Patient specific alignment guide and inter-operative adjustment

[0001] This application is a continuation-in part of U.S. application Ser. No. 11/756,057, filed on May 31, 2007, and published as U.S. Patent Publication No. 2007/0288030 on Dec. 13, 2007, which claims the benefit of U.S. Provisional Application No. 60/812,694, filed on Jun. 9, 2006. This application is also a continuation-in-part of U.S. application Ser. No. 11/363,548, filed on Feb. 27, 2006, now U.S. Pat. No. 7,780,672 issued on Aug. 24, 2010. The disclosures of the above applications are incorporated herein by reference.

[0002] Proper alignment of prosthetic components in knee arthroscopy is an important factor in the longevity and function of the implant. Misalignment can cause increased wear of the implant, patient discomfort, and functional limitation.

[0003] Although various methods and devices are known for addressing the above problems, patient specific alignment methods and alignment guides are still desirable.

[0004] The present teachings provide a method of preparing a joint for a prosthesis in a patient. In one aspect, the method includes obtaining scan data associated with the joint of the patient, preparing a three-dimensional image of the joint based on the scan data, preparing a pre-operative surgical plan based on the scan data, and preparing an image of a patient-specific alignment guide, and intra-operatively modifying the surgical plan.

[0005] In another aspect, the method includes securing a patient-specific alignment guide to a joint surface of the patient, attaching a guide element through the alignment guide to the joint surface, removing the alignment guide without removing the guide element, supporting a cutting block having an adjustable cutting guide on the guide element, adjusting the cutting guide relative to the cutting block, and resecting the joint surface using the guide element.

[0006] The present teachings also provide a method of preparing a knee joint for a prosthesis in a patient. The method includes mating a patient-specific femoral alignment guide to a femoral joint surface of the patient, inserting a first guide element through the femoral alignment guide into the anterior or the anterior-medial side of the femoral joint surface, removing the femoral alignment guide without removing the first guide element, supporting an adjustable resection device having a cutting guide on the first guide element, adjusting the orientation of the cutting guide relative to the resection device, and drilling an aperture into the femur joint surface through the resection device. The method further includes inserting a second guide element into the aperture, removing the adjustable resection device, supporting a cutting block on the second guide element, and resecting the femoral joint surface.

[0007] Further areas of applicability of the present invention will become apparent from the description provided hereinafter. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the invention.

[0042] The following description is merely exemplary in nature and is in no way intended to limit the scope of the present teachings, applications, or uses. For example, although the present teachings are illustrated for alignment guides in knee surgery, the present teachings can be used for other guides, templates, jigs, drills, rasps or other instruments used in various orthopedic procedures.

[0043] The present teachings provide a method for preparing patient-specific alignment guides for use in orthopedic surgery for a joint, such as, for example, the knee joint. Conventional, not patient-specific, prosthesis components available in different sizes can be used with the alignment guides, although patient-specific femoral and tibial prosthesis components prepared with computer-assisted image methods can also be used. Computer modeling for obtaining three dimensional images of the patient's anatomy, such as a patient's joint, for example, the patient-specific prosthesis components, when used, and the alignment guides and templates can be provided by various CAD programs and/or software available from various vendors or developers, such as, for example, from Materialise USA, Ann Arbor, Mich.

[0044] Referring to FIG. 1, an MRI scan or a series of CT scans of the entire leg of the joint to be reconstructed, including hip and ankle, as shown in FIG. 3, can be performed at a medical facility or doctor's office, at aspect 10. In some cases, the scan may be performed with the patient wearing an unloader brace to stress the ligaments. The scan data obtained can be sent to a manufacturer, at aspect 20. The scan data can be used to construct a three-dimensional image of the joint and provide an initial implant fitting and alignment in a computer file form or other computer representation. The initial implant fitting and alignment can be obtained using an alignment method, such as the alignment method illustrated in FIG. 2 and described below. Other alignment methods can also be used, such as alignment protocols used by individual surgeons.

