiments, resection cuts are optimized to preserve the maximum amount of bone for each individual patient, based on a series of two-dimensional images or a three-dimensional representation of the patient's articular anatomy and geometry and the desired limb alignment and/or desired deformity correction. Resection cuts on two opposing articular surfaces can be optimized to achieve the minimum amount of bone resected from one or both articular surfaces.

[0410] By adapting resection cuts in the series of two-dimensional images or the three-dimensional representation on two opposing articular surfaces such as, for example, a femoral head and an acetabulum, one or both femoral condyle(s) and a tibial plateau, a trochlea and a patella, a glenoid and a humeral head, a talar dome and a tibial plafond, a distal humerus and a radial head and/or an ulna, or a radius and a scaphoid, certain embodiments allow for patient individualized, bone-preserving implant designs that can assist with proper ligament balancing and that can help avoid “overstuffing” of the joint, while achieving optimal bone preservation on one or more articular surfaces in each patient.

[0411] The resection cuts also can be designed to meet or exceed a certain minimum material thickness, for example, the minimum amount of thickness required to ensure biomechanical stability and durability of the implant. In certain embodiments, the limiting minimum implant thickness can be defined at the intersection of two adjoining bone cuts on the inner, bone-facing surface of an implant component. For example, in the femoral implant component 2000 shown in FIG. 20, the minimum thickness of the implant component appears at one or more intersections 2100. In certain embodiments of a femoral implant component, the minimum implant thickness can be less than 10 mm, less than 9 mm, less than 8 mm, less than 7 mm, and/or less than 6 mm.

[0412] These optimizations can be performed for 1, 2, or 3 opposing articular surfaces. For example, they can be performed on a tibia, femur and patella of a knee.

[0413] In a knee, different resection cuts can be planned for a medial and lateral femoral condyle. In certain embodiments, a single bone cut can be optimized in a patient to maximize bone preservation in that select area, for example, a posterior condyle. Alternatively, multiple or all resection cuts can be optimized. Since a patient's medial and lateral femoral condyles typically have different geometries, including, for example, width, length and radii of curvature in multiple planes, for example, the coronal and the sagittal plane, then one or more resection cuts can be optimized in the femur individually for each condyle, resulting in resection cuts placed at a different depths, angles, and/or orientations in one condyle relative to the other condyle. For example, a horizontal cut in a medial condyle may be anatomically placed more inferior relative to the limb than a horizontal cut in a lateral condyle. The distance of the horizontal cut from the subchondral bone may be the same in each condyle or it can be different in each condyle. Chamfer cuts in the medial and lateral condyle may be placed in different planes rather than the same plane in order to optimize bone preservation. Moreover, chamfer cuts in the medial and lateral condyle may be placed at a different angle in order to maximize bone preservation. Posterior cuts may be placed in a different plane, parallel or non-parallel, in a medial and a lateral femoral condyle in order to maximize bone preservation. A medial condyle may include more bone cut facets than a lateral condyle in order to enhance bone preservation or vice versa.

[0414] In certain embodiments, a measure of bone preservation can include total volume of bone resected, volume of bone resected from one or more resection cuts, volume of bone resected to fit one or more implant component bone cuts, average thickness of bone resected, average thickness of bone resected from one or more resection cuts, average thickness of bone resected to fit one or more implant component bone cuts, maximum thickness of bone resected, maximum thickness of bone resected from one or more resection cuts, maximum thickness of bone resected to fit one or more implant component bone cuts.

[0415] Certain embodiments of femoral implant components described herein include more than five bone cuts, for example, six, seven, eight, nine or more bone cuts on the inner, bone-facing surface of the implant component. These bone cuts can be standard, in whole or in part, or patient-adapted, in whole or in part. Alternatively, certain embodiments include five bone cuts that are patient-adapted based on one or more images of the patient's knee. A femoral implant component with greater than five bone cuts of and/or with patient-adapted bone cuts can allow for enhanced bone preservation over a traditional femoral implant with five standard bone cuts and therefore can perform as a pre-primary implant.

[0416] A patient-specific implant having bone cuts that are non-parallel to the cuts of a subsequent primary can result in the primary implant having small gaps between the bone and the inner, bone-facing surface of the primary implant. These small gaps can result misalignment intersects between the pre-primary implant and the subsequent primary implant. For example, as shown in FIG. 21, the bone cuts (shown in red) for a pre-primary implant component having a 5-flex cut can retain bone as compared to a traditional primary implant (shown in outline), but a small gap 2110 also can be created by the pre-primary cut. Any such small gaps can be filled with bone cement when fitting a subsequent primary implant.

[0417] In addition to optimizing bone preservation, another factor in determining the depth, number, and/or orientation of resection cuts and/or implant component bone cuts is desired implant thickness. A minimum implant thickness can be included as part of the resection cut and/or bone cut design to ensure a threshold strength for the implant in the face of the stresses and forces associated with joint motion, such as standing, walking, and running. Table 5 shows the results of a finite element analysis (FEA) assessment for femoral implant components of various sizes and with various bone cut numbers and orientations. The maximum principal stress observed in FEA analysis can be used to establish an acceptable minimum implant thickness for an implant component having a particular size and, optionally, for a particular patient (e.g., having a particular weight, age, activity level, etc). Before, during, and/or after establishing a minimum implant component thickness, the optimum depth of resection cuts and optimum number and orientation of resection cuts and bone cuts, for example, for maximum bone preservation, can designed.

[0418] In certain embodiments, an implant component design or selection can depend, at least in part, on a threshold minimum implant component thickness. In turn, the threshold minimum implant component thickness can depend, at least in part, on patient-specific data, such as condylar width, femoral transepicondylar axis length, and/or the patient's specific weight. In this way, the threshold implant thickness, and/or any implant component feature, can be adapted to a particular patient based on a combination of patient-specific geometric data and on patient-specific anthropometric data. This approach can apply to any implant component feature for any joint, for example, the knee, the hip, or the shoulder.

TABLE 5
Finite Element Analysis for Various Implant Designs
				Maximum
	Distal			Principal
	Condyle			Stress,
Implant Description	Geomery	Relative Size	Scan #	mPa
6-Cut, non-flexed	coplanar	Sigma #1.5	3017	161
5-Cut, non-flexed	coplanar	Sigma #1.5	3017	201
6-Cut, flexed 5 degrees	coplanar	Sigma #1.5	3017	229
6-Cut, non-flexed	coplanar	Sigma #3	2825	221
5-Cut, non-flexed	coplanar	Sigma #3	2825	211
6-Cut, flexed 5 degrees	coplanar	Sigma #3	2825	198
5-Cut, non-flexed	coplanar	Sigma #7	1180	292
6-Cut, non-flexed	coplanar	Sigma #7	1180	221
6-Cut, flexed 5 degrees	coplanar	Sigma #7	1180	214
7-Cut non-flexed	coplanar	Sigma #7	1180	203
6-Cut, non-flexed	non-	Sigma #7	1180	173
	coplanar,
	w/step
7-cut, flexed 5 degrees	non-	Sigma #7	1180	202
	coplanar,
	w/out step

[0419] A weighting optionally can be applied to each bone with regard to the degree of bone preservation achieved. For example, if the maximum of bone preservation is desired on a tibia or a sub-segment of a tibia, femoral bone cuts can be adapted and moved accordingly to ensure proper implant alignment and ligament balancing. Conversely, if maximum bone preservation is desired on a femoral condyle, a tibial bone cut can be adjusted accordingly. If maximum bone preservation is desired on a patella, a resection cut on the opposing trochlea can be adjusted accordingly to ensure maximal patellar bone preservation without inducing any extension deficits. If maximum bone preservation is desired on a trochlea, a resection cut on the opposing patella can be adjusted accordingly to ensure maximal patellar bone preservation without inducing any extension deficits. Any combination is possible and different weightings can be applied. The weightings can be applied using mathematical models or, for example, data derived from patient reference databases.

[0420] Implant design and modeling also can be used to achieve ligament sparing, for example, with regard to the PCL and/or the ACL. An imaging test can be utilized to identify, for example, the origin and/or the insertion of the PCL and the ACL on the femur and tibia. The origin and the insertion can be identified by visualizing, for example, the ligaments directly, as is possible with MRI or spiral CT arthrography, or by visualizing bony landmarks known to be the origin or insertion of the ligament such as the medial and lateral tibial spines.

[0421] An implant system can then be selected or designed based on the image data so that, for example, the femoral component preserves the ACL and/or PCL origin, and the tibial component preserves the ACL and/or PCL attachment. The implant can be selected or designed so that bone cuts adjacent to the ACL or PCL attachment or origin do not weaken the bone to induce a potential fracture.

[0422] For ACL preservation, the implant can have two unicompartmental tibial components that can be selected or designed and placed using the image data. Alternatively, the implant can have an anterior bridge component. The width of the anterior bridge in AP dimension, its thickness in the superoinferior dimension or its length in mediolateral dimension can be selected or designed using the imaging data and, specifically, the known insertion of the ACL and/or PCL.

[0423] As can be seen in FIGS. 22A and 22B, the posterior margin of an implant component, e.g. a polyethylene- or metal-backed tray with polyethylene inserts, can be selected and/or designed using the imaging data or shapes derived from the imaging data so that the implant component will not interfere with and stay clear of the PCL. This can be achieved, for example, by including concavities in the outline of the implant that are specifically designed or selected or adapted to avoid the ligament insertion.

[0424] Any implant component can be selected and/or adapted in shape so that it stays clear of important ligament structures. Imaging data can help identify or derive shape or location information on such ligamentous structures. For example, the lateral femoral condyle of a unicompartmental, bicompartmental or total knee system can include a concavity or divot to avoid the popliteus tendon. Imaging data can be used to design a tibial component (all polyethylene or other plastic material or metal backed) that avoids the attachment of the anterior and/or posterior cruciate ligament; specifically, the contour of the implant can be shaped so that it will stay clear of these ligamentous structures. A safety margin, e.g. 2 mm or 3 mm or 5 mm or 7 mm or 10 mm can be applied to the design of the edge of the component to allow the surgeon more intraoperative flexibility. In a shoulder, the glenoid component can include a shape or concavity or divot to avoid a subscapularis tendon or a biceps tendon. In a hip, the femoral component can be selected or designed to avoid an iliopsoas or adductor tendons.

[0425] 4.3 Establishing Normal or Near-Normal Joint Kinematics

[0426] In certain embodiments, bone cuts and implant shape including at least one of a bone-facing or a joint-facing surface of the implant can be designed or selected to achieve normal joint kinematics.

