Expandable fusion device and method of installation thereof

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 body portion, a first endplate, and a second endplate, the first and second endplates capable of being moved in a direction away from the body portion into an expanded configuration or capable of being moved towards the body portion into an unexpanded configuration. The fusion device is capable of being deployed and installed in both configurations.

FIELD OF THE INVENTION

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.

BACKGROUND OF THE INVENTION

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.

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.

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.

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.

SUMMARY OF THE INVENTION

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 body portion, a first endplate, and a second endplate. The first and second endplates are capable of being moved in a direction away from the body portion into an expanded configuration or capable of being moved towards the body portion into an unexpanded configuration. The expandable fusion device is capable of being deployed and installed in the unexpanded configuration or the expanded configuration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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 atFIG. 1, an exemplary embodiment of an expandable fusion device10is shown between adjacent vertebral bodies2and3. The fusion device10engages the endplates4and5of the adjacent vertebral bodies2and3and, in the installed position, maintains normal intervertebral disc spacing and restores spinal stability, thereby facilitating an intervertebral fusion. The expandable fusion device10can 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 exemplary embodiment, bone graft or similar bone growth inducing material can be introduced around and within the fusion device10to further promote and facilitate the intervertebral fusion. The fusion device10, 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.

With reference toFIG. 2, an exploded perspective view of one embodiment of the fusion device10is shown. In an exemplary embodiment, the fusion device10includes a body portion12, a first endplate14, a second endplate16, a translation member18, an actuation member20, and an insert22.

With additional reference toFIGS. 3-6, in an exemplary embodiment, the body portion12has a first end24, a second end26, a first side portion28connecting the first end24and the second end26, and a second side portion29on the opposing side of the body portion12connecting the first end24and the second end26. The body portion12further includes an upper end30, which is sized to receive at least a portion of the first endplate14, and a lower end32, which is sized to receive at least a portion of the second endplate16.

The first end24of the body portion12, in an exemplary embodiment, includes at least one angled surface34, but can include multiple angled surfaces. The angled surface34can serve to distract the adjacent vertebral bodies when the fusion device10is inserted into an intervertebral space. In another preferred embodiment, it is contemplated that there are at least two opposing angled surfaces forming a generally wedge shaped to distract the adjacent vertebral bodies when the fusion device10is inserted into an intervertebral space.

The second end26of the body portion12, in an exemplary embodiment, includes an opening36which may include threading. In another exemplary embodiment, the opening36may include ratchet teeth instead of threading. The opening36extends from the second end26of the body portion12into a central opening (not illustrated) in the body portion12. In one embodiment, the central opening is sized to receive the translation member18, and the opening36is sized to threadingly receive the actuation member20. In another exemplary embodiment, the opening36is sized to receive the actuation member20in a ratcheting fashion. In yet another exemplary embodiment, first side portion28and second side portion29each include a recess38located towards the second end26of the body portion12. The recess38is configured and dimensioned to receive an insertion instrument (not shown) that assists in the insertion of the fusion device10into an intervertebral space.

Although the following discussion relates to the first endplate14, it should be understood that it also equally applies to the second endplate16as the second endplate16is substantially identical to the first endplate14in embodiments of the present invention. Turning now toFIGS. 2-6, in an exemplary embodiment, the first endplate14has an upper surface40, a lower surface42, and a through opening43. The through opening43, 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 body portion12.

In one embodiment, the lower surface42includes at least one extension44extending along at least a portion of the lower surface42. As best seen inFIGS. 3 and 4, in an exemplary embodiment, the extension44can extend along a substantial portion of the lower surface42, including, along each side of the endplate14and along the front end of the endplate14. In another exemplary embodiment, the extension44includes at least one ramped portion46, but can include any number of ramped portions, including two spaced ramped portions46,48in the extension44that extend between each side of the endplate14, as best seen inFIG. 4. It is contemplated that the slope of the ramped portions46,48can be equal or can differ from each other. The effect of varying the slopes of the ramped portions46,48is discussed below.