[0045] The outcome of the initial fitting is an initial surgical plan that can be printed or provided in electronic form with corresponding viewing software. The initial surgical plan can be surgeon-specific, when using surgeon-specific alignment protocols. The initial surgical plan, in a computer file form associated with interactive software, can be sent to the surgeon, or other medical practitioner, for review, at 30. The surgeon can incrementally manipulate the position of images of implant components 502, 504 in an interactive image form 500 of the joint, as illustrated in FIG. 7. After the surgeon modifies and/or approves the surgical plan, the surgeon can send the final, approved plan to the manufacturer, at 40.

[0046] Various methods of sending the initial and final surgeon-approved surgical plans can be used. The surgical plans can be, for example, transferred to an electronic storage medium, such as CD, DVD, flash memory, which can then be mailed using regular posting methods. Alternatively, the surgical plan can be e-mailed in electronic form or transmitted through the internet or other web-based service, without the use of a storage medium.

[0047] After the surgical plan is approved by the surgeon, patient-specific alignment guides for the femur and tibia can be developed using a CAD program or other imaging software, such as the software provided by Materialise, for example, according to the surgical plan, at 50. Computer instructions of tool paths for machining the patient-specific alignment guides can be generated and stored in a tool path data file, at 60. The tool path can be provided as input to a CNC mill or other automated machining system, and the alignment guides can be machined from polymer, ceramic, metal or other suitable material, and sterilized, at 70. In one aspect, the patient-specific alignment guides can be manufactured by rapid prototyping methods, including, for example, stereolithography. The sterilized alignment guides can be shipped to the surgeon or medical facility, at 80 for use during the surgical procedure.

[0048] Referring to FIG. 2, an exemplary method for providing the initial implant fitting and alignment is illustrated. The method can be modified or completely replaced according to a surgeon-specific alignment protocol. After the scan data is converted to three dimensional images of the patient anatomy from hip to ankle, images of the tibial and femoral components can be manipulated for obtaining patient-specific alignment by making use of the femoral and tibial mechanical axes 402, 404, illustrated in FIG. 3, and the transepicondylar and cylindrical axes 406, 408, illustrated in FIG. 4. Images of the knee joint anatomy can include images of the joint surfaces of the distal femur and proximal tibial with or without the associated soft tissues, such as articular cartilage, on the respective bone surfaces.

[0049] Generally, the femoral mechanical axis is defined as the line joining the center of the femoral head and the center of the intercondylar notch. The femoral anatomic axis is defined as the line along the center of the femoral shaft. The tibial mechanical axis is the line joining the center of the tibial plateau to the center of the tibial plafond or the center of the distal end of the tibia. The tibial anatomic axis is the line along the center of the tibial shaft. The transepicondylar axis is the line connecting the most prominent points of the epicondyles. The cylindrical axis is the line connecting the centers of the condyles when the condyles are approximated by coaxial cylinders. A detailed discussion of the various joint-related axes and the relation of the transepicondylar axis 406 and cylindrical axis 408 is provided in Eckhoff et al, Three-Dimensional Mechanics, Kinematics, and Morphology of the Knee Viewed in Virtual Reality, J Bone Joint Surg Am. 87:71-80, 2005, which is incorporated herein by reference.

[0050] The relation of the femoral mechanical axis 402 to the anatomic axis 410 for the femur is illustrated in FIG. 5. The femoral and tibial mechanical axes 402, 404 may or may not coincide, as illustrated in FIG. 3. In the following discussion, reference is made to a single mechanical axis 401 encompassing the femoral and tibial mechanical axes 402, 404. The alignment procedure illustrated in FIG. 2 makes use of the mechanical, anatomic, transepicondylar and cylindrical axes in various degrees. The present teachings, however, are not limited to this alignment procedure. Multiple alignment procedures can be provided to accommodate the experience and preference of individual surgeons. For example, the alignment procedure can be based on the anatomic and mechanical axes, or can be substantially based on the cylindrical axis. Further, the alignment procedure can be deformity-specific, such that is adapted, for example, to a valgus or varus deformity.

