Expandable Fusion Device and Method of Installation Thereof

[0001] This patent application is a divisional application of U.S. patent application Ser. No. 12/875,818 filed on Sep. 3, 2010, which is incorporated by reference herein.

[0002] The present invention relates to the apparatus and method for promoting an intervertebral fusion, and more particularly relates to an expandable fusion device capable of being inserted between adjacent vertebrae to facilitate the fusion process.

[0003] A common procedure for handling pain associated with intervertebral discs that have become degenerated due to various factors such as trauma or aging is the use of intervertebral fusion devices for fusing one or more adjacent vertebral bodies. Generally, to fuse the adjacent vertebral bodies, the intervertebral disc is first partially or fully removed. An intervertebral fusion device is then typically inserted between neighboring vertebrae to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion.

[0004] There are a number of known conventional fusion devices and methodologies in the art for accomplishing the intervertebral fusion. These include screw and rod arrangements, solid bone implants, and fusion devices which include a cage or other implant mechanism which, typically, is packed with bone and/or bone growth inducing substances. These devices are implanted between adjacent vertebral bodies in order to fuse the vertebral bodies together, alleviating the associated pain.

[0005] However, there are drawbacks associated with the known conventional fusion devices and methodologies. For example, present methods for installing a conventional fusion device often require that the adjacent vertebral bodies be distracted to restore a diseased disc space to its normal or healthy height prior to implantation of the fusion device. In order to maintain this height once the fusion device is inserted, the fusion device is usually dimensioned larger in height than the initial distraction height. This difference in height can make it difficult for a surgeon to install the fusion device in the distracted intervertebral space.

[0006] As such, there exists a need for a fusion device capable of being installed inside an intervertebral disc space at a minimum to no distraction height and for a fusion device that can maintain a normal distance between adjacent vertebral bodies when implanted.

[0007] In an exemplary embodiment, the present invention provides an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion. In one embodiment, the fusion device includes a central ramp, a first endplate, and a second endplate. The central ramp may be capable of moving in a first direction to push the first and second endplates outwardly and into an unexpanded configuration. The expandable fusion device may be capable of being placed into the disc space down an endoscopic tube and then expanded into an expanded configuration.

[0008] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred or exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

[0065] The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

[0066] A spinal fusion is typically employed to eliminate pain caused by the motion of degenerated disk material. Upon successful fusion, a fusion device becomes permanently fixed within the intervertebral disc space. Looking at FIG. 1, an exemplary embodiment of an expandable fusion device 10 is shown between adjacent vertebral bodies 2 and 3. The fusion device 10 engages the endplates 4 and 5 of the adjacent vertebral bodies 2 and 3 and, in the installed position, maintains normal intervertebral disc spacing and restores spinal stability, thereby facilitating an intervertebral fusion. The expandable fusion device 10 can be manufactured from a number of materials including titanium, stainless steel, titanium alloys, non-titanium metallic alloys, polymeric materials, plastics, plastic composites, PEEK, ceramic, and elastic materials. In an embodiment, the expandable fusion device 10 can be configured to be placed down an endoscopic tube and into the disc space between the adjacent vertebral bodies 2 and 3.

[0067] In an exemplary embodiment, bone graft or similar bone growth inducing material can be introduced around and within the fusion device 10 to further promote and facilitate the intervertebral fusion. The fusion device 10, in one embodiment, is preferably packed with bone graft or similar bone growth inducing material to promote the growth of bone through and around the fusion device. Such bone graft may be packed between the endplates of the adjacent vertebral bodies prior to, subsequent to, or during implantation of the fusion device.

[0068] With reference to FIGS. 2-7, an embodiment of the fusion device 10 is shown. In an exemplary embodiment, the fusion device 10 includes a first endplate 14, a second endplate 16, a central ramp 18, and a driving ramp 260. In an embodiment, the expandable fusion device 10 can be configured to be placed down an endoscopic tube and into the disc space between the adjacent vertebral bodies 2 and 3. One or more components of the fusion device 10 may contain features, such as through bores, that facilitate placement down an endoscopic tube. In an embodiment, components of the fusion device 10 are placed down the endoscopic tube with assembly of the fusion device 10 in the disc space.

[0069] Although the following discussion relates to the second endplate 16, it should be understood that it also equally applies to the first endplate 14 as the second endplate 16 is substantially identical to the first endplate 14 in embodiments of the present invention. Turning now to FIGS. 2-7 and 10, in an exemplary embodiment, the second endplate 16 has a first end 39 and a second end 41. In the illustrated embodiment, the second endplate 16 further comprise an upper surface 40 connecting the first end 39 and the second end 41, and a lower surface 42 connecting the first end 39 and the second end 41. In an embodiment, the second endplate 16 further comprises a through opening 44, as seen on FIG. 11. The through opening 44, in an exemplary embodiment, is sized to receive bone graft or similar bone growth inducing material and further allow the bone graft or similar bone growth inducing material to be packed in the central opening in the central ramp 18.

[0070] As best seen in FIGS. 7 and 10, the lower surface 42 includes at least one extension 46 extending along at least a portion of the lower surface 42, in an embodiment. In an exemplary embodiment, the extension 46 can extend along a substantial portion of the lower surface 42, including, along the center of the lower surface 42. In the illustrated embodiment, the extension 46 includes a generally concave surface 47. The concave surface 47 can form a through bore with the corresponding concave surface 47 (not illustrated) of the first endplate 14, for example, when the device 10 is in an unexpanded configuration. In another exemplary embodiment, the extension 46 includes at least one ramped surface 48. In another exemplary embodiment, there are two ramped surfaces 48, 50 with the first ramped surface 48 facing the first end 39 and the second ramped surface facing the second end 41. In an embodiment, the first ramped surface 48 can be proximate the first end 39, and the second ramped surface 50 can be proximate the second end 41. It is contemplated that the slope of the ramped surfaces 48, 50 can be equal or can differ from each other. The effect of varying the slopes of the ramped surfaces 48, 50 is discussed below.

[0071] In one embodiment, the extension 46 can include features for securing the endplate 16 when the expandable fusion device 10 is in an expanded position. In an embodiment, the extension 46 includes one or more protuberances 49 extending from the lateral sides 51 of the extension. In the illustrated embodiment, there are two protuberances 49 extending from each of the lateral sides 51 with each of the sides 53 having one of the protuberances 49 extending from a lower portion of either end. As will be discussed in more detail below, the protuberances 49 can be figured to engage the central ramp 18 preventing and/or restricting longitudinal movement of the endplate 16 when the device 10 is in an expanded position.

