Patent Publication Number: US-10327917-B2

Title: Expandable fusion device and method of installation thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This Patent application is a continuation-in-part application of U.S. Ser. No. 13/845,645, filed Apr. 3, 2013, which is a continuation-in-part application of U.S. patent application Ser. No. 13/451,230, filed Apr. 19, 2012, now issued as U.S. Pat. No. 8,518,120, which is a continuation of U.S. patent application Ser. No. 13/440,158, filed Apr. 5, 2012, now issued as U.S. Pat. No. 8,679,183, which is a continuation-in-part application of U.S. patent application Ser. No. 12/823,736, filed Jun. 25, 2010, now issued as U.S. Pat. No. 8,685,098, and a continuation-in-part application of U.S. patent application Ser. No. 13/273,994, filed Oct. 14, 2011, which is a continuation of U.S. patent application Ser. No. 12/579,833, filed Oct. 15, 2009, now issued as U.S. Pat. No. 8,062,375. This Patent Application also claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application 61/877,034, filed Sep. 12, 2013. The entire content of each of these references cited herein is incorporated by reference in its entirety. 
    
    
     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. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a side view of an embodiment of an expandable fusion device shown between adjacent vertebrae according to the present invention; 
         FIG. 2  is an exploded view of the expandable fusion device of  FIG. 1 ; 
         FIG. 3  is a front perspective view of the expandable fusion device of  FIG. 1  shown in an unexpanded position 
         FIG. 4  is a front perspective view of the expandable fusion device of  FIG. 1  shown in an expanded position; 
         FIG. 5  is a rear perspective view of the expandable fusion device of  FIG. 1  shown in an unexpanded position; 
         FIG. 6  is a rear perspective view of the expandable fusion device of  FIG. 1  shown in an expanded position; 
         FIG. 7  is a side view of the expandable fusion device of  FIG. 1  shown in an unexpanded position; 
         FIG. 8  is a side view of the expandable fusion device of  FIG. 1  shown in an expanded position; 
         FIG. 9  is a top view of the expandable fusion device of  FIG. 1 ; 
         FIG. 10 . is a side partial cross-sectional view of the expandable fusion device of  FIG. 1  shown in an unexpanded position; 
         FIG. 11  is a side partial cross-sectional view of the expandable fusion device of  FIG. 1  shown in an expanded position; 
         FIG. 12  is a side schematic view of the expandable fusion device of  FIG. 1  having different endplates; 
         FIG. 13  is a partial side schematic view of the expandable fusion device of  FIG. 1  showing different modes of endplate expansion; and 
         FIG. 14  is a side schematic view of the expandable fusion device of  FIG. 1  with artificial endplates shown between adjacent vertebrae. 
         FIG. 15  is a side view of an embodiment of an expandable fusion device shown between adjacent vertebrae according to the present invention; 
         FIG. 16  is an exploded view of the expandable fusion device of  FIG. 15 ; 
         FIG. 17  is a rear perspective view of the expandable fusion device of  FIG. 15  shown in an unexpanded position; 
         FIG. 18  is a side cross-sectional view of the expandable fusion device of  FIG. 15  shown with one of the endplates removed; 
         FIG. 19  is a side partial cross-sectional view of the expandable fusion device of  FIG. 15  shown in an unexpanded position; 
         FIG. 20  is a side partial cross-sectional view of the expandable fusion device of  FIG. 15  shown in an expanded position; 
         FIG. 21  is a side schematic view of the expandable fusion device of  FIG. 15  having different endplates; 
         FIG. 22  is a partial side schematic view of the expandable fusion device of  FIG. 15  showing different modes of endplate expansion; 
         FIG. 23  is a side schematic view of the expandable fusion device of  FIG. 15  with artificial endplates shown between adjacent vertebrae; 
         FIG. 24  is a side view cross-sectional view of another embodiment of an expandable fusion device shown in an unexpanded position; 
         FIG. 25  is a side view cross-sectional view of the expandable fusion device of  FIG. 24  shown in an expanded position; 
         FIG. 26  is a side view of the expandable fusion device of  FIG. 24  showing the translation member and the ramped insert; 
         FIG. 27  is a front perspective view of the expandable fusion device of  FIG. 24  showing the translation member and the ramped insert; 
         FIG. 28  is a rear perspective of another embodiment of an expandable fusion device with the endplates having a threaded hole; 
         FIG. 29  is a top view of another embodiment of an expandable fusion device shown in an unexpanded position; 
         FIG. 30  is a bottom view of the expandable fusion device of  FIG. 29 ; 
         FIG. 31  is top view of the expandable fusion device of  FIG. 29  shown in an expanded position; 
         FIG. 32  is an exploded perspective view of another embodiment of an expandable fusion device; 
         FIG. 33  is an end view of the expandable fusion device of  FIG. 32  in an unexpanded position; 
         FIG. 34  is an end view of the expandable fusion device of  FIG. 32  in an expanded position; 
         FIG. 35  is a perspective view of another embodiment of an expandable fusion device; 
         FIG. 36  is a top view of the expandable fusion device of  FIG. 35 ; 
         FIG. 37  is a perspective view of the expandable fusion device of  FIG. 35  with a closed end; 
         FIG. 38  is a front view of the expandable fusion device of  FIG. 37  shown between adjacent vertebrae in an unexpanded position; 
         FIG. 39  is a front view of the expandable fusion device of  FIG. 37  shown between adjacent vertebrae in an expanded position; 
         FIG. 40  is an exploded view of an alternative fusion device; 
         FIG. 41  is a top view of the device in  FIG. 40  with a first endplate removed; 
         FIG. 42  is a top view of the alternative fusion device having side stabilization members; 
         FIG. 43  is a perspective view of the device in  FIG. 42 ; 
         FIG. 44  is a side cross-sectional view of the device in  FIG. 42 ; 
         FIG. 45  is a perspective view of a trial member in a non-expanded configuration; 
         FIG. 46  is a side cross-sectional view of the trial member of  FIG. 45  in an expanded configuration; 
         FIG. 47  is a top view of the trial member; 
         FIG. 48  is an exploded view of the trial member; 
         FIG. 49  is a side cross-sectional view of a portion of an alternative fusion device incorporating a ring member therein; 
         FIG. 50  is a perspective view of a portion of the alternative fusion device of  FIG. 49 ; 
         FIG. 51  is a side cross-sectional view of a proximal portion of a trial member in an unlocked configuration; 
         FIG. 52  is a side cross-sectional view of a proximal portion of a trial member in a locked configuration; 
         FIG. 53  is an alternate side cross-sectional view of a proximal portion of a trial member in a locked configuration; 
         FIG. 54  is a perspective cross-sectional view of a proximal portion of a trial member in a locked configuration; 
         FIG. 55  is a front cross-sectional view of a proximal portion of a trial member. 
         FIG. 56  is a side view of an instrument for engaging a fusion device; 
         FIGS. 57A-57C  illustrate a distal portion of an instrument in the process of engaging a fusion device for delivery and actuation; 
         FIGS. 58A and 58B  illustrate a proximal portion of an instrument including a handle for delivering and actuating a fusion device; 
         FIG. 59  is a side cross-sectional view of a proximal portion of an instrument including a handle; 
         FIGS. 60A-60C  illustrate an alternative embodiment of an inserter tube of an instrument; 
         FIG. 61  is an exploded view of another embodiment of an expandable fusion device according to the present invention; 
         FIG. 62  is a side view of the expandable fusion device of  FIG. 61  in an unexpanded configuration; 
         FIG. 63  is a cross-sectional side view of the expandable fusion device of  FIG. 61  in an unexpanded configuration; 
         FIG. 64  is a side view of the expandable fusion device of  FIG. 61  in an expanded configuration; 
         FIG. 65  is a cross-sectional side view of the expandable fusion device of  FIG. 61  in an expanded configuration; 
         FIG. 66  is a cross-sectional side view of the expandable member of the expandable fusion device of  FIG. 61 ; 
         FIG. 67  is a front perspective of the expandable fusion device of  FIG. 61 ; 
         FIG. 68  is a front perspective of the body portion of the expandable fusion device of  FIG. 61 ; 
         FIG. 69  is a cross-sectional side view of an alternative embodiment of the expandable fusion device of  FIG. 61  in an unexpanded configuration; 
         FIG. 70  is a cross-sectional side view of the alternative embodiment of the expandable fusion device shown on  FIG. 69 ; 
         FIG. 71  is a cross-sectional side view of an alternative embodiment of the expandable fusion device of  FIG. 61  in an unexpanded configuration; 
         FIGS. 72-83  are side views of an expandable fusion device showing different modes of lordotic expansion; 
         FIGS. 84A and 84B  are top perspective views of an alternative expandable fusion device having an anterior-based actuation member; 
         FIGS. 85A and 85B  are top views of the alternative expandable fusion device of  FIG. 84A  with endplates removed; 
         FIGS. 86A and 86B  are top perspective views of the alternative expandable fusion device of  FIG. 84A  with endplates removed; 
         FIGS. 87A-87C  are different views of different components of an alternative expandable fusion device for providing lordosis; 
         FIGS. 88A-88C  are different views of different components of an alternate expandable fusion device having a ramped actuator for providing lordosis; 
         FIGS. 89A-89D  are different views of different components of an alternate expandable fusion device having worm gears for providing lordosis; 
         FIGS. 90A-90C  illustrate different views of different components of an alternative expandable fusion device having moveable wedges for providing lordosis; 
         FIGS. 91A-91D  illustrate different views of an alternative expandable fusion device having an internal wedge for providing lordosis; 
         FIGS. 92A and 92B  illustrate different views of an alternative expandable fusion device having linking members for providing lordosis; 
         FIGS. 93A and 93B  illustrate different views of an alternative expandable fusion device having a ramp wedge member for providing lordosis; 
         FIGS. 94A and 94B  illustrates different embodiments of an implant having a lordotic expansion mechanism comprising tapered barrels; 
         FIGS. 95A-95C  illustrate different views of different components of an implant having a lordotic expansion mechanism comprising a serrated plate; 
         FIGS. 96A-96C  show different views of an implant having a lordotic expansion mechanism comprising threaded barrels; 
         FIG. 97  show a different embodiment of an implant comprising one or more ratcheting mechanisms for lordotic expansion; 
         FIGS. 98A-98C  show different views of an implant including a height changing wedge that provides lordotic expansion; 
         FIGS. 99A-99C  show different views of an implant having a driving wedge for providing lordotic expansion; 
         FIGS. 100A-100C  show different views of different components of an implant having connectable side portions for providing lordotic expansion; 
         FIG. 101  shows a locking mechanism for maintaining an expansion height in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     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. 
     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 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. 
     With reference to  FIG. 2 , an exploded perspective view of one embodiment of the fusion device  10  is shown. In an exemplary embodiment, the fusion device  10  includes a body portion  12 , a first endplate  14 , a second endplate  16 , a translation member  18 , a plurality of pins  20 , an actuation member  22 , and a locking mechanism  24 . 
     With additional reference to  FIGS. 3-8 , in an exemplary embodiment, the body portion  12  has a first end  26 , a second end  28 , a first side portion  30  connecting the first end  26  and the second end  28 , and a second side portion  32  connecting the first end  26  and the second end  28 . The body portion  12  further includes an upper end  34 , which is sized to receive at least a portion of the first endplate  14 , and a lower end  36 , which is sized to receive at least a portion of the second endplate  16 . 
     The first end  26  of the fusion device  10 , in an exemplary embodiment, includes at least one angled surface  38 , but can include multiple angled surfaces. The angled surface can serve to distract the adjacent vertebral bodies when the fusion device  10  is 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 device  10  is inserted into an intervertebral space. 
     The second end  28  of the body portion  12 , in an exemplary embodiment, includes an opening  40  which may include threading. In another exemplary embodiment, the opening  40  may include ratchet teeth instead of threading. The opening  40  extends from the second end  28  of the body portion  12  into a central opening  42  in the body portion  12 . In one embodiment, the central opening  42  is sized to receive the translation member  18  and the opening  40  is sized to threadingly receive the actuation member  22 . In another exemplary embodiment, the opening  40  is sized to receive the actuation member  22  in a ratcheting fashion. In yet another exemplary embodiment, first side portion  30  and second side portion  32  each include a recess  44  located towards the second end  28  of the body portion  12 . The recess  44  is configured and dimensioned to receive an insertion instrument (not shown) that assists in the insertion of the fusion device  10  into an intervertebral space. 
     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 . Turning now to  FIGS. 2-11 , in an exemplary embodiment, the first endplate  14  has an upper surface  46 , a lower surface  48 , and a through opening  49 . The through opening  49 , 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  42  in the body portion  12 . 
     In one embodiment, the lower surface  48  includes at least one extension  50  extending along at least a portion of the lower surface  48 . As best seen in  FIGS. 2 and 4 , in an exemplary embodiment, the extension  50  can extend along a substantial portion of the lower surface  48 , including, along each side of the endplate  14  and along the front end of the endplate  14 . In another exemplary embodiment, the extension  50  includes at least one slot  52 , but can include any number of slots  52 , including two sets of slots  52  opposing each other, as best seen in  FIG. 2 . The slots  52  are configured and dimensioned to receive pins  20  and are oriented in an oblique fashion. In another embodiment, the slots  52  may be oriented in a generally vertical orientation. 
     In an exemplary embodiment, the extension  50  is sized to be received within the central opening  42  of the body portion  12 . As best seen in  FIGS. 11-12 , the lower surface  48  of the first endplate  14  further includes, in an exemplary embodiment, at least one ramped surface  54 . In another exemplary embodiment, there are two spaced ramped surfaces  54 ,  56 . It is contemplated that the slope of the ramped surfaces  54 ,  56  can be equal or can differ from each other. The effect of varying the slopes of the ramped surfaces  54 ,  56  is discussed below. 
     Referring now to  FIGS. 2-9 , in one embodiment, the upper surface  46  of the first endplate  14  is flat and generally planar to allow the upper surface  46  of the endplate  14  to engage with the adjacent vertebral body  2 . Alternatively, as shown in  FIG. 12 , the upper surface  46  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  46  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. Turning back to  FIGS. 2-9 , in an exemplary embodiment, the upper surface  46  includes texturing  58  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. 
     With reference to  FIGS. 2 and 10-11 , in an exemplary embodiment, the translation member  18  is sized to be received within the central opening  42  of the body portion  12  and includes at least a first expansion portion  60 . In another embodiment, the translation member  18  includes a first expansion portion  60  and a second expansion portion  62 , the expansion portions  60 ,  62  being connected together via a bridge portion  68 . 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 portions  60 ,  62  each have angled surfaces  64 ,  66  configured and dimensioned to engage the ramp surfaces  54 ,  56  of the first and second endplates  14 ,  16 . In an exemplary embodiment, the translation member  18  also includes recesses  70 ,  72 , the recesses  70 ,  72  are sized to receive and retain pins  20 . In one embodiment, the expansion portion  60  includes an opening  74 , which is sized to receive a portion of the actuation member  22 , and the expansion portion  62  includes a nose  76 , which is received within an opening  78  in the first end  26  to stabilize the translation member  18  in the central opening  42  of the body member  12 . 