In an exemplary embodiment, the ramped portions46,48further include grooved portions47,49that are configured and dimensioned to receive angled surfaces58,60of the translation member18and are oriented in an oblique fashion. In a preferred embodiment, the grooved portions46,48are dovetail grooves configured and dimensioned to hold the angled surfaces58,60of the translation member18while allowing the angles surfaces58,60to slide against the ramped portions46,48.

Referring now toFIGS. 3-6, in one embodiment, the upper surface40of the first endplate14is flat and generally planar to allow the upper surface40of the endplate14to engage with the adjacent vertebral body2. Alternatively, as shown inFIG. 7, the upper surface40can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body2. It is also contemplated that the upper surface40can 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 body2in a lordotic fashion. Turning back toFIGS. 2-6, in an exemplary embodiment, the upper surface40includes texturing50to 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.

With reference to FIGS.2and4-6, in an exemplary embodiment, the translation member18is sized to be received within the central opening of the body portion12and includes at least a first expansion portion52. In another embodiment, the translation member18includes a first expansion portion52and a second expansion portion54, the expansion portions52,54being connected together via a bridge portion56. It is also contemplated that there may be more than two expansion portions where each of the expansion portions is connected by a bridge portion. The expansion portions52,54each have angled surfaces58,60configured and dimensioned to engage the grooved portions46,48of the first and second endplates14,16. In one embodiment, the translation member18includes an opening62in the first expansion portion52, which is sized to receive a portion of the actuation member20, as best seen inFIG. 4. In an exemplary embodiment, the first expansion portion52includes a central bore63that extends from the opening62and through the first expansion portion52. In one embodiment, the translation member18includes a hole64in the second expansion portion54, which is sized to receive nose66, as best seen inFIGS. 5 and 6. In an exemplary embodiment, the hole64includes threading68for threadedly receiving a threaded end70of the nose66, as shown onFIG. 6. The nose66is received in an opening72in the first end34of the body portion12to stabilize the translation member18in the central opening of the body portion12.

In one embodiment, the translation member18includes a locking mechanism74, which is configured and adapted to engage the actuation member20. As illustrated, the locking mechanism74may extend from the first expansion portion52. The locking mechanism74includes a slot76configured and adapted to receive extension87of the actuation member20. In an exemplary embodiment, the locking mechanism74further includes a stop78(e.g., a rim, a lip, etc.) that engages the actuation member20when it is disposed in the slot76.

Referring now toFIGS. 2-6, in an exemplary embodiment, the actuation member20has a first end80, a second end82, and threading (not illustrated) extending along at least a portion thereof from the first end80to the second end82. The threading threadingly engages the threading that extends along a portion of opening36in the body portion12. In another exemplary embodiment, the actuation member20includes ratchet teeth instead of threading. The ratchet teeth engage corresponding ratchet teeth in the opening36in the body portion12. The first end80includes a recess84dimensioned to receive an instrument (not shown) that is capable of advancing the actuation member20with respect to the body portion12of the fusion device10. In an embodiment, the actuation member20includes a bore85, as best seen byFIG. 4, that extends from the recess84in the first end to the second82. The second end82of the actuation member20includes an extension86that is received within the opening62in the first expansion portion52. In one embodiment, the extension88may include a lip portion86and a plurality of slits88. The plurality of slits88are configured to receive inserts22. Inserts22are provided to limit motion of the actuation member20. Once the lip portion86is placed into the slot76of the locking mechanism74, the lip portion86will engage the stop78preventing longitudinal movement of the actuation member20with respect to the translation member18. It is further contemplated that a pin member90can be included to further secure the actuation member20in the translation member19. In an embodiment, the pin member90can be pressed into the central bore85of the actuation member20and the central bore63of the translation member, thereby preventing the actuation member20from disengaging from the translation member18. Additionally, in an exemplary embodiment, the fusion device10can further include a chamfered tip24for distraction of adjacent vertebrae.