[0072] As illustrated in FIGS. 2-5, in one embodiment, the upper surface 40 of the second endplate 16 is flat and generally planar to allow the upper surface 40 of the endplate 16 to engage with the adjacent vertebral body 2. Alternatively, as shown in FIG. 15, the upper surface 40 can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body 2. It is also contemplated that the upper surface 40 can be generally planar but includes a generally straight ramped surface or a curved ramped surface. The ramped surface allows for engagement with the adjacent vertebral body 2 in a lordotic fashion. While not illustrated, in an exemplary embodiment, the upper surface 40 includes texturing to aid in gripping the adjacent vertebral bodies. Although not limited to the following, the texturing can include teeth, ridges, friction increasing elements, keels, or gripping or purchasing projections.

[0073] Referring now to FIGS. 2-8, in an exemplary embodiment, the central ramp 18 has a first end 20, a second end 22, a first side portion 24 connecting the first end 20 and the second end 22, and a second side portion 26 (best seen on FIG. 5) on the opposing side of the central ramp 12 connecting the first end 20 and the second end 22. The first side portion 24 and the second side portion 26 may be curved, in an exemplary embodiment. The central ramp 18 further includes a lower end 28, which is sized to receive at least a portion of the first endplate 14, and an upper end 30, which is sized to receive at least a portion of the second endplate 16.

[0074] The first end 20 of the central ramp 18, in an exemplary embodiment, includes an opening 32. The opening 32 can be configured to receive an endoscopic tube in accordance with one or more embodiments. The first end 20 of the central ramp 18, in an exemplary embodiment, includes at least one angled surface 33, but can include multiple angled surfaces. The angled surface 33 can serve to distract the adjacent vertebral bodies when the fusion device 10 is inserted into an intervertebral space.

[0075] The second end 22 of the central ramp 18, in an exemplary embodiment, includes an opening 36. The opening 36 extends from the second end 22 of the central ramp 18 into a central guide 37 in the central ramp 18.

[0076] In an embodiment, the central ramp 18 further includes one or more ramped surfaces 33. As best seen in FIG. 8, the one or more ramped surfaces 33 positioned between the first side portion 24 and the second side portion 26 and between the central guide 37 and the second end 22. In an embodiment, the one or more ramped surfaces 33 face the second end 22 of the central ramp 18. In one embodiment, the central ramp 18 includes two ramped surfaces 33 with one of the ramped surfaces 33 being sloped upwardly and the other of the ramped surfaces 33 being sloped downwardly. The ramped surfaces 33 of the central ramp can be configured and dimensioned to engage the ramped surface 48 in each of the first and second endplates 14, 16.

[0077] Although the following discussion relates to the second side portion 26 of the central ramp 18, it should be understood that it also equally applies to the first side portion 24 in embodiments of the present invention. In the illustrated embodiment, the second side portion 26 includes an inner surface 27. In an embodiment, the second side portion 26 further includes a lower guide 35, a central guide 37, and an upper guide 38. In the illustrated embodiment, the lower guide 35, central guide 37, and the upper guide 38 extend out from the inner surface 27 from the second end 22 to the one or more ramped surfaces 31. In the illustrated embodiment, the second end 22 of the central ramp 18 further includes one or more guides 38. The guides 38 can serve to guide the translational movement of the first and second endplates 14, 16 with respect to the central ramp 18. For example, protuberances 49 on the second endplate 16 may be sized to be received between the central guide 37 and the upper guide 38. Protuberances 49 of the first endplate 16 may be sized to be received between the central guide 37 and the lower guide 35. A first slot 29 may be formed proximate the middle of the upper guide 38. A second slot 31 may be formed between end of the upper guide 38 and the one or more ramped surfaces 33. The protuberances 49 may be sized to be received within the first slot 29 and/or the second slot 31 when the device 10 is in the expanded position.

[0078] Referring now to FIGS. 4-7 and 9, the driving ramp 260 has a through bore 262. In an embodiment, the driving ramp 260 is generally wedge-shaped. As illustrated, the driving ramp 260 may comprise a wide end 56, a narrow end 58, a first side portion 60 connecting the wide end 56 and the narrow end 58, and a second side portion 62 connecting the wide end 56 and the narrow end 58. The driving ramp 260 further may comprise ramped surfaces, including an upper ramped surface 64 and an opposing lower ramped surface 66. The upper ramped surface 64 and the lower ramped surface 66 may be configured and dimensioned to engage the ramped surface 50 proximate the second end 41 in of the first and the second endplates 14, 16. The first and second side portions 60, 62 may each include grooves 68 that extend, for example, in a direction parallel to the longitudinal axis of the through bore 262. The grooves 68 may be sized to receive the central guide 37 on the interior surface 27 of each of the side portions 24, 26 of the central ramp 18. In this manner, the grooves 68 together with the central guide 37 can surface to guide the translational movement of the driving ramp 260 in the central ramp 18.

[0079] A method of installing the expandable fusion device 10 of FIG. 1 is now discussed in accordance with one embodiment of the present invention. Prior to insertion of the fusion device 10, the intervertebral space is prepared. In one method of installation, a discectomy is performed where the intervertebral disc, in its entirety, is removed. Alternatively, only a portion of the intervertebral disc can be removed. The endplates of the adjacent vertebral bodies 2, 3 are then scraped to create an exposed end surface for facilitating bone growth across the intervertebral space. One or more endoscopic tubes can then be inserted into the disc space. The expandable fusion device 10 can then be introduced into the intervertebral space down an endoscopic tube and seated in an appropriate position in the intervertebral disc space.

[0080] After the fusion device 10 has been inserted into the appropriate position in the intervertebral disc space, the fusion device 10 can then be expanded into the expanded position. To expand the fusion device 10, the driving ramp 260 may moved in a first direction with respect to the central ramp 18. Translational movement of the driving ramp 260 through the central ramp 18 may be guided by the central guide 37 on each of the first and second side portions 24, 26 of the central ramp 18. As the driving ramp 260 moves, the upper ramped surface 64 pushes against the ramped surface 50 proximate the second end 41 of the second endplate 16, and the lower ramped surface 66 pushes against the ramped surface 50 proximate the second end 41 of the first endplate 14. In addition, the ramped surfaces 33 in the central ramp 18 push against the ramped surface 48 proximate the first end 41 of the first and second endplates 14, 16. In this manner, the first and second endplates 14, 16 are pushed outwardly into an expanded configuration. As discussed above, the central ramp 16 includes locking features for securing the endplates 14, 16.

[0081] It should also be noted that the expansion of the endplates 14, 16 can be varied based on the differences in the dimensions of the ramped surfaces 48, 50 and the angled surfaces 62, 64. As best seen in FIG. 16, the endplates 14, 16 can be expanded in any of the following ways: straight rise expansion, straight rise expansion followed by a toggle into a lordotic expanded configuration, or a phase off straight rise into a lordotic expanded configuration.