[0427] In certain embodiments, a computer program simulating biomotion of one or more joints, such as, for example, a knee joint, or a knee and ankle joint, or a hip, knee and/or ankle joint can be utilized. In certain embodiments, patient-specific imaging data can be fed into this computer program. For example, a series of two-dimensional images of a patient's knee joint or a three-dimensional representation of a patient's knee joint can be entered into the program. Additionally, two-dimensional images or a three-dimensional representation of the patient's ankle joint and/or hip joint may be added.

[0428] Alternatively, patient-specific kinematic data, for example obtained in a gait lab, can be fed into the computer program. Alternatively, patient-specific navigation data, for example generated using a surgical navigation system, image guided or non-image guided can be fed into the computer program. This kinematic or navigation data can, for example, be generated by applying optical or RF markers to the limb and by registering the markers and then measuring limb movements, for example, flexion, extension, abduction, adduction, rotation, and other limb movements.

[0429] Optionally, other data including anthropometric data may be added for each patient. These data can include but are not limited to the patient's age, gender, weight, height, size, body mass index, and race. Desired limb alignment and/or deformity correction can be added into the model. The position of bone cuts on one or more articular surfaces as well as the intended location of implant bearing surfaces on one or more articular surfaces can be entered into the model.

[0430] A patient-specific biomotion model can be derived that includes combinations of parameters listed above. The biomotion model can simulate various activities of daily life including normal gait, stair climbing, descending stairs, running, kneeling, squatting, sitting and any other physical activity. The biomotion model can start out with standardized activities, typically derived from reference databases. These reference databases can be, for example, generated using biomotion measurements using force plates and motion trackers using radiofrequency or optical markers and video equipment.

[0431] The biomotion model can then be individualized with use of patient-specific information including at least one of, but not limited to the patient's age, gender, weight, height, body mass index, and race, the desired limb alignment or deformity correction, and the patient's imaging data, for example, a series of two-dimensional images or a three-dimensional representation of the joint for which surgery is contemplated.

[0432] An implant shape including associated bone cuts generated in the preceding optimizations, for example, limb alignment, deformity correction, bone preservation on one or more articular surfaces, can be introduced into the model. Table 6 includes an exemplary list of parameters that can be measured in a patient-specific biomotion model.

TABLE 6
Parameters measured in a patient-specific biomotion model for
various implants
Joint implant	Measured Parameter
knee	Medial femoral rollback during flexion
knee	Lateral femoral rollback during flexion
knee	Patellar position, medial, lateral, superior, inferior for different flexion
	and extension angles
knee	Internal and external rotation of one or more femoral condyles
knee	Internal and external rotation of the tibia
knee	Flexion and extension angles of one or more articular surfaces
knee	Anterior slide and posterior slide of at least one of the medial and
	lateral femoral condyles during flexion or extension
knee	Medial and lateral laxity throughout the range of motion
knee	Contact pressure or forces on at least one or more articular surfaces,
	e.g. a femoral condyle and a tibial plateau, a trochlea and a patella
knee	Contact area on at least one or more articular surfaces, e.g. a femoral
	condyle and a tibial plateau, a trochlea and a patella
knee	Forces between the bone-facing surface of the implant, an optional
	cement interface and the adjacent bone or bone marrow, measured at
	least one or multiple bone cut or bone-facing surface of the implant on
	at least one or multiple articular surfaces or implant components.
knee	Ligament location, e.g. ACL, PCL, MCL, LCL, retinacula, joint capsule,
	estimated or derived, for example using an imaging test.
knee	Ligament tension, strain, shear force, estimated failure forces, loads
	for example for different angles of flexion, extension, rotation,
	abduction, adduction, with the different positions or movements
	optionally simulated in a virtual environment.
knee	Potential implant impingement on other articular structures, e.g. in high
	flexion, high extension, internal or external rotation, abduction or
	adduction or any combinations thereof or other angles/positions/
	movements.
Hip, shoulder or	Internal and external rotation of one or more articular surfaces
other joint
Hip, shoulder or	Flexion and extension angles of one or more articular surfaces
other joint
Hip, shoulder or	Anterior slide and posterior slide of at least one or more articular
other joint	surfaces during flexion or extension, abduction or adduction, elevation,
	internal or external rotation
Hip, shoulder or	Joint laxity throughout the range of motion
other joint
Hip, shoulder or	Contact pressure or forces on at least one or more articular surfaces,
other joint	e.g. an acetabulum and a femoral head, a glenoid and a humeral head
Hip, shoulder or	Forces between the bone-facing surface of the implant, an optional
other joint	cement interface and the adjacent bone or bone marrow, measured at
	least one or multiple bone cut or bone-facing surface of the implant on
	at least one or multiple articular surfaces or implant components.
Hip, shoulder or	Ligament location, e.g. transverse ligament, glenohumeral ligaments,
other joint	retinacula, joint capsule, estimated or derived, for example using an
	imaging test.
Hip, shoulder or	Ligament tension, strain, shear force, estimated failure forces, loads
other joint	for example for different angles of flexion, extension, rotation,
	abduction, adduction, with the different positions or movements
	optionally simulated in a virtual environment.
Hip, shoulder or	Potential implant impingement on other articular structures, e.g. in high
other joint	flexion, high extension, internal or external rotation, abduction or
	adduction or elevation or any combinations thereof or other angles/
	positions/movements.

[0433] The above list is not meant to be exhaustive, but only exemplary. Any other biomechanical parameter known in the art can be included in the analysis.

[0434] The resultant biomotion data can be used to further optimize the implant design with the objective to establish normal or near normal kinematics. The implant optimizations can include one or multiple implant components. Implant optimizations based on patient-specific data including image based biomotion data include, but are not limited to:

• • [0435] Changes to external, joint-facing implant shape in coronal plane
  • [0436] Changes to external, joint-facing implant shape in sagittal plane
  • [0437] Changes to external, joint-facing implant shape in axial plane
  • [0438] Changes to external, joint-facing implant shape in multiple planes or three dimensions
  • [0439] Changes to internal, bone-facing implant shape in coronal plane
  • [0440] Changes to internal, bone-facing implant shape in sagittal plane
  • [0441] Changes to internal, bone-facing implant shape in axial plane
  • [0442] Changes to internal, bone-facing implant shape in multiple planes or three dimensions
  • [0443] Changes to one or more bone cuts, for example with regard to depth of cut, orientation of cut

[0444] Any single one or combinations of the above or all of the above on at least one articular surface or implant component or multiple articular surfaces or implant components.

[0445] When changes are made on multiple articular surfaces or implant components, these can be made in reference to or linked to each other. For example, in the knee, a change made to a femoral bone cut based on patient-specific biomotion data can be referenced to or linked with a concomitant change to a bone cut on an opposing tibial surface, for example, if less femoral bone is resected, the computer program may elect to resect more tibial bone.

[0446] Similarly, if a femoral implant shape is changed, for example on an external surface, this can be accompanied by a change in the tibial component shape. This is, for example, particularly applicable when at least portions of the tibial bearing surface negatively-match the femoral joint-facing surface.

[0447] Similarly, if the footprint of a femoral implant is broadened, this can be accompanied by a widening of the bearing surface of a tibial component. Similarly, if a tibial implant shape is changed, for example on an external surface, this can be accompanied by a change in the femoral component shape. This is, for example, particularly applicable when at least portions of the femoral bearing surface negatively-match the tibial joint-facing surface.

[0448] Similarly, if a patellar component radius is widened, this can be accompanied by a widening of an opposing trochlear bearing surface radius, or vice-versa.

[0449] These linked changes also can apply for hip and/or shoulder implants. For example, in a hip, if a femoral implant shape is changed, for example on an external surface, this can be accompanied by a change in an acetabular component shape. This is, for example, applicable when at least portions of the acetabular bearing surface negatively-match the femoral joint-facing surface. In a shoulder, if a glenoid implant shape is changed, for example on an external surface, this can be accompanied by a change in a humeral component shape. This is, for example, particularly applicable when at least portions of the humeral bearing surface negatively-match the glenoid joint-facing surface, or vice-versa.

[0450] Any combination is possible as it pertains to the shape, orientation, and size of implant components on two or more opposing surfaces.

[0451] By optimizing implant shape in this manner, it is possible to establish normal or near normal kinematics. Moreover, it is possible to avoid implant related complications, including but not limited to anterior notching, notch impingement, posterior femoral component impingement in high flexion, and other complications associated with existing implant designs. For example, certain designs of the femoral components of traditional knee implants have attempted to address limitations associated with traditional knee implants in high flexion by altering the thickness of the distal and/or posterior condyles of the femoral implant component or by altering the height of the posterior condyles of the femoral implant component. Since such traditional implants follow a one-size-fits-all approach, they are limited to altering only one or two aspects of an implant design. However, with the design approaches described herein, various features of an implant component can be designed for an individual to address multiple issues, including issues associated with high flexion motion. For example, designs as described herein can alter an implant component's bone-facing surface (for example, number, angle, and orientation of bone cuts), joint-facing surface (for example, surface contour and curvatures) and other features (for example, implant height, width, and other features) to address issues with high flexion together with other issues.

[0452] Biomotion models for a particular patient can be supplemented with patient-specific finite element modeling or other biomechanical models known in the art. Resultant forces in the knee joint can be calculated for each component for each specific patient. The implant can be engineered to the patient's load and force demands. For instance, a 125 lb. patient may not need a tibial plateau as thick as a patient with 280 lbs. Similarly, the polyethylene can be adjusted in shape, thickness and material properties for each patient. For example, a 3 mm polyethylene insert can be used in a light patient with low force and a heavier or more active patient may need an 8 mm polymer insert or similar device.

[0453] 4.4 Restoration or Optimization of Joint-Line Location and Joint Gap Width

[0454] Traditional implants frequently can alter the location of a patient's existing or natural joint-line. For example, with a traditional implant a patient's joint-line can be offset proximally or distally as compared to the corresponding joint-line on the corresponding limb. This can cause mechanical asymmetry between the limbs and result in uneven movement or mechanical instability when the limbs are used together. An offset joint-line with a traditional implant also can cause the patient's body to appear symmetrical.

[0455] Traditional implants frequently alter the location of a patient's existing or natural joint-line because they have a standard thickness that is thicker or thinner than the bone and/or cartilage that they are replacing. For example, a schematic of a traditional implant component is shown in FIGS. 23A and 23B. In the figure, the dashed line represents the patient's existing or natural joint-line 2340 and the dotted line represents the offset joint-line 2342 following insertion of the traditional implant component 2350. As shown in FIG. 23A, the traditional implant component 2350 with a standard thickness replaces a resected piece 2352 of a first biological structure 2354 at an articulation between the first biological structure 2354 and a second biological structure 2356. The resected piece 2352 of the biological structure can include, for example, bone and/or cartilage, and the biological structure 2354 can include bone and/or cartilage. In the figure, the standard thickness of the traditional implant component 2350 differs from the thickness of the resected piece 2352. Therefore, as shown in FIG. 23B, the replacement of the resected piece 2352 with the traditional implant component 2350 creates a wider joint gap 2358 and/or an offset joint-line. Surgeons can address the widened joint gap 2358 by pulling the second biological structure 2356 toward the first biological structure 2354 and tightening the ligaments associated with the joint. However, while this alteration restores some of the mechanical instability created by a widened joint gap, it also exacerbates the displacement of the joint-line.