Turning now toFIGS. 1-6, a method of installing the expandable fusion device10is now discussed. Prior to insertion of the fusion device10, the intervertebral space is prepared. In one method of installation, a diskectomy 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 bodies2,3are then scraped to create an exposed end surface for facilitating bone growth across the invertebral space. The expandable fusion device10is then introduced into the intervertebral space, with the first end22of the body portion12being inserted first into the disc space followed by the second end24. In an exemplary method, the fusion device10is in the unexpanded position when introduced into the intervertebral space. The wedged-shaped first end22should assist in distracting the adjacent vertebral bodies2,3, if necessary. This allows for the option of having little to no distraction of the intervertebral space prior to the insertion of the fusion device10. In another exemplary method, the intervertebral space may be distracted prior to insertion of the fusion device10. 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 bodies2,3easier.

With the fusion device10inserted 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 inFIGS. 1,5, and6, To expand the fusion device10, an instrument is engaged with recess84in the actuation member20. The instrument is used to rotate actuation member20. As discussed above, actuation member20can be threadingly engaging body portion12and is engaged with translation member18; thus, as the actuation member20is rotated in a first direction, the actuation member20and the translation member18move with respect to the body portion12toward the first end22of the body portion12. In another exemplary embodiment, the actuation member20is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuation member20and the translation member18. As the translation member18moves, the angled surfaces58,60of the expansion portions52,54push against the ramped portions46,48of the endplates14,16pushing endplates14,16outwardly into the expanded position with the angled surfaces58,60riding along the grooved portions47,48of the ramped portions46,48. This can best be seen inFIGS. 5 and 6. Since the expansion of the fusion device10is actuated by a rotational input, the expansion of the fusion device10is infinite. In other words, the endplates14,16can be expanded to an infinite number of heights dependent on the rotational advancement of the actuation member20. As discussed above, the fusion device10includes a locking mechanism22which assists in retaining the endplates14,16at the desired height.

It should also be noted that the expansion of the endplates14,16can be varied based on the differences in the dimensions of the ramped portions46,48and the angled surfaces58,60. As best seen inFIG. 8, the endplates14,16can 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.

Turning back toFIGS. 1-6, in the event the fusion device10needs to be repositioned or revised after being installed and expanded, the fusion device10can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device10, the instrument is engaged with recess84in the actuation member20. The instrument is used to rotate actuation member20. As discussed above, actuation member20can be threadingly engaging body portion12and is engaged with translation member18; thus, as the actuation member20is rotated in a second direction, opposite the first direction, the actuation member20and translation member18move with respect to the body portion12toward the second end26of the body portion12. As the translation member18moves, the angled surfaces58,60of the translation member18ride along the grooved portions47,49pulling the endplates14,16inwardly into the unexpanded position.

With reference now toFIG. 9, fusion device10is shown with an exemplary embodiment of artificial endplates100. Artificial endplates100allows the introduction of lordosis even when the endplates14and16of the fusion device10are generally planar. In one embodiment, the artificial endplates100have an upper surface102and a lower surface104. The upper surfaces102of the artificial endplates100have at least one spike106to engage the adjacent vertebral bodies. The lower surfaces104have complementary texturing or engagement features on their surfaces to engage with the texturing or engagement features on the upper endplate14and the lower endplate16of the fusion device10. In an exemplary embodiment, the upper surface102of the artificial endplates100have a generally convex profile and the lower surfaces104have a generally parallel profile to achieve lordosis. In another exemplary embodiment, fusion device10can be used with only one artificial endplate100to introduce lordosis even when the endplates14and16of the fusion device10are generally planar. The artificial endplate100can either engage endplate14or engage endplate16and function in the same manner as described above with respect to two artificial endplates100.

Referring now toFIGS. 10 and 11, an alternative embodiment of the fusion device10is shown. In an exemplary embodiment, the fusion device10includes a body portion12, a first endplate14, a second endplate16, a translation member18, and an actuation member20. In the illustrated embodiment, the fusion device further includes a first ramped insert120and a second ramped insert122.

