Spinal Fusion Implant

[0001] This Application claims priority to and the benefit of U.S. patent application Ser. No. 11/496,564, titled “SPINAL FUSION IMPLANT”, which was filed on Jul. 31, 2006. The above-identified application is hereby incorporated by reference in its entirety as though fully set forth herein.

[0002] The present invention relates to a spinal implant, the accompanying instrumentation and the method of use of both. More particularly, the present invention relates to a device and instrumentation for use in a minimally invasive vertebral fusion procedure.

[0003] Spinal fusion surgeries that use bone graft material to promote specific vertebrae to grow together into a solid and stable construct are a common method of treating patients with severe back pain. In posterior lumbar interbody fusion (PLIF), damaged disk material is removed and one or more implants are inserted posteriorly to promote bone growth from vertebral body to vertebral body to bridge the gap left by the removed material.

[0004] A larger implant better tills the intervertibral space and distributes compressive loads. A larger implant also reduces the need for multiple implants, which may require multiple approaches to insertion and placement. However, Minimally Invasive Surgery (MIS) necessitates the use of less invasive techniques that use smaller access portals to perform the fusion that limit the size of implant that can be used.

[0005] An example of this is Transforaminal Posterial Lumbar Interbody Fusion (T-PLIF), which is a variation of the PLIF technique. In this procedure, an implant is inserted through a unilateral or bilateral posterior approach. The T-PLIF technique avoids damage to the nerve structures such as the dura, cauda equine, and the nerve root, but the transforaminal window through which the procedure is performed is limited making the insertion and positioning of the implant difficult.

[0006] Thus what is needed is an implant that can suitably fill the intervertebral space but can be inserted and positioned through a small access portal, such as the transforaminal window used in a T-PLIF procedure.

[0007] The present invention provides a device and methodology for use in spinal fusion Surgeries. An implant, instrumentation, and methodology are provided for forming a rigid structure between adjoining vertebrae in a patient. The implant is a cage defined by at least a first end, second end, first side, and second side surface. The cage incorporates one or more flexible joints that allow the cage to be deformed for insertion into a patient. The ability to deform the cage allows a greater ease and flexibility in inserting and positioning the implant. For example, a larger implant can to be used in minimally invasive surgery (MIS) techniques because the cage can be transformed to a smaller profile to pass through the smaller access ports used in minimally invasive surgery.

[0008] In accordance with one aspect of the present invention, an implant is provided for forming a rigid structure between adjoining vertebrae in a patient. The implant includes a cage defined by at least a first end, second end, first side, and second side surface, and one or more flexible joints incorporated into the cage allowing the cage to be deformed for insertion into a patient.

[0009] In certain embodiments, the implant further comprises surface configurations on at least one of the first and second side surfaces of the cage for slidably attaching the implant to an insertion guide. The one or more flexible joints of the implant allow the cage to conform to the shape of the insertion guide as the implant is slid along the length of the guide.

[0010] In accordance with another aspect of the present invention, a method is provided for fusing vertebrae of a patient. The method involves the steps of providing an implant of the present invention, and inserting the implant into the space between adjoining vertebrae in a patient to form a rigid structure between the adjoining vertebrae.

[0011] In accordance with another embodiment, a system is proved for forming a rigid structure between adjoining vertebrae in a patient. The system includes an implant of the present invention having surface configurations on at least one of the first and second side surfaces of the cage for slidably attaching the implant to an insertion guide; and an insertion guide configured to interface with the surface configurations of the implant for positioning the implant during insertion.

[0012] In accordance with another aspect of the present invention, a method is provided for fusing vertebrae of a patient. The method involves providing a system of the present invention comprising a implant with surface configurations and an insertion guide; inserting the insertion guide into the space between adjoining vertebrae in the patient; and sliding the implant along the length of the insertion guide to position the implant in the space between adjoining vertebrae, wherein the implant is slidably attached to the insertion guide by the surface configurations.