     In an exemplary embodiment, the actuation member  22  has a first end  80 , a second end  82  and threading  84  extending along at least a portion thereof from the first end  80  to the second end  82 . The threading  84  threadingly engages the threading extending along a portion of opening  40  in the body portion  12 . In another exemplary embodiment, the actuation member  22  includes ratchet teeth instead of threading. The ratchet teeth engage corresponding ratchet teeth in the opening  40  in the body portion  12 . The first end  80  includes a recess  86  dimensioned to receive an instrument (not shown) that is capable of advancing the actuation member  22  with respect to the body portion  12  of the fusion device  10 . The second end  82  of the actuation member  22  includes an extension  88  that is received within the opening  74  of the expansion portion  60 . In one embodiment, the extension  88  may include a plurality of slits and a lip portion. The plurality of slits allows the extension portion  88  to flex inwardly reducing its diameter when received in the opening  74 . Once the lip portion of the extension portion  88  is advanced beyond the end of the opening  74 , the extension portion  88  will return back to its original diameter and the lip portion will engage the expansion portion  60 . It is further contemplated that a pin member  90  can be included to prevent the extension portion from flexing inwardly thereby preventing the actuation member  22  from disengaging from the translation member  18 . 
     In an exemplary embodiment, the fusion device  10  can further include a locking mechanism  24 . The mechanism  24  is designed to resist rotation of the actuation member  22  rather than prevent rotation of the actuation member  22 . In an exemplary embodiment, either deformable threading can be included on actuation member  22  or a disruption of the threading may be included where a deformable material is included in the threading disruption. It is contemplated that the deformable member or deformable threading can be made from a deformable or elastic, biocompatible material such as nitinol or PEEK. 
     Turning now to  FIGS. 1-8 and 10-11 , a method of installing the expandable fusion device  10  is now discussed. Prior to insertion of the fusion device  10 , 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 bodies  2 ,  3  are then scraped to create an exposed end surface for facilitating bone growth across the invertebral space. The expandable fusion device  10  is then introduced into the intervertebral space, with the first end  26  being inserted first into the disc space followed by the second end  28 . In an exemplary method, the fusion device  10  is in the unexpanded position when introduced into the intervertebral space. The wedged shaped first end  26  will assist in distracting the adjacent vertebral bodies  2 ,  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 device  10 . In another 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. 
     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  FIGS. 1, 4, 6, 8, and 11 . To expand the fusion device  10 , an instrument is engaged with recess  86  in the actuation member  22 . The instrument is used to rotate actuation member  22 . As discussed above, actuation member  22  is threadingly engaged body portion  12  and is engaged with translation member  18 ; thus, as the actuation member  22  is rotated in a first direction, the actuation member  22  and the translation member  18  move with respect to the body portion  12  toward the first end  26  of the body portion  12 . In another exemplary embodiment, the actuation member  22  is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuation member  22  and the translation member  18 . As the translation member  18  moves, the ramped surface  64 ,  66  of the expansion portions  60 ,  62  push against the ramped surfaces  54 ,  56  of the endplates  14 ,  16  pushing endplates  14 ,  16  outwardly into the expanded position. This can best be seen in  FIGS. 10 and 11 . 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 actuation member  22 . As discussed above, the fusion device  10  includes a locking mechanism  24  which assists in retaining the endplates  14 ,  16  at the desired height. 
     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  54 ,  56 ,  64 ,  66 . As best seen in  FIG. 13 , 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. 
     Turning back to  FIGS. 1-8 and 10-11 , 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 is engaged with recess  86  in the actuation member  22 . The instrument is used to rotate actuation member  22 . As discussed above, actuation member  22  is threadingly engaged body portion  12  and is engaged with translation member  18 ; thus, as the actuation member  22  is rotated in a second direction, opposite the first direction, the actuation member  22  and translation member  18  move with respect to the body portion  12  toward the second end  28  of the body portion  12 . As the translation member  18  moves, the pins  20 , a portion of which are located within the slots  52 , ride along the slots  52  pulling the endplates  14 ,  16  inwardly into the unexpanded position. 
     With reference now to  FIG. 14 , 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 . 
     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. 
     With reference to  FIG. 16 , an exploded perspective view of one embodiment of the fusion device  210  is shown. In an exemplary embodiment, the fusion device  210  includes a body portion  212 , a first endplate  214 , a second endplate  216 , a translation member  218 , an actuation member  220 , and an insert  222 . 
     With additional reference to  FIGS. 17-20 , in an exemplary embodiment, the body portion  212  has a first end  224 , a second end  226 , a first side portion  228  connecting the first end  224  and the second end  226 , and a second side portion  229  on the opposing side of the body portion  212  connecting the first end  224  and the second end  226 . The body portion  212  further includes an upper end  230 , which is sized to receive at least a portion of the first endplate  214 , and a lower end  232 , which is sized to receive at least a portion of the second endplate  216 . 
     The first end  224  of the body portion  212 , in an exemplary embodiment, includes at least one angled surface  234 , but can include multiple angled surfaces. The angled surface  234  can serve to distract the adjacent vertebral bodies when the fusion device  210  is 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 device  210  is inserted into an intervertebral space. 
     The second end  226  of the body portion  212 , in an exemplary embodiment, includes an opening  236  which may include threading. In another exemplary embodiment, the opening  236  may include ratchet teeth instead of threading. The opening  236  extends from the second end  226  of the body portion  212  into a central opening (not illustrated) in the body portion  212 . In one embodiment, the central opening is sized to receive the translation member  218 , and the opening  236  is sized to threadingly receive the actuation member  220 . In another exemplary embodiment, the opening  236  is sized to receive the actuation member  220  in a ratcheting fashion. In yet another exemplary embodiment, first side portion  228  and second side portion  229  each include a recess  238  located towards the second end  226  of the body portion  212 . The recess  238  is configured and dimensioned to receive an insertion instrument (not shown) that assists in the insertion of the fusion device  210  into an intervertebral space. 
     Although the following discussion relates to the first endplate  214 , it should be understood that it also equally applies to the second endplate  216  as the second endplate  216  is substantially identical to the first endplate  214  in embodiments of the present invention. Turning now to  FIGS. 16-20 , in an exemplary embodiment, the first endplate  214  has an upper surface  240 , a lower surface  242 , and a through opening  243 . The through opening  243 , 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 portion  212 . 
     In one embodiment, the lower surface  242  includes at least one extension  244  extending along at least a portion of the lower surface  242 . As best seen in  FIGS. 17 and 18 , in an exemplary embodiment, the extension  244  can extend along a substantial portion of the lower surface  242 , including, along each side of the endplate  214  and along the front end of the endplate  214 . In another exemplary embodiment, the extension  244  includes at least one ramped portion  246 , but can include any number of ramped portions, including two spaced ramped portions  246 ,  248  in the extension  244  that extend between each side of the endplate  214 , as best seen in  FIG. 18 . It is contemplated that the slope of the ramped portions  246 ,  248  can be equal or can differ from each other. The effect of varying the slopes of the ramped portions  246 ,  248  is discussed below. 
     In an exemplary embodiment, the ramped portions  246 ,  248  further include grooved portions  247 ,  249  that are configured and dimensioned to receive angled surfaces  258 ,  260  of the translation member  218  and are oriented in an oblique fashion. In a preferred embodiment, the grooved portions  246 ,  248  are dovetail grooves configured and dimensioned to hold the angled surfaces  258 ,  260  of the translation member  218  while allowing the angles surfaces  258 ,  260  to slide against the ramped portions  246 ,  248 . 
     Referring now to  FIGS. 17-20 , in one embodiment, the upper surface  240  of the first endplate  214  is flat and generally planar to allow the upper surface  240  of the endplate  214  to engage with the adjacent vertebral body  202 . Alternatively, as shown in  FIG. 21 , the upper surface  240  can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body  202 . It is also contemplated that the upper surface  240  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  202  in a lordotic fashion. Turning back to  FIGS. 16-20 , in an exemplary embodiment, the upper surface  240  includes texturing  250  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. 
     With reference to  FIGS. 16 and 18-20 , in an exemplary embodiment, the translation member  218  is sized to be received within the central opening of the body portion  212  and includes at least a first expansion portion  252 . In another embodiment, the translation member  218  includes a first expansion portion  252  and a second expansion portion  254 , the expansion portions  252 ,  254  being connected together via a bridge portion  256 . 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 portions  252 ,  254  each have angled surfaces  258 ,  260  configured and dimensioned to engage the grooved portions  246 ,  248  of the first and second endplates  214 ,  216 . In one embodiment, the translation member  218  includes an opening  262  in the first expansion portion  252 , which is sized to receive a portion of the actuation member  220 , as best seen in  FIG. 18 . In an exemplary embodiment, the first expansion portion  252  includes a central bore  263  that extends from the opening  262  and through the first expansion portion  252 . In one embodiment, the translation member  218  includes a hole  264  in the second expansion portion  254 , which is sized to receive nose  266 , as best seen in  FIGS. 19 and 20 . In an exemplary embodiment, the hole  264  includes threading  268  for threadedly receiving a threaded end  270  of the nose  266 , as shown on  FIG. 20 . The nose  266  is received in an opening  272  in the first end  234  of the body portion  212  to stabilize the translation member  218  in the central opening of the body portion  212 . 
     In one embodiment, the translation member  218  includes a locking mechanism  274 , which is configured and adapted to engage the actuation member  220 . As illustrated, the locking mechanism  274  may extend from the first expansion portion  252 . The locking mechanism  274  includes a slot  276  configured and adapted to receive extension  287  of the actuation member  220 . In an exemplary embodiment, the locking mechanism  274  further includes a stop  278  (e.g., a rim, a lip, etc.) that engages the actuation member  220  when it is disposed in the slot  276 . 
     Referring now to  FIGS. 16-20 , in an exemplary embodiment, the actuation member  220  has a first end  280 , a second end  282 , and threading (not illustrated) extending along at least a portion thereof from the first end  280  to the second end  282 . The threading threadingly engages the threading that extends along a portion of opening  236  in the body portion  212 . In another exemplary embodiment, the actuation member  220  includes ratchet teeth instead of threading. The ratchet teeth engage corresponding ratchet teeth in the opening  236  in the body portion  212 . The first end  280  includes a recess  284  dimensioned to receive an instrument (not shown) that is capable of advancing the actuation member  220  with respect to the body portion  212  of the fusion device  210 . In an embodiment, the actuation member  220  includes a bore  285 , as best seen by  FIG. 18 , that extends from the recess  284  in the first end to the second  282 . The second end  282  of the actuation member  220  includes an extension  286  that is received within the opening  262  in the first expansion portion  252 . In one embodiment, the extension  288  may include a lip portion  286  and a plurality of slits  288 . The plurality of slits  288  are configured to receive inserts  222 . Inserts  222  are provided to limit motion of the actuation member  220 . Once the lip portion  286  is placed into the slot  276  of the locking mechanism  274 , the lip portion  286  will engage the stop  278  preventing longitudinal movement of the actuation member  220  with respect to the translation member  218 . It is further contemplated that a pin member  290  can be included to further secure the actuation member  220  in the translation member  219 . In an embodiment, the pin member  290  can be pressed into the central bore  285  of the actuation member  220  and the central bore  263  of the translation member, thereby preventing the actuation member  220  from disengaging from the translation member  218 . Additionally, in an exemplary embodiment, the fusion device  210  can further include a chamfered tip  224  for distraction of adjacent vertebrae. 
     Turning now to  FIGS. 15-20 , a method of installing the expandable fusion device  210  is now discussed. Prior to insertion of the fusion device  210 , 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  202 ,  203  are then scraped to create an exposed end surface for facilitating bone growth across the invertebral space. The expandable fusion device  210  is then introduced into the intervertebral space, with the first end  222  of the body portion  212  being inserted first into the disc space followed by the second end  224 . In an exemplary method, the fusion device  210  is in the unexpanded position when introduced into the intervertebral space. The wedged-shaped first end  222  should assist in distracting the adjacent vertebral bodies  202 ,  203 , if necessary. This allows for the option of having little to no distraction of the intervertebral space prior to the insertion of the fusion device  210 . In another exemplary method, the intervertebral space may be distracted prior to insertion of the fusion device  210 . 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  202 ,  203  easier. 
     With the fusion device  210  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  FIGS. 15, 19, and 20 . To expand the fusion device  210 , an instrument is engaged with recess  284  in the actuation member  220 . The instrument is used to rotate actuation member  220 . As discussed above, actuation member  220  can be threadingly engaging body portion  212  and is engaged with translation member  218 ; thus, as the actuation member  220  is rotated in a first direction, the actuation member  220  and the translation member  218  move with respect to the body portion  212  toward the first end  222  of the body portion  212 . In another exemplary embodiment, the actuation member  220  is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuation member  220  and the translation member  218 . As the translation member  218  moves, the angled surfaces  258 ,  260  of the expansion portions  252 ,  254  push against the ramped portions  246 ,  248  of the endplates  214 ,  216  pushing endplates  214 ,  216  outwardly into the expanded position with the angled surfaces  258 ,  260  riding along the grooved portions  247 ,  248  of the ramped portions  246 ,  248 . This can best be seen in  FIGS. 19 and 20 . Since the expansion of the fusion device  210  is actuated by a rotational input, the expansion of the fusion device  210  is infinite. In other words, the endplates  214 ,  216  can be expanded to an infinite number of heights dependent on the rotational advancement of the actuation member  220 . As discussed above, the fusion device  210  includes a locking mechanism  222  which assists in retaining the endplates  14 ,  16  at the desired height. 
     It should also be noted that the expansion of the endplates  214 ,  216  can be varied based on the differences in the dimensions of the ramped portions  246 ,  248  and the angled surfaces  258 ,  260 . As best seen in  FIG. 22 , the endplates  214 ,  216  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. 
     Turning back to  FIGS. 15-20 , in the event the fusion device  210  needs to be repositioned or revised after being installed and expanded, the fusion device  210  can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device  210 , the instrument is engaged with recess  284  in the actuation member  220 . The instrument is used to rotate actuation member  220 . As discussed above, actuation member  220  can be threadingly engaging body portion  212  and is engaged with translation member  218 ; thus, as the actuation member  220  is rotated in a second direction, opposite the first direction, the actuation member  220  and translation member  218  move with respect to the body portion  212  toward the second end  226  of the body portion  212 . As the translation member  218  moves, the angled surfaces  258 ,  260  of the translation member  218  ride along the grooved portions  247 ,  249  pulling the endplates  214 ,  216  inwardly into the unexpanded position. 
     With reference now to  FIG. 23 , fusion device  210  is shown with an exemplary embodiment of artificial endplates  300 . Artificial endplates  300  allows the introduction of lordosis even when the endplates  214  and  216  of the fusion device  210  are generally planar. In one embodiment, the artificial endplates  300  have an upper surface  302  and a lower surface  304 . The upper surfaces  302  of the artificial endplates  300  have at least one spike  306  to engage the adjacent vertebral bodies. The lower surfaces  304  have complementary texturing or engagement features on their surfaces to engage with the texturing or engagement features on the upper endplate  214  and the lower endplate  216  of the fusion device  210 . In an exemplary embodiment, the upper surface  302  of the artificial endplates  300  have a generally convex profile and the lower surfaces  304  have a generally parallel profile to achieve lordosis. In another exemplary embodiment, fusion device  210  can be used with only one artificial endplate  300  to introduce lordosis even when the endplates  214  and  216  of the fusion device  210  are generally planar. The artificial endplate  300  can either engage endplate  214  or engage endplate  216  and function in the same manner as described above with respect to two artificial endplates  300 . 
     Referring now to  FIGS. 24 and 25 , an alternative embodiment of the fusion device  210  is shown. In an exemplary embodiment, the fusion device  210  includes a body portion  212 , a first endplate  214 , a second endplate  216 , a translation member  218 , and an actuation member  220 . In the illustrated embodiment, the fusion device further includes a first ramped insert  320  and a second ramped insert  322 . 