[0082] Turning back to FIGS. 2-7, in the event the fusion device 10 needs to be repositioned or revised after being installed and expanded, the fusion device 10 can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device 10, the central ramp 18 is moved with respect to the central ramp 260 away from the central ramp 260. As the central ramp 18 moves, the ramped surfaces 33 in the central ramp 18 ride along the ramped surfaces 48 of the first and second endplates 14, 16 with the endplates 14, 16 moving inwardly into the unexpanded position.

[0083] With reference now to FIG. 17, fusion device 10 is shown with an exemplary embodiment of artificial endplates 100. Artificial endplates 100 allows the introduction of lordosis even when the endplates 14 and 16 of the fusion device 10 are generally planar. In one embodiment, the artificial endplates 100 have an upper surface 102 and a lower surface 104. The upper surfaces 102 of the artificial endplates 100 have at least one spike 106 to engage the adjacent vertebral bodies. The lower surfaces 104 have complementary texturing or engagement features on their surfaces to engage with the texturing or engagement features on the upper endplate 14 and the lower endplate 16 of the fusion device 10. In an exemplary embodiment, the upper surface 102 of the artificial endplates 100 have a generally convex profile and the lower surfaces 104 have a generally parallel profile to achieve lordosis. In another exemplary embodiment, fusion device 10 can be used with only one artificial endplate 100 to introduce lordosis even when the endplates 14 and 16 of the fusion device 10 are generally planar. The artificial endplate 100 can either engage endplate 14 or engage endplate 16 and function in the same manner as described above with respect to two artificial endplates 100.

[0084] With reference to FIGS. 11-14, an embodiment for placing an expandable fusion device 10 into an intervertebral disc space is illustrated. The expandable fusion device 10 can be introduced into the intervertebral space down an endoscopic tube utilizing a tool 70 that is attached to endplate 16, with the second endplate 16 being first placed down the tube with tool 70 and into the disc space, as seen in FIG. 11. After insertion of the second endplate 16, the first endplate 14 can be placed down the same endoscopic tube with tool 72 and into the disc space, as shown on FIG. 12. Following the first endplate 14, the central ramp 12 can be placed down the same endoscopic tube and into the disc space guided by tools 70 and 72, as shown on FIGS. 13 and 14.

[0085] Referring now to FIGS. 18-23, an alternative embodiment of the expandable fusion device 10 is shown. In an exemplary embodiment, the fusion device 10 includes a first endplate 14, a second endplate 16, a central ramp 18, and an actuator assembly 200. As will be discussed in more detail below, the actuator assembly 200 drives the central ramp 18 which forces apart the first and second endplates 14, 16 to place the expandable fusion device in an expanded position. One or more components of the fusion device 10 may contain features, such as through bores, that facilitate placement down an endoscopic tube. In an embodiment, components of the fusion device 10 are placed down the endoscopic tube with assembly of the fusion device 10 in the disc space.

[0086] Although the following discussion relates to the second endplate 16, it should be understood that it also equally applies to the first endplate 14 as the second endplate 16 is substantially identical to the first endplate 14 in embodiments of the present invention. With additional reference to FIG. 24, in an exemplary embodiment, the second endplate 16 has a first end 39 and a second end 41. In the illustrated embodiment, the second endplate 16 further comprise an upper surface 40 connecting the first end 39 and the second end 41, and a lower surface 42 connecting the first end 39 and the second end 41. While not illustrated, in an embodiment, the second endplate 16 further comprises a through opening. The through opening, in an exemplary embodiment, is sized to receive bone graft or similar bone growth inducing material.

[0087] In one embodiment, the upper surface 40 of the second endplate 16 is flat and generally planar to allow the upper surface 40 of the endplate 16 to engage with the adjacent vertebral body 2. Alternatively, as shown in FIG. 15, the upper surface 40 can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body 2. It is also contemplated that the upper surface 40 can be generally planar but includes a generally straight ramped surface or a curved ramped surface. The ramped surface allows for engagement with the adjacent vertebral body 2 in a lordotic fashion. While not illustrated, in an exemplary embodiment, the upper surface 40 includes texturing to aid in gripping the adjacent vertebral bodies. Although not limited to the following, the texturing can include teeth, ridges, friction increasing elements, keels, or gripping or purchasing projections.

[0088] In one embodiment, the second endplate 16 further comprises a first side portion 202 connecting the first end 39 and the second end 41, and a second side portion 204 connecting the first end 39 and the second end 41. In the illustrated embodiment, the first and second side portions 202, 204 are extensions from the lower surface 42. In an exemplary embodiment, the first and second side portions 202, 204 each include ramped surfaces 206, 208. In the illustrated embodiment, the ramped surfaces 206, 208 extend from the first end 39 of the second endplate 16 to bottom surfaces 210, 212 of each of the side portions 202, 204. In one embodiment, the ramped surfaces 206, 208 are forward facing in that the ramped surfaces 206, 208 face the first end 39 of the second endplate. As previously discussed, the slope of the ramped surfaces 206, 208 may be varied as desired for a particular application.

[0089] In an embodiment, the first and second side portions 202, 204 each comprise at least one protuberance 214. In an exemplary embodiment, the first and second side portions 202, 204 each comprise a first protuberance 214, a second protuberance 216, and a third protuberance 218. In one embodiment, the protuberances 214, 216, 218 extend from the interior surface 220 of the first and second side portions 202, 204. In an exemplary embodiment, the protuberances 214, 216, 218 extend at the lower side of the interior surface 220. As best seen in FIG. 24, the first and the second protuberances 214, 216 form a first slot 222, and the second and third protuberances 216, 218 form a second slot 224.

[0090] As best seen in FIG. 24, the lower surface 42 of the second endplate 16, in an embodiment, includes a central extension 224 extending along at least a portion of the lower surface. In the illustrated embodiment, the central extension 224 extends between the first and second side portions 202 and 204. In an exemplary embodiment, the central extension 224 can extend from the second end 41 of the endplate 16 to the central portion of the endplate. In one embodiment, the central extension 224 includes a generally concave surface 226 configured and dimensioned to form a through bore with the corresponding concave surface 226 (not illustrated) of the first endplate 14. The central extension 224 can further include, in an exemplary embodiment, a ramped surface 228. In the illustrated embodiment, the ramped surface 228 faces the first end 39 of the endplate 16. The ramped surface 228 can be at one end of the central extension 224. In an embodiment, the other end of the central extension 224 forms a stop 230. In the illustrated embodiment, the stop 230 is recessed from the second end 41 of the second endplate 16.