[0456] Certain embodiments are directed to implant components, and related designs and methods, having one or more features that are engineered from patient-specific data to restore or optimize the particular patient's joint-line location. In addition or alternatively, certain patient-specific implant components, and related designs and methods, can have one or more features that are engineered from patient-specific data to restore or optimize the particular patient's joint gap width.

[0457] In certain embodiments, an implant component can be designed based on patient-specific data to include a thickness profile between its joint-facing surface and its bone-facing surface to restore and/or optimize the particular patient's joint-line location. For example, as schematically depicted in FIG. 23C, the thickness profile (shown as A) of the patient-specific implant component 2360 can be designed to, at least in part, substantially positively-match the distance from the patient's existing or natural joint-line 2340 to the articular surface of the biological structure 2354 that the implant 2360 engages. In the schematic depicted in the figure, the patient joint gap width also is retained.

[0458] The matching thickness profile can be designed based on one or more of the following considerations: the thickness (shown as A′ in FIG. 23C) of a resected piece of biological structure that the implant replaces; the thickness of absent or decayed biological structure that the implant replaces; the relative compressibility of the implant material(s) and the biological material(s) that the implant replaces; and the thickness of the saw blade(s) used for resectioning and/or material lost in removing a resected piece.

[0459] For embodiments directed to an implant component thickness that is engineered based on patient-specific data to optimize joint-line location (and/or other parameters such as preserving bone), the minimum acceptable thickness of the implant can be a significant consideration. Minimal acceptable thickness can be determined based on any criteria, such as a minimum mechanical strength, for example, as determined by FEA. Accordingly, in certain embodiments, an implant or implant design includes an implant component having a minimal thickness profile. For example, in certain embodiments a pre-primary or primary femoral implant component can include a thickness between the joint-facing surface and the bone-facing surface of the implant component that is less than 5 mm, less than 4 mm, less than 3 mm, and/or less than 2 mm.

[0460] In certain embodiments, the implant component thickness can range from about 2 mm to about 3 mm. Therefore, for patients that require only minimal bone resectioning of no more than 2-3 mm depth from the joint-line, an implant component designed with a thickness to substantially positively-match the 2-3 mm bone resectioning can maintain the joint-line location. Moreover, a subsequent traditional primary implant, for example, of 5 mm or greater thickness can be applied later with an additional cut depth of 3-2 mm or greater (for a total 5 mm cut depth). This can allow for maintenance of the joint-line with the subsequent, traditional primary as well.

[0461] Certain embodiments directed to implants or implant designs optimized to achieve minimal implant thickness can include a higher number of bone cuts, for example, six, seven, eight, nine or more bone cuts, on the inner, bone-facing surface of the implant. The bone cuts can be oriented in various dimensions, for example, in a flexed-orientation. Moreover, certain embodiments can include on the inner, bone-facing surface any combination of straight cuts and curvilinear cuts. One or more curvilinear cuts can be designed to substantially positively-match the patient's uncut articular surface, such as a subchondral bone surface exposed by resurfacing. Alternatively, one or more curvilinear cuts can be designed to substantially positively-match a cut surface of the patient's bone, for example, a cut curvilinear surface. Example 5 describes an example of an implant and implant design that includes a straight anterior cut, a straight posterior cut, and a curvilinear cut in between. Moreover, as depicted in FIG. 24, an implant 2400 can include a planar distal cut 2410, a straight anterior cut 2420, a straight posterior cut 2430, and curvilinear chamfer cuts 2440 in between to substantially negatively-match corresponding resected surface(s) of the femur 2450. Example 6 describes an example of an implant or implant design that includes on the inner, bone-facing surface one or no straight cuts and portions that substantially positively-match an uncut articular bone surface.

[0462] The inner, bone-facing surface of the implant component can be designed to substantially negatively-match the cut bone surface, both curved and straight portions. The curved cuts to the bone can be performed with a router saw, as described in Example 5. Any number of the cuts can have a depth of 2-3 mm, and the implant component thickness can be designed to positively-match the cut depth across a portion of the implant or across the entire implant.

[0463] By positively-matching the implant component thickness profile with the cut depth profile, and by negatively-matching the component bone-facing surface with the resected articular surface of the biological structure, certain features of the component joint-facing surface can positively-match the corresponding biological features that it replaces. For example, if the component bone-facing surface and thickness match the corresponding features of the biological structure, the component joint-facing curvature, such as a j-curve, also can match the corresponding surface curvature of the patient's biological structure.

[0464] In certain embodiments, one or more implant components can be designed based on patient-specific data to include a thickness profile that retains, restores, and/or optimizes the particular patient's joint gap width. For example, as schematically depicted in FIGS. 25A and 25B, the patient-specific implant components 2585, 2586 can be designed to, at least in part, substantially positively-match the patient's existing or natural joint gap 2588. In the figure, the dashed line represents the patient's existing or natural joint-line 2590. The patient-specific implant components 2585, 2586 do not have thicknesses that match the corresponding resected pieces 2592, 2594 of biological structures 2596, 2598. However, as shown in FIG. 25B, the implant components 2585, 2586 are designed to retain the patient's specific gap width 2588.

[0465] If the thickness of an implant component is greater than the depth of the corresponding bone cut, then the thicker implant component can shift the joint-line down. However, as shown in FIGS. 25A and 25B, the joint gap width can be retained by designing a second implant component to offset the greater thickness of the first implant component. For example, in total knee replacements that include both a femoral implant component and a tibial implant component, if the femoral implant component is thicker than the depth of the corresponding bone cut, more tibial bone can be cut and/or a thinner tibial implant can be used.

[0466] One or more components of a tibial implant can be designed thinner to retain, restore, and/or optimize a patient's joint-line and/or joint gap width. For example, one or both of a tibial tray and a tibial tray insert (e.g., a poly insert) can be designed and/or selected (e.g., preoperatively selected) to be thinner in one or more locations in order to address joint-line and/or joint-gap issues for a particular patient. In certain embodiments, a tibial bone cut and/or the thickness of a corresponding portion of a tibial implant component may be less than about 6 mm, less than about 5 mm, less than about 4 mm, less than about 3 mm, and/or less than about 2 mm.

[0467] If desired, the one or more materials and/or material properties of an implant can be varied to accommodate unique or localized requirements. For example, it may be desirable for the strength and/or elasticity of the polymer in a tibial tray insert to vary along the surface or cross-sectional profile of the implant. In a similar manner, it may be desirous for a surface of such an implant to posses differing mechanical properties than subsurface portions of the implant. Likewise, it may be desirous for a periphery of such an implant to posses differing mechanical properties than central portions of the implant. In such a case, it may be advantageous to alter the material properties of such an implant in some manner, such as by chemical or physical processing or crosslinking (via chemical vulcanization or via low or high-energy irradiation), to accommodate the varying demands placed upon the polymer implant. Alternatively, the implant may comprise various materials that are adhered, layered or otherwise arranged in some fashion to accomplish various objectives of the present invention. In a similar manner, implants comprising metals and/or ceramic constituents may be formed of two or more materials, or may comprise a single material with sections or portions having varying material characteristics (i.e., by radiation, heating, cooling, hipping, annealing, chemical action, work hardening, peening, carburizing, hardening, surface treating, oxidation, etc.) For example, the medial and/or lateral and/or superior and/or inferior portions of a tibial tray inset maybe formed from two or more materials adhered or otherwise connected in some manner, each material having a unique material property, resulting in an implant with differing mechanical properties on its medial and/or lateral and/or superior and/or inferior sides. Such an implant could alternatively comprise a multi-layered material, with different materials exposed on the surface during the machining process (with the processing tools extending to differing depths), thereby resulting in a generally uniform layered material with different surface properties on the surface of its medial and lateral sides.

[0468] One alternative processing device for crosslinking various materials may comprise a focused radiation beam and/or x-ray source (or gamma or beta or alpha source) 19600 (See FIG. 193A) that can desirably be directed towards various areas or subregions or portions of the tibial tray insert. If desired, the beam/source may also be used to sterilize or otherwise render the insert safer for medical use while simultaneously altering the material properties and/or chemistry in a desired manner. For example, the beam can be centered around a central portion of the implant (FIG. 193B), with less or no radiation exposure to the medial and/or lateral and/or other peripheral portions of the implant. Alternatively, the beam can be directed to expose primarily a joint facing portion of the implant, with little or no radiation exposure to a bone (or metal tray/component) facing portion of the implant (FIG. 193A). If desired, the beam can be focused vertically, horizontally or combinations thereof.

[0469] In the case of one embodiment of a polymer tibial tray insert, the implant may be formed of a single-type of polymer that is crosslinked or otherwise altered so as to have different mechanical properties on its medial and lateral sides. In another alternative, the polymer tibial try insert may incorporate an outer perimeter (i.e. lateral circumference) having one set of material characteristics, while the interior of the implant comprises a different set of material characteristics. In a similar fashion, the articulating surfaces of the medial and lateral insert may be altered to improve strength and/or wear resistance while the flexibility and/or durability of the remainder of the implant is maintained (FIG. 193C). Similarly, medial and lateral inserts may have different material properties and related mechanical properties, e.g. a medial insert can be cross-linked, while a lateral insert is not cross-linked or less cross-linked.

[0470] Material alteration can be accomplished in various ways, including by using radiation emitting apparatus to crosslink or otherwise alter the material structure. Depending upon the focus and intensity of such apparatus, it can be possible to irradiate and/or crosslink some portions of the implant while leaving other portions unaffected. For example, the top layer of an implant may be irradiated and crosslinked while the remaining lower layers are unaffected. In a similar manner, concentric or elliptical or other shaped portions of an implant (i.e., one or two surfaces approximate the opposing surfaces of the medial and lateral condyles) can be crosslinked (in a manner similar to the rings of an onion) while other portions remain unlinked. Similarly, radiation shields can be used to protect select regions of an insert or polyethylene component from radiation exposure and resultant crosslinking.

[0471] An alternative embodiment of a tibial tray insert could comprise a tibial insert having a central section that is crosslinked, with a peripheral portion that is not crosslinked or only minimally crosslinked. Another alternative embodiment of a tibial tray insert could comprise an tibial tray that is not crosslinked in the vicinity of a lock or other securing device, but is crosslinked in other locations of the insert. In this manner, the material retains its greatest amount flexibility and/or durability (and/or elasticity) in the region of the locking device (which could potentially be the region of greatest stress, where a more brittle material may be undesirable), while providing for alternative material properties in other area of the implant where they may be more appropriate.

