Patent Publication Number: US-2023143226-A1

Title: Expandable intervertebral implant

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/813,810, filed on Mar. 10, 2020 (published as U.S. Pat. Pub. No. 2020-0205993), which is a continuation of U.S. patent application Ser. No. 15/912,989, filed Mar. 6, 2018, which is a continuation of U.S. patent application Ser. No. 15/401,326, filed Jan. 9, 2017, now issued as U.S. Pat. No. 9,943,418, which is a continuation of U.S. patent application Ser. No. 15/144,014, filed May 2, 2016, now issued as U.S. Pat. No. 9,572,677, which is a continuation-in-part of U.S. patent application Ser. No. 14/878,433, filed Oct. 8, 2015, now issued as U.S. Pat. No. 9,480,579, which is a continuation of U.S. patent application Ser. No. 13/968,865, filed Aug. 16, 2013, now issued as U.S. Pat. No. 9,456,906, which is a continuation-in-part of U.S. patent application Ser. No. 13/836,687, filed Mar. 15, 2013, now issued as U.S. Pat. No. 9,034,045, all of the foregoing being incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to stabilizing adjacent vertebrae of the spine by inserting an intervertebral implant, and more particularly an intervertebral implant that is adjustable in height. 
     BACKGROUND OF THE INVENTION 
     Bones and bony structures are susceptible to a variety of weaknesses that can affect their ability to provide support and structure. Weaknesses in bony structures have numerous potential causes, including degenerative diseases, tumors, fractures, and dislocations. Advances in medicine and engineering have provided doctors with a plurality of devices and techniques for alleviating or curing these weaknesses. 
     In some cases, the spinal column requires additional support in order to address such weaknesses. One technique for providing support is to insert a spacer between adjacent vertebrae. 
     SUMMARY OF THE INVENTION 
     In accordance with the disclosure, an implant for therapeutically separating bones of a joint, the implant defining a longitudinal axis extending between distal and proximal ends, the implant comprises a first endplate configured to engage a first bone of the joint, and having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side; a second endplate configured to engage a second bone of the joint, and having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side; a frame slideably connected to the first and second endplates to enable the first and second endplates to move relative to each other at an angle with respect to the longitudinal axis, in sliding connection with the frame; an actuator screw rotatably connected to the frame; and a carriage (a) forming an open area aligned with the openings in the first and second endplates and defining thereby a proximal carriage side and a distal carriage side with respect to the longitudinal axis, (b) threadably connected to the actuator screw, whereby rotation of the actuator screw moves the carriage with respect to the frame and the first and second endplates, the actuator screw not crossing between the proximal carriage side and the distal carriage side; and (c) including a plurality of ramps each mateable with at least one of the at least one ramped surfaces of the first and second endplates, wherein when the carriage is moved by rotation of the actuator screw, at least one of the at least one ramped surface of the first endplate and at least one of the at least one ramped surface of the second endplate each slide along at least one of the plurality of ramps of the carriage to cause the endplates to move relative to each other in sliding connection with the frame. 
     In various embodiments thereof, the first and second endplates are confined by the frame to move relative to each other only along an axis substantially transverse to the longitudinal axis; at least one of the first and second endplates includes at least one aperture through which a fastener may pass to secure the implant to bone of the joint; the implant further includes a blocking mechanism configured to prevent backing out of a fastener passed through at least one of the first and second endplates and into body tissue; the blocking mechanism includes a blocking member slideably retained within a channel between an unblocking position and a blocking position in which a portion of the blocking member overlaps a portion of the faster; at least one of the first and second endplates includes one or more projections configured to engage bone of the joint when the implant is positioned between bones of the joint; at least one of the first and second endplates is composed of two interconnected portions of dissimilar materials; one of the dissimilar materials is metallic and includes at least one aperture through which a fastener may be passed to attach the implant to a bone of the joint; one dissimilar material is polymeric, and another dissimilar material is metallic; and, the implant further includes a polymeric material configured to press against the actuator screw to reduce a potential for unintended rotation of the actuator screw. 
     In further embodiments thereof, when the actuator screw is rotated in a first direction, a height of the implant transverse to the longitudinal axis is increased, and when the actuator screw is rotated in a second direction, a height of the implant transverse to the longitudinal axis is decreased; the actuator screw is threadably connected to the carriage along a proximal side of the carriage; the frame extends from the proximal end of the implant to the distal end of the implant, and the actuator screw is connected to the frame and threadably connected to the carriage along a distal side of the carriage; the frame is disposed within the proximal end of the implant; the frame extends from the proximal end of the implant towards the distal end of the implant; and, the implant further includes at least one post extending through the frame and into the carriage, slideably received in one of the frame or the carriage, thereby configured to maintain an alignment of the carriage along the longitudinal axis. 