[0091] Referring to FIGS. 25-27, in an exemplary embodiment, the central ramp 18 includes a body portion 232 having a first end 234 and a second end 236. In an embodiment, the body portion 232 includes at least a first expansion portion 238. In an exemplary embodiment, the body portion 232 includes a first expansion portion 238 and a second expansion portion 240 extending from opposing sides of the body portion with each of the first and second expansion portions 238, 240 having a generally triangular cross-section. In one embodiment, the expansion portions 238, 240 each have angled surfaces 242, 244 configured and dimensioned to engage the ramped surfaces 206, 208 of the first and second endplates 14, 16 and force apart the first and second endplates 14, 16. In an embodiment, the engagement between the angled surfaces 242, 244 of the expansion portions 238, 240 with the ramped surfaces 206, 208 of the first and second endplates 14, 16 may be described as a dovetail connection.

[0092] The second end 236 of the central ramp 18, in an exemplary embodiment, includes opposing angled surfaces 246. The angled surfaces 246 can be configured and dimensioned to engage the ramped surface 228 in the central extension 224 in each of the first and second endplates 14, 16. In other words, one of the angled surfaces 246 can be upwardly facing and configured, in one embodiment, to engage the ramped surface 228 in the central extension 224 in the second endplate 16. In an embodiment, the engagement between the angled surfaces 246 of the second end 236 of the central ramp 18 with the ramped surface 228 in the first and second endplates 14, 16 may be described as a dovetail connection.

[0093] The second end 236, in an exemplary embodiment, can further include an extension 252. In the illustrated embodiment, the extension 252 is generally cylindrical in shape with a through bore 254 extending longitudinally therethrough. In one embodiment, the extension 252 can include a beveled end 256. While not illustrated, at least a portion of the extension 252 can be threaded.

[0094] Referring still to FIGS. 25-27, the central ramp 18 can further include features for securing the first and second endplates 14, 16 when the expandable fusion device 10 is in an expanded position. In an embodiment, the body portion 232 of the central ramp 18 includes one or more protuberances 248, 250 extending from opposing sides of the body portion 232. As illustrated, the protuberances 248, 250, in one embodiment, can be spaced along the body portion 232. In an exemplary embodiment, the protuberances 248, 250 can be configured and dimensioned for insertion into the corresponding slots 222, 224 in the first and second endplates 14, 16 when the device 10 is in an expanded position, as best seen in FIGS. 19 and 21. The protuberances 248, 250 can engage the endplates 14, 16 preventing and/or restricting movement of the endplates 14, 16 with respect to the central ramp 18 after expansion of the device 10.

[0095] With reference to FIGS. 20-23, in an exemplary embodiment, the actuator assembly 200 has a flanged end 253 configured and dimensioned to engage the stop 232 in the central extension 224 of the first and the second endplates 14, 16. In an embodiment, the actuator assembly 200 further includes an extension 254 that extends from the flanged end 253. In a further embodiment, the actuator assembly 200 includes a threaded hole 256 that extends through the actuator assembly 200. It should be understood that, while the threaded hole 256 in the actuator assembly 200 is referred to as threaded, the threaded hole 256 may only be partially threaded in accordance with one embodiment. In an exemplary embodiment, the threaded hole 256 is configured and dimensioned to threadingly receive the extension 252 of the central ramp 18.

[0096] With additional reference to FIGS. 28-32, a method of installing the expandable fusion device 10 of FIGS. 18-27 is now discussed in accordance with one embodiment of the present invention. Prior to insertion of the fusion device, the disc space may be prepared as described above and then one or more endoscopic tubes may then inserted into the disc space. The expandable fusion device 10 can then be inserted into and seated in the appropriate position in the intervertebral disc space, as best seen in FIGS. 28-32. The expandable fusion device 10 can be introduced into the intervertebral space down an endoscopic tube (not illustrated), with the central ramp 18 being first placed down the tube and into the disc space, as seen in FIG. 28. After insertion of the central ramp, the first endplate 14 can be placed down an endoscopic tube, as shown on FIG. 29, followed by insertion of the second endplate 16, as shown on FIG. 30. After the second endplate 16, the actuator assembly 200 can then be inserted to complete assembly of the device 10, as best seen in FIG. 31.

[0097] After the fusion device 10 has been inserted into and assembled in the appropriate position in the intervertebral disc space, the fusion device 10 can then be expanded into the expanded position. To expand the fusion device 10, the actuator assembly 200 can be rotated. As discussed above, the actuator assembly 200 is in threaded engagement with the extension 250 of the central ramp 18. Thus, as the actuator assembly 200 is rotated in a first direction, the central ramp 18 moves toward the flanged end 253 of the actuator assembly 200. In another exemplary embodiment, the actuator assembly 200 can be moved in a linear direction with the ratchet teeth as means for controlling the movement of the central ramp 18. As the central ramp 18 moves, the angled surfaces 242, 244 in the expansion portions 238, 240 of the central ramp 18 push against the ramped surfaces 206, 208 in the first and second side portions 202, 204 of the first and second endplates 14, 16. In addition, the angled surfaces 246 in the second end 236 of the central ramp 18 also push against the ramped surfaces 228 in the central extension 224 of each of the endplates 14, 16. This is best seen in FIGS. 22-23.

[0098] Since the expansion of the fusion device 10 is actuated by a rotational input, the expansion of the fusion device 10 is infinite. In other words, the endplates 14, 16 can be expanded to an infinite number of heights dependent on the rotational advancement of the actuator assembly 200. As discussed above, the central ramp 16 includes locking features for securing the endplates 14, 16.

[0099] In the event the fusion device 10 needs to be repositioned or revised after being installed and expanded, the fusion device 10 can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device 10, the actuator assembly 200 can be rotated in a second direction. As discussed above, actuator assembly 200 is in threaded engagement with the extension 250 of the central ramp 18; thus, as the actuator assembly 200 is rotated in a second direction, opposite the first direction, the central ramp 18 moves with respect to the actuator assembly 200 and the first and second endplates 14, 16 away from the flanged end 253. As the central ramp 18 moves, the first and second endplates are pulled inwardly into the unexpanded position.

[0100] Referring now to FIGS. 33-38, an alternative embodiment of the expandable fusion device 10 is shown. In the illustrated embodiment, the fusion device includes a first endplate 14, a second endplate 16, a central ramp 18, and an actuator assembly 200. The fusion device 10 of FIGS. 33-38 and its individual components are similar to the device 10 illustrated on FIGS. 18-23 with several modifications. The modifications to the device 10 will be described in turn below.

[0101] Although the following discussion relates to the second endplate 16, it should be understood that it also equally applies to the first endplate 14 as the second endplate 16 is substantially identical to the first endplate 14 in embodiments of the present invention. With additional reference to FIG. 39, in an exemplary embodiment, the lower surface 42 of the second endplate 16 has been modified. In one embodiment, the central extension 224 extending from the lower surface 42 has been modified to include a second ramped surface 258 rather than a stop. In an exemplary embodiment, the second ramped surface 258 faces the second end 41 of the second endplate 16. In contrast, ramped surface 228 on the central extension 228 faces the first end 39 of the second endplate. The concave surface 228 connects the ramped surface 228 and the second ramped surface 258.