     Although the following discussion relates to the first ramped insert  320 , it should be understood that it also equally applies to the second ramped insert  322  as the second ramped insert  322  is substantially identical to the first ramped insert  320  in embodiments of the present invention. Turning now to  FIGS. 24-27 , in an exemplary embodiment, the first ramped insert  320  includes a first ramped portion  324  and a second ramped portion  326 , the first and second ramped portions  324 ,  326  being connected by a bridge portion  328 . The ramped portions  324 ,  326  each have grooved portions  330 ,  332  configured and dimensioned to receive angled surfaces  258 ,  260  of the translation member. The ramped portions  324 ,  326  can be oriented in an oblique fashion, as illustrated. In a preferred embodiment, the grooved portions  330 ,  332  are dovetail grooves configured and dimensioned to hold the angled surfaces  258 ,  260  of the translation member  218  while allowing the angles surfaces  258 ,  260  to slide against the ramped portions  324 ,  326 . 
     In an exemplary embodiment, the first ramped insert  320  should be configured and dimensioned to be engaged with the first endplate  214 . In an embodiment, the first and second ramped portions  324 ,  326  include snap connectors  334 ,  336  for securing the first ramped insert  320  to the first endplate. It should be understood that the snap connectors  334 ,  336  are merely illustrative and that other suitable mechanisms for securing the first ramped inserted  320  with the first endplate  214  may be used. 
     Referring to  FIGS. 24-27 , in an exemplary embodiment, the translation member  218  is sized to be received within the central opening of the body portion  212  and includes at least a first expansion portion  252 . In another embodiment, the translation member  218  includes a first expansion portion  252  and a second expansion portion  254 , the expansion portions  252 ,  254  being connected together via a bridge portion  256 . 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 portions  252 ,  254  each have angled surfaces  258 ,  260  configured and dimensioned to engage the grooved portions  330 ,  332  of the first and second ramped inserts  320 ,  322 . In one embodiment, the angled surfaces  258 ,  260  include corresponding grooved portions  338 ,  340 , as best seen in  FIG. 27 , that slidingly engaged the grooved portions  330 ,  332  of the first and second ramped inserts  320 ,  322 . 
     In one embodiment, the expansion portion  252  includes an opening  262 , which is sized to receive a portion of the actuation member  220 , and the expansion portion  262  includes a nose  266 , which is received within an opening  272  in the first end  234  of the body portion  212  to stabilize the translation member  218  in the central opening of the body portion  212 . In an embodiment, the nose  266  is integral with the expansion portion  262 . In an embodiment (shown on  FIGS. 16 and 18-20 ), the nose  266  is threadingly engaged with the expansion portion  262 . In an embodiment, the translation member  218  includes a locking mechanism  274  to engage the actuation member  220 , as illustrated in  FIGS. 16-20 . However, it should be understood that other suitable mechanisms may be used to secure the actuation member  220  within the translation member  218 . For example, the actuation member  220  may include an extension  287  having a lip portion  286  (shown on  FIGS. 16 and 18-20 ) that engages the expansion portion  262 . The extension  287  may, for example, be configured to flex inwardly reducing its diameter when received in the opening  262 . Once the lip portion  286  of the extension  287  is advanced beyond the end of the opening  262 , the extension portion  287  will return back to its original diameter and the lip portion  286  will engage the expansion portion  260 . 
     The expandable fusion device  210  of  FIGS. 24-27  can be inserted into the intervertebral space in a manner similar to that the previously described with respect to  FIGS. 15-20 . After insertion, the expandable fusion device  210  of  FIGS. 24-27  can be expanded into the expanded position, as best seen in  FIGS. 24 and 25 . To expand the fusion device  210 , an instrument is engaged with recess  284  in the actuation member  220 . The instrument is used to rotate actuation member  220 . As discussed above, actuation member  220  can be threadingly engaging body portion  212  and is engaged with translation member  218 ; thus, as the actuation member  220  is rotated in a first direction, the actuation member  220  and the translation member  218  move with respect to the body portion  212  toward the first end  222  of the body portion  212 . In another exemplary embodiment, the actuation member  220  is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the actuation member  220  and the translation member  218 . As the translation member  218  moves, the angled surfaces  258 ,  260  of the expansion portions  252 ,  254  push against the ramped portions  324 ,  326  of the first and second ramped inserts  320 ,  322  while riding along the grooved portions  330 ,  332 , thus pushing first and second ramped inserts  320 ,  322  outwardly. Because the first and second ramped inserts  320 ,  322  are engaged with the endplates  214 ,  216 , the endplates  214 ,  216  are also pushed outwardly into the expanded position. 
     After expansion, the expandable fusion device  210  can be contracted back to the unexpanded configuration. To contract the fusion device  210 , the instrument is engaged with recess  284  in the actuation member  220 . The instrument is used to rotate actuation member  220 . As discussed above, actuation member  220  can be threadingly engaging body portion  212  and is engaged with translation member  218 ; thus, as the actuation member  220  is rotated in a second direction, opposite the first direction, the actuation member  220  and translation member  218  move with respect to the body portion  212  toward the second end  226  of the body portion  212 . As the translation member  218  moves, the angled surfaces  258 ,  260  of the translation member  218  ride along the grooved portions  330 ,  332  pulling the first and second ramped inserts  320 ,  322  and thus, the endplates  214 ,  216  inwardly into the unexpanded position. 
     Referring now to  FIG. 28 , an alternative embodiment of the fusion device  210  is shown. In an exemplary embodiment, the first endplate  214  and the second endplate  216  each include additional geometry to help securely hold the endplates  214 ,  216  in place. In an embodiment, the first endplate  214  and/or the second endplate  216  include threaded holes  341  through which the fasteners, such as screws  342 , may be inserted. In an embodiment, the threaded holes  341  penetrate through the first endplate  214  and/or the second endplate  216  in an oblique fashion. It is contemplated that the screws  342  may inserted through the threaded holes  341  and into adjacent vertebral bodies  202 ,  203 , to further secure the first endplate  214  and the second endplate  216  to the vertebral bodies  202 ,  203 . 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 device  210  needs adjustment and/or replacement. 
     With reference now  FIGS. 29-31 , an alternative embodiment of the fusion device  210  is 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 device  210  includes body portion  212 , first endplate  344 , and second endplate  346 . 
     Although the following discussion relates to the first endplate  344 , it should be understood that it also equally applies to the second endplate  346  as the second endplate  346  is substantially identical to the first endplate  344  in embodiments of the present invention. Turning now to  FIGS. 31-33 , in an exemplary embodiment, the first endplate  344  has an upper surface  348 , a lower surface  350 , and an inner surface  351  facing the body portion  212 . It is contemplated that the upper surface  348  will engage adjacent vertebral body  202  (seen on  FIG. 15 ) and the lower surface  350  will engage adjacent vertebral body  203  (seen on  FIG. 15 ). In one embodiment, the upper surface  348  and the lower surface  350  are each flat and generally planar to allow the upper surface  348  to engage with the adjacent vertebral body  203 . Alternatively, the upper surface  348  and/or the lower surface  350  can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral bodies  202 ,  203 . It is also contemplated that the upper surface  348  and/or the lower surface  350  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  202  and/or the adjacent vertebral body  203  in a lordotic fashion. In an exemplary embodiment, the upper surface  348  and/or lower surface  350  includes textures  352  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. 
     In one embodiment, the inner surface  351  includes at least one extension  354  extending along at least a portion of the inner surface  351 . In an exemplary embodiment, the extension  354  can extend along a substantial portion of the inner surface  354 , including, along each side of the endplate  344  and along the front end of the endplate  214 . 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 surfaces  246 ,  248  and grooved portion  247 ,  249  in extension  244  shown on  FIGS. 18-20 . In an embodiment, the extension  354  may include slots  356  oriented in an oblique fashion through which pins  358  may be inserted. 
     While not illustrated, the fusion device  210  further includes features to effectuate the lateral expansion of the first and second endplates  344 ,  346 . In one embodiment, the fusion device  210  using a ramping system—similar to the system illustrated in  FIGS. 16 and 18-20 —for expanding the first and second endplates  344 ,  346 . In an exemplary embodiment, the fusion device  210  further includes a translation member and actuation member, such as translation member  218  and actuation member  220  shown on  FIGS. 16 and 18-20 . It is contemplated that the translation member may include angled surfaces that push against ramped surfaces in the extension  354 , expanding the first and second endplates  344 ,  346  outwardly and away from the body portion  212 . In an embodiment, pins  356  disposed through the slots  354  may 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 member  218  and actuation member  220  described above with respect  FIGS. 15-20 . In another embodiment, the fusion device  210  further includes first and second ramped inserts that are secured within the first and second endplates  344 ,  346 . The first and second ramped inserts may be similar to the first and second ramped inserts  320 ,  322  described above with respect to  FIGS. 24-27 . 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 endplates  344 ,  346 , the first and second endplates  344 ,  346  may thus be expanded outwardly. In this manner, the first and second endplates  344 ,  346  may be laterally expanded away from the body portion  212 . It should be understood that other suitable techniques may also be used to effectuate this lateral expansion. 
     With reference to  FIG. 32 , an exploded perspective view of another embodiment of fusion device  210  is shown. In an exemplary embodiment, the fusion device  210  includes a body portion  212 , a first endplate  400 , a second endplate  402 , a third endplate  404 , a fourth endplate  406 , and a translation member  218 . In this embodiment, the fusion device  210  is configured to expand both vertically and laterally. 
     In an exemplary embodiment, the body portion  212  has a first end  224 , a second end  226 , a first side portion  228  connecting the first end  224  and the second end  226 , and a second side portion  229  on the opposing side of the body portion  212  connecting the first end  224  and the second end  226 . The body portion  212  further includes a top side portion  408  connecting the first end  224  and the second end  226 , and a bottom side portion  410  on the opposing side of the body portion  212  connecting the first end  224  and the second end  226 . The body portion  212  further includes first gap  412  between the top side portion  408  and the first side portion  228 , which is sized to receive at least a portion of the first endplate  400 . The body portion  212  further includes second gap  414  between the top side portion  408  and the second side portion  229 , which is sized to receive at least a portion of the second endplate  402 . The body portion  212  further includes third gap  416  between the bottom side portion  410  and the first side portion  228 , which is sized to receive at least a portion of the third endplate  404 . The body portion  212  further includes fourth gap  418  between the bottom side portion  410  and the second side portion  229 , which is sized to receive at least a portion of the fourth endplate  406 . 
     The first end  224  of the body portion  212 , in an exemplary embodiment, includes an opening  420 . The opening  420  extends from the first end  224  of the body portion  212  into a central opening  422 . In one embodiment, the central opening  422  is sized to receive the translation member  218 . The second end  226  of the body portion  212 , in an exemplary embodiment, includes an opening  236 , which extends from the second end  226  of the body portion  212  into the central opening  422 . 
     Although the following discussion relates to the first endplate  400 , it should be understood that it also equally applies to the second endplate  402 , the third endplate  404 , and the fourth endplate  406 , as these endplates  402 ,  404 ,  406  are substantially identical to the first endplate  400  in embodiments of the present invention. Turning now to  FIGS. 32-34 , in an exemplary embodiment, the first endplate  214  has a first end  424  and a second end  426 . The first endplate further includes an upper surface  240  connecting the first end  424  and the second end  426  and a lower surface  442  on an opposing side of the endplate  400  connecting the first end  424  and the second end  426 . While not illustrated, the first endplate  214  may 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 opening  422  in the body portion  212 . 
     In one embodiment, the lower surface  242  includes at least one first retaining socket  428  on the lower surface  242 . In an exemplary embodiment, the lower surface  242  includes a first retaining socket  428  at the interior corner of the intersection of the first end  424  and the lower surface  242 , and a second retaining socket  430  at the interior corner of the intersection of the first end  424  and the lower surface  242 . 
     Referring now to  FIGS. 32-34 , in one embodiment, the upper surface  240  of the first endplate  400  is curved convexly. Alternatively, the upper surface  240  is flat or curved concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral body  202 . It is also contemplated that the upper surface  240  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  202  in a lordotic fashion. In an exemplary embodiment, the upper surface  240  includes texturing  250  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. 
     With reference to  FIG. 32 , in an exemplary embodiment, the translation member  218  is sized to be received within the central opening  422  of the body portion  212 . The translation member  218  should be sized to allow longitudinal translation within the central opening  422 . In an embodiment, the translation member  218  includes at least a first expansion portion  252 . In another embodiment, the translation member  218  includes a first expansion portion  252  and a second expansion portion  254 , the expansion portions  252 ,  254  being connected together via a bridge portion  256 . 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 portions  252 ,  254  each have angled surfaces  258 ,  260 . In an embodiment, the angles surfaces  258 ,  260  each comprise first end  429  and second end  431  with second end  431  being wider than the first end  429 . In an exemplary embodiment, the expansion portions  252 ,  254  include grooved portions  432 ,  434  on the edges of at least two sides (e.g., the lateral sides) of the angled surfaces  258 ,  260 . The grooved portions  432 ,  434  are configured and dimensioned to engage the first and second retaining sockets  428 ,  430  on the endplates  400 ,  402 ,  404 ,  406 . In an exemplary embodiment, the grooved portions  432 ,  434  retain the first and second retaining sockets  428 ,  430  in sliding engagement. 
     In one embodiment, the translation member  218  includes a first end  436  and a second end  438 . The first end  436  of the translation member includes an extension  440  sized to be received within the opening  420  in the first end  224  of the body portion  212 . While not illustrated, the second end  438  also can include a similar extension sized to be received within opening  232  in the second end  226  of the body portion  212 . 
     The expandable fusion device  210  of  FIGS. 32-34  can be inserted into the intervertebral space in a manner similar to that the previously described with respect to  FIGS. 15-20 . After insertion, the expandable fusion device  210  of  FIGS. 32-34  can be expanded into the expanded position. As previously mentioned, the fusion device  210  shown on  FIGS. 32-34  expands both vertically and laterally. To expand the fusion device  210 , the translation member  218  can be moved with respect to the body portion  212  toward the first end  224  of the body portion. An instrument can be used, in an exemplary embodiment. As the translation member  218  moves, the first retaining socket  428  and the second retaining socket  430  ride along the grooved portions  432 ,  434  of the expansion portions  252 ,  254  pushing the endplates  400 ,  402 ,  404 ,  406  outwardly in the direction indicated by arrows  442 . In an embodiment, the endplates  400 ,  402 ,  404 ,  406  move outwardly in an oblique fashion to expand the fusion device  210  both vertically and laterally. The expanded configuration of the expansion device  210  is best seen in  FIG. 34 . 
     After expansion, the expandable fusion device  210  can be contracted back to the unexpanded configuration. The unexpanded configuration of the fusion device  210  is best seen in  FIG. 34 . To contract the fusion device  210 , the translation member  218  is moved with respect to the body portion  212  toward the second end  226  of the body portion  212 . As the translation member  218  moves, the first retaining socket  428  and the second retaining socket  430  ride along the grooved portions  432 ,  434  of the expansion portions  252 ,  254  pulling the endplates  400 ,  402 ,  404 ,  406  inwardly in a direction opposite that indicated by arrows  442 . In an embodiment, the endplates  400 ,  402 ,  404 ,  406  move inwardly in an oblique fashion to contract the fusion device  210  both vertically and laterally. The unexpanded configuration of the expansion device  210  is best seen in  FIG. 33 . 