     In yet further embodiments thereof, the implant further includes a first passage formed in a proximal end of at least one of the first and second endplates, and a second passage formed in a proximal side of the carriage, the first and second passages aligned to admit introduction of a therapeutic matter into the open area of the carriage when the implant is implanted between bones of the joint; the frame connects to the first and second endplates with a dovetail connection; the implant further includes at least one radiopaque marker positioned in connection with at least one of the first and second endplates, whereby an extent of movement of the connected endplate can be determined using imaging by a relative alignment of the radiopaque marker and a radiopaque element of the implant which does not move together with the connected endplate; ends of the at least one of the plurality of ramps of the carriage slide within grooves in at least one of the first and second endplates. 
     In another embodiment thereof, the frame includes an actuator screw bearing, a first tab extending away from the bearing in a first direction, and a second tab extending away from the bearing in a direction opposite to the upper tab, the first and second tabs forming edges; and the first and second endplates including grooves sized and dimensioned to slidingly receive the edges of the first and second tabs, respectively. 
     In accordance with another embodiment of the disclosure, an implant for therapeutically separating bones of a joint, the implant defining a longitudinal axis extending between distal and proximal ends, the implant comprises a first endplate configured to engage a first bone of the joint, and having an opening through the endplate transverse to the longitudinal axis, and at least one ramped surface on a side opposite a bone engaging side; a second endplate configured to engage a second bone of the joint, and having an opening through the endplate transverse to the longitudinal axis, and at least one ramped surface on a side opposite a bone engaging side; 
     a frame slideably connected to the first and second endplates to enable the first and second endplates to move relative to each other at an angle substantially transverse to the longitudinal axis, in sliding connection with the frame; an actuator screw rotatably connected to the frame; and a carriage (a) forming an open area aligned with the openings in the first and second endplates and defining thereby a proximal carriage side and a distal carriage side with respect to the longitudinal axis, (b) threadably connected to the actuator screw, whereby rotation of the actuator screw moves the carriage with respect to the frame and the first and second endplates, the actuator screw not crossing between the proximal carriage side and the distal carriage side; (c) including a plurality of ramps each mateable with at least one of the at least one ramped surfaces of the first and second endplates, wherein when the carriage is moved by rotation of the actuator screw, at least one of the at least one ramped surface of the first endplate and at least one of the at least one ramped surface of the second endplate each slide along at least one of the plurality of ramps of the carriage to cause the endplates to move relative to each other in sliding connection with the frame; and (d) at least one passage formed in a proximal side of the carriage in communication with at least one proximal passage in at least one of the first or second endplates, the communicating passages configured to admit introduction of a therapeutic matter into the open area of the carriage when the implant is implanted between bones of the joint. 
     In accordance with the disclosure, a method of therapeutically separating bones of a joint, comprises inserting an implant defining a longitudinal axis extending between distal and proximal ends between bones of the joint, the implant including—a first endplate configured to engage a first bone of the joint, and having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side; a second endplate configured to engage a second bone of the joint, and having an opening through the endplate, and at least one ramped surface on a side opposite a bone engaging side; a frame slideably connected to the first and second endplates to enable the first and second endplates to move relative to each other at an angle with respect to the longitudinal axis, in sliding connection with the frame; an actuator screw rotatably connected to the frame; and a carriage (a) forming an open area aligned with the openings in the first and second endplates and defining thereby a proximal carriage side and a distal carriage side with respect to the longitudinal axis, (b) threadably connected to the actuator screw, whereby rotation of the actuator screw moves the carriage with respect to the frame and the first and second endplates, the actuator screw not crossing between the proximal carriage side and the distal carriage side; and (c) including a plurality of ramps each mateable with at least one of the at least one ramped surfaces of the first and second endplates, wherein when the carriage is moved by rotation of the actuator screw, at least one of the at least one ramped surface of the first endplate and at least one of the at least one ramped surface of the second endplate each slide along at least one of the plurality of ramps of the carriage to cause the endplates to move relative to each other in sliding connection with the frame; and rotating the actuator screw after the implant is inserted to move the first and second endplates relatively farther apart to separate bones of the joint. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: 
         FIG.  1    depicts an implant of the disclosure, together with three mounted bone screws; 
         FIG.  2    depicts the implant of  FIG.  1   , in a compressed or reduced height configuration; 
         FIG.  3    depicts the implant of  FIG.  1   , in an expanded or increased height configuration; 
         FIG.  4    depicts a carriage and frame of the implant of  FIG.  1   ; 
         FIG.  5    depicts an endplate of the implant of  FIG.  1   ; 
         FIG.  6 A  depicts a sagittal cross-section of the implant of  FIG.  2   ; 
         FIG.  6 B  depicts a sagittal cross-section of the implant of  FIG.  3   ; 
         FIG.  7 A  depicts a transverse cross-section of the implant of  FIG.  2   ; 
         FIG.  7 B  depicts a transverse cross-section of the implant of  FIG.  3   ; 
         FIG.  8    depicts an exploded view of the implant of  FIG.  1   ; 