[0472] FIGS. 193D and 193E depict a femoral head resurfacing implant 19605 for use in a hip resurfacing procedure. In this embodiment, a focused energy beam 19600 from a device suitable for crosslinking of various polymers is directed towards a peripheral surface of the implant 19605. As crosslinking of the surface occurs, the beam is rotated 19610 in a counterclockwise direction along the periphery of the implant 19605. This desirably accomplishes crosslinking of the periphery 19620 of the implant, but leaving the inner surface 19630 relatively unaffected by the beam's crosslinking effect. In this manner, crosslinking of an implant surface may be accomplished. In a similar manner, an implant may be deformed or flexed and placed in the beam's path, and after treatment the implant may be relaxed, potentially creating an implant that is crosslinked in virtually any manner, shape and/or orientation. If desired, the methods of crosslinking or otherwise altering the material properties of such implants can be incorporated into the components of almost any joint implant, including a medial condyle, a lateral condyle, a trochlea, a medial tibia, a lateral tibia, the entire tibia, a medial patella, a lateral patella, an entire patella, a medial trochlea, a central trochlea, a lateral trochlea, a portion of a femoral head, an entire femoral head, a portion of an acetabulum, an entire acetabulum, a portion of a glenoid, an entire glenoid, a portion of a humeral head, an entire humeral head, a portion of an ankle joint, an entire ankle joint, and/or a portion or an entire elbow, wrist, hand, finger, spine, or facet joint.

[0473] In certain embodiments, one or more implant components can designed based on patient-specific data to include a thickness profile that retains or alters a particular patient's joint gap width to retain or correct another patient-specific feature. For example, the patient-specific data can include data regarding the length of the patient's corresponding limbs (e.g., left and right limbs) and the implant component(s) can be designed to, at least in part, alter the length of one limb to better match the length of the corresponding limb.

[0474] 5. Selecting and/or Designing an Implant Component and, Optionally, Related Surgical Steps and Guide Tools

[0475] Any combination of one or more of the above-identified parameters and/or one or more additional parameters can be used in the design and/or selection of a patient-adapted (e.g., patient-specific and/or patient-engineered) implant component and, in certain embodiments, in the design and/or selection of corresponding patient-adapted resection cuts and/or patient-adapted guide tools. In particular assessments, a patient's biological features and feature measurements are used to select and/or design one or more implant component features and feature measurements, resection cut features and feature measurements, and/or guide tool features and feature measurements.

[0476] In certain embodiments, the assessment process includes selecting and/or designing one or more features and/or feature measurements of an implant component and, optionally, of a corresponding resection cut strategy and/or guide tool that is adapted (e.g., patient-adapted based on one or more of a particular patient's biological features and/or feature measurements) to achieve or address, at least in part, one or more of the following parameters for the particular patient: (1) correction of a joint deformity; (2) correction of a limb alignment deformity; (3) preservation of bone, cartilage, and/or ligaments at the joint; (4) preservation, restoration, or enhancement of one or more features of the patient's biology, for example, trochlea and trochlear shape; (5) preservation, restoration, or enhancement of joint kinematics, including, for example, ligament function and implant impingement; (6) preservation, restoration, or enhancement of the patient's joint-line location and/or joint gap width; and (7) preservation, restoration, or enhancement of other target features.

[0477] Correcting a joint deformity and/or a limb alignment deformity can include, for example, generating a virtual model of the patient's joint, limb, and/or other relevant biological structure(s); virtually correcting the deformity and/or aligning the limb; and selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components to physically perform and/or accommodate the correction.

[0478] Preserving, restoring, or enhancing bone, cartilage, and/or ligaments can include, for example, identifying diseased tissue from one or more images of the patient's joint, identifying a minimum implant thickness for the patient (based on, for example, femur and/or condyle size and patient weight); virtually assessing combinations of resection cuts and implant component features, such as variable implant thickness, bone cut numbers, bone cut angles, and/or bone cut orientations; identifying a combination of resection cuts and/or implant component features that, for example, remove diseased tissue and also provide maximum bone preservation (i.e., minimum amount of resected bone) and at least the minimum implant thickness for the particular patient; and selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components to provide the resection cuts and/or implant component features that provide removal of the diseased tissue, maximum bone preservation, and at least the minimum implant thickness for the particular patient.

[0479] Preserving or restoring one or more features of a patient's biology can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components so that one or more of the patient's postoperative implant features substantially match the patient's preoperative biological features or the patient's healthy biological features (e.g., as identified from a previous image of the patient's joint when it was healthy or from an image of the patient's contralateral healthy joint).

[0480] Enhancing one or more features of a patient's biology can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components so that the implant component, once implanted, includes features that approximate one or more features of a healthy biological feature for the particular patient.

[0481] Preservation or restoration of the patient's joint kinematics can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components so that the patient's post-operative joint kinematics substantially match the patient's pre-operative joint kinematics and/or substantially match the patient's healthy joint kinematics (e.g., as identified from previous images of the patient's joint when it was healthy or from an image of the patient's contralateral healthy joint).

[0482] Enhancing the patient's joint kinematics can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components that provide healthy joint kinematics estimated for the particular patient and/or that provide proper joint kinematics to the patient. Optimization of joint kinematics also can include optimizing ligament loading or ligament function during motion.

[0483] Preservation or restoration of the patient's joint-line location and/or joint gap width can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components so that the patient's joint-line and or joint-gap width substantially match the patient's existing joint-line and or joint-gap width or the patient's healthy joint-line and/or joint-gap width (e.g., as identified from previous images of the patient's joint when it was healthy or from an image of the patient's contralateral healthy joint).

[0484] Enhancing the patient's joint-line location and/or joint gap width can include, for example, selecting and/or designing one or more surgical steps (e.g., one or more resection cuts), one or more guide tools, and/or one or more implant components that provide a healthy joint-line location and/or joint gap width and/or estimated for the particular patient and/or that provide proper kinematics to the patient.

[0485] 5.1 Using Parameters to Assess and Select and/or Design an Implant Component

[0486] Assessment of the above-identified parameters, optionally with one or more additional parameters, can be conducted using various formats. For example, the assessment of one or more parameters can be performed in series, in parallel, or in a combination of serial and parallel steps, optionally with a software-directed computer. For example, one or more selected implant component features and feature measurements, optionally with one or more selected resection cut features and feature measurements and one or more selected guide tool features and feature measurements can be altered and assessed in series, in parallel, or in a combination format, to assess the fit between selected parameter thresholds and the selected features and feature measurements. Any one or more of the parameters and features and/or feature measurements can be the first to be selected and/or designed. Alternatively, one or more, or all, of the parameters and/or features can be assessed simultaneously.

[0487] The assessment process can be iterative in nature. For example, one or more first parameters can be assessed and the related implant component and/or resection cut features and feature measurements tentatively or conditionally can be determined. Next, one or more second parameters can be assessed and, optionally, one or more features and/or feature measurements determined. Then, the tentative or conditional features and/or feature measurements for the first assessed parameter(s) optionally can be altered based on the assessment and optional determinations for the second assessed parameters. The assessment process can be fully automated or it can be partially automated allowing for user interaction. User interaction can be particularly useful for quality assurance purposes.

[0488] In the assessment, different weighting can be applied to any of the parameters or parameter thresholds, for example, based on the patient's age, the surgeon's preference or the patient's preference. Feedback mechanisms can be used to show the user or the software the effect that certain feature and/or feature measurement changes can have on desired changes to parameters values, e.g., relative to selected parameter thresholds. For example, a feedback mechanism can be used to determine the effect that changes in features intended to maximize bone preservation (e.g., implant component thickness(es), bone cut number, cut angles, cut orientations, and related resection cut number, angles, and orientations) have on other parameters such as limb alignment, deformity correction, and/or joint kinematic parameters, for example, relative to selected parameter thresholds. Accordingly, implant component features and/or feature measurements (and, optionally, resection cut and guide tool features and/or feature measurements) can be modeled virtually and modified reiteratively to achieve an optimum solution for a particular patient.

[0489] FIG. 26 is a flow chart illustrating the process of assessing and selecting and/or designing one or more implant component features and/or feature measurements, and, optionally assessing and selecting and/or designing one or more resection cut features and feature measurements, for a particular patient. Using the techniques described herein or those suitable and known in the art, one or more of the patient's biological features and/or feature measurements are obtained 2600. In addition, one or more variable implant component features and/or feature measurements are obtained 2610. Optionally, one or more variable resection cut features and/or feature measurements are obtained 2620. Moreover, one or more variable guide tool features and/or feature measurements also can optionally be obtained. Each one of these step can be repeated multiple times, as desired.

[0490] The obtained patient's biological features and feature measurements, implant component features and feature measurements, and, optionally, resection cut and/or guide tool features and/or feature measurements then can be assessed to determine the optimum implant component features and/or feature measurements, and optionally, resection cut and/or guide tool features and/or feature measurements, that achieve one or more target or threshold values for parameters of interest 2630 (e.g., by maintaining or restoring a patient's healthy joint feature). As noted, parameters of interest can include, for example, one or more of (1) joint deformity correction; (2) limb alignment correction; (3) bone, cartilage, and/or ligaments preservation at the joint; (4) preservation, restoration, or enhancement of one or more features of the patient's biology, for example, trochlea and trochlear shape; (5) preservation, restoration, or enhancement of joint kinematics, including, for example, ligament function and implant impingement; (6) preservation, restoration, or enhancement of the patient's joint-line location and/or joint gap width; and (7) preservation, restoration, or enhancement of other target features. This step can be repeated as desired. For example, the assessment step 2630 can be reiteratively repeated after obtaining various feature and feature measurement information 2600, 2610, 2620.

[0491] Once the one or more optimum implant component features and/or feature measurements are determined, the implant component(s) can be selected 2640, designed 2650, or selected and designed 2640, 2650. For example, an implant component having some optimum features and/or feature measurements can be designed using one or more CAD software programs or other specialized software to optimize additional features or feature measurements of the implant component. One or more manufacturing techniques described herein or known in the art can be used in the design step to produce the additional optimized features and/or feature measurements. This process can be repeated as desired.

[0492] Optionally, one or more resection cut features and/or feature measurements can be selected 2660, designed 2670, or selected and further designed 2660, 2670. For example, a resection cut strategy selected to have some optimum features and/or feature measurements can be designed further using one or more CAD software programs or other specialized software to optimize additional features or measurements of the resection cuts, for example, so that the resected surfaces substantially match optimized bone-facing surfaces of the selected and designed implant component. This process can be repeated as desired.