[0023] The present invention provides an improved surgical implant and method for performing spinal fusion surgery in a patient. The implant comprises a cage having one or more flexible joints. The cage is defined by at least a first end, second end, first side, and second side surface. The first and second side surfaces extend substantially parallel to each other to span a space between adjoining vertebrae and the first and second ends interconnect the first side surface and the second side surface. The one or more flexible joints allow the cage to be deformed for insertion into a patient. The ability to deform the cage allows a greater ease and flexibility in inserting and positioning the implant. For example, a larger implant can to be used in minimally invasive surgery (MIS) techniques because the cage can be transformed to a smaller profile to pass through the smaller access ports used in minimally invasive surgery. In certain embodiments the implant may further have surface configurations for slidably attaching the implant to a guide used to insert the implant, Embodiments of the implant and methods of use are described below.

[0024] FIGS. 1A and 1B depict one embodiment of an implant 100 for forming a rigid structure between adjoining vertebrae in a patient. In this example the implant comprises a cage 110 having first end 120, second end 130, first side 140, and second side 150 surfaces. The first 140 and second 150 side surfaces extend substantially parallel to each other to span a space between adjoining vertebrae. The first 120 and second 130 end surfaces interconnect said first side surface 140 and second side surface 150. A flexible joint 160 is incorporated into the cage allowing the cage to be deformed for insertion into a patient. FIG. 1A depicts the cage 110 of the implant in a rest state. In this example, the first 140 and second 150 side surfaces are curved giving the cage a curved kidney shape. This curvature and shape provide greater coverage and support then tradition straight-sided implants and is particularly adapted for use in a T-PLIF procedure. While, this shape provides greater biomechanical stability it makes it more difficult to insert and position due to its increased width.

[0025] FIG. 1B shows the cage 110 in a deformed state wherein the first side surface 140 has been divided or split at the flexible joint 160 giving the cage a substantially straight-sided profile. This allows the cage implant 100 to be used with traditional insertion devices configured to be used with traditional straight-sided implants.

[0026] The cage is designed to provide spacing between adjoining vertebrae while encouraging bone growth. As such, the cage 110 may be formed of any biocompatible material suitable for surgical implantation in a patient. Preferably the cage is form of a polymer or composite through a process such as injection molding. Bio-compatible metals may also be used to add strength or rigidity. Examples of suitable materials include, but are not limited to, PEAK, carbon fiber, titanium, stainless steel, Nitinol, and the like, or any combination thereof.

[0027] The cavities 170 created by the cage 110 allow the bone to grow through the cage to fuse the vertebrae. In some embodiments a substance, such as bone chips, or bone graft may be placed in the cavities 170 to encourage bone growth.

[0028] In the example of FIGS. 1A and 1B, the flexible joint 160 comprises a living hinge that is formed as part of the cage during the injection molding process. In other embodiments, the joint may not be formed as part of the cage. For example, the cage may comprise two parts that are joined together using a non-unitary joint mechanism that is embedded in or secured to the two parts. Other implementations and embodiments will be apparent to one skilled in the art given the benefit of this disclosure.

[0029] FIGS. 2A and 2B depict another embodiment of the implant 200 of the invention. As with the implant 100 of FIGS. 1A and 1B this implant 200 comprises a cage 210 having first end 220, second end 230, first side 240, and second side 250 surfaces. As in the previous embodiment, the first 240 and second 250 side surfaces are curved and extend substantially parallel to each other to span a space between adjoining vertebrae. The first 220 and second 230 end surfaces interconnect said first side surface 240 and second side surface 250 providing cavities 270 within the cage 210. However, in this embodiment, multiple flexible joints 260 are used to allow the cage to be deformed for insertion into a patient. As with FIG. 1A, FIG. 2A depicts the cage 210 of the implant 200 in a rest state with first 240 and second 250 side surfaces curved to give the cage a curved kidney shape. FIG. 2B shows the cage 210 in a deformed state wherein the first side surface 240 has been divided or split at two flexible joints 160 to give the cage a substantially straight-sided profile.