         FIG.  9    depicts a diagrammatic view of aspects of an implant in accordance with the disclosure, in a reduced height configuration; 
         FIG.  10    depicts the implant of  FIG.  9   , in an expanded height configuration; 
         FIG.  11    depicts the implant of  FIG.  1   , implanted between adjacent vertebrae; 
         FIG.  12 A  depicts a front view of the implant of  FIG.  1    having an alternative blocking configuration, in a reduced height configuration; 
         FIG.  12 B  depicts the implant of  FIG.  12 A  in an expanded height configuration; 
         FIG.  13    depicts the implant of  FIG.  12 B , with bones screws inserted into the implant; 
         FIG.  14    depicts inserting a trial of the disclosure, the trial representing an implant of the disclosure, into the disc space, using a trialing tool of the disclosure; 
         FIG.  15    depicts an implantation and actuating tool of the disclosure inserting an implant of the disclosure into the disc space; 
         FIG.  16    depicts the implant and tool of  FIG.  14   , the tool having expanded the implant; 
         FIG.  17    depicts the implant and tool of  FIG.  15   , and a bone screw driver inserting a bone screw; 
         FIG.  18    depicts the implant of  FIG.  13    secured between vertebrae; 
         FIG.  19    depicts an implant of the disclosure including a proximally driven carriage; 
         FIG.  20    depicts the carriage of the implant of  FIG.  19   ; 
         FIG.  21    depicts a lower endplate of the implant of  FIG.  19   ; 
         FIG.  22    depicts an exploded view of the implant of  FIG.  19   ; 
         FIG.  23    depicts a reduced height configuration of the implant of  FIG.  19   ; 
         FIG.  24    depicts an expanded height configuration of the implant of  FIG.  23   ; 
         FIG.  25    depicts a cross section of the implant of  FIG.  23   ; 
         FIG.  26    depicts a cross section of the implant of  FIG.  24   ; 
         FIG.  27    depicts the implant of  FIG.  23   , with bone screws inserted into the implant; 
         FIG.  28    depicts the implant of  FIG.  24   , with bone screws inserted into the implant; 
         FIG.  29    depicts a front view of the implant of  FIG.  27   ; 
         FIG.  30    depicts a front view of the implant of  FIG.  28   ; 
         FIG.  31    depicts a perspective view of the implant of  FIG.  19   , without bone screws inserted; 
         FIG.  32    depicts a front view of the implant of  FIG.  30   , without bone screws inserted; 
         FIG.  33    depicts a side view of an alternative implant in accordance with the disclosure, in a reduced height configuration; 
         FIG.  34    depicts the implant of  FIG.  33   , in an expanded height configuration; 
         FIG.  35    depicts an exploded view of the implant of  FIG.  33   ; 
         FIG.  36    depicts an enlarged cross section of a dovetail connection of the implant of  FIG.  33   ; 
         FIG.  37    depicts a front view of the implant of  FIG.  33   , illustrating passages for bone graft material; 
         FIG.  38    depicts a simulating of radiographic imaging of an implant of the disclosure, illustrating radiographic markers, the implant in a reduced height configuration; 
         FIG.  39    depicts the implant of  FIG.  38   , the implant in an expanded height configuration; 
         FIG.  40    depicts a bone funnel of the disclosure, used in connection with an implant of the disclosure; 
         FIG.  41    depicts an alternative implant of the disclosure, including hinged endplates, in a reduced height configuration; 
         FIG.  42    depicts the implant of  FIG.  41   , in an expanded configuration; 
         FIG.  43    depicts the implant of  FIG.  41   , with a frame portion removed; 
         FIG.  44    depicts a cross section of an alternative implant of the disclosure, in perspective, having an elongate actuator screw; 
         FIG.  45    depicts the implant of  FIG.  44   , having a shortened actuator screw; 
         FIG.  46    depicts an exploded view of an alternative expandable implant including guide pins in accordance with embodiments of the present application; 
         FIGS.  47 A and  47 B  depict unexpanded and expanded configurations of the expandable implant in  FIG.  46   ; 
         FIG.  48    depicts an exploded view of an alternative expandable implant including endplates formed primarily of metal in accordance with embodiments of the present application; 
         FIGS.  49 A and  49 B  depict unexpanded and expanded configurations of the expandable implant in  FIG.  48   ; 
         FIGS.  50 A and  50 B  depict unexpanded and expanded configurations of an alternative expandable implant having an alternate means to capture the blocking mechanism in accordance with embodiments of the present application; 
         FIGS.  51 A-D  depict an alternative expandable implant including anchors consistent with the present disclosure; 
         FIGS.  52 A-C  depict exemplary anchors consistent with the present disclosure; 
         FIG.  53    depicts an implant consistent with the present disclosure in a compressed or reduced height configuration, together with three mounted anchors; 
         FIG.  54    depicts a different view of the implant of  FIG.  53    consistent with the present disclosure; 
         FIG.  55    depicts a different view of the implant of  FIG.  53    consistent with the present disclosure; 
         FIG.  56    depicts a different view of the implant of  FIG.  53    consistent with the present disclosure; 
         FIG.  57    depicts a different view of the implant of  FIG.  53    consistent with the present disclosure; 
         FIG.  58    depicts an implant consistent with the disclosure in an expanded or increased height configuration, together with three mounted anchors; 
         FIG.  59    depicts a different view of the implant of  FIG.  58    consistent with the present disclosure; 
         FIG.  60    depicts a different view of the implant of  FIG.  58    consistent with the present disclosure; 
         FIG.  61    depicts a different view of the implant of  FIG.  58    consistent with the present disclosure; and 
         FIG.  62    depicts a different view of the implant of  FIG.  58    consistent with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As required, detailed embodiments are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples and that the systems and methods described below can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present subject matter in virtually any appropriately detailed structure and function. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the concepts. 