Although the following discussion relates to the first ramped insert120, it should be understood that it also equally applies to the second ramped insert122as the second ramped insert122is substantially identical to the first ramped insert120in embodiments of the present invention. Turning now toFIGS. 10-13, in an exemplary embodiment, the first ramped insert120includes a first ramped portion124and a second ramped portion126, the first and second ramped portions124,126being connected by a bridge portion128. The ramped portions124,126each have grooved portions130,132configured and dimensioned to receive angled surfaces58,60of the translation member. The ramped portions124,126can be oriented in an oblique fashion, as illustrated. In a preferred embodiment, the grooved portions130,132are dovetail grooves configured and dimensioned to hold the angled surfaces58,60of the translation member18while allowing the angles surfaces58,60to slide against the ramped portions124,126.

In an exemplary embodiment, the first ramped insert120should be configured and dimensioned to be engaged with the first endplate14. In an embodiment, the first and second ramped portions124,126include snap connectors134,136for securing the first ramped insert120to the first endplate. It should be understood that the snap connectors134,136are merely illustrative and that other suitable mechanisms for securing the first ramped inserted120with the first endplate14may be used.

Referring toFIGS. 10-13, in an exemplary embodiment, the translation member18is sized to be received within the central opening of the body portion12and includes at least a first expansion portion52. In another embodiment, the translation member18includes a first expansion portion52and a second expansion portion54, the expansion portions52,54being connected together via a bridge portion56. It is also contemplated that there may be more than two expansion portions where each of the expansion portions is connected by a bridge portion. The expansion portions52,54each have angled surfaces58,60configured and dimensioned to engage the grooved portions130,132of the first and second ramped inserts120,122. In one embodiment, the angled surfaces58,60include corresponding grooved portions138,140, as best seen inFIG. 13, that slidingly engaged the grooved portions130,132of the first and second ramped inserts120,122.

In one embodiment, the expansion portion52includes an opening62, which is sized to receive a portion of the actuation member20, and the expansion portion62includes a nose66, which is received within an opening72in the first end34of the body portion12to stabilize the translation member18in the central opening of the body portion12. In an embodiment, the nose66is integral with the expansion portion62. In an embodiment (shown on FIGS.2and4-6), the nose66is threadingly engaged with the expansion portion62. In an embodiment, the translation member18includes a locking mechanism74to engage the actuation member20, as illustrated inFIGS. 2-6. However, it should be understood that other suitable mechanisms may be used to secure the actuation member20within the translation member18. For example, the actuation member20may include an extension87having a lip portion86(shown on FIGS.2and4-6) that engages the expansion portion62. The extension87may, for example, be configured to flex inwardly reducing its diameter when received in the opening62. Once the lip portion86of the extension87is advanced beyond the end of the opening62, the extension portion87will return back to its original diameter and the lip portion86will engage the expansion portion60.

The expandable fusion device10ofFIGS. 10-13can be inserted into the intervertebral space in a manner similar to that the previously described with respect toFIGS. 1-6. After insertion, the expandable fusion device10ofFIGS. 10-13can be expanded into the expanded position, as best seen inFIGS. 10 and 11. To expand the fusion device10, an instrument is engaged with recess84in the actuation member20. The instrument is used to rotate actuation member20. As discussed above, actuation member20can be threadingly engaging body portion12and is engaged with translation member18; thus, as the actuation member20is rotated in a first direction, the actuation member20and the translation member18move with respect to the body portion12toward the first end22of the body portion12. In another exemplary embodiment, the actuation member20is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuation member20and the translation member18. As the translation member18moves, the angled surfaces58,60of the expansion portions52,54push against the ramped portions124,126of the first and second ramped inserts120,122while riding along the grooved portions130,132, thus pushing first and second ramped inserts120,122outwardly. Because the first and second ramped inserts120,122are engaged with the endplates14,16, the endplates14,16are also pushed outwardly into the expanded position.