[0030] Similar to the embodiment of FIGS. 1A and 1B, the flexible joints 260 comprise living hinges that are formed as part of the cage during the injection molding process. In this example the flexible joints 260 also include a spring mechanism 280 to reinforce the living hinges and return the cage 210 to a rest state after being deformed. In this example, the spring 280 is formed of a piece of metal attached to the cage. In other embodiments, the spring 280 may be formed of plastic or a composite material. In certain embodiments, the spring 280 may be embedded in the cage 210 during the formation of the cage 210, for example, during injection molding. In other embodiments the spring 280 may be attached to the cage 210 using adhesive, rivets, or other fastening means. In certain embodiments the spring 280 may also serve as the flexible joint 260. Other embodiments and configurations will be apparent to one skilled in the art given the benefit of this disclosure.

[0031] The example of FIGS. 2A and 2B also includes an opening 225 in the first end surface 220 for receiving an instrument such as an inserter for attaching the implant to the inserter. In certain embodiments the opening 225 may be in the second end surface 230 or each end surface may have such an opening. Examples of inserters the use of inserters in conjunction with implants can be seen in W02005077288 A1

[0032] While many of the examples and embodiments discussed in this disclosure focus on curved or kidney-shaped implants, it should be understood that the teaching of the invention are not limited to such shapes. FIGS. 3A-3B depict another example of other possible shapes and flexible joints.

[0033] FIGS. 3A and 3B are a top view depicting a straight sided square shaped implant 300. In this example, flexible joints are used to connect the first 340 and second 350 side surfaces to the first 320 and second 330 end surfaces of the cage 310. This allows the cage 310 to be transformed down to a smaller size as shown in FIG. 3B. The ability to transform the cage 310 allows the cage to be inserted through a smaller access port for insertion in between vertebrae.

[0034] FIG. 4 is a flow chart 400 of an exemplary method for fusing vertebrae of a patient. The method involves substantially the steps of providing an implant of the present invention (step 420) and inserting the implant into the space between adjoining vertebrae in a patient to form a rigid structure between the adjoining vertebrae (step 430).

[0035] In some embodiments the method 400 may further include the steps of preparing the space between adjoining vertebrae (step 410) as well as the steps of transforming the cage of the implant to a smaller profile (step 425) before implantation and transforming the cage back to the original profile after insertion (435).

[0036] The step of preparing the space between adjoining vertebrae (step 410) may include removing the disk material between the vertebrae. Then the space between the vertebrae may be distracted to relieve pressure from neural elements and provide space for the entry of surgical tools and the insertion of the implant. Preferably the surgery including the insertion is performed using a MIS technique such a T-PLIF procedure.

[0037] Because MIS techniques such as T-PLIF procedures use a more limited access port or window, the cage of the implant may need to be transformed or otherwise deformed in order to fit through the access port or window (step 425) and be positioned in the space between vertebrae. Once in position, the cage may then be transformed back or otherwise returned to its rest state (step 435). In certain embodiments this is performed by a spring incorporated or attached to the one or more flexible joints.

[0038] In some embodiments, the implant 500 may further include surface configurations 590 on at least one of the first 540 and second 550 side surfaces of the cage 510 for slidably attaching the implant 500 to an insertion guide. An example of this can be seen in FIGS. 5A and 5B. Here the surface configurations 590 are tabs or fingers formed on the first side surface 540. When used in conjunction with an insertion guide, the flexible joints 560 of the implant 500 allow the cage 510 to deform (i.e. straighten) to conform to the shape of the insertion guide. This is described in more detail below.

[0039] In the embodiments of FIGS. 5A and 5B, the cage 510 further includes textured edges 515 on the first end 520, second end 530, first side 540, and second side 550 surfaces for engaging the bone of the adjoining vertebrae to secure the implant in place in the space between vertebrae. Other possible configurations and textures for securing the implant 500 will be apparent to one skilled in the art given the benefit of this disclosure.

[0040] FIG. 6 depicts one advantage of the cage 510 of the implant being able to deform. The ability of the implant 500 of the present invention to deform allows the profile of the cage to be transformed to a smaller profile. When thus transformed, the implant can be passed through a passage smaller than what is required by a traditional curved implant 600. As shown here, the deformed (compressed) implant 500 (including surface configurations) requires only 11.9 mm of space as opposed to the 12.7 mm of space required for a fixed, non-deformable, curved implant 600 of the same size.