     The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms “including” and “having,” as used herein, are defined as comprising (i.e., open language). 
     Implants of the disclosure allow continuous expansion and retraction within a range of expansion. Lordosis of certain embodiments of implants herein can be custom tailored to fit the anatomy of a specific patient. Additionally, implants of the disclosure enable distraction of vertebral bodies to a desired height, but can also be collapsed and repositioned, as therapeutically indicated for the patient. 
     With reference to  FIGS.  1 - 3   , implant or implant  100  is operative, when positioned between adjacent bones of a joint, such as for example vertebrae  10 ,  12  (shown in  FIG.  11   ), to stabilize a joint formed by adjacent vertebrae. Implant  100  has a collapsed state or height, illustrated in  FIG.  2   , and an expanded state or height, illustrated in  FIG.  3   . Implants  100  of the disclosure may be inset into the intervertebral disc space at a collapsed height, and then expand axially (superior/inferior) to restore height loss in the disc space. The implant provides distraction as well as achieves optimal height restoration. When inserted in a collapsed state, implants  100  reduce impaction to tissue in the joint space during insertion, and form the least visually blocking or obstructing profile. 
     Implant  100  includes two separable endplates  110 ,  112 . A surface  114  of an endplate  110 ,  112  can be provided with teeth or other projections  116  which can penetrate body tissue to reduce a likelihood of migration of implant  100  after implantation. Implant  100  is further secured with one or more bone screws  300 , which pass through bone screw socket  118  within implant  100 , and into body tissue of the patient. In the embodiment illustrated in  FIGS.  1 - 3   , three sockets  118  for three bone screws are provided, the bone screws  300  further retained in connection with implant  100  by blocking fasteners  120 . Bone screw  300  can be a polyaxial screw, and sockets  118  correspondingly shaped, whereby bone screw  300  may be inserted into body tissue at an optimal angle with respect to implant  100 , whereby optimal purchase may be obtained, or certain body tissue may be avoided. 
     Endplates  110 ,  112  are moveably connectable to an actuator  150  operable to change a relative relationship of endplates  110  and  112 . Actuator  150  includes a frame  152  rotatably supporting an actuator screw  154 , and a moveable carriage  156 . As actuator screw  154  rotates within frame  152 , carriage  156  slides within frame  152 , driven by cooperation between threads  158  ( FIG.  8   ) upon actuator screw  154 , and mating threads  160  within carriage  156 . In the embodiment of  FIGS.  1 - 3   , endplates  110  and  112  are formed in two connected portions, including a portion  122 ,  122 A which can be polymeric, and a portion  124 ,  124 A, which can be metallic. The portions are joined in the embodiment shown by screws  162 , although other methods of combining the two connected portions  122 ,  124  or  122 A and  124 A may be used, including a dovetail connection, or adhesive, possibly in combination with each other, or with endplate connector screws  162 . Metallic portions  124 ,  124 A can provide greater strength for portions of implant  100  which are under relatively greater stress, for example portions through which a fastener may pass to anchor implant  100  within the body. While portions  122 ,  122 A,  124 ,  124 A are described as polymeric or metallic, it should be understood that other materials may be used, and that the portions can be of dissimilar materials. 
     With reference to  FIG.  2   , it may be seen that implant  100  is in a compressed state, having a lower height relative to an expanded state, as shown in  FIG.  3   . A functioning of device  100  may be best understood with reference to  FIGS.  9 - 10   , which correlate with  FIGS.  2 - 3   , respectively, but which present a simplified view having certain elements eliminated or exaggerated, to ease understanding. Endplates  110  and  112  are provided with ramped channels  164 ,  164 A, and an open ramp  166 ,  166 A, sized to slidingly receive ramps  168 ,  168 A and  170 ,  170 A disposed upon carriage  156 . While two mating channels and ramps are illustrated for each endplate  110 ,  112 , it should be understood that one, or more than two, sets of channels and or ramps may be provided. Further, channels  164 ,  164 A may alternatively be formed as ramps. However, a channel can operate to enable a reduction of height, having an opposing ramp face, whereby rotation of actuator screw  154  in an opposite direction to expansion can drive endplates  110 ,  112  together, for example when pressure from body tissue is insufficient to collapse endplates  110 ,  112 . Additionally, at least one channel can operate to foster the maintenance of a connection between carriage  156  and an endplate  110 ,  112 . 
     Carriage  156  is supported by frame  152  by lateral engagement means, in this embodiment two support screws  174  engaged with carriage  156 , and passable through respective channels  176  formed in frame  152 . Distal end  172  of actuator screw  154  provides additional support for carriage  156 . Actuator screw  154  is supported by a set screw  178 , which passes through and is rotatably supported within frame  152 . 