     With reference to  FIGS. 35-36 , another embodiment of expandable fusion device  210  is shown. In an exemplary embodiment, the fusion device  210  includes a body portion  212 , a vertically expanding plate  500 , and a gear  502 . In this embodiment, a portion of the fusion device  210  is configured to expand vertically in at least one direction. In an exemplary embodiment, the vertically expanding plate  500  is configured to expand outwardly from the body portion  212 . It is contemplated that an expandable fusion device  210  may be used to correct spinal curvature due to, for example, scoliosis, lordosis, and the like. 
     In an exemplary embodiment, the body portion  212  has a first end  224 , a second end  226 , a first side portion  228  connecting the first end  224  and the second end  226 , and a second side portion  229  on the opposing side of the body portion  212  connecting the first end  224  and the second end  226 . The first end  224  of the body portion  212 , in an exemplary embodiment, includes at least one angled surface  234 , but can include multiple angled surfaces. The angled surface  234  can serve to distract the adjacent vertebral bodies when the fusion device  210  is 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 device  210  is inserted into an intervertebral space. In yet another preferred embodiment, first side portion  228  and second side portion  229  each include a recess  238  located towards the second end  226  of the body portion  212 . The recess  238  is configured and dimensioned to receive an insertion instrument  504  that assists in the insertion of the fusion device  210  into an intervertebral space. 
     In an exemplary embodiment, the body portion  212  includes an upper engagement surface  506  extending from the first end  224  towards the second end  226 , and a lower engagement surface  508  extending between the first end  224  and the second end  226 . In an embodiment, the upper engagement surface  506  has a through opening  510 . Although not illustrated, the lower engagement surface  508  may have a through opening that is similar to through opening  510 . The through opening  510 , 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 portion  212 . In an embodiment, at least a portion of the body portion  212  is removed to form a landing  512  in the body portion  212 . In an exemplary embodiment, a portion of the upper engagement surface  506  and the second end  226  are removed to form the landing  512  having an upper surface  514 . While not illustrated, a portion of the lower engagement surface  508  and the second end  226  may be cut away, in an alternative embodiment, to form the landing  512 . 
     In one embodiment, the upper engagement surface  506  and the lower engagement surface  508  are flat and generally planar to allow engagement surfaces  506  to engage with the adjacent vertebral body  202  and the lower engagement surface  508  to engage with the adjacent vertebral body  203 . Alternatively, the upper engagement surface  506  and/or the lower engagement surface  508  can be curved convexly or concavely to allow for a greater or lesser degree of engagement with the adjacent vertebral bodies  202 ,  203 . In an exemplary embodiment, the upper engagement surface  506  and/or the lower engagement surface includes texturing  512  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. 
     In an exemplary embodiment, vertically expanding plate  500  is coupled to an end of threaded bolt  518 , which is coupled to the gear  502 . In one embodiment, the threaded bolt  518  is in threaded engagement with the gear  502 . In an alternative embodiment, a bolt having ratchet teeth may be used instead of threaded bolt  518 . In an embodiment, the gear  502  is coupled to the landing  512 . In one embodiment, the gear  502  is rotatably coupled to the landing  512 . 
     The vertically expanding plate  500  includes a throughbore  519  and an upper surface  520 . In one embodiment, the vertically expanding plate  500  is generally circular in shape. Other suitable configurations of the expanding plate  500  may also be suitable. In an embodiment, the vertically expanding plate may be generally rectangular in shape with rounded corners, as best seen in  FIG. 37 . In one embodiment, the vertically expanding plate  500  is flat and generally planar to allow upper surface  520  to engage with the adjacent vertebral body  202 . Alternatively, the upper surface  520  can 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 surface  520  includes texturing  522  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. 
     With reference to  FIG. 37 , an alternative embodiment of the expandable fusion device  210  of  FIGS. 35-36  is shown. In this embodiment, the gear  502  is enclosed within the body portion  212  towards the second end  226  of the body portion  212  with the vertically expanding plate  500  disposed at or above the upper engagement surface  506  of the body portion  212 . In an embodiment, the vertically expanding plate  500  is positioned towards the second end  226  of the body portion  212 . While not illustrated, the threaded bolt  518  extends through the upper engagement surface  506  and couples the vertically expanding plate  500  and the gear  502 . An actuator screw  524  extends through the first end  224  of the body portion  212  to engage the gear  502 . 
     The expandable fusion device  210  of  FIGS. 35-37  can be inserted in the intervertebral space in a manner similar to that the previously described with respect to  FIGS. 15-20 .  FIG. 38  illustrates the expandable fusion device  210  of  FIG. 37  between adjacent vertebral bodies  202 ,  203  in an unexpanded position. After insertion, the expandable fusion device  210  of  FIGS. 35-37  can be expanded into the expanded position. As previously mentioned, a portion of the fusion device shown on  FIGS. 35-37  expands vertically in at least one direction. To partially expand the fusion device  210 , the gear  502  can be rotated in a first direction. An instrument  526  having a gear  528  disposed on a distal end  530  of the instrument may be used to rotate the gear  502 , as best seen on  FIG. 36 . In another embodiment, an instrument (not illustrated) may be used to rotate actuation member  524  in a first direction. As discussed above, the actuation member  524  is engaged with gear  502 ; thus, as the actuation member  524  is rotated in first direction, the gear  502  rotated in a first direction. The embodiment with the actuation member  524  is best seen in  FIG. 37 . As the gear  502  rotates, the threaded bolt  518  extends outward from the gear  502 , thus extending the laterally expanding plate  500  outward from the body portion  212 .  FIG. 39  illustrates the expandable fusion device  210  of  FIG. 37  in an expanded position. 
     After expansion, the expandable fusion device  210  can be contracted back to the unexpanded position. The unexpanded position of the fusion device  210  is best seen in  FIG. 38 . To contract the fusion device  210 , the gear  502  is rotated in a second direction that is opposite the first direction. The instrument  526  with the gear  528  may be used to rotate the gear  502 . Alternatively, an instrument may be used to rotate the actuation member  524  to turn the gear  502  in the second direction. As the gear  502  rotates in the second direction, the threaded bolt  518  retracts pulling the laterally expanding plate  500  inward into the unexpanded position. 
     In some embodiments, the fusion devices  210  can include additional features that provide additional benefits such as preventing screw loosening and added stability. These embodiments are discussed below. 
       FIGS. 40 and 41  show different views of a fusion device  210  including an advantageous interference nut  610  and stabilization members  622 ,  624  according to some embodiments. The fusion device  210  includes many features similar to the above-described devices, including a body portion  212 , a first endplate  214 , a second endplate  216 , a translation member  218 , and an actuation member  220 . The first endplate  214  can include a pair of openings  243   a  and  243   b  through which bone graft material can be received or deposited. Likewise, the second endplate  16  can have similar openings, although they are not shown from the illustrated viewpoints. In addition to these features, the fusion device  210  includes a novel interference nut  610  that is operably attached to a rear section of the body portion  212 , as well as a pair of stabilization members  622 ,  624 . 
       FIG. 40  illustrates an exploded view of the alternative fusion device  210 , while  FIG. 41  shows a top view of the same device with the first endplate  214  removed. As shown in both views, the translation member  218  includes three expansion portions  251 ,  252 , and  254 , which are connected via bridge portions  256 . The expansion portions  251 ,  252 , and  254  each have angled surfaces that are configured to engage grooved portions of the first and second endplates  214  and  216 . In some embodiments, the angled surfaces are of similar angles, while in other embodiments, the angled surfaces are of different angles. Advantageously, by providing at least three expansion portions  251 ,  252  and  254 , this allows for an even expansion along a majority of the length of the body portion  212  of the fusion device  210 . 
     The translation member  218  is received in the central opening of the body portion  212 . The body portion  212  can include a first end  224  and a second end  226 . In some embodiments, the first end  224  includes one or more apertures  602 ,  604  as shown in  FIGS. 40 and 41 . These apertures  602 ,  604  advantageously receive one or more stabilization members  622 ,  624 . 
     In some embodiments, the stabilization members  622 ,  624  each include a first substantially smooth portion  632 ,  634  and a second threaded portion  634 ,  644 . The stabilization members  622 ,  624  can be inserted through the apertures  602 ,  604  of the body portion  212 , with the threaded portions  634 ,  644  serving as the leading end that enters the apertures. After passing through the apertures  602 ,  604  of the body portion  212 , the stabilization members  622 ,  624  can come into contact with a side of the translation member  218 . In some embodiments, the threaded portions  634 ,  644  of the stabilization members  622 ,  624  can be threaded into mateable threaded surfaces of the translation member  218 . Advantageously, by using a pair of stabilization members  622 ,  624  as shown in  FIGS. 40 and 41  on a first end of the body portion  212 , this serves to prevent rocking of the body portion  212  during expansion and contraction of the device  210 . 
     While the illustrated embodiment in  FIGS. 40 and 41  show a pair of stabilization members  622 ,  624 , in other embodiments, a single stabilization member or more than two stabilization members can be used to assist in preventing rocking of the body portion  212 . In addition, while the stabilization members  622 ,  624  are illustrated as having a substantially cylindrical surface section, in other embodiments, the stabilization members  622 ,  624  can assume other shapes and geometries. For example, in other embodiments, the stabilization members  622 ,  624  can have a surface that includes at least one edge or corner. 
     As shown in  FIGS. 40 and 41 , the body portion  212  also includes an interference nut  610  that is positioned within a rear section of the body portion  212 . In some embodiments, the interference nut  610  is separate and removable from the body portion  212 , while in other embodiments, the interference nut  610  is not removable from the body portion  212 . In some embodiments, the interference nut  610  comprises a square nut that is operably connected to a rear section of the body portion  212 . The interference nut  610  can be mateably connected to a rear of the body portion  212 , for example, via a dove-tail type cut that encapsulates the interference nut. The interference nut  610  can be advantageously formed of a biocompatible material. In some embodiments, the interference nut  610  is formed of PEEK. 
     The interference nut  610  can include a hole (not shown) that is capable of receiving the actuation member  220  therethrough. The actuation member  220 , which can comprise a threaded set screw, passes through the interference nut  610  and into contact with the translation member  218 , as best shown in  FIG. 41 . Advantageously, the interference nut  610  serves to add drag to the actuation member  220  as it passes therethrough, thereby establishing an interference fit. By providing an interference fit, the risk of the actuation member  220  being loosened prior to or during use is minimized. 
       FIGS. 42-44  show different views of an alternative fusion device  210  including novel side stabilization members  652 ,  654  and a low profile actuation member  220 . The fusion device  210  includes many features similar to the above-described devices, including a body portion  212 , a translation member  218 , and an actuation member  220 . The fusion device  210  can also include a first endplate  214  and a second endplate  216  for contacting vertebral surfaces, as best shown in  FIG. 44 . Both the first endplate  214  and second endplate  216  can include a pair of openings through which bone graft material can be received or deposited. In addition to these features, the fusion device  210  includes novel side stabilization members  652 ,  654  that are introduced through side slots  213  and  214  of the body portion  212 . The fusion device  210  also includes a configuration that allows the actuation member  220  to be of low profile, as shown in  FIG. 42 . 
       FIG. 42  illustrates a top view of the alternative fusion device  210  having side stabilization members with the first endplate  214  removed, while  FIG. 43  illustrates a perspective view of the same device.  FIG. 44  illustrates a side cross-sectional view of the alternative fusion device  210  having side stabilization members. As shown in all three views, the translation member  218  includes three expansion portions  251 ,  252 , and  254 , which are connected via bridge portions  256 . The expansion portions  251 ,  252 , and  254  each have angled surfaces that are configured to engage grooved portions of the first and second endplates  214  and  216 . In some embodiments, the angled surfaces are of similar angles, while in other embodiments, the angled surfaces can be of different angles. Advantageously, by providing at least three expansion portions  251 ,  252  and  254 , this allows for an even expansion along a majority of the length of the body portion  212  of the fusion device  210 . 
     The translation member  218  is received in the central opening of the body portion  212 . The body portion  212  can include sidewalls that extend between the first end  224  and a second end  226 . As shown in  FIG. 43 , each of the sidewalls can include side slots  213 ,  214  for receiving one or more side stabilization members  652 ,  654 . 
     In some embodiments, the side stabilization members  652 ,  654  are similar to the stabilization members  622 ,  624  (shown in  FIG. 40 ). That is, the side stabilization members  652 ,  654  can include a threaded portion and a substantially smooth portion. The side stabilization members  652  can be inserted through the side slots  213 ,  214  of the body portion  212  and can operably attach (e.g., via threads) to the translation member  218 . Advantageously, the side slots  213 ,  214  help to provide rotational stability to the translation member  218  relative to the body portion  212  prior to or during use of the fusion device  210 . 
     In addition to providing side stabilization members, the fusion device  210  provides a configuration that includes a low profile actuation member  220 . Advantageously, as shown in  FIG. 42 , the actuation member  220  (which can comprise a screw) can have a head portion that is substantially flush against the surface of the body portion  212 , while a distal portion  221  of the actuation member  220  can extend through a wall of the translation member  218 . 
     As shown in  FIG. 44 , in some embodiments, the actuation member  220  can comprise a set screw  772  accompanied by a flange  773  and an actuation element  774 . The set screw  772  and actuation element  774  can both be threaded. Upon rotation of the set screw  772 , the actuation element  774  is threaded forward, thereby pushing the first endplate  214  upwardly and the second endplate  216  downwardly to cause expansion of the actuation member  220 . The flange  773 , which can be cylindrical, advantageously resists the opposing forces as the actuation element  774  is threaded forward, thereby helping to keep the fusion device  210  in an expanded configuration. Upon reverse rotation of the set screw  772 , the fusion device  210  can collapse. As shown in  FIG. 44 , a blocking nut  771  can be provided that is threaded onto the back side of the set screw  772  to secure the set screw into place when the device  210  is collapsed. 
     Additional embodiments of an expandable fusion device  210  are shown in  FIGS. 49 and 50 . This fusion device  210  incorporates a ring member  802  into a pocket  820  formed in the translation member  218 . 
     The fusion device  210  in  FIGS. 49 and 50  include many features similar to the above-described devices, including a body portion  212 , a first endplate  214 , a second endplate  216 , a translation member  218 , an actuation member  220 , and a pin member  290 . The first endplate  214  can include one or more openings through which bone graft material can be received or deposited. Likewise, the second endplate  216  can have similar openings, although they are not shown from the illustrated viewpoints. The translation member  218  can be comprised of one or more ramped expansion portions, such as expansion portions  251  and  252 , which are configured to assist in expansion and contraction of the fusion device  210 , as discussed above. 
     In addition to these features, the fusion device  210  incorporates a ring member  802  that is positioned between the actuation member  220  and the translation member  218 . In some embodiments, the ring member  802  is received in a pocket  820  that is formed in one of the expansion portions (such as expansion portion  251 ) of the translation member  218 . As shown in  FIG. 50 , the ring member  802  can comprise a closed annular body that can be received in a similarly shaped recess  820  formed in the body of an expansion portion  251  of the translation member  218 . Each of expansion portion  251 , ring member  802  and actuation member  220  can be placed over a pin member  290 . 