[0102] With reference to FIGS. 35-38, in an exemplary embodiment, the actuator assembly 200 has been modified to further include a driving ramp 260. In the illustrated embodiment, the driving ramp 260 has a through bore 262 through which the extension 254 extends. In an embodiment, the driving ramp 260 is generally wedge-shaped. As illustrated, the driving ramp 260 may comprise a blunt end 264 in engagement with the flanged end 253. In an exemplary embodiment, the driving ramp 260 further comprises angled surfaces 266 configured and dimensioned to engage the second ramped surface 258 of each of the endplates 14, 16 and force apart the first and second endplates 14, 16.

[0103] Referring now to FIGS. 40-44, an alternative embodiment of the expandable fusion device 10 is shown. In the illustrated embodiment, the fusion device 10 includes a first endplate 14, a second endplate 16, a central ramp 18, an actuator assembly 200, and a driving ramp 300. As will be discussed in more detail below, the actuator assembly 200 functions, in an embodiment, to pull the central ramp 18 and the driving ramp 300 together, which forces apart the first and second endplates 14, 16. In an embodiment, the expandable fusion device

[0104] Although the following discussion relates to the first endplate 14, it should be understood that it also equally applies to the second endplate 16 as the second endplate 16 is substantially identical to the first endplate 14 in embodiments of the present invention. With reference to FIGS. 40-45, in an exemplary embodiment, the first endplate 14 has a first end 39 and a second end 41. In the illustrated embodiment, the first endplate 14 further comprises an upper surface 40 connecting the first end 39 and the second end 41, and a lower surface 42 connecting the first end 39 and the second end 41. While not illustrated, in an embodiment, the first endplate 14 may comprise further comprises a through opening. The through opening, in an exemplary embodiment, is sized to receive bone graft or similar bone growth inducing material.

[0105] In one embodiment, the upper surface 40 of the first endplate 14 is flat and generally planar to allow the upper surface 40 of the endplate 14 to engage with the adjacent vertebral body 2. Alternatively, as shown in FIG. 15, the upper surface 40 can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body 2. It is also contemplated that the upper surface 40 can be generally planar but includes a generally straight ramped surface or a curved ramped surface. The ramped surface allows for engagement with the adjacent vertebral body 2 in a lordotic fashion. While not illustrated, in an exemplary embodiment, the upper surface 40 includes texturing to aid in gripping the adjacent vertebral bodies. Although not limited to the following, the texturing can include teeth, ridges, friction increasing elements, keels, or gripping or purchasing projections.

[0106] In one embodiment, the first endplate 14 further comprises a first side portion 202 connecting the first end 39 and the second end 41, and a second side portion 204 connecting the first end 39 and the second end 41. In the illustrated embodiment, the first and second side portions 202, 204 are extensions from the lower surface 42. In an embodiment, the first and second side portions each have an interior surface 302 and an exterior surface 304. In an exemplary embodiment, the first and second side portions 202, 204 each include one or more ramped portions. In the illustrated embodiment, the first and second side portions 202, 204 include first ramped portions 306, 308 at the first end 39 of the endplate 14 and second ramped portions 310, 312 at the second end 41 of the endplate. The first and second side portions 202, 204 each can include a bridge portion 314 connecting the first ramped portions 306, 308 and the second ramped portions 310, 312. In an embodiment, the first ramped portions 306, 308 abut the exterior surface 304 of the respective side portions 202, 204, and the second ramped portions 310, 312 abut the interior surface 302 of the respective side portions 202, 204. As illustrated, the first ramped portions 306, 308 may include tongue portions 316, 318 with the tongue portions 316, 318 extending in an oblique direction with respect to the upper surface 40 of the endplate 14. As further illustrated, the second ramped portions 310, 312 may include tongue portions 320, 322 that extend in an oblique direction with respect to the upper surface 40 of the endplate 14.

[0107] As best seen in FIG. 45, the lower surface 42 of the second endplate 16, in an embodiment, includes a central extension 224 extending along at least a portion of the lower surface. In the illustrated embodiment, the central extension 224 extends between the first and second side portions 202 and 204. In an exemplary embodiment, the central extension 224 can extend generally between the first ramped portions 306, 308 and the second ramped portions 310, 312. In one embodiment, the central extension 224 includes a generally concave surface 226 configured and dimensioned to form a through bore with the corresponding concave surface 226 (not illustrated) of the second endplate 16.

[0108] With reference to FIGS. 43 and 44, the actuator assembly 200 includes a head portion 324, a rod receiving extension 326, and a connecting portion 328 that connecting portions that connects the head portion 324 and the rod receiving extension 326. As illustrated, the head portion 324 may include one or more instrument gripping features 330 that can allow it to be turned by a suitable instrument. In addition, the head portion 324 has a larger diameter than the other components of the actuator assembly 200 to provide a contact surface with the driving ramp 300. In the illustrated embodiment, the head portion 324 includes a rim 332 that provides a surface for contacting the driving ramp 300. As can be seen in FIG. 44, in an exemplary embodiment, the rod receiving extension 326 includes an opening sized and dimensioned to receive the extension 336 of the central ramp 18. In an embodiment, the rod receiving extension 326 includes threading for threadingly engaging the extension 336. In another embodiment, the rod receiving extension 326 includes ratchet teeth for engaging the extension 336. In the illustrated embodiment, the head portion 324 and the rod receiving extension 326 are connected by connecting portion 328 which can be generally cylindrical in shape.

[0109] With reference to FIGS. 43, 44, and 46, the central ramp 18 includes expansion portion 334 and extension 336. As best seen in FIG. 46, the expansion portion 334 may include an upper portion 338 and side portions 340, 342 that extend down from the upper portion 338. In an embodiment, each of the side portions 340, 342 include dual, overlapping ramped portions. For example, side portions 340, 342 each include a first ramped portion 344 that overlaps a second ramped portion 346. In the illustrated embodiment, the first ramped portion 344 faces the extension 336 while the second ramped portion 344 faces away from the extension 336. In one embodiment, angled grooves 348, 350 are formed in each of the first and second ramped portions 344, 346. In another embodiment, the angled grooves 348, 350 are sized to receive the corresponding tongues 316, 318, 320, 322 in the first and second endplates with angled grooves 348 receiving tongues 320, 322 in the second endplate 16 and angled grooves 350 receiving tongues 316, 318 in the first endplate 14. Although the device 10 is described with tongues 316, 318, 320, 322 on the endplates 14, 16 and angled grooves 348, 350 on the central ramp 18, it should be understood that that device 10 can also be configured with grooves on the endplates 14, 16 and tongues on the central ramp 18, in accordance with one embodiment of the present invention.