     An actuator access port  180  permits passage of a tool, for example a hex driver (not shown), into engagement with a proximal end  182  of actuator screw  154 . As actuator screw  154  is turned, distal end  172  bears against a thrust washer  184 , and an end portion of frame  152 . As actuator screw  154 , carriage  156  is driven along actuator screw by interaction of threads  158  and  160 . As carriage  156  moves, endplates  110 ,  112  are urged to move along ramps  168 ,  168 A and  170 ,  170 A, moving relatively apart, and increasing a height of implant  100 . Endplates  110 ,  112  are prevented from moving together with carriage  156  by abutting against an end portion  186  of frame  152 . In a given orientation, one of endplate  110  and  112  is an upper endplate with respect to an orientation in a standing patient. However, implant  100  may, in some embodiments, be implantable in either of opposite orientations, and therefore designations of upper and lower are provided for ease of understanding, only. It should be understood that only one of endplate  110 ,  112  may be moveable with respect to the other. For example, in one embodiment, ramps  168 A,  170 A may not be provided, and endplate  112  may be attached to frame  152 . 
       FIG.  11    illustrates an implant  100  of the disclosure implanted between adjacent vertebrae  10 ,  12 . Frame  152  defines a distal or leading end  152 A which is inserted first into the body, and a proximal or trailing end  152 B which passes last into the body, the distal and proximal ends defining a longitudinal axis extending therebetween. Implant  100  can be inserted into the body, and into a position between vertebrae, using minimally invasive methods, for example using a small incision, and implant  100  may be passed through a cannula or other structure which maintains a pathway through body tissue. Implant  100  may be inserted into the spinal column through any approach, including anterior, anterolateral, lateral, or posterolateral. A portion of the disc annulus, and nucleus pulposus may be removed in order to form a space into which implant  100  may be inserted. When implant  100  is in a compressed, or reduced height configuration, dovetail guides  200 ,  202  can be provided to foster maintenance of a relative orientation of upper and lower endplates during insertion or removal of device  100 . Dovetail guides  200 ,  202  further stabilize endplates  110 ,  112  during expansion, and when implant  100  is expanded. Dovetail guides  200 ,  202 , can have the form of a tongue and groove configuration, or other sliding mating configuration, with ends of ramps  168 ,  168 A, for example. 
     Implant  100  can be inserted configured to have a lower height profile, as shown in  FIG.  2   , whereby an extent of distraction of body tissue may be reduced during insertion. Moreover, to the extent that implant  100  is used to open a pathway towards an implantation site, trauma to adjacent tissue is reduced relative to inserting an implant having a final height profile. Once implant  100  is positioned between adjacent vertebrae, actuator screw is rotated by a tool. The tool may be positioned entirely within the body, or can extend from in interior of the body to outside the body, for example having a driving tip at one end and having a handle at an opposite end, with a shaft extending into the body between each end. 
     Once actuator screw  154  has been rotated to separate endplates  110 ,  112  a desired amount, the tool is removed. At this point, actuator screw  154  may be secured in place, for example using a mechanical block, or an adhesive, to prevent unintended rotation of actuator screw  154 . As carriage  156  is slideably moved by rotation of actuator screw  154 , a ramp  166 ,  166 A or a ramped surface of channel  164 ,  164 A of at least one of endplate  110 ,  112  slides against at least one ramp  168 ,  168 A,  170 , or  170 A of carriage  156 , to cause the endplate to move along an axis transverse to the longitudinal axis of the frame, to increase a height of the implant. Rotation of actuator screw  154  in an opposite direction causes movement along an axis transverse to the longitudinal axis of the frame to decrease a height of the implant. 
     Polymeric insets, or a polymeric square nut, for example PEEK, can be provided, engageable with threads  158  or other portion of actuator screw  154 , to provide additional friction to prevent height loss under load, particularly under cyclic loading. Similarly, once bone screws  300  have been inserted, blocking elements  120  may be rotated to extend over an end of bone screw head  302 , preventing screw  300  from backing out. A similar mechanical block (not shown) may be provided for actuator screw  154 . 
     With reference to  FIGS.  1 - 3 ,  5 - 8   , it may be seen that a socket  118  for a polyaxial screw head  302  can be formed entirely within one of upper or lower endplate  110 ,  112 , or may be formed partially within each of endplate  110  and  112 , whereby when implant  100  has been expanded to a final height, the proportions of an interior of socket  118  are correct or substantially correct for retaining screw head  302 . For example, in  FIG.  8   , metallic portion  124  forms an upper portion  190  of socket  118 , and mating metallic portion  124 A forms a lower portion  192  of socket  118 . In the embodiment illustrated in the figures, there are three sockets  118 , and all are formed of upper and lower portions. However, there may be more or fewer sockets  118 , and one or more sockets may be formed entirely in an upper or lower endplate. 