     In some embodiments, the ring member  802  can be formed of a material that is different from the translation member  218  and/or actuation member  220 . For example, while in some embodiments the translation member  18  and/or actuation member  220  are comprised of a metal, such as a biocompatible stainless steel, titanium or metal alloy, the ring member  802  can be formed of a polymer such as polyether ether ketone (PEEK). The advantage of providing a PEEK ring member  802  is that a more lubricious material is positioned between the face of the actuation member  220  and the surface of the translation member  218 , thereby reducing the friction between the two parts. With the PEEK ring member&#39;s  802  reduced coefficient of friction, this increases the amount of force transmitted when the actuation member  220  is screwed into the translation member  218 , thereby increasing the amount of expansion force provided to the ramped translation member  218 . In some embodiments, the use of a PEEK ring member between the interface of the actuation member  220  and translation member  218  increases the expansion force of the ramped translation member  218  while using the same force as would be applied if the PEEK ring member was not in place. In some embodiments, the use of a PEEK ring member between the translation member  218  and actuation member  220  provides a buffer that can prevent galling that would occur due to metal-on-metal contact between the translation member and actuation member. 
     In some embodiments, rather than receive an insert in the shape of ring member  802 , the translation member  218  can receive an insert having a different shape. For example, the translation member  218  can include one or more recesses that accommodate a wedge-shaped PEEK member between the translation member  218  and the actuation member  220 . Like the ring member  802 , the wedge-shaped PEEK member can also serve as a lubricious material that reduces the friction between the translation member  218  and the actuation member  220 . 
     In addition, in some embodiments, an insert can be placed between the translation member  218  and actuation member  220  without having to form a recess in the translation member. For example, a PEEK washer can be provided between the interface of the translation member  218  and actuation member  220 . 
     Although the preceding discussions only discussed having a single fusion device  210  in the intervertebral space, it is contemplated that more than one fusion device  210  can be inserted in the intervertebral space. It is further contemplated that each fusion device  210  does not have to be finally installed in the fully expanded state. Rather, depending on the location of the fusion device  210  in the intervertebral disc space, the height of the fusion device  210  may vary from unexpanded to fully expanded. 
     In some embodiments, the fusion devices  210  can be put into place with the assistance of a novel expandable trial member. The expandable trial member can be used prior to inserting an expandable fusion device in between vertebral bodies to obtain an accurate size measurement for the fusion device. The expandable trial member can help a user determine a fusion device of an appropriate size to use in a vertebra. Advantageously, the novel expandable trial member disclosed herein is configured such that the amount of distraction force applied to the trial member is linear and constant over its entire expansion range. 
       FIGS. 45-48  show different perspectives of an expandable trial member according to some embodiments.  FIG. 45  illustrates a perspective view of the trial member in a non-expanded configuration.  FIG. 46  illustrates a side cross-sectional view of the trial member in an expanded configuration.  FIG. 47  illustrates a top view of the trial member.  FIG. 48  shows an exploded view of the trial member. 
     As shown in the figures, the expandable trial member  700  comprises a body portion  712 , an upper endplate  714 , a lower endplate  716 , a translation member  718  and an actuation member  720 . The trial member  700  is configured such that when the actuation member  720  (shown in  FIG. 46 ) is pulled in a backward or proximal direction toward a handle portion  782  (shown in  FIG. 47 ), inner shaft or rod member  722  (shown in  FIG. 46 ) will push forward and cause inner ramped surfaces of the translation member  718  to translate relative to inner angled grooves cut into the upper endplate  714  and/or lower endplate  716 , thereby causing expansion of the trial member  700 . When the actuation member  720  is pushed in a forward or distal direction away from the handle portion  782 , the trial member  700  can collapse. In other embodiments, distal movement of the actuation member  720  can result in expansion of the expandable trial member, while proximal movement of the actuation member  720  can result in collapse of the trial member. The configuration of the trial member  700  thus allows pushing and pulling of the actuation member  720  to actuate the shaft or inner rod  722 , thereby causing expansion or contraction of the trial member  700 . Advantageously, because movement along the ramped surfaces of the upper endplate  714  and lower endplate  716  cause expansion or contraction, the amount of distraction force is linear over the entire expansion range of the trial member  700 . 
     The expandable trial member  700  includes an upper endplate  714  and a lower endplate  716 . As shown best in  FIG. 46 , both the upper endplate  714  and lower endplate  716  can include one or more surface grooves  780 . While the trial member  700  need not remain over an extended period of time within a vertebra, the surface grooves  780  advantageously help to retain the trial member  700  within a vertebra during its operational use. 
     A body portion  712  can be placed in between the upper endplate  714  and lower endplate  716 . The body portion  712  can include a sloped or chamfered anterior portion  734  (shown in  FIG. 45 ) that assists in distraction of vertebral bodies. 
     Within the body portion  712 , the translation member  718  can be received therein. As shown best in  FIG. 48 , the translation member  718  includes a plurality of upper ramped surfaces  751 ,  752  and  754  and a plurality of lower ramped surfaces  756 ,  757  and  758 . As shown in  FIG. 45 , the upper and lower endplates  714  and  716  can include one or more holes  711  that accommodate the upper and lower ramped surfaces when the trial member  700  is in a closed configuration. The upper ramped surfaces and lower ramped surfaces are configured to slidably mate with corresponding grooves (such as upper grooves  746  and  748  and lower groove  749  shown in  FIG. 46 ). When the actuation member  720  is pulled distally, the upper ramped surfaces slide downwardly through the grooves and the lower ramped surfaces slide upwardly through the grooves, thereby causing the expandable trial member  700  to expand from its closed configuration, shown in  FIG. 45 , to an expanded configuration, shown in  FIG. 46 . 
     In some embodiments, the body portion  712  can include a pair of side slots  713 , as shown in  FIG. 45 . The side slots  713  are configured to each receive a side stabilization member  762 . In some embodiments, the stabilization members  762  comprise stabilizer screws that contact the translation member  718 . Advantageously, the stabilization members  762  help keep the translation member  718  centered inside the body portion  712  to prevent twisting as it translates forward and backwards. 
     In some embodiments, the trial member  700  is configured to expand to have a trial height that is at least fifty percent higher than a height of the trial member  700  in its closed configuration. In other embodiments, the trial member  700  is configured to expand to have a trial height that is at least two times the height of the trial member  700  in its closed configuration. By having a trial member  700  with a wide variety of expansion configurations, a user can advantageously choose a properly sized fusion implant to accommodate a number of different patients of different sizes. 
       FIGS. 51-55  show different views of some embodiments of a proximal portion  750  of a trial member  700 . In some embodiments, the trial member  700  can be a single piece that extends from a proximal end to a distal end. In other embodiments, which are reflected in  FIGS. 51-55 , the proximal portion  750  can comprise a removable handle portion  782  that is configured to operably attach to a body of the trial member  700 . Advantageously, by providing a removable handle portion  782 , this helps to facilitate easier cleaning of the trial member  700 . The proximal portion  750  is configured to assist in movement of the inner shaft  722  of the trial member, thereby causing expansion and contraction of the trial member upper and lower endplates. In addition, the proximal portion  750  can comprise a novel locking member that operably mates the proximal portion  750  to the inner shaft  722 , thereby allowing the inner shaft  722  to be pulled back. Once the upper and lower endplates of the trial member are separated a desired distance, the trial member  700  can be removed, and an appropriately sized expandable implant can be inserted based on the separation distance between the upper and lower endplates. 
     In the trial member  700  shown in  FIG. 51 , the removable proximal portion  750  is configured to operably attach to a body of the trial member (such as shown in  FIG. 47 ). The proximal portion  750  is comprised of a handle  782  in the form of a housing member, a removable engagement insert  816 , and a slidable locking member  740 . The interior of the proximal portion  750  is configured to have a threaded insert  816  that mates with an exterior threaded surface  724  along the body of the trial member  700 . As the proximal portion  750  is rotatably threaded onto the body portion, a surface of the slidable locking member  740  pushes against the inner shaft  722  (shown in  FIG. 53  as within the exterior threaded surface  724 ), thereby causing expansion of the trial member endplates. 
     The body of the handle portion  782  is configured to receive a threaded insert  816  therein. While in some embodiments, the threaded insert  816  is comprised of the same material as the exterior threaded surface  724  of the body, in other embodiments, the threaded insert  816  and threaded surface  724  are of different materials. For example, in some embodiments, the threaded insert  816  can be a polymer, such as PEEK, while the exterior threaded surface  724  can be a metal, such as stainless steel. One skilled in the art will appreciate that other materials can also be used. By providing a PEEK insert  816  that threads onto the metal threads, this advantageously reduces the friction between the two components, thereby reducing the amount of work that is absorbed by the two components and increasing the expansion forces transmitted to the endplates. In addition, the use of a threaded PEEK insert  816  on metal prevents thread galling over multiple uses under high loading. To prevent rotation of the insert  816 , pin members  826  can be provided to contact the surface of the insert  816  along with the inner wall of the handle portion  782  (as shown in  FIG. 54 ). As shown in  FIG. 55 , a plurality of pin members  826  can be provided that align with the longitudinal axis of the insert  816  to prevent rotation of the insert  816 . 
     As the insert  816  of the removable proximal portion  750  is rotatably threaded onto the exterior threads of the body of the trial member, a surface of the slidable locking member  740  pushes against the inner shaft  722  of trial member, thereby causing expansion of the endplates. Reverse rotation of the threads of the insert  816  will result in contraction of the endplates. In some embodiments, the slidable locking member  740  can be moved from an unlocked to a locked configuration such that the inner shaft  722  is operably mated with the proximal portion  750  via the locking member  740 . More details regarding the slidable locking member  740  are discussed below. 
       FIG. 39  illustrates the proximal portion  750  of the trial member with the slidable locking member  740  in an unlocked configuration, while  FIG. 54  illustrates the proximal portion  750  of the trial member with the slidable locking member  740  in a locked configuration. In the unlocked configuration, the proximal portion  750  is able to translate along the body of the trial member, thereby pushing on the inner shaft  722  and causing expansion of the trial member endplates. In the locked configuration, the proximal portion  750  is operably mated to the inner shaft  722 , thereby allowing the inner shaft  722  to be pulled back via the proximal portion  750  in situ. 
     The slidable locking member  7540  comprises an insert attached to the proximal portion  750  of the trial member. In some embodiments, the locking member  740  comprises a J-shaped or hook-shaped body that is configured to slide up and down in order to provide unlocked and locked configurations, as shown in  FIGS. 51 and 52  respectively. The body of the locking member  740  can include a nub  749  (identified in  FIGS. 53 and 54 ) that can be received in a snap-fit into corresponding grooves  751   a  and  751   b  formed in the proximal portion  750 . When the nub  749  is in groove  7511   a , the locking member  740  is in an unlocked configuration. When the nub  749  is in groove  751   b , the locking member  740  is in a locked configuration. 
     As shown in  FIG. 54 , the hook-shaped body of the locking member  740  also includes a mating end  747  that can be received in a complementary mating portion  723  of the inner shaft  722 . When the mating end  747  is received in the mating portion  723  of the inner shaft  722 , this advantageously mates the proximal portion  750  to the inner shaft  722 , thereby allowing the inner shaft  722  to be pulled back in situ if desired. 
     In some embodiments, the locking member  740  is of the same material as surfaces of the proximal portion  750  and/or the inner shaft  722 . In other embodiments, the locking member  740  is of a different material from surfaces of the proximal portion  750  and/or the inner shaft  722 . For example, the locking member  740  can be formed of a polymer such as PEEK, while an adjacent surface of the proximal portion  750  is a metal such as stainless steel. By providing a locking member  740  that is of a lubricious material such as PEEK, this advantageously reduces the friction between the locking member  740  and adjacent surfaces, thereby resulting in less galling between adjacent surfaces. 
     Various methods are provided for utilizing fusion devices and trial members are provided. In some embodiments, a cavity is formed in a vertebral space between two vertebrae. An expandable trial member including a first endplate, a second endplate, a translation member with ramped surfaces, a body portion and an actuation member can be provided. In an unexpanded form, the trial member can be introduced into the vertebral space. Once in the vertebral space, the actuation member can be rotated, thereby causing expansion of the first endplate and second endplate via motion of the translation member. With the trial member in the vertebral space, an assessment can be made as to the proper size of an expandable fusion device. 
     Once the trial member is removed, an expandable fusion device comprising a first endplate, a second endplate, a translation member with ramped surfaces, a body portion and an actuation member can be provided. Optionally, the trial member can include an interference nut that is attached to a rear section of the body portion, one or more front or side stabilization members, a flange, a blocking nut, or combinations thereof. The expandable fusion device can be inserted into the vertebral space in an unexpanded form. Once in the vertebral space, the actuation member of the fusion device can be rotated, thereby causing expansion of the first endplate and second endplate via motion of the translation member. Once in its expanded form, the fusion device is kept in place and can remain in the vertebral space for an extended period of time. 
     In some embodiments, an instrument can be provided to deliver and actuate a fusion device as described above. Advantageously, the instrument can hold or grasp the fusion device to assist in inserting the fusion device in a desired location within a vertebral space. In addition, the instrument can advantageously be cannulated to provide a space for a driver to actuate or expand the fusion device. While the instrument is described with respect to any of the fusion devices described above, one skilled in the art will appreciate that the instrument should not be limited to these specific devices, and that the benefits of any instrument described herein can be used with respect to other implants as well. 
       FIG. 56  illustrates an instrument for delivering and actuating a fusion device. In some embodiments, the instrument  900  includes an inserter tube  920 , an inserter fork  905  having gripping fingers  908  that is slidable relative to the inserter tube  920 , a coupler  950  and a handle  960 . The instrument  900  is advantageously capable of both gripping a fusion device for insertion, and providing a driver therethrough to actuate (e.g., expand or contract) the fusion device. In addition, each of the components—the inserter fork, inserter tube, coupler and handle—can be removed from another in order to facilitate easy cleaning. More details regarding the components of the instrument  900  are discussed below. 
       FIGS. 57A-57C  illustrate a distal portion of an instrument in the process of engaging a fusion device for delivery and actuation. The instrument  900  comprises an inserter fork  905  having tines or fingers  908  that can hold or grasp a portion of the fusion device  10 . The inserter fork  905  slides relative to an inserter tube  920 , thereby causing the fingers  908  to close or open to either grip or release the fusion device  10 . 
     As shown in  FIGS. 57A-57C , the instrument  900  comprises an inserter fork  905  for engaging and gripping recessed surfaces  44  on the fusion device  10 . The inserter fork  905  comprises fingers  908  for holding the fusion device  10 . In some embodiments, the fingers  908  can include additional protrusions  909  that can be fitted into scalloped or deepened recessed surfaces  45  formed on the sides of the fusion device. The added protrusions  909  can advantageously help to further secure the fingers  908  to the fusion device  10 . In other embodiments, the additional protrusions  909  on the fingers  908  are absent. The fingers  908  on the inserter fork  905  are formed on a distal portion of the instrument  900 . 
     In some embodiments, the fingers  908  extend distally from a shaft portion  910  of the inserter fork  905 . The shaft portion  910  surrounds and encloses an inner space or lumen  930 , through which a driver can be inserted to expand and contract the fusion device  10 . As discussed in more detail below, the instrument  900  can thus hold the fusion device  10  in place and deliver a driver to expand the fusion device  10  in a convenient fashion. 
     The inserter fork  905  can slide distally and proximally relative to an inserter tube  920 , thereby causing the fingers  908  to open and close.  FIG. 57A  illustrates the fingers  908  of the inserter fork in an “open” configuration, in which the fingers  908  are capable of receiving the fusion device  10  therebetween.  FIG. 57B  illustrates the fingers  908  of the inserter fork in a “closed” configuration, in which the fingers  908  have clamped down on the fusion device  10 . To move the inserter fork  905  from the open to closed configuration, the inserter fork  905  can slide proximally relative to the inserter tube  920 , such that a distal portion of the inserter tube  920  is positioned over a proximal portion of the fingers  908 . This causes the fingers  908  to close and contract on the fusion device  10  (as shown in  FIG. 57B ). To release the fusion device  10  from the fingers  908 , the inserter fork  905  can slide in an opposite direction relative to the inserter tube  920 . 