[0110] In an exemplary embodiment, the extension 336 is sized to be received within the rod receiving extension 326 of the actuator assembly 200. In one embodiment, the extension 336 has threading with the extension 336 being threadingly received within the rod receiving extension 326. In another embodiment, the extension 336 has ratchet teeth with the extension 336 being ratcheted into the rod receiving extension 336. In an embodiment, the extension 336 include nose 352 at the end of the extension 336.

[0111] With reference to FIGS. 47-49, in an exemplary embodiment, the driving ramp 300 includes an upper portion 354 having an upper surface 356 and an oblique surface 358. In an embodiment, the driving ramp 300 further includes side portions 360, 362 that extend from the upper portion 354 connecting the upper portion 354 with the lower portion 364 of the driving ramp 300. As best seen in FIGS. 48-49, the driving ramp 300 further includes a bore 366, in an exemplary embodiment, sized to receive the connection portion 328 of the actuator assembly 200. In one embodiment, the driving ramp 300 moves along the connection portion 328 when the actuator assembly 200 is pushing the driving ramp 300. In an exemplary embodiment, the driving ramp 300 further includes contact surface 368 that engages the rim 332 of the head portion 324 of the actuator assembly 200. In the illustrated embodiment, the contact surface 368 has a generally annular shape.

[0112] In an exemplary embodiment, the side portions 360, 362 of the driving ramp 300 each include overlapping ramped portions. For example, the side portions 360, 362 each include first ramped portions 370 that overlap second ramped portions 372. In the illustrated embodiment, the first ramped portions 370 face central ramp 18 while the second ramped portions 372 face the opposite direction. In one embodiment, angled grooves 374, 376 are formed in each of the first and second ramped portions 370, 372. FIG. 48 is a perspective view of the driving ramp 300 that shows the top ends of the angled grooves 374 in ramped portions 370. FIG. 49 is a perspective view of the driving ramp 300 that shows the top ends of the angled grooves 376 in ramped portions 372. In an exemplary embodiment, the angled grooves 374, 376 are sized to receive corresponding tongues 316, 318, 320, 322 in the first and second endplates 14, 16 with angled grooves 370 receiving tongues 316, 318 in the second endplate 16 and angled grooves 372 receiving tongues 320, 322 in the first endplate 14. Although the device 10 is described with tongues 316, 318, 320, 322 in the first and second endplates 14, 16 and angled grooves 370, 372, 374, 376 on the driving ramp 300, it should be understood that that device 10 can also be configured with grooves on the second endplate 16 and tongues on the driving ramp 300, in accordance with one embodiment of the present invention.

[0113] Turning now to FIGS. 40-42, a method of installing the expandable fusion device 10 of FIGS. 40-49 is now discussed in accordance with one embodiment of the present invention. Prior to insertion of the fusion device, the disc space may be prepared as described above. The expandable fusion device 10 can then be inserted into and seated in the appropriate position in the intervertebral disc space. The expandable fusion device 10 is then introduced into the intervertebral space, with the end having the expansion portion 334 of the central ramp 18 being inserted. In an exemplary method, the fusion device 10 is in the unexpanded position when introduced into the intervertebral space. In an exemplary method, the intervertebral space may be distracted prior to insertion of the fusion device 10. The distraction provide some benefits by providing greater access to the surgical site making removal of the intervertebral disc easier and making scraping of the endplates of the vertebral bodies 2, 3 easier.

[0114] With the fusion device 10 inserted into and seated in the appropriate position in the intervertebral disc space, the fusion device can then expanded into the expanded position, as best seen in FIG. 42. To expand the fusion device 10, an instrument is engaged with the head portion 324 of the actuator assembly 200. The instrument is used to rotate actuator assembly 200. As discussed above, actuator assembly 200 is threadingly engaged with the extension 336 of the central ramp 18; thus, as the actuator assembly 200 is rotated in a first direction, the central ramp 18 is pulled toward the actuator assembly 200. In an exemplary embodiment, the actuator assembly 200 is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuator assembly 200 and the central ramp 18. As the central ramp 18 is pulled towards the actuator assembly 200, the first ramped portions 344 of the central ramp 18 push against the second ramped portions 310, 312 of the second endplate 16 and the second ramped portions 346 of the central ramp 18 push against first ramped portions 306, 308 of the first endplate 14. In this manner, the central ramp 18 acts to push the endplates 14, 16 outwardly into the expanded position. This can best be seen in FIGS. 40-42. As the endplates 14, 16 move outwardly the tongues 316, 318, 320, 322 in the endplates 14, 16 ride in the angled grooves 348, 350 with the tongues 320, 322 in the second endplate 16 riding in angled grooves 348 and the tongues 316, 318 in the first endplate 14 riding in angled grooves 350.

[0115] As discussed above, the actuator assembly 200 also engages driving ramp 300; thus, as the actuator assembly 200 is rotated in a first direction, the actuator assembly 200 pushes the driving ramp 300 towards the central ramp 18 in a linear direction. As the driving ramp 300 is pushed towards the central ramp 18, the first ramped portions 370 of the driving ramp 300 push against the first ramped portions 306, 308 of the second endplate 16 and the second ramped portions 372 of the driving ramp 300 push against the second ramped portions 310, 312 of the first endplate 14. In this manner, the driving ramp 300 also acts to push the endplates 14, 16 outwardly into the expanded position. This can best be seen in FIGS. 40-42. As the endplates 14, 16 move outwardly the tongues 316, 318, 320, 322 in the endplates 14, 16 ride in the angled grooves 370, 372 with the tongues 316, 318 in the second endplate 16 riding in angled grooves 370 and the tongues 320, 322 in the first endplate 14 riding in angled grooves 372.

[0116] Since the expansion of the fusion device 10 is actuated by a rotational input, the expansion of the fusion device 10 is infinite. In other words, the endplates 14, 16 can be expanded to an infinite number of heights dependent on the rotational advancement of the actuator assembly 200.

[0117] Referring now to FIGS. 50-54, an alternative embodiment of the expandable fusion device 10 is shown. In the illustrated embodiment, the fusion device 10 includes a first endplate 14, a second endplate 16, a central ramp 18, an actuator assembly 200, and a driving ramp 300. As will be discussed in more detail below, the actuator assembly 200 functions, in an embodiment, to pull the central ramp 18 and the driving ramp 300 together, which forces apart the first and second endplates 14, 16. In an embodiment, the expandable fusion device may contain features, such as a through bore, that facilitate placement down an endoscopic tube. In an embodiment, the assembled fusion device 10 may be placed down the endoscopic tube and then expanded.