[0493] Moreover, optionally, one or more guide tool features and/or feature measurements can be selected, designed, or selected and further designed. For example, a guide tool having some optimum features and/or feature measurements can be designed further using one or more CAD software programs or other specialized software to optimize additional features or feature measurements of the guide tool. One or more manufacturing techniques described herein or known in the art can be used in the design step to produce the additional, optimized features and/or feature measurements, for example, to facilitate one or more resection cuts that, optionally, substantially match one or more optimized bone-facing surfaces of a selected and designed implant component. This process can be repeated as desired.

[0494] As will be appreciated by those of skill in the art, the process of selecting and/or designing an implant component feature and/or feature measurement, resection cut feature and/or feature measurement, and/or guide tool feature and/or feature measurement can be tested against the information obtained regarding the patient's biological features, for example, from one or more MRI or CT or x-ray images from the patient, to ensure that the features and/or feature measurements are optimum with respect to the selected parameter targets or thresholds. Testing can be accomplished by, for example, superimposing the implant image over the image for the patient's joint. In a similar manner, load-bearing measurements and/or virtual simulations thereof may be utilized to optimize or otherwise alter a derived implant design. For example, where a proposed implant for a knee implant has been designed, it may then be virtually inserted into a biomechanical model or otherwise analyzed relative to the load-bearing conditions (or virtually simulations thereof) it may encounter after implantation. These conditions may indicate that one or more features of the implant are undesirable for varying reasons (i.e., the implant design creates unwanted anatomical impingement points, the implant design causes the joint to function in an undesirable fashion, the joint design somehow interferes with surrounding anatomy, the joint design creates a cosmetically-undesirable feature on the repaired limb or skin covering thereof, FEA or other loading analysis of the joint design indicates areas of high material failure risk, FEA or other loading analysis of the joint design indicates areas of high design failure risk, FEA or other loading analysis of the joint design indicates areas of high failure risk of the supporting or surrounding anatomical structures, etc.). In such a case, such undesirable features may be accommodated or otherwise ameliorated by further design iteration and/or modification that might not have been discovered without such analysis relative to the “real world” measurements and/or simulation.

[0495] Such load-bearing/modeling analysis may also be used to further optimize or otherwise modify the implant design, such as where the implant analysis indicates that the current design is “over-engineered” in some manner than required to accommodate the patient's biomechanical needs. In such a case, the implant design may be further modified and/or redesigned to more accurately accommodate the patient's needs, which may have an unintended (but potentially highly-desirable) consequence of reducing implant size or thickness, increasing or altering the number of potential implant component materials (due to altered requirements for material strength and/or flexibility), increasing estimate life of the implant, reduce wear or otherwise altering one or more of the various design “constraints” or limitations currently accommodated by the present design features of the implant.

[0496] Once optimum features and/or feature measurements for the implant component, and optionally for the resection cuts and/or guide tools, have been selected and/or designed, the implant site can be prepared, for example by removing cartilage and/or resectioning bone from the joint surface, and the implant component can be implanted into the joint 2680.

[0497] The joint implant component bone-facing surface, and optionally the resection cuts and guide tools, can be selected and/or designed to include one or more features that achieve an anatomic or near anatomic fit with the existing surface or with a resected surface of the joint. Moreover, the joint implant component joint-facing surface, and optionally the resection cuts and guide tools, can be selected and/or designed, for example, to replicate the patient's existing joint anatomy, to replicate the patient's healthy joint anatomy, to enhance the patient's joint anatomy, and/or to optimize fit with an opposing implant component. Accordingly, both the existing surface of the joint and the desired resulting surface of the joint can be assessed. This technique can be particularly useful for implants that are not anchored into the bone.

[0498] As will be appreciated by those of skill in the art, the physician, or other person can obtain a measurement of a biological feature (e.g., a target joint) 2600 and then directly select 2640, design, 2650, or select and design 2640, 2650 a joint implant component having desired patient-adapted features and/or feature measurements. Designing can include, for example, design and manufacturing.

[0499] 5.2 Setting and Weighing Parameters

[0500] As described herein, certain embodiments can apply modeling, for example, virtual modeling and/or mathematical modeling, to identify optimum implant component features and measurements, and optionally resection features and measurements, to achieve or advance one or more parameter targets or thresholds. For example, a model of patient's joint or limb can be used to identify, select, and/or design one or more optimum features and/or feature measurements relative to selected parameters for an implant component and, optionally, for corresponding resection cuts and/or guide tools. In certain embodiments, a physician, clinician, or other user can select one or more parameters, parameter thresholds or targets, and/or relative weightings for the parameters included in the model. Alternatively or in addition, clinical data, for example obtained from clinical trials, or intraoperative data, can be included in selecting parameter targets or thresholds, and/or in determining optimum features and/or feature measurements for an implant component, resection cut, and/or guide tool.

[0501] Certain embodiments described herein include generating and/or using a model, for example, a virtual model, of the patient's joint that includes selected parameters and/or parameter measurements and virtually selecting and/or designing one or more implant components, and optionally resection cuts and/or guide tools to fit the virtual model in accordance with the selected parameters and/or parameter measurements. This approach allows for iterative selection and/or design improvement and can include steps to virtually assess fit relative to the selected parameters and/or parameter measurements, such as (1) correction of a joint deformity; (2) correction of a limb alignment deformity; (3) preservation of bone, cartilage, and/or ligaments at the joint; (4) preservation, restoration, or enhancement of one or more features of the patient's biology, for example, trochlea and trochlear shape; (5) preservation, restoration, or enhancement of joint kinematics, including, for example, ligament function and implant impingement; (6) preservation, restoration, or enhancement of the patient's joint-line location and/or joint gap width; and (7) preservation, restoration, or enhancement of other target features.

[0502] One or more parametric thresholds and/or weightings can be applied for the selection and/or designing process. Different parameters can have the same weighting or they can have different weightings. A parameter can include one or more thresholds for selecting one or more implants. The thresholds can include one or more minimum threshold values (e.g., with different weightings), for example, 80%, greater than 80%, 85%, greater than 85%, 90%, greater than 90%, 95%, greater than 95%, 97%, greater than 97%, 98%, greater than 98%, 99%, greater than 99%, 100%, and/or greater than 100% a target value, such as minimum implant coverage of a certain surface on the patient's anatomical structure. Alternatively or in addition, the thresholds can include one or more maximum threshold values (e.g., with different weightings), such as 105%, less than 105%, 103%, less than 103%, 102%, less than 102%, 101%, less than 101%, 100%, and/or less than 100% a target value, such as maximum implant coverage of a certain surface on the patient's anatomical structure.

[0503] One or more parameter thresholds can be absolute, for example, by selecting and/or designing for only implants that meet the threshold, for example, a threshold for a particular patient of 95% mediolateral femoral condyle coverage all around the condyle(s). An example of a selection and/or design process having multiple absolute thresholds is a process that selects and/or designs femoral implant components that must meet both a minimum threshold for a particular patient of 95% mediolateral femoral condyle coverage in the central weight-bearing region, and a minimum threshold of greater than 80% mediolateral femoral condyle coverage outside the weight-bearing area.

[0504] Alternatively or in addition, one or more parameter thresholds can be contingent on one or more other factors. In particular, a selection and/or designing process can successively search a library for implants based on contingent thresholds. For example, femoral implant components meeting a minimum threshold of 99% mediolateral femoral condyle coverage initially can be selected. If no implant meets the threshold, or if some implants meet the threshold but do not meet other parameter thresholds, then a second selection round can include implants meeting a minimum threshold of 98% mediolateral femoral condyle coverage. The process can continue to use additional, contingent thresholds until an implant with the selected parameter thresholds is identified.

[0505] Different thresholds can be defined in different anatomic regions and for different parameters. For example, in certain embodiments of a knee implant design, the amount of mediolateral tibial implant component coverage can be set at 90%, while the amount of anteroposterior tibial implant component coverage can be set at 85%. In another illustrative example, the congruency in intercondylar notch shape can be set at 80% required, while the required mediolateral condylar coverage can be set at 95%.

[0506] 5.3 Computer-Aided Optimization

[0507] Any of the methods described herein can be performed, at least in part, using a computer-readable medium having instructions stored thereon, which, when executed by one or more processors, causes the one or more processors to perform one or more operations corresponding to one or more steps in the method. Any of the methods can include the steps of receiving input from a device or user and producing an output for a user, for example, a physician, clinician, technician, or other user. Executed instructions on the computer-readable medium (i.e., a software program) can be used, for example, to receive as input patient-specific information (e.g., images of a patient's biological structure) and provide as output a virtual model of the patient's biological structure. Similarly, executed instructions on a computer-readable medium can be used to receive as input patient-specific information and user-selected and/or weighted parameters and then provide as output to a user values or ranges of values for those parameters and/or for resection cut features, guide tool features, and/or implant component features. For example, in certain embodiments, patient-specific information can be input into a computer software program for selecting and/or designing one or more resection cuts, guide tools, and/or implant components, and one or more of the following parameters can be optimization in the design process: (1) correction of joint deformity; (2) correction of a limb alignment deformity; (3) preservation of bone, cartilage, and/or ligaments at the joint; (4) preservation, restoration, or enhancement of one or more features of the patient's biology, for example, trochlea and trochlear shape; (5) preservation, restoration, or enhancement of joint kinematics, including, for example, ligament function and implant impingement; (6) preservation, restoration, or enhancement of the patient's joint-line location and/or joint gap width; and (7) preservation, restoration, or enhancement of other target features.

[0508] Optimization of multiple parameters may result in conflicting constraints; for example, optimizing one parameter may cause an undesired deviation to one or more other parameters. In cases where not all constraints can be achieved at the same time, parameters can be assigned a priority or weight in the software program. The priority or weighting can be automated (e.g., part of the computer program) and/or it can be selected by a user depending on the user's desired design goals, for example, minimization of bone loss, or retention of existing joint-line to preserve kinematics, or combination to accommodate both parameters in overall design. As an illustrative example, in certain embodiments, selection and/or design of a knee implant can include obtaining patient-specific information (e.g., from radiographic images or CT images) of a patient's knee and inputting that information into the computer program to model features such as minimum thickness of femoral component (to minimize resected bone on femur), tibial resection cut height (to minimize resected bone on tibia), and joint-line position (preferably to preserve for natural kinematics). These features can be modeled and analyzed relative to a weighting of parameters such as preserving bone and preserving joint kinematics. As output, one or more resection cut features, guide tool features, and/or implant component features that optimize the identified parameters relative to the selective weightings can be provided.