After expansion, the expandable fusion device10can be contracted back to the unexpanded configuration. To contract the fusion device10, the instrument is engaged with recess84in the actuation member20. The instrument is used to rotate actuation member20. As discussed above, actuation member20can be threadingly engaging body portion12and is engaged with translation member18; thus, as the actuation member20is rotated in a second direction, opposite the first direction, the actuation member20and translation member18move with respect to the body portion12toward the second end26of the body portion12. As the translation member18moves, the angled surfaces58,60of the translation member18ride along the grooved portions130,132pulling the first and second ramped inserts120,122and thus, the endplates14,16inwardly into the unexpanded position.

Referring now toFIG. 14, an alternative embodiment of the fusion device10is shown. In an exemplary embodiment, the first endplate14and the second endplate16each include additional geometry to help securely hold the endplates14,16in place. In an embodiment, the first endplate14and/or the second endplate16include threaded holes141through which the fasteners, such as screws142, may be inserted. In an embodiment, the threaded holes141penetrate through the first endplate14and/or the second endplate16in an oblique fashion. It is contemplated that the screws142may inserted through the threaded holes141and into adjacent vertebral bodies2,3, to further secure the first endplate14and the second endplate16to the vertebral bodies2,3. In some embodiments, these fasteners may be removed once a more long-term interface has been established, or alternatively the fasteners may remain in place indefinitely or until the fusion device10needs adjustment and/or replacement.

With reference nowFIGS. 15-17, an alternative embodiment of the fusion device10is shown that expands laterally. Lateral expansion maximizes coverage of the intravertebral disc space for wider load distribution and stability providing a rigid foundation for fusion. In one embodiment, the fusion device10includes body portion12, first endplate144, and second endplate146.

Although the following discussion relates to the first endplate144, it should be understood that it also equally applies to the second endplate146as the second endplate146is substantially identical to the first endplate144in embodiments of the present invention. Turning now toFIGS. 15-17, in an exemplary embodiment, the first endplate144has an upper surface148, a lower surface150, and an inner surface151facing the body portion12. It is contemplated that the upper surface148will engage adjacent vertebral body2(seen onFIG. 1) and the lower surface150will engage adjacent vertebral body3(seen onFIG. 1). In one embodiment, the upper surface148and the lower surface150are each flat and generally planar to allow the upper surface148to engage with the adjacent vertebral body3. Alternatively, the upper surface148and/or the lower surface150can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral bodies2,3. It is also contemplated that the upper surface148and/or the lower surface150can 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 body2and/or the adjacent vertebral body3in a lordotic fashion. In an exemplary embodiment, the upper surface148and/or lower surface150includes textures152to 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.

In one embodiment, the inner surface151includes at least one extension154extending along at least a portion of the inner surface151. In an exemplary embodiment, the extension154can extend along a substantial portion of the inner surface154, including, along each side of the endplate144and along the front end of the endplate14. While not illustrated, the inner surface may include ramped surfaces and grooved portions in an exemplary embodiment. It is contemplated that the ramped surfaces and/or grooved portions may be similar to the ramped surfaces46,48and grooved portion47,49in extension44shown onFIGS. 4-6. In an embodiment, the extension154may include slots156oriented in an oblique fashion through which pins158may be inserted.

While not illustrated, the fusion device10further includes features to effectuate the lateral expansion of the first and second endplates144,146. In one embodiment, the fusion device10using a ramping system—similar to the system illustrated in FIGS.2and4-6—for expanding the first and second endplates144,146. In an exemplary embodiment, the fusion device10further includes a translation member and actuation member, such as translation member18and actuation member20shown on FIGS.2and4-6. It is contemplated that the translation member may include angled surfaces that push against ramped surfaces in the extension154, expanding the first and second endplates144,146outwardly and away from the body portion12. In an embodiment, pins156disposed through the slots154may be retained in the translation member. In an alternative embodiment, dovetailing may be used for engagement of the angled surfaces and ramped surfaces. It should be understood that the translation member and actuation member in this embodiment may be similar to the translation member18and actuation member20described above with respectFIGS. 1-6. In another embodiment, the fusion device10further includes first and second ramped inserts that are secured within the first and second endplates144,146. The first and second ramped inserts may be similar to the first and second ramped inserts120,122described above with respect toFIGS. 10-13. It is contemplated that angled surfaces in the translation member may push against ramped surfaces in the ramped inserts pushing the ramped inserts outwardly. Because of their engagement with the first and second endplates144,146, the first and second endplates144,146may thus be expanded outwardly. In this manner, the first and second endplates144,146may be laterally expanded away from the body portion12. It should be understood that other suitable techniques may also be used to effectuate this lateral expansion.