[0118] Although the following discussion relates to the first endplate 14, it should be understood that it also equally applies to the second endplate 16 as the second endplate 16 is substantially identical to the first endplate 14 in embodiments of the present invention. It should be understood that, in an embodiment, the first endplate 14 is configured to interlock with the second endplate 16. With additional reference to FIG. 55, in an exemplary embodiment, the first endplate 14 has a first end 39 and a second end 41. As illustrated, the first end 39 may be wider than the second end 41. In the illustrated embodiment, the first endplate 14 further comprises an upper surface 40 connecting the first end 39 and the second end 41, and a lower surface 42 connecting the first end 39 and the second end 41. As best seen in FIG. 54, the lower surface 42 can be curved concavely such that the first and second endplates 14, 16 form a through bore when the device 10 is in a closed position. In an embodiment, the first endplate 14 may comprise a through opening 44. The through opening 44, in an exemplary embodiment, is sized to receive bone graft or similar bone growth inducing material.

[0119] In one embodiment, the upper surface 40 of the first endplate 14 is flat and generally planar to allow the upper surface 40 of the endplate 14 to engage with the adjacent vertebral body 2. Alternatively, as shown in FIG. 15, the upper surface 40 can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body 2. It is also contemplated that the upper surface 40 can be generally planar but includes a generally straight ramped surface or a curved ramped surface. The ramped surface allows for engagement with the adjacent vertebral body 2 in a lordotic fashion. As illustrated, in an exemplary embodiment, the upper surface 40 includes texturing to aid in gripping the adjacent vertebral bodies. For example, the upper surface 40 may further comprise texturing 400 to engage the adjacent vertebral bodies. Although not limited to the following, the texturing can include teeth, ridges, friction increasing elements, keels, or gripping or purchasing projections.

[0120] In one embodiment, the first endplate 14 further comprises a first side portion 202 connecting the first end 39 and the second end 41, and a second side portion 204 connecting the first end 39 and the second end 41. In the illustrated embodiment, the first and second side portions 202, 204 are extensions from the lower surface 42. In an embodiment, the first and second side portions 202, 204 each include an interior surface 302 and an exterior surface 304. In an embodiment, the first end 39 of the first endplate 14 is generally designed and configured to fit over the second end 41 of the second endplate 16 when the device 10 is in a closed position. As illustrated, the first and second side portions 202, 204 each may include first ramped portions 306, 308, second ramped portions 310, 312, and/or central ramped portion 402.

[0121] In an embodiment, the first ramped portions 306, 308 are proximate the first end 39 of the endplate 14. In accordance with embodiment of the present invention, the first ramped portions 306, 308 of the first endplate 14 are generally designed and configured to fit over the second ramped portions 310, 312 of the second endplate 16 when the device 10 is in a closed position. In an exemplary embodiment, the first ramped portions 306, 308 generally face the first end 39 and can extend in an oblique direction with respect to the upper surface 40, for example. As illustrated, the first ramped portions 306, 308 may include tongue portions 316, 318 extending in an oblique direction with respect to the upper surface 40 of the endplate 14.

[0122] In an embodiment, the second ramped portions 310, 312 are proximate the second end 41 of the endplate 14. In an exemplary embodiment, the second ramped portions 310, 312 can extend in an oblique direction with respect to the upper surface 40 and generally face the second end 41. The first and second side portions 202, 204, in an embodiment, each can include a bridge portion 314 connecting the first ramped portions 306, 308 and the second ramped portions 310, 312. As further illustrated, the second ramped portions 310, 312 may include tongue portions 320, 322 that extend in an oblique direction with respect to the upper surface 40 of the endplate 14.

[0123] In an embodiment, the endplate 14 further may include a central ramped portion 402 proximate the bridge portion 314. In the illustrated embodiment, the endplate 14 includes a central ramped portion 402 proximate the bridge portion 314 of the second side portion 204. In an exemplary embodiment, the central ramped portion 402 can extend in an oblique direction with respect to the upper surface 40 and face the first end 39 of the endplate 14. As illustrated, the first ramped portions 306, 308 may include tongue portions 316, 318 with the tongue portions 316, 318 extending in an oblique direction with respect to the upper surface 40 of the endplate 14.

[0124] With reference to FIGS. 50-52 and 54, in an embodiment, the actuator assembly 200 includes a head portion 324, an extension 404, and a through bore 406 that extends longitudinally through the actuator assembly 200. As illustrated, the head portion 324 may include one or more instrument gripping features 330 that can allow it to be turned by a suitable instrument. In addition, the head portion 324 has a larger diameter than the other components of the actuator assembly 200 to provide a contact surface with the driving ramp 300. In the illustrated embodiment, the head portion 324 includes a rim 332 that provides a surface for contacting the driving ramp 300. In an embodiment, the extension 404 is a generally rod-like extension. In another embodiment, the extension 404 includes ratchet teeth for engaging the extension 336.

[0125] With reference to FIGS. 51, 52, and 56, the central ramp 18 has a first end 408 and a second end 410. In an embodiment, the central ramp 18 includes a first expansion portion 412, a second expansion portion 414, a rod-receiving extension 416, and a through bore 418 that extends longitudinally through the central ramp 18. In an exemplary embodiment, first expansion portion 412 can be proximate the first end 408 of the central ramp 18. As best seen in FIG. 56, the first expansion portion 412 may include side portions 420, 422. In an embodiment, each of the side portions 420, 422 includes dual, overlapping ramped portions that extend in oblique directions with respect to the through bore 418. For example, side portions 420, 422 each include a first ramped portion 424 that overlaps a second ramped portion 426. In the illustrated embodiment, the first ramped portion 424 faces the rod-receiving extension 416 while the second ramped portion 426 faces the opposite direction. In one embodiment, angled grooves 428, 430 are formed in each of the first and second ramped portions 424, 426. In an exemplary embodiment, the angled grooves 428, 430 are sized to receive the corresponding tongues 316, 318, 320, 322 in the first and second endplates 14, 16 with angled grooves 428 receiving tongues 320, 322 in the second endplate 16 and angled grooves 430 receiving tongues 316, 318 in the first endplate 14. Although the device 10 is described with tongues 316, 318, 320, 322 on the endplates 14, 16 and angled grooves 428, 430 on the central ramp 18, it should be understood that that device 10 can also be configured with grooves on the endplates 14, 16 and tongues on the central ramp 18, in accordance with one embodiment of the present invention.

[0126] In an embodiment, the second expansion portion 414 is located on the rod-receiving extension 416 between the first end 408 and the second end 410 of the central ramp 18. In an exemplary embodiment, the second expansion portion 414 includes central ramped portions 432. In one embodiment, the second expansion portion 414 includes two central ramped portions 432 on opposite sides of the rod-receiving extension 416. In an exemplary embodiment, the central ramped portions 424 extend in an oblique direction with respect to the through bore 418 and face the second end 410 of the central ramp 18.