     In an embodiment, implant  100  of the disclosure provides an actuator that translates relative to the body by means of a threaded actuator screw  154 . Ramps  168 ,  168 A and  170 ,  170 A on a carrier  152  mate with channels  164 ,  164 A, and or ramps  166 , on endplates  110 ,  112 . Linear translation of carriage  156  causes endplates  110 ,  112  to expand implant  100  along an S/I axis with respect to the body. There can be dovetail guides that capture endplates  110 ,  112  when collapsing the implant. 
     Assembly screws  162  fasten endplates made of dissimilar materials, for example PEEK polymeric portions  122 ,  122 A to Titanium metallic portions  124 ,  124 A. A dovetail and press fit design can be used to connect the dissimilar endplate portions. A PEEK bushing or washer  184  is used between the threaded actuator screw  154  and frame  152  to minimize friction during expansion of implant  100 . Support screws  174  and channels  176  cooperate to form side or lateral stabilizers, and set screw  178  supports a nose or leading end of carriage  156 . Additionally, cooperating slots and projections (not shown) in carriage  156  and frame  152  can be provided for further relative guidance and stability. 
     In one embodiment, three bone screws  300  are used to provide fixation into adjacent vertebral bodies, two screws  300  passing through implant  100  and into one vertebra, and one screw  300  passing through implant  100  into another vertebra, although other combinations may be used. Bone screws  300  can have spherical or otherwise curved heads, facilitating insertion at a desired angle, or may be provided to mate with socket  118  in a fixed orientation, particularly depending on a diameter of a neck portion of screw  300 . Cam style blocking fasteners  120  can be used to block bone screws  300  from backing out after being inserted. 
     Implants of the disclosure enable a continuous expansion and retraction over a range of displacements according to predetermined dimensions of a specific implant  100  design. This provides the ability to distract vertebral bodies to a desired height, but also to collapse the implant  100  for repositioning, if therapeutically advantageous for the patient. Endplates  110 ,  112  may be shaped to form planes or surfaces which converge relative to each, to provide for lordosis, and can be provided with openings, forming a graft chamber  204  through the openings and between the respective openings through which bone may grow, and into which bone graft material may be placed. Implant  100  may be used to distract, or force bones of a joint apart, or may be used to maintain a separation of bones created by other means, for example a retractor. 
     Implant  100  may be fabricated using any biocompatible materials known to one skilled in the art, having sufficient strength, flexibility, resiliency, and durability for the patient, and for the term during which the device is to be implanted. Examples include but are not limited to metal, such as, for example titanium and chromium alloys; polymers, including for example, PEEK or high molecular weight polyethylene (HMWPE); and ceramics. There are many other biocompatible materials which may be used, including other plastics and metals, as well as fabrication using living or preserved tissue, including autograft, allograft, and xenograft material. 
     Portions or all of the implant may be radiopaque or radiolucent, or materials having such properties may be added or incorporated into the implant to improve imaging of the device during and after implantation. 
     For example, metallic portions  124 ,  124 A of endplates  110 ,  112  may be manufactured from Titanium, or a cobalt-chrome-molybdenum alloy, Co—Cr—Mo, for example as specified in ASTM F1537 (and ISO 5832-12). The smooth surfaces may be plasma sprayed with commercially pure titanium, as specified in ASTM F1580, F1978, F1147 and C-633 (and ISO 5832-2). Polymeric portions  122 ,  122 A may be manufactured from ultra-high molecular weight polyethylene, UHMWPE, for example as specified in ASTM F648 (and ISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark of Invibio Ltd Corp, United Kingdom) may be used for one or more components of implant  100 . For example, polymeric portions  122 ,  122 A can be formed with PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may be observed. Other polymeric materials with suitable flexibility, durability, and biocompatibility may also be used. 
     In accordance with the invention, implants of various sizes may be provided to best fit the anatomy of the patient. Components of matching or divergent sizes may be assembled during the implantation procedure by a medical practitioner as best meets the therapeutic needs of the patient, the assembly inserted within the body using an insertion tool. Implants of the invention may also be provided with an overall angular geometry, for example an angular mating disposition of endplates  110 ,  112 , to provide for a natural lordosis, or a corrective lordosis, for example of from 0° to 6° for a cervical application, although much different values may be advantageous for other joints. Lordotic angles may also be formed by shaping one or both of plates  110 ,  112  to have relatively non-coplanar surfaces. Expanded implant heights, for use in the cervical vertebrae for example, may typically range from 7 mm to 12 mm, but may be larger or smaller, including as small as 5 mm, and as large as 16 mm, although the size is dependent on the patient, and the joint into which an implant of the invention is to be implanted. Implants  100  may be implanted within any level of the spine, and may also be implanted in other joints of the body, including joints of the hand, wrist, elbow, shoulder, hip, knee, ankle, or foot. 
     In accordance with the invention, a single implant  100  may be used, to provide stabilization for a weakened joint or joint portion. Alternatively, two, three, or more implants  100  may be used, at a single joint level, or in multiple joints. Moreover, implants  100  may be combined with other stabilizing means. 
     Additionally, implant  100  may be fabricated using material that biodegrades in the body during a therapeutically advantageous time interval, for example after sufficient bone ingrowth has taken place. Further, implant  100  is advantageously provided with smooth and or rounded exterior surfaces, which reduce a potential for deleterious mechanical effects on neighboring tissues. 