[0051] With continued reference to FIGS. 2-5 and 7, in the image space, the tibial component 504 can be aligned 90° to the mechanical axis 401, at aspect 90. In the frontal plane, the femoral component 502 can be aligned 90° to the mechanical axis 401, at aspect 100. The femoral component 502 can be positioned for “x” mm distal resection, at 110, where “x” can be about 9 mm or other measurement as indicated for a specific patient. The femoral component 502 can be rotated until its distal surfaces are at 90° to the distal femoral bow (component flexion/extension), at 120. The femoral component 502 can be moved anteriorly/posteriorly until the posterior medial condyle resection is greater or equal to “x” mm, at aspect 130.

[0052] The femoral component size can be determined by observing the anterior resection relative to anterior cortex, at 140. If the femoral size is adjusted, the new size can be positioned at the same location relative to the distal and posterior cut planes.

[0053] The cylindrical axis 408 of the femur can be located, at aspect 150. The tibia can be flexed 90° relative to the femur about the cylindrical axis 408, at aspect 160. The femoral component 502 can be rotated about the medial condyle until a rectangular flexion space is achieved, at aspect 170. Alternatively, the rotation can be relative to the transepicondylar axis, anterior/posterior axis, and posterior condylar axis, or a combination of all four axes. The femoral component 502 can be centered or lateralized on the femur, at aspect 180. The location for various distal holes for locating the femoral resection block can be also determined.

[0054] Referring to FIGS. 6, and 8-15B, an exemplary alignment guide 600 and method of use is illustrated in connection with the patient's femur 80. Reference numbers 200-250 relate to aspects of the method of FIG. 6 and are described in connection with the instruments shown in FIGS. 8-15B for the femur 80.

[0055] The alignment guide 600 includes an inner guide surface 640 designed to closely conform, mate and match the femoral joint surface 82 of the patient in three-dimensional space such that the alignment guide 600 and the femoral joint surface are in a nesting relationship to one another. Accordingly, the alignment guide 600 can conform, mate and snap on or “lock” onto the distal surface of the femur 80 in a unique position determined in the final surgical plan, at 200. The alignment guide 600 can have variable thickness. In general, the alignment guide 600 can be made as thin as possible while maintaining structural stiffness. For example, certain areas around and adjacent various securing or guiding apertures 602, 606 can be thickened to provide structural support for guiding a drill or for holding a drill guide or supporting other tools or devices. Exemplary thickened areas 642 are indicated with dotted lines in FIGS. 9A and 9B. Other areas can be cut out for viewing the underlying bone or cartilage of femoral joint surface 82. Viewing areas 644 are indicated with dotted lines in FIGS. 9A and 9B.

[0056] Referring to FIGS. 10A and 10B, the alignment guide 600 can be secured to the femoral joint surface 82 with fixation members or fasteners 624, such as, for example, spring pins, or other securing fasteners that are received through distal apertures 602 of the alignment guide 600. Locating holes 602a corresponding to the apertures 602 of the alignment guide 600 can be drilled in the distal femur 80 to locate a femoral resection block or other cutting device 620, such as a 4-in-1 cutting block, at 220. The alignment guide 600 can also include guiding apertures 606. Guiding apertures 606 are shown in the anterior-medial side relative to the femur 80, but can also be made in the anterior side of the femur 80 or in other locations and orientations. The guiding apertures 606 can be counter-bored and have a partially open portion 608 in their perimeter for sliding the alignment guide off pins or other fasteners without removing such fasteners, as shown in FIG. 13A and discussed below.

[0057] Referring to FIGS. 11A and 11B, a drill guide 700 can be placed in alignment with the guiding apertures 606. The drill guide 700 can include a body 702 having guiding bores 704 corresponding to the guiding apertures 606. The guiding bores 704 can have portions 706 that extend beyond the body 702 and into the guiding apertures 606 for facilitating alignment. The drill guide 700 can also include a handle 710 extending sideways from the body 702 and clear from the drilling path.