[0041] In another embodiment of the present invention, a system is provided for forming a rigid structure between adjoining vertebrae in a patient. An example of such a system can be seen in FIG. 7. The system 700 includes an implant 500 of the present invention as shown in FIGS. 5A and 5B having surface configurations 590 for slidably attaching the implant 500 to an insertion guide 710. As shown in this embodiment, the flexible joints 560 of the implant may allow the cage 510 to conform to the shape of the insertion guide 710. In this case the cage 510 is deformed so as to have a smaller straight-sided profile when attached to a straight portion of the insertion guide 710.

[0042] In certain embodiments, such as shown in FIG. 7, the insertion guide 710 may have a curved end 720 to further assist in the insertion and positioning of the implant 510. In use, when the implant is slid along the insertion guide 710 in the direction of arrow 730, the flexible joints 560 of the implant 500 allow the implant to curve to conform to the curved end 720 of the insertion guide 710. The implant 500 may slide along the insertion guide 710 using an inserter configured to mate with opening 525.

[0043] FIG. 8 is a flow chart 800 of an exemplary method for fusing vertebrae of a patient. The method involves substantially the steps of providing a system of the present invention having an implant with surface configurations and an insertion guide (Step 820), inserting the insertion guide into the space between adjoining vertebrae (Step 830), and sliding the implant along the length of the insertion guide to position the implant in the space between adjoining vertebrae, (Step 840).

[0044] In some embodiments the method 800 may further include the steps of preparing the space between adjoining vertebrae (Step 810) as well as the step of removing the insertion guide after the implant has been inserted (Step 850).

[0045] The step of preparing the space between adjoining vertebrae (Step 810) may include removing the disk material between the vertebrae. Then the space between the vertebrae may be distracted to relieve pressure from neural elements and provide space for the entry of surgical tools and the insertion of the implant. Preferably the surgery including the insertion is performed using a MIS technique such a T-PLIF procedure.

[0046] Examples of this methodology using a T-PLIF technique can be seen in FIGS. 9A-D. Because MIS techniques such as T-PLIF procedures use a more limited access port or window 910, the insertion guide with a curved tip 720 is used to deform and guide the implant 500 so as to be inserted into and positioned in the space 920 between vertebrae as seen in FIGS. 9A.

[0047] In FIGS. 9B, the implant is slid along the length of the insertion guide 710. The implant 600 may be slid along the insertion guide 710 using an insertion tool (not shown) mated with the opening 525 configured to receive the insertion tool. Examples of suitable insertion devices and their use is discussed in W02005077288 A1.

[0048] In FIG. 9C, the insertion guide 710 is used to guide the implant 500 through the access window 910 and position the implant in location in the space 920 between vertebrae. The use of the curved tip 720 allows the implant 510 to be positioned at a desired angle, preferably around 45°, even though the angle of approach through the access window 910 may be closer to 35°.

[0049] Once in position, the insertion guide 710 may be removed and the implant allowed to transform or otherwise return to its rest state as seen in FIG. 9D. In certain embodiments this is performed by a spring incorporated or attached to the one or more flexible joints.

[0050] The apparatus and techniques of the present invention provide numerous advantages. The implant of the present invention can be used in minimally invasive surgery (MIS) wherein the cage can be deformed for easier insertion and positioning through a smaller access port. In certain embodiments, the cage may have surface configurations for use with an insertion guide. The cage of the implant can be deformed to conform to the shape of the guide which allows for curved guides which in turn provide more accurate insertion and positioning.

[0051] Although, the present invention has been described relative to an illustrative embodiment and application in spinal correction surgery. It should be apparent that the present invention may be used in any number of surgical procedures. Since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be interpreted as illustrative and not in a limiting sense.

[0052] It is also to be understood that the following claims are to cover all generic and specific features of the invention described herein, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.