[0127] The rod-receiving extension 416 extends from the first expansion portion 412 and has an opening 434 at the second end of the central ramp 18. In an embodiment, the rod-receiving extension 416 is sized and configured to receive the extension 404 of the actuator assembly 200. In an embodiment, the rod-receiving extension 416 has threading with the rod-receiving extension 416 threadingly receiving extension 404 of the actuator assembly 200. In another embodiment, the rod-receiving extension 416 has ratchet teeth with the extension 404 being ratcheted into the rod-receiving extension 416.

[0128] With reference to FIGS. 50-52 and 57, in an exemplary embodiment, the driving ramp 300 includes an upper portion 354 having an upper surface 356 and an oblique surface 358. In an embodiment, the driving ramp 300 further includes a bore 366, in an exemplary embodiment, sized to receive the extension 404 of the actuator assembly 200. In the illustrated, embodiment, the upper portion 354 has a hole 436 that extends through the upper surface 356 to the bore 366. Set screw 438 may be inserted through the hole 436 to secure the driving ramp 300 to the actuator assembly 200. In one embodiment, the driving ramp 300 further includes contact surface 368 that engages the rim 332 of the head portion 324 of the actuator assembly 200. In the illustrated embodiment, the contact surface 368 has a generally annular shape.

[0129] In an embodiment, the driving ramp 300 further includes side portions 360, 362 that extend from the upper portion 354 connecting the upper portion 354 with the lower portion 364 of the driving ramp 300. In an exemplary embodiment, the side portions 360, 362 of the driving ramp 300 each include a ramped portion 438. In the illustrated embodiment, the ramped portion 438 faces central ramp 300. In an embodiment, the ramped portion 438 is configured and dimensioned to engage the ramped portions 306, 308 at the first end 39 of the second endplate 16. In one embodiment, angled grooves 440 are formed in the ramped portions 316, 318. In an exemplary embodiment, the angled grooves 440 are sized to receive the corresponding tongues 316, 318 in the second endplate 16. Although the device 10 is described with tongues 316, 318 on the second endplate 16 and angled grooves 440 on the driving ramp 300, it should be understood that that device 10 can also be configured with grooves on the second endplate 16 and tongues on the driving ramp 300, in accordance with one embodiment of the present invention.

[0130] A method of installing the expandable fusion device 10 of FIGS. 50-57 is now discussed in accordance with one embodiment of the present invention. Prior to insertion of the fusion device, the disc space may be prepared as described above. The expandable fusion device 10 can then be inserted into and seated in the appropriate position in the intervertebral disc space. In an embodiment, the device 10 is assembled prior to insertion. The expandable fusion device 10 can be introduced into the intervertebral space, with the end having the first end 408 of the central ramp 18 being inserted. In an exemplary method, the fusion device 10 is in the unexpanded position when introduced into the intervertebral space. In an exemplary method, the intervertebral space may be distracted prior to insertion of the fusion device 10. The distraction provide some benefits by providing greater access to the surgical site making removal of the intervertebral disc easier and making scraping of the endplates of the vertebral bodies 2, 3 easier.

[0131] With the fusion device 10 inserted into and seated in the appropriate position in the intervertebral disc space, the fusion device can then expand into the expanded position. To expand the fusion device 10, an instrument is engaged with the head portion 324 of the actuator assembly 200. The instrument is used to rotate actuator assembly 200. As discussed above, actuator assembly 200 is threadingly engaged with the rod receiving extension 416 of the central ramp 18; thus, as the actuator assembly 200 is rotated in a first direction, the central ramp 18 is pulled toward the actuator assembly 200. In an exemplary embodiment, the actuator assembly 200 is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuator assembly 200 and the central ramp 18.

[0132] As the central ramp space 18 is pulled towards the actuator assembly 200, the central ramp 18 acts to push endplates 14, 16 outwardly into the expanded position. By way of example, the first ramped portions 424, second ramped portions 426, and central ramped portions 432 push against the corresponding ramped portions in the first and second endplates 14, 16. The first ramped portions 424 in the first expansion portion 412 of the central ramp 18 push against the second ramped portions 310, 312 of the second endplate 16 with the corresponding tongues 320, 322 in the second ramped portions 310, 312 of the second endplate 16 riding in angled grooves 428 in the first ramped portions 424 in the first expansion portion 412. The second ramped portions 426 in the first expansion portion 412 push against the first ramped portions 316, 318 of the first endplate 14 with the corresponding tongues 316, 318 in first ramped portions 316, 318 of the first endplate 14 riding in angled grooves 430 in the second ramped portions 426 in the first expansion portion 412. The central ramped portions 432 in the second expansion portion 414 push against the central ramped portion 402 in the first and second endplates 14, 16.

[0133] As discussed above, the actuator assembly 200 also engages driving ramp 300; thus, as the actuator assembly 200 is rotated in a first direction, the actuator assembly 200 pushes the driving ramp 300 towards the central ramp 18 in a linear direction. As the driving ramp 300 is pushed towards the central ramp 18, the driving ramp 300 also acts to push the endplates 14, 16 outwardly into the expanded position. By way of example, the ramped portions 438 of the driving ramp 300 push against ramped portions 306, 308 at the first end 39 of the second endplate 16. As the endplates 14, 16 move outwardly, the tongues 316, 318 in the ramped portions 306, 308 of the second endplate 16 ride in the angled grooves 440 in the ramped portions 438 of the driving ramp 300.

[0134] It should also be noted that the expansion of the endplates 14, 16 can be varied based on the differences in the dimensions of the various ramped portions in the central ramp 18, the driving ramp 300, and the first and second endplates 14, 16. As best seen in FIG. 16, the endplates 14, 16 can be expanded in any of the following ways: straight rise expansion, straight rise expansion followed by a toggle into a lordotic expanded configuration, or a phase off straight rise into a lordotic expanded configuration.

[0135] In the event the fusion device 10 needs to be repositioned or revised after being installed and expanded, the fusion device 10 can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device 10, the instrument can be used to rotate the actuator assembly 200 in a second direction that is opposite the first direction. Rotation of the actuator assembly 200 results in movement of the central ramp 18 and the driving ramp 300 away from one another. As the central ramp 18 and the driving ramp 300 move, the endplates 14, 16 move inwardly into the unexpanded position.

[0136] Although the preceding discussion only discussed having a single fusion device 10 in the intervertebral space, it is contemplated that more than one fusion device 10 can be inserted in the intervertebral space. It is further contemplated that each fusion device 10 does not have to be finally installed in the fully expanded state. Rather, depending on the location of the fusion device 10 in the intervertebral disc space, the height of the fusion device 10 may vary from unexpanded to fully expanded. It should be noted that, as well as the height being varied from an unexpanded state to an expanded state, the fusion 10 may be positioned permanently anywhere between the expanded state and the unexpanded state.

[0137] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.