     In some embodiments, the relative movement between the inserter fork  905  and the inserter tube  920  is controlled by threads on both components. Inserter fork  905  can have threads  906  that engage corresponding threads  921  on the inserter tube  920  (as shown in  FIG. 59 ). The inserter tube  920  can be threadingly rotated in a proximal or distal direction relative to the inserter fork  905 , thereby causing opening and closing of the fingers  908  as desired. 
     Once the fingers  908  of the inserter fork  905  are secured to the fusion device (as shown in  FIG. 57B ), a driver, such as a hex driver, can be inserted through the lumen  930  that extends between the inserter fork  905  and the inserter tube  920 .  FIG. 57C  illustrates a driver  945  inserted through the lumen  930 . The driver  945  is configured to engage and actuate the actuation member  22 . Rotation of the driver  945 , and thus, the actuation member  22 , in one direction causes the fusion device  10  to expand, while rotation in the opposite direction causes the fusion device  10  to contract. The instrument  900  thus advantageously provides a convenient means to both hold and secure the fusion device  10  (e.g., via the fingers  905 ) while simultaneously delivering a driver  945  therethrough to expand or contract the fusion device  10 . In addition, by providing an inner lumen  930  for the driver  945 , this provides a clean pathway for the driver  945  with little to no tissue interference. 
     In addition to having a novel cooperating inserter fork  905  and inserter tube  920 , the instrument  900  can also include a novel handle  950 , as shown in  FIGS. 58A and 58B . A surgeon can hold the handle  950  to advantageously stabilize and maintain control of the instrument in or outside of the body. 
     As shown in  FIGS. 58A and 58B , the handle  950  can be accompanied by a coupler  960  which is configured to receive a portion of the inserter fork  905  therein.  FIG. 58A  illustrates the inserter fork  905  outside of the coupler  960 , while  FIG. 58B  illustrates the inserter fork  905  received within the coupler  960 . Once the inserter fork  905  is received in the coupler  960 , a set screw within the handle (shown in  FIG. 59  and discussed below) can be downwardly threaded to secure the handle  950  to the inserter fork  905 . Thus, the inserter fork  905 , inserter tube  920  and handle  950  can all be viewed as separate components that are capable of assembly or disassembly, thereby advantageously allowing easy cleaning of each of the components. 
       FIG. 59  is a side cross-sectional view of a proximal portion of an instrument including a handle  950 , a coupler  960  and an inserter fork  905 . From this view, one can see how the inserter fork  905  is received in the coupler  960 . As shown in  FIG. 59 , in some embodiments, the inserter fork  905  can have one or more flats  909  (e.g., two, three, four or more) machined into its surface. The flats  909  are advantageously provided to direct the orientation of the coupler  960  (and thus the handle  950 ) relative to the fusion device  10 . In some embodiments, the coupler  960  can be positioned over the flats  909  such that the handle  950  can be oriented in two directions—either parallel to the implant or perpendicular to the implant. In other embodiments, the inserter fork  905  is provided with even more flats  909  such that the handle  950  can be oriented in more than two directions. By providing the handle with the ability to have multiple orientations, this advantageously provides a surgeon with more options when using the instrument. In some embodiments, the coupler can include an orientation pin  961  that can glide over the flats  909  (and not on other surfaces), thereby helping to further orient the coupler and handle relative to the fusion device  10 . 
     As shown in  FIG. 59 , a threaded set screw  952  is provided within the handle  950 . The set screw  952  is configured to have outer threads that engage with complementary threads  962  of the coupler  962 , thereby allowing upward and downward movement of the handle  950  relative to the coupler  962 . As the handle  950  is moved downwardly, a distal portion of the set screw  952  contacts and engages a surface (e.g., the flats) of the inserter fork  905 , thereby securing the handle  950  to the inserter fork  905 . 
       FIGS. 60A-60C  illustrate an alternative embodiment of an inserter tube of an instrument according to some embodiments. As shown in  FIG. 60A , the alternate inserter tube  920  includes a flared distal portion  924 . The advantage of the flared distal portion  924  is that it provides for more surface engagement over the inserter fork  905 , thereby preventing the inserting fork  905  from accidental splaying and disengagement from the fusion device  10 . 
       FIGS. 60B and 60C  illustrate a proximal portion of the alternate inserter tube  920 . From these views, one can see that the alternate inserter tube  920  can be formed of a first sleeve portion  928  and a second sleeve portion  929  that is mateable to the first sleeve portion  928 . The first sleeve portion  928  can have a first mateable portion  932  and the second sleeve portion  929  can have a second mateable portion  933  that is coupled to the first mateable portion  932 . As shown in  FIG. 60C , the first mateable portion  932  and the second mateable portion  933  can comprise complementary flanges or lips. 
     As shown in  FIG. 60B , the second sleeve portion  929  of the alternate inserter tube  920  can have inner threads that mate with threads on the inserter fork. When the first sleeve portion  928  and second sleeve portion  929  are mated on the inserter fork, rotation of the second sleeve portion  929  (e.g., via its threads) relative to the inserter fork can help translate the first sleeve portion  928  back and forth along the length of the inserter fork. Accordingly, the entire body of the alternate inserter tube  920 , including the flared distal portion  924 , can be translated along the length of the inserter fork. 
     With reference now to  FIGS. 61-66 , the expandable member  1004  will now be described in more detail in accordance with example embodiments. It is contemplated that the expandable member  1004  can be made from a flexible material, such as PEEK, or any other biocompatible material such as stainless steel or titanium. However, other materials may also be used for the expandable member  1004  in accordance with embodiments of the present invention. As illustrated, the expandable member  1004  may include two or more arms, such as first arm  1038  and second arm  1040 , separated by a channel  1042 . The expandable member  1004  may further include a fixed end  1044  and an expandable end  1046  with the channel  1042  running between the first and second arms  1038 ,  1040  from the fixed end  1044  to the expandable end  1046 . The first arm  1038  and the second arm  1040  may be connected at the fixed end  1044  which links the first and second arms  1038 ,  1040 . The first and second arms  1038 ,  1040  may move substantially independent from one another at the expandable end  1046  while remaining connected at the fixed end  1044 . As illustrated, the first and second arms  1038 ,  1040  may be separated by the channel  1042 . In the illustrated embodiment, the channel  1042  ends at the fixed end  1044  in a slightly larger diameter which acts a hinge during expansion of the fusion device  1000 . Markers  1058  ( FIG. 61 ) may be seated in recesses (such as blind holes  1060  shown on  FIG. 66 ) formed in each of the first and second arms  1038 ,  1040  to, for example, to assist in imaging of the device, such as fluoroscopy. In addition, the expandable member  1004  may also include a posterior opening  1062  in the fixed end  1044 , such as a cylindrical bore, through which the actuation member  1008  can extend, as best seen in  FIGS. 63 and 65 . 
     As best seen in  FIGS. 63, 65, and 66 , the first and second arms  1038 ,  1040  of the expandable member  1004  each include ramped surfaces  1048 ,  1050 , respectively. In the illustrated embodiment, the ramped surfaces  1048 ,  1050  are at or near the expandable end  1046 . In the illustrated embodiment, the first and second arms  1038  each include one ramped surface (e.g., ramped surface  1048  and ramped surface  1050 ), but can include any number of ramped surfaces. 
     In the illustrated embodiment, the first and second arms  1038 ,  1040  each include bone engagement surfaces  1052 ,  1054 , respectively, that face outward. As illustrated, the bone engagement surfaces  1052 ,  1054  may be flat and generally planar to allow for engagement of the first and second arms  1038  with the adjacent vertebral bodies  2 ,  3  (e.g., shown on  FIG. 1 ). Alternatively (not illustrated), the bone engagement surfaces  1052 ,  1054  may be curved convexly or concavely to allow for a greater or less degree of engagement with the adjacent vertebral bodies  2 ,  3 . It also contemplated that the bone engagement surfaces  1052 ,  1054  may be generally planar, but include a generally straight ramped or a curved ramped surface. The ramped surface may allow for an even greater degree of angled expansion. In some embodiments, the bone engagement surfaces  1052 ,  1054  may include texturing  1056  to aid in gripping the adjacent vertebral bodies  2 ,  3 . Although not limited to the following, the texturing can include teeth, ridges, friction increasing elements, keels, or gripping or purchasing projections. 
     With reference now to  FIGS. 61, 63, and 65 , the ramped translation member  1006  will now be described in more detail in accordance with example embodiments. As illustrated, the ramped translation member  1006  includes a first expansion portion  1064  and a second expansion portion  1066 , the first and second expansion portions  1064 ,  1066  being connected by one or more bridge portions  1068 . It is also contemplated that there may be more than two expansion portions. The first expansion portion  1064  may have ramped surfaces  1070 ,  1072 , which may be dimensioned and configured to engage the ramped surfaces  1048 ,  1050  in the expandable end  1046  of the expansion member  1004 . In the illustrated embodiment, the first expansion portion  1064  includes two ramped surfaces  1070 ,  1072 . In the illustrated embodiment, the ramped surfaces  1070 ,  1072  of the first expansion portion  1064  are rear facing. With additional reference to  FIGS. 62 and 67 , an embodiment further includes one or more screws  1074  that are received in the first expansion portion  1064  with the screws  1074  being threaded through openings  1076  in the posterior end  1012  of the body portion  1002  to stabilize the ramped translation member  1006  in the internal cavity  1018  of the body portion  1002 . The ramped translation member  1006 , in an exemplary embodiment, may further include an opening  1080 , such as a cylindrical bore, sized to receive the actuation member  1008 . In the illustrated embodiment, the opening  1080  is disposed in the second expansion portion  1066 . 
     With reference to  FIGS. 61, 63, and 65 , the actuation member  1008  will now be described in more detail in accordance with example embodiments. In an exemplary embodiment, the actuation member  1008  has a first end  1082  and a second end  1084 . As illustrated, the actuation member  1008  may include a head portion  1086  at the second end  1084  and a extension portion  1088  extending from the head portion. Threading  1090  disposed on the extension portion  1088  should threadingly engage corresponding threading  1092  along a portion of the opening  1080  of the ramped translation member  1006 . In another embodiment (not shown), the actuation member  1008  may include ratchet teeth instead of the threading  1090  with the ratchet teach engaging corresponding ratchet teeth in the opening  1080  of the ramped translation member  1006 . The second end  1084  includes a recess  1094  dimensioned to receive an instrument (not shown) that is capable of rotating or otherwise moving the actuation member  1008 . 
     As illustrated, the head portion  1086  of the actuation member  1008  may further include a flange  1096  or other suitable projection. In some embodiments, the flange  1096  of the actuation member  608  may engage the mechanical stop  1032  projecting from the interior surface  1034  of the opening  1023  in the body portion  1002 . Engagement of the flange  1096  with the mechanical stop  1032  may restrict forward movement of the actuation member  1008  into the opening  1023  in the body portion  1002 . As illustrated, a ring  1098  (e.g., a PEEK ring) may be disposed between the mechanical stop  1032  and the flange  1096  to reduce friction between the actuation member  1008  and the body portion  1002 , for example, when the fusion device  1000  is actuated, such as by rotation of the actuation member  1008 , for example. As further illustrated, a retaining ring  1099  may be used to engage the head portion  1086  and hold the actuation member  1008  in the opening  1023  in the body portion  1002 , for example, preventing threading out of the actuation member  608  when rotated. The retaining ring  1099  may be disposed in the internal groove  1036  in the opening  1023  of the body portion  1002 , for example. In one embodiment, the retaining ring  1099  may be a snap ring. 
     Turning now to  FIGS. 61, 62-65 and 67 , an example method of installing the expandable fusion device  1000  is now discussed. Prior to insertion of the fusion device  1000 , 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 bodies  2 ,  3  (shown on  FIG. 1 , for example) are then scraped to create an exposed end surface for facilitating bone growth across the intervertebral space. The expandable fusion device  1000  is then introduced into the intervertebral space, with the anterior end  1010  of the body portion  1002  being inserted first into the disc space followed by the posterior end  1012 . In an exemplary method, the fusion device  600  is in the unexpanded position when introduced into the intervertebral space. The wedged-shaped of the anterior end  1010  in the illustrated embodiment should assist in distracting the adjacent vertebral bodies  2 ,  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 device  1000 . In another exemplary method, the intervertebral space may be distracted prior to insertion of the fusion device  1000 . 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. 
     With the fusion device  1000  inserted into and seated in the appropriate position in the intervertebral disc space, the fusion device  1000  can then be expanded into the expanded position, as best seen in  FIGS. 62-65 .  FIGS. 62 and 63  show the fusion device  1000  prior to expansion while  FIGS. 64 and 65  show the fusion device  1000  in the expanded position. To expand the fusion device  1000 , an instrument is engaged with the recess  1094  in the second end  1084  of the actuation member  1008 . The instrument is used to rotate actuation member  1008 . As discussed above, actuation member  1008  can be engaged (e.g., threadingly engaged) with the ramped translation member  1006 ; thus, as the actuation member  1008  is rotated in a first direction, the ramped translation member  1006  moves with respect to the body portion  1002  toward the posterior end  1012  of the body portion  1002 . In another exemplary embodiment, the ramped translation member  1006  is moved in a linear direction with the ratchet teeth engaging as means for controlling the movement of the ramped translation member  1006 . As the ramped translation member  1006  moves, the ramped surfaces  1070 ,  1072  of the first expansion portion  1064  push against the ramped surfaces  1048 ,  1050  in the expandable end  1046  of the expandable member  1004  pushing the first and second arms  1038 ,  1040  outwardly into the expanded position. This can best be seen in  FIGS. 64 and 65 . Since the expansion of the fusion device  1000  is actuated by a rotational input, the expansion of the fusion device  1000  is infinite. In other words, the first and second arms  1038 ,  1040  can be expanded to an infinite number of heights dependent on the rotational advancement of the actuation member  1008 . 
     In the event the fusion device  1000  needs to be repositioned or revised after being installed and expanded, the fusion device  1000  can be contracted back to the unexpanded configuration, repositioned, and expanded again once the desired positioning is achieved. To contract the fusion device  1000 , the instrument is engaged with the recess  1094  in the second end  1084  of the actuation member  1008 . The instrument is used to rotate actuation member  1008 . As discussed above, actuation member  1008  can be threadingly engaging the ramped translation member  1006 ; thus, as the actuation member  1008  is rotated in a second direction, opposite the first direction, the ramped translation member  1006  moves with respect to the body portion  1002  toward the anterior end  1010  of the body portion  1002 . As the ramped translation member  1006  moves, the first and second arms  1038 ,  1040  should contract inwardly back into their unexpanded position, for example. 