With reference toFIG. 18, an exploded perspective view of another embodiment of fusion device10is shown. In an exemplary embodiment, the fusion device10includes a body portion12, a first endplate200, a second endplate202, a third endplate204, a fourth endplate206, and a translation member18. In this embodiment, the fusion device10is configured to expand both vertically and laterally.

In an exemplary embodiment, the body portion12has a first end24, a second end26, a first side portion28connecting the first end24and the second end26, and a second side portion29on the opposing side of the body portion12connecting the first end24and the second end26. The body portion12further includes a top side portion208connecting the first end24and the second end26, and a bottom side portion210on the opposing side of the body portion12connecting the first end24and the second end26. The body portion12further includes first gap212between the top side portion208and the first side portion28, which is sized to receive at least a portion of the first endplate200. The body portion12further includes second gap214between the top side portion208and the second side portion29, which is sized to receive at least a portion of the second endplate202. The body portion12further includes third gap216between the bottom side portion210and the first side portion28, which is sized to receive at least a portion of the third endplate204. The body portion12further includes fourth gap218between the bottom side portion210and the second side portion29, which is sized to receive at least a portion of the fourth endplate206.

The first end24of the body portion12, in an exemplary embodiment, includes an opening220. The opening220extends from the first end24of the body portion12into a central opening222. In one embodiment, the central opening222is sized to receive the translation member18. The second end26of the body portion12, in an exemplary embodiment, includes an opening36, which extends from the second end26of the body portion12into the central opening222.

Although the following discussion relates to the first endplate200, it should be understood that it also equally applies to the second endplate202, the third endplate204, and the fourth endplate206, as these endplates202,204,206are substantially identical to the first endplate200in embodiments of the present invention. Turning now toFIGS. 18-20, in an exemplary embodiment, the first endplate14has a first end224and a second end226. The first endplate further includes an upper surface40connecting the first end224and the second end226and a lower surface42on an opposing side of the endplate200connecting the first end224and the second end226. While not illustrated, the first endplate14may include a through opening 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 opening222in the body portion12.

In one embodiment, the lower surface42includes at least one first retaining socket228on the lower surface42. In an exemplary embodiment, the lower surface42includes a first retaining socket228at the interior corner of the intersection of the first end224and the lower surface42, and a second retaining socket230at the interior corner of the intersection of the first end224and the lower surface42.

Referring now toFIGS. 18-20, in one embodiment, the upper surface40of the first endplate200is curved convexly. Alternatively, the upper surface40is flat or curved concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body2. It is also contemplated that the upper surface40can 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 body2in a lordotic fashion. In an exemplary embodiment, the upper surface40includes texturing50to 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.

With reference toFIG. 18, in an exemplary embodiment, the translation member18is sized to be received within the central opening222of the body portion12. The translation member18should be sized to allow longitudinal translation within the central opening222. In an embodiment, the translation member18includes at least a first expansion portion52. In another embodiment, the translation member18includes a first expansion portion52and a second expansion portion54, the expansion portions52,54being connected together via a bridge portion56. It is also contemplated that there may be more than two expansion portions where each of the expansion portions is connected by a bridge portion. The expansion portions52,54each have angled surfaces58,60. In an embodiment, the angles surfaces58,60each comprise first end229and second end231with second end231being wider than the first end229. In an exemplary embodiment, the expansion portions52,54include grooved portions232,234on the edges of at least two sides (e.g., the lateral sides) of the angled surfaces58,60. The grooved portions232,234are configured and dimensioned to engage the first and second retaining sockets228,230on the endplates200,202,204,206. In an exemplary embodiment, the grooved portions232,234retain the first and second retaining sockets228,230in sliding engagement.

