# Patent

## Title
Expandable spinal fusion implants and related methods

## Abstract

A system and methods for promoting fusion across an intervertebral disc space, the system including an expandable system of spinal fusion implants wherein the system of implants is inserted into an intervertebral disc space in a smaller profile, collapsed insertion state, and then expanded anteriorly to an expanded state.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a continuation of U.S. patent application Ser. No. 13/665,787 filed Oct. 31, 2012, which claims the benefit of the filing date of U.S. Provisional Application No. 61/553,895 filed Oct. 31, 2011. The contents of U.S. application Ser. No. 13/665,787 and 61/553,895 are incorporated by reference in their entirety as a part of this application.


BACKGROUND
The present application relates to spinal fusion surgery, and more particularly, to a system for promoting fusion across an intervertebral disc space.



BRIEF DESCRIPTION OF THE DRAWINGS
Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein:
FIG. 1 is a top view of the expandable system of spinal fusion implants in its insertion state resting on the superior endplate of a vertebral body;
FIG. 2 is a top view of the expandable system of spinal fusion implants in its expanded state resting on the superior endplate of a vertebral body;
FIG. 3 is a top view of the expandable system of spinal fusion implants in its insertion state, prior to insertion into an intervertebral disc space;
FIG. 4a is a top view of the first implant of the expandable system of spinal fusion implants;
FIG. 4b is a posterior view of the second implant of the expandable system of spinal fusion implants;
FIG. 5 illustrates the expandable system of implants in its insertion state while attached to an inserter;
FIGS. 6-7 illustrate the method of expanding the system of implants once the system is inserted into the intervertebral disc space;
FIG. 8 is an anterior view of the expandable system of implants post-insertion and expansion within the intervertebral disc space;
FIG. 9 is a lateral view of the expandable system of implants post-insertion and expansion within the intervertebral disc space;
FIGS. 10-12 illustrate a method of expanding the system of implants according to an alternative embodiment.