     Any surface or component of the invention may be coated with or impregnated with therapeutic agents, including bone growth, healing, antimicrobial, or drug materials, which may be released at a therapeutic rate, using methods known to those skilled in the art. 
     Devices of the disclosure provide for adjacent vertebrae to be supported during flexion/extension, lateral bending, and axial rotation. In one embodiment, implant  100  is indicated for spinal arthroplasty in treating skeletally mature patients with degenerative disc disease, primary or recurrent disc herniation, spinal stenosis, or spondylosis in the lumbosacral spine (LI-SI). Degenerative disc disease is advantageously defined as discogenic back pain with degeneration of the disc confirmed by patient history and radiographic studies, with or without leg (radicular) pain. Patients are advantageously treated, for example, who may have spondylolisthesis up to Grade 1 at the involved level. The surgery position implant  100  may be performed through an Anterior, Anterolateral, Posterolateral, and/or Lateral approach. 
     In a typical embodiment, implant  100  has an uncompressed height, before insertion, of 12 to 18 mm, and may advantageously be provided in cross-sections of 23×32 mm, 26×38 mm and 26×42 mm, with 4, 8, 12, or 16 degree lordotic angles, although these are only representative sizes, and substantially smaller or larger sizes can be therapeutically beneficial. In one embodiment an implant  100  in accordance with the instant disclosure is sized to be inserted using an MIS approach (a reduced incision size, with fewer and shorter cuts through body tissue). 
     Implant  100  may advantageously be used in combination with other known or hereinafter developed forms of stabilization or fixation, including for example rods and plates. 
     Referring now to  FIGS.  13 - 18   , implant  100  can be insert it into the intervertebral disc space at a collapsed height, and then expand it to restore the disc space height. Implant  100  provides distraction as well as achieves optimal sagittal balance. As discussed, there are multiple methods and approaches by which implant  100  can be inserted.  FIGS.  14 - 18    illustrate one possible method and approach of the disclosure. While a series of numbered steps are described, it should be understood that there can be numerous other steps pertaining to the procedure, and that the steps described emphasize useful steps in the deployment of implant  100  of the disclosure. 
     Step 1: Approach—An approach to the desired section of the spine is performed using surgical instruments such as scalpels and retractors, for example using minimally invasive techniques. 
     Step 2: Preparation—Disc preparation instruments can be used to expose the disc and remove disc material, for example using rongeurs and other suitable instruments (not shown), to create a disc space  14 . 
     Step 3: Trialing—As may be seen in  FIG.  14   , trialing for implant footprint, height and wedge angle is performed to indicate which size or type of implant  100  is to be used. An expandable trial, static trials, or a combination of each may be used. In  FIG.  14   , trial implant  320  is trial fit using trial insertion tool  400 . 
     Step 4: Insertion—Graft material or other therapeutically beneficial material is packed into graft chamber  204  of the selected implant  100  when it is collapsed or partially expanded. As may be seen in  FIG.  15   , implant  100  is inserted into disc space  14  using insertion tool  410 . Tool engagement formations  206  are provided on opposite sides of frame  152  or one of endplate  124  or  124 A, as can be seen in  FIG.  1   . Tool arms  412  securely and releasably engage tool engagement formations  206 , and align an expansion driver  414  with actuator screw  154 . 
     Step 5: Expansion—In  FIG.  16   , implant  100  is expanded, as described herein, by turning actuator screw  154  using expansion driver  414 . After expansion, additional bone graft material can be packed through graft portals  208  into the central graft chamber  204  using a bone funnel  440  ( FIG.  40   ). A push rod (not shown) can be used for driving graft material through funnel  440 . 
     Step 6: Hole Preparation—Bone screw pilot holes can be formed into one or more adjacent vertebrae, prepared using, for example, awls, drills and or taps. Multiple pilot holes can be prepared first, or pilot holes can be prepared one at a time, before the insertion of each screw  300 . During any of the steps herein, imaging can be carried out to avoid damage to adjacent tissue. 
     Step 7: Screw Insertion—In  FIG.  17   , bone screws  300  are inserted using bone screw driver  416 . To facilitate access for bone screw driver  416 , expansion driver  414  may be withdrawn from insertion tool  410 . After bone screws  300  are inserted, they can be blocked from backing out using blocking element  120 . Lagging of the vertebral bodies can be performed before or after the bone screws are locked. Fluoroscopy or other imaging can be used to confirm final placement. Imaging can also be used at any of the steps to confirm work performed. Further, bone screw hole preparation and bone screw  300  insertion can be carried out prior to implant  100  expansion, to promote anchoring of the implant during expansion. In  FIG.  18   , an expanded implant  100  can be seen between vertebrae, secured by bone screws  300 . The foregoing method provides a customized fit using implant  100 , and minimizes disruption to patient anatomy. 