[0509] In any automated process or process step performed by the computer system, constraints pertaining to a specific implant model, to a group of patients or to the individual patient may be taken into account. For example, the maximum implant thickness or allowable positions of implant anchors can depend on the type of implant. The minimum allowable implant thickness can depend on the patient's bone quality.

[0510] Any one or more steps of the assessment, selection, and/or design may be partially or fully automated, for example, using a computer-run software program and/or one or more robots. For example, processing of the patient data, the assessment of biological features and/or feature measurements, the assessment of implant component features and/or feature measurements, the optional assessment of resection cut and/or guide tool features and/or feature measurements, the selection and/or design of one or more features of a patient-adapted implant component, and/or the implantation procedure(s) may be partially or wholly automated. For example, patient data, with optional user-defined parameters, may be inputted or transferred by a user and/or by electronic transfer into a software-directed computer system that can identify variable implant component features and/or feature measurements and perform operations to generate one or more virtual models and/or implant design specifications, for example, in accordance with one or more target or threshold parameters. Implant selection and/or design data, with optional user-defined parameters, may be inputted or transferred by a user and/or by electronic transfer into a software-directed computer system that performs a series of operations to transform the data and optional parameters into one or more implant manufacturing specifications. Implant design data or implant manufacturing data, optionally with user-defined parameters, may be inputted or transferred by a user and/or by electronic transfer into a software-directed computer system that directs one or more manufacturing instruments to produce one or more implant components from a starting material, such as a raw material or starting blank material. Implant design data, implant manufacturing data, or implant data, optionally with user-defined parameters, may be inputted or transferred by a user and/or by electronic transfer into a software-directed computer system that performs a series of operations to transform the data and optional parameters into one or more surgical procedure specifications or instructions. Implant design data, implant manufacturing data, implant data, or surgical procedure data, optionally with user-defined parameters, may be inputted or transferred by a user and/or by electronic transfer into a software-directed computer system that directs one or more automated surgical instruments, for example, a robot, to perform one or more surgical steps. In certain embodiments, one or more of these actions can be performed as steps in a single process by one or more software-directed computer systems.

[0511] In certain embodiments, the implant component includes one or more bone cuts on its bone-facing surface. Features of these bone cuts, and optionally features of corresponding resection cuts, can be optimized by a computer system based on patient-specific data. For example, the bone cut number and one or more bone cut planes, angles, or depths, as well as the corresponding resection cut number and one or more resection cut planes, angles, or depths, can be optimized, for example, to preserve the maximum amount of bone for each individual patient based on a series of two-dimensional images or a three-dimensional representation of the articular anatomy and geometry and/or on a target limb alignment and/or deformity correction. Optionally, one or more of the bone cut features and/or resection cut features can be adjusted by the operator.

[0512] The computer system also can construct the implant surfaces. Surfaces may be composed of different elements. In certain embodiments, elements of the surfaces can conform to the patient's anatomy. In these situations, the computer system can build a surface using the patient's anatomical model, for example by constructing a surface that is identical with or mostly parallel to the patient's anatomical surface. In certain embodiments, the computer system can use geometric elements such as arcs or planes to construct a surface. Transitions between surfaces can be smoothed using tapers or fillets. Additionally, the computer system may take into account constraints such as a minimum or maximum threshold thickness or length or curvature of parts or features of the implant component when constructing the surfaces.

[0513] In another embodiment, the computer system can automatically or semi-automatically add other features to the implant design. For example, the computer system can add pegs or anchors or other attachment mechanisms. The system can place the features using anatomical landmarks. Constraints can be used to restrict the placement of the features. Examples of constraints for placement of pegs are the distance between pegs and from the pegs to the edge of the implant, the height of the pegs that results from their position on the implant, and forcing the pegs to be located on the center line. Optionally, the system can allow the user to fine-tune the peg placement, with or without enforcing the constraints.

[0514] 5.4 Selecting and/or Designing an Implant Component

[0515] Using patient-specific features and feature measurements, and selected parameters and parameter thresholds, an implant component, resection cut strategy, and/or guide tool can be selected (e.g., from a library) and/or designed (e.g. virtually designed and manufactured) to have one or more patient-adapted features. In certain embodiments, one or more features of an implant component (and, optionally, one or more features of a resection cut strategy and/or guide tool) are selected for a particular patient based on patient-specific data and desired parameter targets or thresholds. For example, an implant component or implant component features can be selected from a virtual library of implant components and/or component features to include one or more patient-specific features and/or optimized features for a particular patient. Alternatively or in addition, an implant component can be selected from an actual library of implant components to include one or more patient-specific features and/or optimized features for the particular patient.

[0516] In certain embodiments, one or more features of an implant component (and, optionally, one or more features of a resection cut strategy and/or guide tool) can be designed (e.g., designed and manufactured) to include one or more patient-specific features and/or optimized features for a particular patient. In certain embodiments, one or more features of an implant component (and, optionally, one or more features of a resection cut strategy and/or guide tool) can be both selected and designed (e.g., designed and manufactured) to include one or more patient-specific features and/or optimized features for the particular patient. For example, an implant component having features that achieve certain parameter thresholds but having other features that do not achieve other parameter thresholds (e.g., a blank feature or a smaller or larger feature) can be selected, for example, from a library of implant components. The selected component then can be further designed (e.g. virtually designed and machined) to alter the blank or smaller or larger feature to be achieve the selected parameter, for example, a patient-specific or patient-engineered feature or feature measurement.

[0517] In various alternative embodiments, implant bearing surfaces can combine patient-specific with standard features. For example the bearing surface of a femoral implant in the knee can have a patient-specific curvature in one direction and a standard curvature in another direction. One way to construct such a bearing surface is to generate one or more patient-specific curves for the first direction as shown in FIG. 192A (three shaded curves approximately parallel to the longitudinal axis of the femur, which could be cyan, magenta and gray curves, if desired). These curves can be derived directly from the patient's 2D or 3D images such as CT or MRI scans or radiographs. The curves may also be constructed using measurements derived from the patient's anatomy, such as curvature radii or dimensions.

[0518] Once the patient-specific curves for the first direction have been constructed, a set of standard cross section profile curves can be calculated in the second direction along the patient-specific curves as illustrated in FIGS. 192A and 192B (multiple curves essentially transverse to the three shaded curves, which could be green curves, if desired). Each of the cross section profile curves can be the same. The curves can also be rotated with respect to each other. The standard properties of the cross section profile curves such as the curvature radius can change in a step by step fashion from profile to profile.

[0519] The profile curves can consist of standard segments, e.g. segments with a standard curvature radius. Different segments may have different curvature radii. The segments can be convex or concave. They can be connected to form smooth transitions between the segments.

[0520] Once the cross section profile curves have been defined, the bearing surface can be constructed, for example using a sweep operation, wherein the cross section profile curves are moved along the paths of the patient-specific curves to form a continuous surface as shown in FIG. 192B.

[0521] An implant component can include one or more selected features and one or more designed features. Alternatively or in addition, an implant component can include one or more features that are selected and designed or altered to be patient-specific or patient-engineered. Moreover, an implant component can include any number of selected and/or designed features derived from any number of patient-specific measurements, including one or more of the exemplary measurements described above in Table 4. Depending on the clinical application a single or any combination or all of the measurements described in Table 4 and/or known in the art can be used. Additional patient-specific measurements and information that be used in the evaluation can include, for example, joint kinematic measurements, bone density measurements, bone porosity measurements, identification of damaged or deformed tissues or structures, and patient information, such as patient age, weight, gender, ethnicity, activity level, and overall health status.

[0522] The patient-specific measurements selected for the evaluation can be used to select and/or design any selected implant features, including one or more of the exemplary features described in Table 1. The features can be selected and/or designed to be either patient-specific and/or patient-engineered.

[0523] For example, one or more of an M-L measurement, an A-P measurement, and an S-I measurement of a patient's joint can be obtained from the subject preoperatively, for example, from one or more images of the subject's joint. Then, based on the one or more measurements, an implant or implant component for the subject's joint can be selected and/or designed preoperatively to include an M-L, A-P, and/or S-I measurement that is selected from a library to match the patient's M-L, A-P, and/or S-I measurement.

[0524] The process can include generating and/or using a model, for example, a virtual model, of the patient's joint that includes the selected measurements and virtually fitting one or more selected and/or designed implants into the virtual model. This approach allows for iterative selection and/or design improvement and can include steps to virtually assess the fit, such as virtual kinematics assessment.

[0525] In another embodiment, the process of selecting an implant component also includes selecting one or more component features that optimizes fit with another implant component. In particular, for an implant that includes a first implant component and a second implant component that engage, for example, at a joint interface, selection of the second implant component can include selecting a component having a surface that provides best fit to the engaging surface of the first implant component. For example, for a knee implant that includes a femoral implant component and a tibial implant component, one or both of components can be selected based, at least in part, on the fit of the outer, joint-facing surface with the outer-joint-facing surface of the other component. The fit assessment can include, for example, selecting one or both of the medial and lateral tibial grooves on the tibial component and/or one or both of the medial and lateral condyles on the femoral component that substantially negatively-matches the fit or optimizes engagement in one or more dimensions, for example, in the coronal and/or sagittal dimensions. For example, a surface shape of a non-metallic component that best matches the dimensions and shape of an opposing metallic or ceramic or other hard material suitable for an implant component. By performing this component matching, component wear can be reduced.

[0526] For example, if a metal backed tibial component is used with a polyethylene insert or if an all polyethylene tibial component is used, the polyethylene will typically have one or two curved portions typically designed to mate with the femoral component in a low friction form. This mating can be optimized by selecting a polyethylene insert that is optimized or achieves an optimal fit with regard to one or more of: depth of the concavity, width of the concavity, length of the concavity, radius or radii of curvature of the concavity, and/or distance between two (e.g., medial and lateral) concavities. For example, the distance between a medial tibial concavity and a lateral tibial concavity can be selected so that it matches or approximates the distance between a medial and a lateral implant condyle component.

[0527] Not only the distance between two concavities, but also the radius/radii of curvature can be selected or designed so that it best matches the radius/radii of curvature on the femoral component. A medial and a lateral femoral condyle and opposite tibial component(s) can have a single radius of curvature in one or more dimensions, e.g., a coronal plane. They can also have multiple radii of curvature. The radius or radii of curvature on the medial condyle and/or lateral tibial component can be different from that/those on a lateral condyle and/or lateral tibial component.

[0528] Similar matching of polyethylene or other plastic shape to opposing metal or ceramic component shape can be performed in the shoulder, e.g. with a glenoid component, or in a hip, e.g. with an acetabular cup, or in an ankle, e.g. with a talar component.