DETAILED DESCRIPTION
Illustrative embodiments of the invention are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. The expandable system of spinal fusion implants disclosed herein boasts a variety of inventive features and components that warrant patent protection, both individually and in combination.
FIGS. 1-9 illustrate an expandable system of spinal fusion implants for promoting fusion across an intervertebral disc space according to an exemplary embodiment. The system 10 includes a first intervertebral implant 20 and a second intervertebral implant 30, dimensioned for insertion into an intervertebral disc space via a lateral approach. The expandable system of implants 10 is configured to be inserted into the intervertebral disc space in a smaller profile collapsed state (as shown in FIGS. 1 and 3) and manipulated into an expanded state (as shown in FIG. 2) within the intervertebral disc space. The first implant 20 and second implant 30 are constructed of any suitable biocompatible material. According to an exemplary embodiment, the system of implants 10 is constructed primarily of radiolucent material and comprises radiopaque markers to aid in the positioning of the implant during surgery or visualization of the implants in postoperative imaging.
The first implant 20 of the expandable system 10 has a posterior wall 22, an anterior wall 24, a leading end lateral wall 23, a trailing end lateral wall 25, a first bone contacting (top) surface 26 and a second bone contacting (bottom) surface 28. The second implant 30 of the expandable system 10 has a posterior wall 32, an anterior wall 34, a leading end lateral wall 33, a trailing end lateral wall 35, a first bone contacting (top) surface 36 and a second bone contacting (bottom) surface 38. The leading end walls 23, 33 and the trailing end walls 25, 35 may also be referred to as the distal end 23, 33 and proximal end 25, 35, respectively. The expandable system 10 is configured such that in the smaller profile insertion state, the anterior wall 24 of the first implant 20 is in close proximity with the posterior wall 32 of the second implant 30. Upon complete insertion into the intervertebral disc space in the insertion state, the second implant 30 is moved anteriorly; away from the first implant 20 such that the distance between the anterior wall 24 of the first implant 20 and the posterior wall 32 of the second implant 30 increases. Preferably, the anterior wall 34 of the second implant 30 rests on the hard cortical bone anterior rim of the inferior vertebral body V2 of the disc space when the system of implants 10 is in its fully expanded state.
According to one embodiment, the first implant 20 and second implant 30 each have a length extending between the respective proximal end 25, 35 and distal end 23, 33. It is contemplated that the length of each of the first implant 20 and second implant 30 may vary according to the needs of the user. For example, the length of the first implant may be dimensioned to span the width of the intervertebral disc space, such that the distal end 23 of the implant rests on the hard cortical bone rim on the distal lateral aspect of the inferior vertebral body V2 of the intervertebral disc space, and the proximal end 25 of the first implant 20 rests on the hard cortical bone of the proximal lateral aspect of the inferior vertebral body V2 of the intervertebral disc space. According to another exemplary embodiment, the length of the first implant 20 is not greater that the greatest depth dimension of the intervertebral disc space, as measured from the anterior most aspect of the inferior vertebral body V2 to the posterior aspect of the inferior vertebral body V2. The length of the second implant 30 may be equal to or less than the length of the first implant 20.
Similarly, the first implant 20 and second implant 30 each have a height extending between the top surface 26, 36 and the bottom surface 28, 38. The height of the first 20 and second implants 30 is dimensioned to restore the height of the intervertebral disc space to a healthy height. The height of the first implant 20 may be equal to, greater than or less than the height of the second implant 30, depending on the desired degree of kyphosis or lordosis at the treated intervertebral level. Further, the first implant 20 and second implant 30 each have a width extending from the anterior surface 24, 34 to the 9 posterior surface 22, 32. The width of the first implant 20 may be equal to, greater than or less than the width of the second implant 30.
According to an exemplary embodiment, the first implant further includes one or more first mating elements 27 for coupling the first implant 20 to the second implant 30 during insertion into the intervertebral disc space. In the exemplary embodiment shown in FIGS. 1-9, the first mating element 27 are male mating elements projecting from the anterior surface 24 of the first implant 20. According to this embodiment, the second implant 30 further includes one or more second mating elements 37 that complement the first mating element(s) 27 of the first implant 27. As shown in FIGS. 1-9, the second mating element 37 is a female mating element, dimensioned to receive therein the first mating element 27 of the first implant 20. However, it will be appreciated that the male mating element may instead extend from the second implant 30 and the complementary female mating element formed on the first implant 20. According to the exemplary embodiment, the first mating elements 27 of the first implant 20 are slidably received within the second mating elements 37 of the second implant 30, such that the alignment of the second implant 30 with respect to the first implant 20 is maintained during insertion of the system of implants 10 and while the second implant 20 is displaced anteriorly upon complete insertion of the system 10 into the intervertebral disc space.
FIGS. 5-7 illustrate the steps of a method of inserting the expandable system of spinal fusion implants 10 into an intervertebral disc space. According to the exemplary embodiment shown in FIGS. 5-7, the first implant 20 and second implant 30 are coupled via the first mating element 27 and the second mating element 37. The system of implants 10 is coupled to an insertion tool 40 on the distal end 25 of the first implant 20. The system of implants 20 is inserted into the intervertebral disc space in a smaller profile, collapsed state, as best shown in FIG. 5. Upon complete insertion into the disc space, a positioning tool 46 is used to displace the second implant 30 anteriorly within the disc space, away from the first implant 20. Displacement of the second implant 30 relative to the substantially stationary first implant 20 creates a greater distance between the anterior surface 24 of the first implant 20 and the posterior surface 32 of the second implant. The second implant 30 is displaced anteriorly until the anterior wall 34 of the second implant is resting on the cortical anterior rim of the inferior vertebral body V2, as best illustrated by FIGS. 2 and 9. According to an exemplary embodiment, the first implant 20 is positioned within the intervertebral disc space such that at least a portion of the posterior wall 22 of the first implant 20 is resting on the cortical posterior aspect of the inferior vertebral body V2. According to one exemplary embodiment, the space created between the first implant 20 and the second implant 30 after the anterior displacement of the second implant 30 is packed with bone growth promoting material. By way of example only, the bone growth enhancing material is autograft bone, allograft bone, bone graft substitute, a combination thereof, or any other suitable fusion enhancing scaffold.
While FIGS. 5-7 show the system of implants 10 coupled to a single inserter, an alternative embodiment is also contemplated wherein the system of implants 10 is coupled to two separate inserters, a first inserter coupled to the distal end of the first implant 20 and the second inserter coupled to the distal end 35 of the second implant 30. According to this alternative embodiment, the first 20 and second implants 30 may or may not be coupled via mating elements 27, 37.
FIGS. 10-12 illustrate an alternative embodiment of the expandable system of spinal fusion implants. This alternative embodiment includes all of the features described above and is inserted according to the same method described above, but further includes a flexible tether 48 coupled to the distal ends 23, 33 of the first 20 and second 30 implants. When the system of implants 10 is in the collapsed insertion state, there is slack in the flexible tether 48, as shown in FIGS. 10 and 11. As the system of implants 10 is expanded to its fully expanded state, the flexible tether 48 becomes increasingly taut. When the system of implants 10 reaches its fully expanded state, the flexible tether 48 is taut and acts as a wall connecting the distal ends 23, 33 of the first 20 and second implant 30 and a barrier to maintain bone growth enhancing material within the gap between the first 20 and second implants 30 when the system of implants 10 is in its fully expanded state and filled with bone growth enhancing material 44, as best shown in FIG. 12.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined herein.

## Claims

1. A method for promoting fusion across an intervertebral disc space, the method comprising the steps of:
accessing an intervertebral disc space via a lateral approach;
inserting an expandable system of spinal fusion implants in an insertion state into the intervertebral disc space, wherein said expandable system of spinal fusion implants comprises a first implant having a leading end and a trailing end, an anterior wall and a posterior wall, and a top surface and a bottom surface and a second implant having a leading end and a trailing end, an anterior wall and a posterior wall, and a top surface and a bottom surface, wherein the first implant and the second implant are equal in height, and wherein in the insertion state, the anterior wall of the first implant is adjacent to the posterior wall of the second implant;
displacing said second implant anteriorly relative to first implant within the intervertebral disc space until the expandable system of spinal fusion implants achieves a fully expanded state, wherein the anterior wall of the second implant rests on an anterior cortical rim of an inferior vertebral body adjacent the intervertebral disc space, thereby creating a gap between the first implant and the second implant.

2. The method of claim 1, further comprising the step of filling the gap between the first implant and the second implant with bone growth enhancing material.

3. The method of claim 1, wherein the second implant has a length extending between the leading end and the trailing end that is shorter than a length of the first implant.

4. The method of claim 1, wherein the first implant is coupled to the second implant during insertion.

5. The method of claim 1, wherein the system of implants is inserted simultaneously using a single insertion tool.

6. The method of claim 1, wherein the first implant is inserted with a first insertion tool and the second implant is inserted with a second insertion tool.