     With continued reference to  FIGS. 61, 62-65 and 67 , an example method of assembly the expandable fusion device  1000  is now discussed. In accordance with present embodiments, the ramped translation member  1006  may be inserted into the expandable member  1004 . By way of example, the second expansion portion  1066  may be inserted into the channel  1042  of the expandable member  1004  at the expandable end  646  and advanced to the fixed end  1044 . After insertion of the ramped translation member  1006 , the expandable member  1004  may then be placed into the internal cavity  1018  in the body portion  1002 . For example, the expandable member  1004  may be inserted through window (e.g., upper window  1020 ) into the internal cavity  1018 . As illustrated, the fixed end  1044  of the expandable member  1004  should be positioned near the posterior end  1012  of the body portion  1002 . The one or more screws  1074  may then be inserted through the body portion  1002  and into the ramped translation member  1006  to, for example, stabilize the ramped translation member  1006  preventing rotation. The actuation member  1008  may also be inserted into the opening  1023  in the posterior end  1012  of the body portion and advanced until it is in engagement with the ramped translation member  1006 . In one embodiment, the actuation member  1008  may be advanced into threaded engagement with the opening  1080  in the ramped translation member. 
     In an embodiment, the expandable fusion device  1000  can be configured and sized to be placed into an intervertebral disc space between the adjacent vertebral bodies  2  and  3  (shown on  FIG. 1 , for example) and expanded. In some embodiments, the expandable fusion device  1000  may have a width in a range of from about 8 mm to about 22 mm and a length in a range of from about 15 mm to about 65 mm. In further embodiments, the expandable fusion device  1000  may have a width in a range of from about 8 mm to about 12 mm and a length in a range of from about 20 mm to about 30 mm. In some embodiments, the expandable fusion device  10  may have an initial height in an unexpanded position in a range of from about 7 mm to about 20 mm and, alternatively from about 7 mm to about 15 mm. In some embodiments, the maximum expansion of the first and second arms  1038 ,  1040  at the anterior end  1010  of the body portion  1002  is about 4 mm or potentially even more. 
       FIGS. 69 and 70  illustrate an alternative embodiment of the expandable fusion device  1000  according to the present invention. For longer configurations of the expandable fusion device  1000 , the first and second arms  1038 ,  1040  may sag or flex, for example, when engaging the adjacent vertebral bodies  2 ,  3  (shown on  FIG. 1 , for example). Accordingly, embodiments shown on  FIGS. 69 and 70  further include one or more protruding support members  1100  on the ramped translation member  1006 . As illustrated, the protruding support members  1100  may be disposed on the one or more of the bridge portions  1068  between the first and second expansion portions  1064 ,  1066 . The protruding support members  1100  may engage corresponding recesses  1102  in the first and second arms  1038 ,  1040 . The protruding support members  1100  may act to support the first and second arms  1038 ,  1040  and prevent undesired flexing during expansion. In alternative embodiments (not shown), the actuation member  1008  may engage the expandable member  1004  (for example, with a slot and a groove) so that, as the first and second arms  1038 ,  1040  expands, the actuation member  1008  may engage the expandable member  1004  to cause convexity. 
       FIG. 71  illustrates an alternative embodiment of the expandable fusion device  1000  according to the present invention. The embodiments illustrated on  FIGS. 61, 62-65 and 67  illustrate the ramped surfaces  1070 ,  1072  on the first expansion portion  664  of the ramped translation member  1006  being rear facing. In the embodiment illustrated on  FIG. 71 , the ramps have been reversed with the ramped surfaces  1070 ,  1072  on the first expansion portion  1064  being forward facing. Accordingly, the corresponding ramped surfaces  1048 ,  1050  on the first and second arms  1038 ,  1040  of the expandable member  1004  have also been reversed and are shown on  FIG. 71  as being rear facing. Accordingly, rotation of the actuation member  1008  should move the ramped translation member  1006  forward to the anterior end  1010  of the body portion  1002  such that the ramped surfaces  1070 ,  1072  of the ramped translation member  1006  push against the ramped surfaces  1048 ,  1050  of the first and second arms  1038 ,  1040  pushing the first and second arms  1038 ,  1040  outwardly into the expanded position. 
     As previously mentioned, embodiments of the expandable fusion devices, such as expandable fusion device  1000  shown on  FIGS. 61, 62-65 and 67  in which the endplates (e.g., endplates  14 ,  16  or first and second arms  1038 ,  1040 ) may expand into an angled configuration. As illustrated by  FIGS. 72-83 , the endplates  1104 ,  1106  of an expandable fusion device  1000  may be expanded in a number of different ways. For example,  FIGS. 72-74  illustrate an expandable fusion device  1000  in which the endplates  1104 ,  1106  only expand at the anterior side  1108  while remaining fixed at the posterior side  1110 .  FIGS. 75-77  illustrate an additional example of an expandable fusion device  1000  in which the endplates  1104 ,  1106  expand at both the anterior side  1108  and the posterior side  1110  but at different rates.  FIGS. 78-80  illustrate yet another example of an expandable fusion device  1000  in which the endplates  1104 ,  1106  first expand at only the anterior side  1108  to achieve lordotic angle followed by expansion at both the anterior side  1108  and the posterior side  1110  at constant rates to achieve height increase. Advantageously, the embodiment shown on  FIGS. 78-80  allows for full angulation without the corresponding height increase.  FIGS. 81-83  illustrate yet another example of an expandable fusion device  1000 . As illustrated, the expandable fusion device  1000  has two separate degrees of freedom, allowing for independent angulation and expansion of the endplates  1104 ,  1106 . 
     Although the preceding discussion only discussed having a single fusion device (e.g., fusion device  10 , fusion device  210 , or fusion device  1000 ) in the intervertebral space, it is contemplated that more than one fusion device can be inserted in the intervertebral space. It is further contemplated that each fusion device does not have to be finally installed in the fully expanded state. Rather, depending on the location of the fusion device in the intervertebral disc space, the height of the fusion device may vary from unexpanded to fully expanded. 
     One skilled in the art will appreciate that the instrument described herein is not limited to the expandable fusion device  10  described above, but can be applied to assist in the delivery and/or actuation of other implants as well. For example, in some embodiments, the instrument described can be used to deliver a non-expandable device having side recesses. In addition, the instrument can be used to deliver different types of expandable devices, including expandable TLIFs and other types of spinal implants. 
     Additional embodiments of expandable fusion devices are shown in  FIGS. 84A-86B . In these embodiments, the fusion device  1210  includes an actuation member  1220  that is operatively attached to a translation member  1218 . Rotation of the actuation member  1220  causes linear translation of the translation member  1218 , thereby causing expansion of the fusion device  1210 . Advantageously, in these embodiments, the actuation member  1220  is fixed at an anterior portion of the fusion device  1210 , thereby leaving a posterior opening  1222  available for which material (e.g., bone graft material) can be easily inserted therethrough. The ability to insert and pack bone graft material through the posterior opening  1222  is highly beneficial, as such material can be packed even when the expandable fusion device has already been expanded, thereby maximizing the amount of bone graft material in the device  1210 . 
     As shown in  FIGS. 84A and 84B , the expandable fusion device  1210  comprises an upper endplate  1214 , a lower endplate  1216 , sidewalls including one or more inserter instrument recesses  1238 , a body portion  1202 , a threaded actuation member  1220  and a translation member  1218  having angled surfaces or ramps. The upper endplate  1214  and lower endplate  1216  can include texturing, such as teeth or ridges, to assist in gripping of adjacent vertebral bodies. On the inner sides of the upper endplate  1214  and the lower endplate  1216  are inner angled surfaces or ramps (similar to prior embodiments) that are configured to interact with ramps on the translation member  1218  to cause expansion or contraction of the device. The sidewalls include one or more inserter instrument recesses  1238  that serve as gripping surfaces to deliver the device  1210 . 
     The translation member  1218  can include one or more angled surfaces or ramps  1251 ,  1252 ,  1254 . The ramps can be separated by bridge members  1256 . As in prior embodiments, the ramps  1251 ,  1252 ,  1254  are configured to engage and interact with ramps on the upper and lower endplates  1214 ,  1216 , thereby causing expansion or contraction of the fusion device  1210 . The translation member  1218  can include upwardly facing ramps that interact with downwardly facing ramps from the upper endplate  1214 , and downwardly facing ramps that interact with upwardly facing ramps from the lower endplate  1216 . Thus, while only the upwardly facing ramps  1251 ,  1252  and  1254  are visible from the top views in  FIGS. 85A and 85B , one skilled in the art will appreciate that downwardly facing ramps can also be provided. In addition, while the translation member  1218  is illustrated as having three ramps along a length of the translation member, in other embodiments, the translation member  1218  can have one, two, four, five or more ramps separated by bridges. 
     In addition to the ramps, the translation member  1218  includes an engaging portion  1219  that engages the actuation member  1220  (as shown in  FIG. 85A ). The engaging portion  1219  is configured to include inner threads that engage with threads of the actuation member  1220 . Rotation of the actuation member  1220  causes the translation member  1218  to move linearly along the threads of the actuation member  1220 . 
     In the present embodiments, the actuation member  1220  is threaded through the translation member  1218  near the anterior or front side of the body portion  1202 , which can be tapered (e.g., to assist in distraction of bone members). With the actuation member  1220  near the anterior side of the body, a posterior opening  1222  remains exposed. In some embodiments, the posterior opening  1222  is configured to receive an expansion instrument or tool that can expand or contract the height of the spacer  1210 . In addition, the posterior opening  1222  is capable of advantageously receiving bone graft material therein, even when the fusion device  1210  has already been expanded, thereby maximizing the amount of bone graft material in the device. 
       FIG. 84A  shows the expandable fusion device  1210  in a collapsed or unexpanded state. In the collapsed state, the device  1210  is capable of being delivered through a relatively small surgical opening to a desired anatomical location. To assist in delivering the device  1210  to a desired anatomical location, a surgeon can use an inserter tool to grasp the device  1210  along its sidewalls via inserter instrument recesses  1238 . 
       FIG. 84B  shows the expandable fusion device  1210  in an extended or expanded state. To expand the device  1210 , an expansion tool is inserted through the posterior opening  1222  and into the threaded actuation member  1220 . The expansion tool can rotate the threaded actuation member  1220 . As the actuation member  1220  is rotated in a first direction, the translation member  1220  (which threadingly engages the actuation member  1220 ), translates in a linear direction along the length of the actuation member  1220  (as shown in  FIGS. 85A and 85B ). As the translation member  1220  translates from an anterior-to-posterior direction, ramps  1251 ,  1252 ,  1254  of the translation member  1220  engage corresponding ramps on the endplates, thereby causing expansion of the device  1210 . To reduce the height of the device  1210 , the expansion tool can rotate the actuation member  1220  in a reversed second direction, thereby causing the translation member  1220  to translate from a posterior-to-anterior direction, and reduce the height of the device  1210 . 
       FIGS. 85A and 85B  are top views of the alternative expandable fusion device of  FIG. 84A  with endplates removed. From this view, one can see the actuation member  1220  screwed within the threaded engagement portion  1219  of the translation member  1218  according to some embodiments. The actuation member  1220  and the translation member  1218  both fit within the body  1202  of the fusion device  1210 . 
       FIG. 85A  shows the expandable fusion device  1210  in a collapsed state. From this view, one can see an anterior end of the translation member  1218  is adjacent the anterior wall of the body  1202 . In some embodiments, the translation member  1218  is pressed against the anterior wall of the body  1202 . 
       FIG. 85B  shows the expandable fusion device  1210  in an expanded state. From this view, one can see how the translation member  1218  has translated in anterior-to-posterior direction, such that the anterior end of the translation member  1218  is removed away from the anterior wall of the body  1202 . The translation member  1218  has shifted slightly in the posterior direction, such that upper and lower ramps of the translation member  1218  would engage corresponding ramps on the upper and lower endplates (not shown), thereby causing the expansion of the device. 
       FIGS. 86A and 86B  are top perspective views of the alternative expandable fusion device of  FIG. 84A  with endplates removed. In  FIG. 86A , the fusion device  1210  is in a collapsed configuration, while in  FIG. 86B , the fusion device  1210  is in an expanded configuration. From these views, one can see additional features not shown in  FIGS. 85A and 85B , such as the side recess  1238  for receiving an insertion instrument. 
     In operation, the fusion device  1210  of  FIGS. 84A-86B  can be used as follows. A surgeon can deliver the fusion device  1210  in a collapsed configuration through an opening. The fusion device  1210  can be delivered into a desired anatomical space, whereby its tapered anterior end is a leading end. Once the fusion device  1210  is placed in a desired anatomical space, the surgeon can insert an expansion tool through a posterior opening  1222  in the body  1202  of the device  1210 . The expansion tool can extend through the body  1202  and into the actuation member  1220 , whereby it can rotate the actuation member  1220 . Upon rotation of the actuation member  1220 , the translation member  1218  translates in a posterior direction, such that its ramps engage with corresponding ramps of endplates. This translation of the translation member  1218  causes expansion of the fusion device  1210 . Once the device  1210  has been properly expanded, the expansion tool can be removed from the posterior opening  1222 , thereby leaving the posterior opening  1222  exposed. The surgeon can then insert bone graft material or other desirable materials into the posterior opening  1222  to assist in the proper fusion in the disc space. 
     Various mechanisms (shown in  FIGS. 87A-102C ) for providing lordotic expansion are now described below. These mechanisms can be used, for example, with the embodiments in  FIGS. 72-83  to assist in providing lordotic expansion for the expandable devices. One skilled in the art will appreciate, however, that these mechanisms are not limited to those in  FIGS. 72-83 , and that any of the expandable implants shown above can benefit from these lordotic expansion mechanisms. For example, in some embodiments, an implant having an upper plate, lower plate, translation member having ramps and an actuation member can be provided with one of the lordotic mechanisms provided below in order to provide lordotic expansion. In some embodiments, an endplate can be angled in an anterior-posterior direction, such that either an anterior or posterior portion of the endplate is higher or lower than the opposite end. In other embodiments, an endplate can be angled in a side-to-side direction, such that either side of the endplate is higher or lower than the opposite end. 
     In  FIGS. 87A-87C , an implant having a lordotic mechanism is provided comprising one or more rounded pivots that can slide back and forth and rotate in order to provide lordosis. The expandable implant  1310  comprises a first endplate  1314 , a second endplate  1316 , a graft opening  1349  through each of the first endplate and second endplate, and at least one rounded pivot mechanism. Like previous embodiments, the implant  1310  is configured to be placed in a disc space, whereby the first endplate  1314  can engage an upper vertebra and the second endplate  1316  can engage a lower vertebra. As shown in  FIG. 87A , the implant  1310  comprises an upper rounded pivot  1322  and a lower rounded pivot  1324 . In some embodiments, a single actuation member (e.g., the drive screw  1333 ) can rotate both the upper rounded pivot  1322  and the lower rounded pivot  1324 . In other embodiments, each of the upper rounded pivot  1322  and the lower rounded pivot  1324  has its own actuation member for individual rotation. When the upper rounded pivot  1322  is rotated, this causes the upper rounded pivot  1322  to engage a contact surface of the first endplate  1314 , thereby causing the first endplate  1314  to advantageously tilt and angle. Likewise, when the lower rounded pivot  1324  is rotated, this causes the lower rounded pivot  1324  to engage a contact surface of the second endplate  1316 , thereby causing the second endplate  1316  to advantageously tilt and angle. Accordingly, these rounded pivots  1322 ,  1324  allow one side of an endplate to be higher than another side of an endplate, thereby better accommodating different anatomies. 
     Once a desired amount of lordosis, tilting or angulation is achieved by the rounded pivots  1322 ,  1324 , a locking mechanism can be provided to lock the degree of lordosis. In some embodiments, each of the rounded pivots  1322 ,  1324  can include one or more lock wings  1330  that lock the degree of lordosis. In some embodiments, the lock wings  1330  can be hooks, grips or other protrusions that extend from the rounded pivots  1322 ,  1324  that prevent further rotation of the rounded pivots. 