[0529] FIG. 27 is an illustrative flow chart showing exemplary steps taken by a practitioner in assessing a joint and selecting and/or designing a suitable replacement implant component. First, a practitioner obtains a measurement of a target joint 2710. The step of obtaining a measurement can be accomplished, for example, based on an image of the joint. This step can be repeated 2711 as necessary to obtain a plurality of measurements, for example, from one or more images of the patient's joint, in order to further refine the joint assessment process. Once the practitioner has obtained the necessary measurements, the information can be used to generate a model representation of the target joint being assessed 2730. This model representation can be in the form of a topographical map or image. The model representation of the joint can be in one, two, or three dimensions. It can include a virtual model and/or a physical model. More than one model can be created 2731, if desired. Either the original model, or a subsequently created model, or both can be used.

[0530] After the model representation of the joint is generated 2730, the practitioner optionally can generate a projected model representation of the target joint in a corrected condition 2740, e.g., based on a previous image of the patient's joint when it was healthy, based on an image of the patient's contralateral healthy joint, based on a projected image of a surface that negatively-matches the opposing surface, or a combination thereof. This step can be repeated 2741, as necessary or as desired. Using the difference between the topographical condition of the joint and the projected image of the joint, the practitioner can then select a joint implant 2750 that is suitable to achieve the corrected joint anatomy. As will be appreciated by those of skill in the art, the selection and/or design process 2750 can be repeated 2751 as often as desired to achieve the desired result. Additionally, it is contemplated that a practitioner can obtain a measurement of a target joint 2710 by obtaining, for example, an x-ray, and then selects a suitable joint replacement implant 2750.

[0531] One or more of these steps can be repeated reiteratively 2724, 2725, 2726. Moreover, the practitioner can proceed directly from the step of generating a model representation of the target joint 2730 to the step of selecting a suitable joint implant component 2750. Additionally, following selection and/or design of the suitable joint implant component 2750, the steps of obtaining measurement of a target joint 2710, generating model representation of target joint 2730 and generating projected model 40, can be repeated in series or parallel as shown by the flow 2724, 2725, 2726.

[0532] 5.5 Libraries

[0533] As described herein, implants of various sizes, shapes, curvatures and thicknesses with various types and locations and orientations and number of bone cuts can be selected and/or designed and manufactured. The implant designs and/or implant components can be selected from, catalogued in, and/or stored in a library. The library can be a virtual library of implants, or components, or component features that can be combined and/or altered to create a final implant. The library can include a catalogue of physical implant components. In certain embodiments, physical implant components can be identified and selected using the library. The library can include previously-generated implant components having one or more patient-adapted features, and/or components with standard or blank features that can be altered to be patient-adapted. Accordingly, implants and/or implant features can be selected from the library.

[0534] FIGS. 28A to 28K show implant components with exemplary features that can be included in a library and selected based on patient-specific data to be patient-specific and/or patient engineered.

[0535] A virtual or physical implant component can be selected from the library based on similarity to prior or baseline parameter optimizations, such as one or more of (1) deformity correction and limb alignment (2) maximum preservation of bone, cartilage, or ligaments, (3) preservation and/or optimization of other features of the patient's biology, such as trochlea and trochlear shape, (4) restoration and/or optimization of joint kinematics, and (5) restoration or optimization of joint-line location and/or joint gap width. Accordingly, one or more implant component features, such as (a) component shape, external and/or internal, (b) component size, and/or (c) component thickness, can be determined precisely and/or determined within a range from the library selection. Then, the selected implant component can be designed or engineered further to include one or more patient-specific features. For example, a joint can be assessed in a particular subject and a pre-existing implant design having the closest shape and size and performance characteristics can be selected from the library for further manipulation (e.g., shaping) and manufacturing prior to implantation. For a library including physical implant components, the selected physical component can be altered to include a patient-specific feature by adding material (e.g., laser sintering) and/or subtracting material (e.g., machining).

[0536] Accordingly, in certain embodiments an implant can include one or more features designed patient-specifically and one or more features selected from one or more library sources. For example, in designing an implant for a total knee replacement comprising a femoral component and a tibial component, one component can include one or more patient-specific features and the other component can be selected from a library. Table 7 includes an exemplary list of possible combinations.

TABLE 7
Illustrative Combinations of Patient-Specific and Library-Derived
Components
		Implant component(s)
	Implant component(s)	having a
	having a patient-specific	library derived
Implant component(s)	feature	feature
Femoral, Tibial	Femoral and Tibial	Femoral and Tibial
Femoral, Tibial	Femoral	Femoral and Tibial
Femoral, Tibial	Tibial	Femoral and Tibial
Femoral, Tibial	Femoral and Tibial	Femoral
Femoral, Tibial	Femoral and Tibial	Tibial
Femoral, Tibial	Femoral and Tibial	none

[0537] In certain embodiments, a library can be generated to include images from a particular patient at one or more ages prior to the time that the patient needs a joint implant. For example, a method can include identifying patients eliciting one or more risk factors for a joint problem, such as low bone mineral density score, and collecting one or more images of the patient's joints into a library. In certain embodiments, all patients below a certain age, for example, all patients below 40 years of age can be scanned to collect one or more images of the patient's joint. The images and data collected from the patient can be banked or stored in a patient-specific database. For example, the articular shape of the patient's joint or joints can be stored in an electronic database until the time when the patient needs an implant. Then, the images and data in the patient-specific database can be accessed and a patient-specific and/or patient-engineered partial or total joint replacement implant using the patient's original anatomy, not affected by arthritic deformity yet, can be generated. This process results in a more functional and more anatomic implant.

[0538] 5.6 Generating an Articular Repair System

[0539] The articular repair systems (e.g., resection cut strategy, guide tools, and implant components) described herein can be formed or selected to achieve various parameters including a near anatomic fit or match with the surrounding or adjacent cartilage, subchondral bone, menisci and/or other tissue. The shape of the repair system can be based on the analysis of an electronic image (e.g., MRI, CT, digital tomosynthesis, optical coherence tomography or the like). If the articular repair system is intended to replace an area of diseased cartilage or lost cartilage, the near anatomic fit can be achieved using a method that provides a virtual reconstruction of the shape of healthy cartilage in an electronic image.

[0540] In one embodiments, a near normal cartilage surface at the position of the cartilage defect can be reconstructed by interpolating the healthy cartilage surface across the cartilage defect or area of diseased cartilage. This can, for example, be achieved by describing the healthy cartilage by means of a parametric surface (e.g. a B-spline surface), for which the control points are placed such that the parametric surface follows the contour of the healthy cartilage and bridges the cartilage defect or area of diseased cartilage. The continuity properties of the parametric surface will provide a smooth integration of the part that bridges the cartilage defect or area of diseased cartilage with the contour of the surrounding healthy cartilage. The part of the parametric surface over the area of the cartilage defect or area of diseased cartilage can be used to determine the shape or part of the shape of the articular repair system to match with the surrounding cartilage.

[0541] In another embodiment, a near normal cartilage surface at the position of the cartilage defect or area of diseased cartilage can be reconstructed using morphological image processing. In a first step, the cartilage can be extracted from the electronic image using manual, semi-automated and/or automated segmentation techniques (e.g., manual tracing, region growing, live wire, model-based segmentation), resulting in a binary image. Defects in the cartilage appear as indentations that can be filled with a morphological closing operation performed in 2-D or 3-D with an appropriately selected structuring element. The closing operation is typically defined as a dilation followed by an erosion. A dilation operator sets the current pixel in the output image to 1 if at least one pixel of the structuring element lies inside a region in the source image. An erosion operator sets the current pixel in the output image to 1 if the whole structuring element lies inside a region in the source image. The filling of the cartilage defect or area of diseased cartilage creates a new surface over the area of the cartilage defect or area of diseased cartilage that can be used to determine the shape or part of the shape of the articular repair system to match with the surrounding cartilage or subchondral bone.

[0542] As described above, the articular repair system can be formed or selected from a library or database of systems of various sizes, including various medio-lateral (ML) antero-posterior (AP) and supero-inferior (SI) dimensions, curvatures and thicknesses, so that it achieves a near anatomic fit or match with the surrounding or adjacent cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site. These systems can be pre-made or made to order for an individual patient. In order to control the fit or match of the articular repair system with the surrounding or adjacent cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone before or after preparing an implantation site or menisci and other tissues preoperatively, a software program can be used that projects the articular repair system over the anatomic position where it will be implanted. Suitable software is commercially available and/or readily modified or designed by a skilled programmer.

[0543] In yet another embodiment, the articular surface repair system can be projected over the implantation site prior to, during or after planning or simulating the surgery virtually using one or more 3-D images. The cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site and other anatomic structures are extracted from a 3-D electronic image such as an MRI or a CT using manual, semi-automated and/or automated segmentation techniques. In select embodiments, segmentation is not necessary and data are directly displayed using the grayscale image information.

[0544] Optionally, a 3-D representation of the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site and other anatomic structures as well as the articular repair system is generated, for example using a polygon or non-uniform rational B-spline (NURBS) surface or other parametric surface representation. For a description of various parametric surface representations see, for example Foley, J. D. et al., Computer Graphics: Principles and Practice in C; Addison-Wesley, 2nd edition (1995).

[0545] The 3D representations of the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site and other anatomic structures and the articular repair system can be merged into a common coordinate system. The articular repair system can then be placed at the desired implantation site. The representations of the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site, menisci and other anatomic structures and the articular repair system are rendered into a 3-D image, for example application programming interfaces (APIs) OpenGL® (standard library of advanced 3-D graphics functions developed by SG), Inc.; available as part of the drivers for PC-based video cards, for example from www.nvidia.com for NVIDIA video cards or www.3dlabs.com for 3Dlabs products, or as part of the system software for Unix workstations) or DirectX® (multimedia API for Microsoft Windows® based PC systems; available from www.microsoft.com). The 3-D image can be rendered showing the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site, menisci or other anatomic objects, and the articular repair system from varying angles, e.g., by rotating or moving them interactively or non-interactively, in real-time or non-real-time.

[0546] The software can be designed so that the articular repair system, including surgical tools and instruments with the best fit relative to the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site is automatically selected, for example using some of the techniques described above. Alternatively, the operator can select an articular repair system, including surgical tools and instruments and project it or drag it onto the implantation site using suitable tools and techniques. The operator can move and rotate the articular repair system in three dimensions relative to the implantation site, cut or uncut, and can perform a visual inspection of the fit between the articular repair system and the implantation site, cut or uncut. The visual inspection can be computer assisted. The procedure can be repeated until a satisfactory fit has been achieved. The procedure can be performed manually by the operator; or it can be computer assisted in whole or part. For example, the software can select a first trial implant that the operator can test. The operator can evaluate the fit. The software can be designed and used to highlight areas of poor alignment between the implant and the surrounding cartilage or subchondral bone or menisci or other tissues. Based on this information, the software or the operator can then select another implant and test its alignment. One of skill in the art will readily be able to select, modify and/or create suitable computer programs for the purposes described herein.