[0058] Referring to FIG. 11C, guide elements 604, such as pins or other fasteners, for example, can be drilled through the guiding bores 704 of the drill guide 700 on the anterior or anterior-medial side of the femur 80, at aspect 210 of the method of FIG. 6. The guide elements 604 can be parallel or at other angles relative to another. The guide elements 604 can define a plane that is parallel to a distal resection plane for the femur.

[0059] Referring to FIG. 12A, the drill guide 700 can be removed. Referring to FIGS. 12B-13B, the fasteners 624 can be removed, and the alignment guide 600 can be removed from the femur 80 by sliding the alignment guide 600 off the guide elements 604 through the open portions 608 of the guiding apertures 606 without removing the guide elements 604 at the anterior/medial corner of the knee, at aspect 230 of FIG. 6.

[0060] The guide elements 604 can be used to prepare the joint surfaces for the prosthesis by mounting cutting guides/blocks for resecting the joint surface. Alternatively, a robotic arm or other automated, guided or computer controlled device that can guide the resections based on the pre-operative surgical plan can be mounted on the guide elements 604 and assist the surgeon in preparing the joint surface for the prosthesis.

[0061] Referring to FIGS. 14A and 14B, exemplary distal cutting blocks 610a, 610b that can be mounted over the guide element 604 for making the distal resection, at aspect 640 of FIG. 6, are illustrated. A third fixation element 605, obliquely oriented relative to the guide elements 604 can also be used. The distal cutting blocks 610a, 610b can have an inner surface 612a, 612b that generally follows the shape of the femur 80 to a lesser or greater degree. The distal cutting blocks 610a, 610b can be disposable or re-usable.

[0062] Referring to FIGS. 15A and 15B, after the distal resections are made with the distal cutting block 610a or 610b, the femoral resection block 620 can be mounted with pegs or other supporting elements 622 into the holes 602a corresponding to the fasteners 624. The femoral resections can be made using, for example, a cutting blade 630 through slots 632 of the femoral resection block 620, at aspect 250 of FIG. 6.

[0063] Referring to FIGS. 6 and 16A-D, an exemplary alignment guide 600 is illustrated in connection with the patient's tibia 81. Reference numbers 260-300 relate to aspects of the method of FIG. 6 and are described in connection with the instruments shown in FIGS. 16A-16D for the tibia.

[0064] The alignment guide 600 can conform, nestingly mate in three-dimensional space and snap on or “lock” by design onto the tibia 81 in a unique position, at aspect 260 of FIG. 6. The alignment guide 600 can wrap around the anterior-medial edge of the tibia 81, as shown in FIG. 16A. The drill guide 700 can be aligned with the counter-bored guiding apertures 606 of the alignment guide 600, as shown in FIG. 16B. Two or more guide elements 604 can be placed on the anterior medial side of the tibia, at aspect 270 of FIG. 6. An additional fixation element can also be used for additional securing for the alignment guide 600. The drill guide 700 and the alignment guide 600 can be removed, leaving behind the guide elements 604 attached, at aspect 280 of FIG. 6, and as shown in FIG. 16C. A disposable or reusable tibial cutting block 750 can be slid over the guide elements 604, at aspect 290 of FIG. 6, and as shown in FIG. 16D. The tibial cutting block 750 can include a series of holes 752, allowing the cutting block 750 to be translated proximally or distally to adjust the level of the distal resection. The tibial resection can be made, at 300.

[0065] The present teachings provide patient-specific alignment guides that can be used for alignment in orthopedic surgery. Each alignment guide includes an inner surface that nestingly mates and conforms in three-dimensional space with a corresponding joint surface of a specific patient. The alignment guides can be used for locating guide elements on the joint surface. After the alignment guides are removed, cutting guides or other cutting devices, including automated or robotic devices, can be mounted on the guide elements for making various resection cuts. Because the alignment guides are not used for cutting, the alignment guides do not require substantive thickness to extend anteriorly, and consequently have a lower profile, and less weight. Additionally, because the alignment guides are removed before cutting, the present teachings provide increased ability to visualize the cuts and the cutting process.