In one embodiment, the translation member18includes a first end236and a second end238. The first end236of the translation member includes an extension240sized to be received within the opening220in the first end24of the body portion12. While not illustrated, the second end238also can include a similar extension sized to be received within opening32in the second end26of the body portion12.

The expandable fusion device10ofFIGS. 18-20can be inserted into the intervertebral space in a manner similar to that the previously described with respect toFIGS. 1-6. After insertion, the expandable fusion device10ofFIGS. 18-20can be expanded into the expanded position. As previously mentioned, the fusion device10shown onFIGS. 18-20expands both vertically and laterally. To expand the fusion device10, the translation member18can be moved with respect to the body portion12toward the first end24of the body portion. An instrument can be used, in an exemplary embodiment. As the translation member18moves, the first retaining socket228and the second retaining socket230ride along the grooved portions232,234of the expansion portions52,54pushing the endplates200,202,204,206outwardly in the direction indicated by arrows242. In an embodiment, the endplates200,202,204,206move outwardly in an oblique fashion to expand the fusion device10both vertically and laterally. The expanded configuration of the expansion device10is best seen inFIG. 20.

After expansion, the expandable fusion device10can be contracted back to the unexpanded configuration. The unexpanded configuration of the fusion device10is best seen inFIG. 20. To contract the fusion device10, the translation member18is moved with respect to the body portion12toward the second end26of the body portion12. As the translation member18moves, the first retaining socket228and the second retaining socket230ride along the grooved portions232,234of the expansion portions52,54pulling the endplates200,202,204,206inwardly in a direction opposite that indicated by arrows242. In an embodiment, the endplates200,202,204,206move inwardly in an oblique fashion to contract the fusion device10both vertically and laterally. The unexpanded configuration of the expansion device10is best seen inFIG. 19.

With reference toFIGS. 21-22, another embodiment of expandable fusion device10is shown. In an exemplary embodiment, the fusion device10includes a body portion12, a vertically expanding plate300, and a gear302. In this embodiment, a portion of the fusion device10is configured to expand vertically in at least one direction. In an exemplary embodiment, the vertically expanding plate300is configured to expand outwardly from the body portion12. It is contemplated that an expandable fusion device10may be used to correct spinal curvature due to, for example, scoliosis, lordosis, and the like.

In an exemplary embodiment, the body portion12has a first end24, a second end26, a first side portion28connecting the first end24and the second end26, and a second side portion29on the opposing side of the body portion12connecting the first end24and the second end26. The first end24of the body portion12, in an exemplary embodiment, includes at least one angled surface34, but can include multiple angled surfaces. The angled surface34can serve to distract the adjacent vertebral bodies when the fusion device10is inserted into an intervertebral space. In another preferred embodiment, it is contemplated that there are at least two opposing angled surfaces forming a generally wedge shaped to distract the adjacent vertebral bodies when the fusion device10is inserted into an intervertebral space. In yet another preferred embodiment, first side portion28and second side portion29each include a recess38located towards the second end26of the body portion12. The recess38is configured and dimensioned to receive an insertion instrument304that assists in the insertion of the fusion device10into an intervertebral space.

In an exemplary embodiment, the body portion12includes an upper engagement surface306extending from the first end24towards the second end26, and a lower engagement surface308extending between the first end24and the second end26. In an embodiment, the upper engagement surface306has a through opening310. Although not illustrated, the lower engagement surface308may have a through opening that is similar to through opening310. The through opening310, 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 body portion12. In an embodiment, at least a portion of the body portion12is removed to form a landing312in the body portion12. In an exemplary embodiment, a portion of the upper engagement surface306and the second end26are removed to form the landing312having an upper surface314. While not illustrated, a portion of the lower engagement surface308and the second end26may be cut away, in an alternative embodiment, to form the landing312.