       FIG. 87B  shows a close-up view of a first endplate  1314  in accordance with some embodiments. The second endplate  1316  can include similar features. The endplate  1314  comprises an upper surface  1318 , an opposing lower surface  1319 , and a graft opening  1349  extending therethrough. The upper surface  1318  is configured to engage a vertebra while the lower surface  1319  provides a contact surface that engages the upper rounded pivot  1322 . As shown in  FIG. 87B , the first endplate  1314  is configured such that the upper surface  1318  and the lower surface  1319  are each curved. By having a curved lower surface  1319 , the upper rounded pivot  1322  is capable of being nested within the opening created by the curvature of the curved lower surface  1319 . The upper rounded pivot  1322  can be nested in the opening in a first configuration such that the first endplate  1314  is not tilted (as shown in  FIG. 87A ). If tilting is necessary, the upper rounded pivot  1322  can rotate, thereby causing the first endplate  1314  to angle. 
       FIG. 87C  illustrates an alternate embodiment of a single-bodied rounded pivot  1326 . In contrast to the embodiment in  FIG. 87A  that utilizes an upper rounded pivot  1322  and a lower rounded pivot  1324 ,  FIG. 87C  provides a single-bodied rounded pivot  1326  that can engage both the first endplate  1314  and the second endplate  1316 . Advantageously, these rounded pivots can allow for lordotic expansion. In some embodiments, these rounded pivots can accommodate coronal and sagittal correction. 
       FIGS. 88A-88C  illustrate different views of an alternate embodiment of an implant having a mechanism having a ramped actuator for providing lordotic expansion in accordance with some embodiments. As shown in  FIG. 88A , the implant  1410  comprises a first endplate  1414 , a second endplate  1416 , and a ramped actuator  1428  positioned between the first endplate  1414  and the second endplate  1416 . The ramped actuator  1428  is configured to have a ramped upper surface that engages a ramped lower surface of the first endplate  1414 , as well as a ramped lower surface that engages a ramped upper surface of the second endplate  1416 . As the ramped actuator  1428  translates linearly, this advantageously causes lordotic expansion of the implant. 
       FIG. 88B  shows one embodiment of the opposing endplates  1414 ,  1416  in accordance with some embodiments. Each of the endplates can include one or more slots  1419  for receiving overhanging portions  1444 ,  1446  (shown in  FIG. 88C ) of the ramped actuator  1428 . These slots  1419  advantageously serve as a guide for the ramped actuator  1428  as it linearly translates and causes lordotic expansion. 
       FIG. 88C  shows one embodiment of the ramped actuator  1428  in accordance with some embodiments. The ramped actuator  1428  comprises an upper ramped surface  1433  configured to engage a lower ramped surface of the first endplate  1414  and a lower ramped surface  1434  configured to engage an upper ramped surface of the second endplate  1416 . The upper ramped surface  1433  includes one or more overhangs  1444 , while the lower ramped surface  1434  includes one or more overhangs  1446 . These overhangs  1444 ,  1446  are received in slots  1419  formed in the first endplate  1414  and the second endplate  1416 . In addition, as shown in FIG.  88 C, the ramped actuator  1428  advantageously includes a hole or opening for receiving graft material therein. 
       FIGS. 89A-89D  are different views of different components of an alternate expandable fusion device having one or more worm gears for providing lordosis. As shown in  FIG. 89A , the implant  1510  can comprise a first endplate  1514 , a second endplate  1516 , at least one worm gear  1520 , and an actuator for the worm gear  1530 . The one or more worm gears  1530  can be used to expand one portion (e.g., a corner) of the implant, thereby providing lordosis to the implant. As shown in  FIG. 89B , in some embodiments, the implant  1510  can include four worm gears  1520   a ,  1520   b ,  1520   c , and  1520   d , wherein each is responsible for increasing the height or lordosis of one portion (e.g., a corner) of the implant. 
       FIGS. 89C and 89D  illustrate different embodiments of an instrument that engages the worm gears to provide lordosis to the implant. The instrument  1570  is capable of operating on a single worm gear at a time.  FIG. 89D  illustrates a distal end of the instrument  1570  that engages the worm gears. As shown in the figure, the distal end can include both endplate threads  1572  and worm gear threads  1574 . Having dual threads advantageously allows the instrument  1570  to actuate different components. For example, the endplate threads  1572  can engage threads to cause the endplates to separate, while the worm gear threads  1574  can work specifically with threads of the worm gear to cause lordotic expansion. 
       FIGS. 90A-90C  illustrate different embodiments of different components of an alternative expandable fusion device having moveable wedges for providing lordosis. The implant  1610  comprises an upper endplate  1614  and a lower endplate  1616 . In between the upper and lower endplates are wedge members. As shown in  FIG. 90A , the implant  1610  can include at least a first wedge member  1634  and a second wedge member  1636 . The wedge members  1634 ,  1636  are attached to a shaft  1640 . The wedge members  1634 ,  1636  are configured to have angled or ramped surfaces that cause lordotic expansion of the implant  1610 . In some embodiments, the wedge members  1634 ,  1636  are configured to move at the same rate relative to one another. In another embodiment, the wedge members  1634 ,  1636  are configured to move at different rates relative to one another. In some embodiments, the shaft  1640  can include one type of thread correspond to wedge member  1634  and a second type of thread corresponding to wedge member  1636 , such that the rate of translation of the wedge members differ from another. If one wedge members moves inwardly faster than another, this can cause lordotic expansion of the implant  1610 . 
       FIG. 90C  shows one embodiment of an implant  1610  having two sets of wedges: a first set of wedges  1634   a ,  1636   a  on a first shaft  1640   a , and a second set of wedges  1634   b ,  1636   b  on a second shaft  1640   b . Each of the wedges can be controlled by their own individual actuation nut  1647 . This set of four wedges, each individually controlled, allows for any type of angling or lordotic expansion of the implant  1610 . For example, if one desires lordotic expansion of one side of the implant (e.g., an anterior side), one can simply actuate wedges  1634   a  and  1634   b . If one desires lordotic expansion of the other side of the implant (e.g., a posterior side), one can simply actuate the opposing wedges  1636   a  and  1636   b.    
       FIGS. 91A-91D  illustrate different views of an alternative expandable fusion device having an internal wedge mechanism for providing lordosis. The device  1710  comprises an upper endplate  1714  and a lower endplate  1716 . In some embodiments, the upper endplate  1714  and the lower endplate  1716  can be separate from another, as in prior embodiments. In other embodiments, the upper endplate  1714  and the lower endplate  1716  are attached to one another via a hinge mechanism  1719  (as shown in  FIG. 91A ). As shown in  FIG. 91A , an internal wedge  1730  can be received between the upper endplate  1714  and the lower endplate  1716 . When the internal wedge  1730  rotates (as shown in  FIG. 91B ), it causes portions of the upper endplate  1714  to separate further away from the lower endplate  1716 , thereby providing an implant with lordosis.  FIG. 91A  shows the internal wedge  1730  in a first reduced height configuration, while  FIG. 91B  shows the internal wedge  1730  in a second expanded height configuration. In some embodiments, the internal wedge  1730  can comprise a rotatable ramp mechanism that rotates via a keyed actuator. 
       FIGS. 91C and 91D  show additional embodiments of an implant having an internal wedge mechanism to provide lordosis. From these views, one can see how the internal wedge  1730  can include an actuator  1734 . In some embodiments, the actuator  1734  can receive an instrument that causes rotation of the internal wedge  1730 , thereby changing its height and adjusting lordosis. In other embodiments, the actuator  1734  can receive an instrument that increases the height of the internal wedge  1730 , thereby adjusting lordosis. 
       FIGS. 92A and 92B  illustrate different views of an alternative expandable fusion device having linking members for providing lordosis. The implant  1810  comprises an upper endplate  1814  and a lower endplate  1816  separated by linking members. Linking members  1832  and  1834  work in associate with one another on one side of the implant, while linking members  1836  and  1838  work in associate with one another on an opposing side of the implant. Advantageously, the linking members enable each side of the implant to have a different degree of lordosis if desired. 
       FIGS. 93A and 93B  illustrate different views of an alternative expandable fusion device having a ramp wedge member for providing lordosis. The expandable fusion device  1910  includes a first endplate  1914  and a second endplate  1916 . In some embodiments, the first endplate  1914  and the second endplate  1916  are independent of one another. In other embodiments, as shown in  FIG. 93A , the first endplate  1914  is connected to the second endplate  1916  via a hinged member  1920 . A ramped wedge member  1928  is inserted between the first endplate  1914  and the second endplate  1916 , thereby causing lordotic expansion of the implant, as shown in  FIG. 93B . 
       FIGS. 94A and 94B  illustrate different embodiments of an implant having a lordotic expansion mechanism comprising tapered barrels.  FIG. 94A  illustrates an implant having an upper endplate  2014  and a lower endplate  2016 . A first tapered barrel  2034  and a second tapered barrel  2036  are positioned on a shaft  2040  in between the upper endplate and the lower endplate. Like the wedge members in  FIG. 90A , the tapered barrels  2034  and  2036  are capable of independently moving from one another, thereby causing lordosis of the implant. 
       FIG. 94B  illustrates an alternative embodiment of an implant having tapered barrels. As opposed to the embodiment in  FIG. 94A , in which the tapered barrels  2034 ,  2036  faced in different directions, the tapered barrels  2034 ,  2036  in  FIG. 94B  face in the same direction on the shaft  2040 . In some embodiments, each of the tapered barrels  2034 ,  2036  can be independently controlled to cause a desired amount of angling or lordotic expansion of the upper and/or lower endplates. 
       FIGS. 95A-95C  illustrate different views of different components of an implant having a lordotic expansion mechanism comprising a serrated plate. The implant  2110  comprises a first endplate  2114  and a second endplate  2116 . While in some embodiments, the first endplate  2114  and the second endplate  2116  are independent from one another, in the present embodiment (as shown in  FIG. 95A ), the first endplate  2114  is connected via a hinged portion  2160  to the second endplate  2116 . In an opposite end of the implant  2110 , a ratchet plate  2126  is provided having ratchet members or teeth. In between the first endplate  2114  and the second endplate  2116  is a serrated plate  2122 . 
       FIG. 95A  shows a first configuration in which the serrated plate  2122  is lay sideways or flat, while  FIG. 95B  shows a second configuration in which the serrated plate  2122  is propped upwards to cause lordosis of the implant. An instrument (e.g., an actuator) can be used to prop the serrated plate  2122  upwards into the second configuration. When the serrated plate  2122  is brought upwards, its serrations or teeth can engage the teeth of the ratchet plate  2126 , thereby creating a ratchet mechanism for controlling the lordotic height of the implant. 
       FIGS. 96A-96C  show different views of an implant having a lordotic expansion mechanism comprising threaded barrels. The implant  2210  comprises an upper endplate  2214  and a lower endplate  2216 . Positioned in between the endplates are threaded barrels  2232  and  2234  positioned on a shaft  2240 . Each of the threaded barrels  2232 ,  2234  are movable along the shaft to cause lordosis of the implant. Advantageously, the threaded barrels  2232 ,  2234  have threads that engage corresponding threads on the endplates. The threads on the threaded barrels  2232 ,  2234  advantageously provide controlled, gradual lordotic expansion of the implant. As shown in  FIG. 96B , a single implant  2210  can include multiple thread barrels (e.g., four threaded barrels  2032 ,  2034 ,  2036 ,  2038 ) thereby providing lordotic expansion on different portions (e.g., different corners) of the implant. 
       FIG. 97  show a different embodiment of an implant comprising one or more ratcheting mechanisms for lordotic expansion. In the present embodiment, the implant  2310  includes an upper endplate  2314  and a lower endplate  2316 . The upper endplate  2314  includes a downwardly facing first arm  2374  having ratcheting teeth and a downwardly facing second arm  2384  having ratcheting teeth. The lower endplate  2316  includes an upwardly facing first arm  2372  having ratcheting teeth and an upwardly facing second arm  2382  having ratcheting teeth. In some embodiments, the first arm  2374  of the upper endplate  2314  engages the first arm  2372  of the lower endplate, while the second arm  2372  of the upper endplate  2314  engages the second arm  2382  of the second endplate, thereby creating two pairs of ratcheting mechanisms. Each pair of ratcheting mechanism advantageously allows one side of the implant to be angled relative to another, thereby providing desirable lordotic expansion. 
       FIGS. 98A-98C  show different views of an implant including a height changing wedge that provides lordosis and expansion. The implant  2410  comprises an upper endplate  2414  and a lower endplate  2416  separated by a first wedge  2432  and a second wedge  2434 . As shown in  FIG. 98A , the first wedge  2432  and the second wedge  2434  can be at a substantially equal height such that the upper endplate  2414  and the lower endplate  2416  are substantially parallel to one another. As shown in  FIG. 98B , the first wedge  2432  has been expanded to a different height, thereby creating an implant having variable lordosis and expansion. As shown in  FIG. 98C , both the first wedge  2432  and the second wedge  2434  include their own individual drive mechanism for modifying their specific height. First wedge  2432  includes drive screw  2445 , while second wedge  2445  includes its own drive screw  2446 . These drive screws  2445 ,  2446  provide an infinite number of height changes and combinations between the first wedge  2432  and the second wedge  2445 , thereby providing variable lordosis in the implant. 
       FIGS. 99A-99C  show different views of an implant having a driving wedge for providing lordotic expansion. The implant  2510  comprises an upper endplate  2514  and a lower endplate  2516  that are expandable away from one another. In some embodiments, the upper endplate  2514  and the lower endplate  2516  are detached from one another. In other embodiments, as shown in  FIG. 99A , the upper endplate  2514  is attached to the lower endplate  2516  via a hinge  2519 . In between the upper endplate  2514  and lower endplate  2516  is a driving wedge  2532 . The driving wedge  2532  can be linearly translated (e.g., along a track or grooves formed in the upper and lower endplates) to thereby cause separation of the endplates. As the endplates are connected via a hinge  2519 , the hinged portion will have a height that is less than the expanded portion, thereby creating an implant with lordotic expansion, as shown in  FIG. 99B .  FIG. 99C  shows a top view of the implant  2510 , which includes a graft window  2440  for receiving graft material therein. 
       FIGS. 100A-100C  show different views of different components of an implant having connectable side portions for providing lordotic expansion. The implant  2610  comprises a body  2615  having a first connectable side portion  2622  and a second connectable side portion  2624  for providing height changes and lordotic expansion. In some embodiments, the body and connectable side portions form the implant that is inserted into a disc space. In other embodiments, the body and connectable side portions are received between endplates to be inserted into a disc space. In some embodiments, the body  2615  can be static in height, while in other embodiments, the body  2615  can be expandable. 
       FIG. 100B  shows a close-up view of a connectable side portion in accordance with some embodiments. The connectable side portion  2622  comprises an upper layer  2622 A that is spaced from a lower layer  2622 B. In some embodiments (as shown in  FIG. 100A ), the two layers are connected. In other embodiments, the upper layer  2622 A is detached from the lower layer  2622 B. 
     For each of the embodiments described above, it may be useful to maintain the expanded height of the implant.  FIG. 101  shows an implant  2810  having an expandable upper endplate  2814 , a lower endplate  2816  and a ratcheting lock mechanism  2820  that can be used to secure the height expansion between the two endplates. The ratcheting lock mechanism  2820  can include teeth (e.g., ratchet teeth) that are designed to mate with other teeth (e.g., found on an endplate) to thereby secure the height expansion of the implant. 
     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.