[0066] The preoperative plan and the alignment guides can provide a known starting point for the surgeon in the event that intra-operative changes are desired by the surgeon. The preoperative plan can be intra-operatively changed by the surgeon by using an adjustable resection device 800 having a cutting guide 806, such as the device disclosed in co-pending patent application Ser. No. 11/363,548, filed on Feb. 27, 2006, which is incorporated herein by reference and discussed below in reference with FIGS. 17-22. During the surgical procedure, the adjustable resection guide 800 can be mounted on the distal femur 80 using supporting elements 622, such as fasteners 624, pins or guide elements 604 through the locating holes 602a, 602b illustrated in FIGS. 15A and 15B. After soft tissue adjustment, the surgeon may intra-operatively adjust the surgical plan by changing the orientation of the femoral resection planes, for example. The cutting guide 806 of the adjustable resection guide 800 can be rotationally and translationally moved relative to the femur, and can be used to perform the modified resections. Alternatively, the adjustable resection device 800 can be used to drill new location holes 602a, 602b in new positions on the femur. The new holes 602a, 602b can be used to support a cutting block 620, as discussed in reference with FIGS. 15A and 15B.

[0067] Referring to FIGS. 17-22, an exemplary adjustable resection device 800 can include a body 802 attachable to a resected surface of a distal femur, and at least one cutting member 804 coupled to the body 802 and defining a cutting guide 806, such as, for example, a slot, or an edge or other appropriate guide for cutting with a saw blade or other cutting instrument. Two cutting members 804 are illustrated in FIG. 17 and are disposed on opposite sides of the body 802 such that the adjustable resection device 800 can be used selectively to make, for example, posterior cuts for the distal femur of the left or right knee by an appropriate 180-degree rigid body rotation. It will be appreciated, however, that the adjustable resection device 800 can also be used to make anterior, posterior, chamfer and other cuts in either the right or the left knee, as determined by the surgeon, and by appropriate rigid body rotations and relative adjustments. FIG. 17A illustrates an exemplary adjustable resection device 800 having only one cutting member 804. Further, the cutting guide 806 can be defined directly in the body 802.

[0068] The adjustable resection device 800 can include a linear adjustment mechanism 808 for adjusting a linear displacement of the cutting guide 806 relative to the resected surface of the distal femur in a direction substantially perpendicular to the cutting guide 806, as indicated by a double arrow “A”, and corresponding to the anterior-posterior (A/P) direction. The linear adjustment mechanism 808 can include a linear actuator 810 for incrementally displacing the cutting guide 806 relative to the body 802 in the direction defined by the linear displacement. The linear actuator 810 can include a knob or nut 816 threadably coupled to a threaded portion 814 of a post 812 which is coupled to one of the cutting members 804, such that rotating the knob 816 clockwise or counterclockwise incrementally changes the position of the cutting guide 806 relative to the body 802. Linear displacements of 2 mm, for example, can be achieved in the directions indicated by the double arrow A and corresponding to the anterior or posterior surfaces of the distal femur, when the adjustable resection device 800 is mounted on a resected surface of the distal femur, as shown in FIG. 22. Other linear actuators 810 can be used to the same effect with cutting guides 106 defined in cutting members 804, and cutting guides 806 defined directly in the body 802, such as ratchet mechanisms, slide mechanism, guiding slots, etc.

[0069] Referring to FIGS. 18-22, the adjustable resection device 800 can include a rotational adjustment mechanism 840 for adjusting a rotational displacement of the cutting guide 806 relative to the resected surface of the femur. The rotational adjustment mechanism 840 can include a rotational member 842 having a first end 844 and a second end 846. The first end 844 can be narrower than the second end 846 such that the rotational member 842 can be tapered in width between its first and second ends 814, 846. The first end 844 can be pivotably coupled to the body 802 for rotation about an axis C perpendicular to the body 802. The rotational member 842 can be received in a recess 850 defined in the body 802 such that the rotational member 842 is substantially flush with or does not protrude outside of the second surface 826 of the body 802.