[0547] In another embodiment, the implantation site can be visualized using one or more cross-sectional 2D images. Typically, a series of 2D cross-sectional images will be used. The 2D images can be generated with imaging tests such as CT, MRI, digital tomosynthesis, ultrasound, or optical coherence tomography using methods and tools known to those of skill in the art. The articular repair system can then be superimposed onto one or more of these 2-D images. The 2-D cross-sectional images can be reconstructed in other planes, e.g., from sagittal to coronal, etc. Isotropic data sets (e.g., data sets where the slice thickness is the same or nearly the same as the in-plane resolution) or near isotropic data sets can also be used. Multiple planes can be displayed simultaneously, for example using a split screen display. The operator can also scroll through the 2D images in any desired orientation in real-time or near-real-time; the operator can rotate the imaged tissue volume while doing this. The articular repair system can be displayed in cross-section utilizing different display planes, e.g., sagittal, coronal or axial, typically matching those of the 2-D images demonstrating the cartilage, cortical bone, trabecular bone, subchondral bone, as well as cut bone, before or after preparing an implantation site, menisci or other tissue. Alternatively or in addition, a three-dimensional display can be used for the articular repair system. The 2D electronic image and the 2D or 3-D representation of the articular repair system can be merged into a common coordinate system. The articular repair system can then be placed at the desired implantation site. The series of 2D cross-sections of the anatomic structures, the implantation site and the articular repair system can be displayed interactively (e.g., the operator can scroll through a series of slices) or non interactively (e.g., as an animation that moves through the series of slices), in real-time or non-real-time.

[0548] In another embodiment, the fit between the implant and the implantation site is evaluated. The implant can be available in a range of different dimensions, sizes, shapes and thicknesses. Different dimensions, sizes, shapes and thicknesses can be available for a medial condyle, a lateral condyle, a trochlea, a medial tibia, a lateral tibia, the entire tibia, a medial patella, a lateral patella, an entire patella, a medial trochlea, a central trochlea, a lateral trochlea, a portion of a femoral head, an entire femoral head, a portion of an acetabulum, an entire acetabulum, a portion of a glenoid, an entire glenoid, a portion of a humeral head, an entire humeral head, a portion of an ankle joint, an entire ankle joint, and/or a portion or an entire elbow, wrist, hand, finger, spine, or facet joint.

[0549] In certain embodiments, a combination of parameters can be selected. For example, one or more of an M-L measurement, an A-P measurement, and an S-I measurement of a patient's joint can be obtained from the subject preoperatively, for example, from one or more images of the subject's joint. Then, based on the one or measurements, an implant or implant component for the subject's joint can be designed or selected preoperatively.

[0550] 6. Designing and/or Selecting a Femoral Implant Component

[0551] The following subsections describe aspects of certain embodiments of models, implant designs, implants, and implant components related to a knee replacement. While the sections particularly describe embodiments of total knee implants, it is understood that the teachings are applicable to other embodiments including, but not limited to, unicompartmental knee implants, bicompartmental knee implants, and other articular implants such as shoulder implants, hip implants, and spinal facet implants.

[0552] 6.1 Femoral Implant Component

[0553] A traditional femoral implant component used in a primary total knee arthroplasty (“TKA”) includes: an outer, joint-facing surface (i.e., inferior surface) having a standard topography; an inner, bone-facing surface (i.e., superior surface) that includes five standard bone cuts; and a standard implant thickness between the joint-facing surface and the bone-facing surface. FIG. 29 shows a coronal view of a patient's femoral bone 2900 and (in dashed lines) the five standard resection cuts used to remove portions of the subject's distal femur in order to fit the traditional femoral implant component. As shown by the dashed lines in the figure, a traditional resection performed in a TKA includes a horizontal resection cut 2910, an anterior resection cut 2920, a posterior resection cut 2930, an anterior chamfer resection cut 2940, and a posterior chamfer resection cut 2950. The anterior and posterior resection cuts 2920, 2930 typically are placed in a substantially coronal plane. With a traditional implant, the five standard resection cuts are performed so that the patient's distal femur approximately negatively-matches the standard five bone cuts on the inner, bone-facing surface of the traditional femoral implant component. In other words, the patient's bone is resected to fit the shape of the traditional femoral implant component.

[0554] Dissimilarly, in various embodiments described herein, one or more features of an implant component and/or implant procedure are designed and/or selected to provide a patient-adapted implant component. For example, in certain embodiments, one or more features of an implant component and/or implant procedure are designed and/or selected preoperatively, based on patient-specific data, to substantially match (e.g., substantially negatively-match and/or substantially positively-match) one or more of the patient's biological structures or a predetermined percentage thereof. For example, in certain embodiments, a femoral implant component can include an outer, joint-facing surface (i.e., inferior surface) having a sagittal or j-curve on one or both condyles that, at least in part, positively-matches the corresponding bone or cartilage curvature on the patient's uncut femur. This patient-specific implant component feature can be preoperatively selected and/or designed based on the patient's joint dimensions as seen, for example, on a series of two-dimensional images or a three-dimensional representation generated, for example, from a CT scan or MRI scan.

[0555] Alternatively or in addition, one or more features of an implant component and/or implant procedure can be preoperatively derived from patient-specific data to provide a patient-engineered feature, for example, to optimize one or more parameters, such as one or more of the parameters described above. For example, in certain embodiments, a bone preserving femoral implant component can include an inner, bone-facing surface (i.e., superior surface) having one or bone cuts that, at least in part, are patient-derived, optionally together with matching patient-derived resection cuts, to minimize the amount of resected bone (and maximize the amount of retained bone), for example, on the patient's femur. This patient-engineered implant component feature can be preoperatively selected and/or designed based on the patient's joint dimensions as seen, for example, on a series of two-dimensional images or a three-dimensional representation generated, for example, from a CT scan or MRI scan.

[0556] In certain embodiments, the size of an implant component can be designed and/or selected to substantially match the size of a patient's corresponding biological structure or a predetermined percentage thereof. For example, the ML and/or AP and/or proximal-distal dimensions of one or more sections of a femoral implant component can be preoperatively designed and/or selected to substantially match the corresponding dimension(s) of a patient's distal femur as determined, for example, from one or more images of the patient's joint. In certain embodiments, the size of the femoral implant component can be designed and/or selected based on one or more patient-specific dimensions, such as the length of the patient's epicondylar axis, which can be determined from preoperatively collected patient data, such as image data.

[0557] In certain embodiments, an area measurement on the implant component can be designed and/or selected preoperatively to match, in whole or in part, a corresponding area measurement on the patient's femur or a predetermined percentage thereof. For example, as shown in FIGS. 30A and 30B, the surface area of all or part of the bone-facing surface of the implant component can be designed and/or selected from patient-specific data, in conjunction with a preoperatively designed resection strategy, to substantially match the corresponding resected surface area of the patient's femur. As shown in the figures, the surface area of the implant component is a close fit to the resected surface area. In certain embodiments, the implant component substantially covers the resected surface area, for example, by covering up to 100% and at least 90%, greater than 90%, at least 95%, greater than 95%, at least 97%, greater than 97%, at least 98%, greater than 98%, at least 99%, and/or greater than 99% of the resected surface area of the patient's distal femur.

[0558] In certain embodiments, the thickness of one or portions of an implant component can be designed and/or selected to match the corresponding dimension of the patient's biological structure. For example, the implant component thickness can be designed and/or selected to substantially match in one or more sections the thickness of the patient's cartilage, the thickness of the patient's resected bone, the total thickness of the patient's cartilage and resected bone, or an optimized thickness based on one or more of the parameters described above. In certain embodiments, the additive thickness of two or more implant components, for example, femoral and tibial implant components, can be designed and/or selected together to substantially match in one or more sections the patient's joint-gap distance, for example, the distance between the patient's femoral and tibial bone surfaces, uncut or resected.

[0559] As will be appreciated by those of skill in the art, the thickness of any implant component described herein can vary between different locations across its surface depending upon the patient's anatomy and/or the depth of the damage to the cartilage and/or bone to be corrected at any particular location on the patient's articular surface.

[0560] In certain embodiments, the implant component design and/or selection can include a thickness, a minimum implant thickness, and/or a maximum implant thickness that is engineered from patient-specific data to provide to the patient an optimized implant fit with respect to one or more parameters. Moreover, the additive thickness of two or more implant components can be engineered from patient-specific data to optimize the implant thickness for meeting one or more of the parameters described above. For example, the femoral and/or tibial implant thicknesses can be engineered from patient-specific data to optimize or correct the patient's joint-gap distance. The patient-specific data that may be used to engineer a minimum implant thickness can include, for example, one or more of patient height, patient weight, patient age, patient activity level, patient joint-size (e.g., epicondylar distance or condylar width), and other patient-specific data.

[0561] In preferred embodiments, the minimum implant component thickness can be engineered based on, or together with, other patient-engineered dimensions or features of the implant component, for example, one or more of implant component size, implant component condyle width, and one or more implant component surface curvatures. For example, as shown in FIG. 31A, the thinnest part of a femoral implant component frequently appears at the intersection of the implant component's distal bone cut and a posterior bone cut 3100. This portion of an implant component also frequently shows the highest stress load, as exemplified by the FEA analysis results shown in FIG. 31B. Accordingly, the minimum implant component thickness for this or any portion of the implant component can be engineered based on one or more factors related to stress load, for example: the size of the patient; the size of the patient's femur; the size of the patient's condyle; the size of the patient-engineered implant component; the size of the implant component condyle; and the implant component's joint-facing surface curvature in the region that is opposite the intersection of the distal bone cut and posterior bone cut. In this way, a patient-specific minimum implant thickness can be engineered from patient-specific data, such as image data, and designed into the patient-adapted implant. This allows for minimal bone to be resected in the implant procedure and thereby can help to maximize bone preservation for any particular patient. Preservation of bone can allow for a subsequent knee implant to be a primary knee implant procedure, rather than a revision procedure. The above embodiments are not only applicable to knee implants, but are applicable to implants in other parts of the body, e.g. an acetabulum, a femoral head, a glenoid, a humeral head, an elbow joint, a wrist joint, an ankle joint, a spine etc.

[0562] In addition or alternatively, the implant component can be designed to include a standard minimum thickness and/or a standard maximum thickness in one or more locations. For example, in certain embodiments, the implant component can include a minimum implant thickness of 9 mm, less than 9 mm, 8 mm, less than 8 mm, 7 mm, less than 7 mm, 6 mm, less than 6 mm, 5 mm, and/or less than 5 mm.

[0563] In certain embodiments, both medial and lateral condyles include the same minimum implant thickness.