In one embodiment, the upper engagement surface306and the lower engagement surface308are flat and generally planar to allow engagement surfaces306to engage with the adjacent vertebral body2and the lower engagement surface308to engage with the adjacent vertebral body3. Alternatively, the upper engagement surface306and/or the lower engagement surface308can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral bodies2,3. In an exemplary embodiment, the upper engagement surface306and/or the lower engagement surface includes texturing312to 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.

In an exemplary embodiment, vertically expanding plate300is coupled to an end of threaded bolt318, which is coupled to the gear302. In one embodiment, the threaded bolt318is in threaded engagement with the gear302. In an alternative embodiment, a bolt having ratchet teeth may be used instead of threaded bolt318. In an embodiment, the gear302is coupled to the landing312. In one embodiment, the gear302is rotatably coupled to the landing312.

The vertically expanding plate300includes a throughbore319and an upper surface320. In one embodiment, the vertically expanding plate300is generally circular in shape. Other suitable configurations of the expanding plate300may also be suitable. In an embodiment, the vertically expanding plate may be generally rectangular in shape with rounded corners, as best seen inFIG. 23. In one embodiment, the vertically expanding plate300is flat and generally planar to allow upper surface320to engage with the adjacent vertebral body2. Alternatively, the upper surface320can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral bodies. In an exemplary embodiment, the upper surface320includes texturing322to 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.

With reference toFIG. 23, an alternative embodiment of the expandable fusion device10ofFIGS. 21-22is shown. In this embodiment, the gear302is enclosed within the body portion12towards the second end26of the body portion12with the vertically expanding plate300disposed at or above the upper engagement surface306of the body portion12. In an embodiment, the vertically expanding plate300is positioned towards the second end26of the body portion12. While not illustrated, the threaded bolt318extends through the upper engagement surface306and couples the vertically expanding plate300and the gear302. An actuator screw324extends through the first end24of the body portion12to engage the gear302.

The expandable fusion device10ofFIGS. 21-23can be inserted in the intervertebral space in a manner similar to that the previously described with respect toFIGS. 1-6.FIG. 24illustrates the expandable fusion device10ofFIG. 23between adjacent vertebral bodies3,4in an unexpanded position. After insertion, the expandable fusion device10ofFIGS. 21-23can be expanded into the expanded position. As previously mentioned, a portion of the fusion device shown onFIGS. 21-23expands vertically in at least one direction. To partially expand the fusion device10, the gear302can be rotated in a first direction. An instrument326having a gear328disposed on a distal end330of the instrument may be used to rotate the gear302, as best seen onFIG. 22. In another embodiment, an instrument (not illustrated) may be used to rotate actuation member324in a first direction. As discussed above, the actuation member324is engaged with gear302; thus, as the actuation member324is rotated in first direction, the gear302rotated in a first direction. The embodiment with the actuation member324is best seen inFIG. 23. As the gear302rotates, the threaded bolt318extends outward from the gear302, thus extending the laterally expanding plate300outward from the body portion12.FIG. 25illustrates the expandable fusion device10ofFIG. 23in an expanded position.

After expansion, the expandable fusion device10can be contracted back to the unexpanded position. The unexpanded position of the fusion device10is best seen inFIG. 24. To contract the fusion device10, the gear302is rotated in a second direction that is opposite the first direction. The instrument326with the gear328may be used to rotate the gear302. Alternatively, an instrument may be used to rotate the actuation member324to turn the gear302in the second direction. As the gear302rotates in the second direction, the threaded bolt318retracts pulling the laterally expanding plate300inward into the unexpanded position.

Although the preceding discussion only discussed having a single fusion device10in the intervertebral space, it is contemplated that more than one fusion device10can be inserted in the intervertebral space. It is further contemplated that each fusion device10does not have to be finally installed in the fully expanded state. Rather, depending on the location of the fusion device10in the intervertebral disc space, the height of the fusion device10may vary from unexpanded to fully expanded.