[0070] The second end 846 of the rotational member 842 can be releasably coupled to the body 802 for permitting rotation between the body 802 and the rotational member 842 about the first end 844 of the rotational member 842, as indicated by the curved double arrow “B” in FIG. 18, by the operation of a lever 852. The lever 852 can be rotationally coupled to the body 802 for rotation about an axis D, shown in FIG. 21A. The lever 852 can include first and second portions 854, 856 arranged in an L-shape configuration. The first portion 854 can include a ridge or flange or other engagement member 858 capable of engaging any one of a plurality of slots or grooves or other engagement receivers 860 that are shaped and configured to receive the engagement member 858, such that the rotational member 842 can be held in a plurality of orientations relative to the body 802. These orientations can be indicated on a scale 862 marked on the first surface 824 of the body 802 by an indicator 864 attached to the rotational member 842. The lever 852 is biased in an engagement position that prevents relative rotation between the rotational member 842 and the body 802 by a spring, coil or other biasing member 866. The biasing member 866 is coupled between the main body 802 and the second portion 856 of the lever 852, as shown in FIGS. 20 and 21A. Pressing the lever 852 towards the body 802 compresses the biasing member 866 and causes the lever 852 to rotate, thereby disengaging the engagement member 858 from the engagement receiver 860 and allowing relative rotation between the rotational member 842 and the body about axis C. Because the cutting members 804 are supported on and rotate with the body 802, the direction of the cutting guides 806 relative to the rotational member 842 can be accordingly rotationally adjusted.

[0071] The linear adjustment mechanism 808 and the rotational adjustment mechanism 840 together define a two-degree of freedom adjustment mechanism for one or two cutting guides 806 of the adjustable resection/cutting block device 800. The adjustable resection device 800 can be used in knee procedures to balance the flexion gap before various femoral cuts are made for inserting a knee implant. As known in the art, too small flexion gap can result in loss of motion, while too large flexion gap can result in instability. The flexion gap can be measured by placing one or more spacer blocks 880 of increasing thickness on the resected tibia in the flexion gap, as shown in FIG. 22.

[0072] Linear adjustments in the A/P (anterior-posterior) direction as well as rotational adjustments can be made as described above using the linear and rotational adjustment mechanisms 808, 840, respectively, until the flexion gap is balanced and matched with the extension gap, and the medial and lateral ligaments of the knee joint are appropriately tensioned. For example, if the medial and lateral ligaments are equally too lax, linear adjustment is made to reduce the flexion gap and move the cutting guides 806 in the A/P direction closer to the body. If the medial and lateral ligaments are equally too taut, linear adjustment can be made to increase the flexion gap and move the cutting guides 806 in the A/P direction away from the body 802. If the medial and lateral ligaments are unequally tensioned, rotational adjustments can be made relative to the longitudinal axis E of the distal femur (substantially perpendicularly to the resected surface of the distal femur), until the medial and lateral ligaments are equally tensioned, resulting in a balanced flexion gap. A posterior cut or at least one cut can then be performed through one of the cutting guides 806, as appropriate for the right or left knee.

[0073] It will be appreciated that the adjustable resection device 800 can be used to make posterior, anterior, chamfer or other cuts in either knee after balancing the flexion gap of the particular knee, and as determined by the operating surgeon. The adjustable resection device 800 can include an adjustment mechanism (808 and 840) operable to provide adjustment in two degrees of freedom for balancing the flexion gap. The two-degrees-of-freedom adjustments include a linear adjustment and a rotational adjustment. In posterior stabilized knee arthroplasty, for example, the linear adjustment can be in the A/P direction, and the rotational adjustment can be about the longitudinal axis E of the distal femur as shown in FIG. 22. The adjustable resection device 800 can be used to guide drilling holes into the distal femur for properly attaching other cutting blocks or cutting guides after a posterior or other cut is made and the adjustable resection device 800 is removed. The adjustable resection or cutting block device 800 can also be used for A/P sizing using the stylus 890, as shown in FIG. 17A.

[0074] The foregoing discussion discloses and describes merely exemplary arrangements of the present teachings. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings, that various changes, modifications and variations can be made therein without departing from the spirit and scope of the present teachings.