     Referring now to  FIGS.  19 - 32   , an alternative implant  100 B of the disclosure has a shorter actuator screw  154 B relative to actuator screw  154  of implant  100  of  FIG.  1   . Actuator screw  154 B engages a proximal end of carriage  156 B, and does not pass through graft portal  208 B. A compact actuator frame  212  includes a screw bearing  210 , and upper and lower tabs  214 ,  216 , respectively. Endplate slots  218 ,  220  within endplates  110 B and  112 B slidingly receive upper and lower tabs  214 ,  216 . In this manner, actuator screw  154 B is rotatably fixed along a longitudinal axis with respect to endplates  110 B and  112 B, the longitudinal axis indicated in  FIG.  19    to extend between distal (“D”) and proximal (“P”) ends. Endplates  110 B,  112 B can slide upon collar tabs  214 ,  216  to mutually separate to form an expanded configuration of implant  100 B. Actuator screw  154 B can be rotatably retained within compact actuator frame  212 , so that carriage  156 B can be pushed or pulled in threaded engagement with actuator screw  154 B, without an axial displacement of actuator screw  154 B. This can be accomplished, for example, by a clip or other cooperative engagement between compact actuator frame  212  or bearing  210 , and actuator screw  154 B, or a blocking element (not shown) partially covering an end portion of actuator screw  154 B. In an embodiment, tabs  214  and  216  form a dovetail connection with endplate slots  218 ,  220 . 
     It should be understood that implant  100  may identified with a suffix herein, for example  100 B,  100 C,  100 D,  100 E, to indicate embodiments illustrating various features of the disclosure. In consideration of the impracticality of illustrating and describing every possible permutation of features, it should be understood that, where logical, features of the various implants may be substituted among the implants. Thus, all of the implants may collectively be referred to as implant  100 , unless a specific reference is made to a feature illustrated by a particular embodiment. 
     Actuator screw  1546 B threadably engages carriage  156 B at threads  160 B, whereby rotation of screw  154 B causes carriage  156 B to move towards or away from compact actuator frame  212 . Carriage  156 B has ramps  168 ,  168 A and  170 ,  170 A, which engage corresponding endplate ramps  164 ,  164 A,  166 ,  166 A as described with respect to implant  100 . As actuator screw  154 B is rotated, carriage  156  translates with respect to endplates  110 B,  112 B. As a result, carriage ramps  168 ,  168 A and  170 ,  170 A slide against endplate ramps  164 ,  164 A,  166 ,  166 A, causing endplates  110 B,  112 B to mutually separate. In an embodiment, carriage  156 B is polymeric at threads  160 B, and an interference fit is formed between actuator screw  154 B and threads  160 B, whereby sufficient friction is created to resist unintended rotation of actuator screw  154 B, with a consequential change in height of implant  100 B. 
     Frame  152  slidingly bears against frame support edges  224  extending along endplates  110 B,  112 B, and is slidingly connected to carriage  156 B by carriage support screws  174 . In this manner, carriage  156 B is laterally supported, and inhibited from rotational movement, but may move longitudinally along a path defined by carriage support channel  176  and actuator screw  154 B. Additionally, channels or dovetail guides  200 ,  202  in endplates  110 B,  112 B receive mating end portions  200 A,  202 A of carriage ramps  168 ,  168 A,  170 ,  170 A, to further guide and stabilize endplates  110 B,  112 B. 
       FIGS.  19 - 32    further illustrate an alternative blocking element  120 B, which, as with other of the various alternative elements herein, may be combined with other implant embodiments herein. Element  120 B forms a sliding block  226  within a block groove  228 , block  226  and block groove  228  forming a dovetail or other sliding mating engagement, wherein block  226  is confined to movement along a path defined by block groove  228 . Once bone screw head  302  is fully seated within bone screw socket  118 , block  226  may be slid partially out of engagement with block groove  228  to a position over bone screw head  302 , thereby blocking a movement of bone screw  300  out of engagement with body tissue. In the embodiment shown, two blocking elements  120 B are illustrated, wherein a tool having two end portions (not shown) can be inserted adjacent each block  226 , and the tool rotated to move both blocks into a blocking position. Accordingly, blocks  226  together form substantially concentric arcs pivoting about the same or close axes. 
     Implant  100 B is configured to facilitate the insertion of graft material or other therapeutic material through one or more of bone screw socket  118  into graft chamber  204  formed by openings within endplates  110 B,  112 B, and carriage  156 B. After the material is inserted, bone screws  300  may then be inserted into socket  118  and fastened to body tissue as otherwise shown and described herein. A bone funnel  440  ( FIG.  40   ) may be used to urge material into graft chamber  204 . Alternatively, once implant  100 B is expanded, materials may be inserted into an endplate gap  230  formed by a separation of endplates  110 B,  112 B, as may best be seen in  FIGS.  30  and  32   , which are cross-sections taken through compact actuator frame  212 , and upper and lower tabs  214 ,  216 . 
     It should be understood that endplates of the disclosure, in all embodiments, may be formed of a unitary material, as illustrated in  FIGS.  19 - 32    for example, or multiple materials, as illustrated in  FIGS.  1 - 6    for example. Accordingly, endplates  110 B,  112 B may be formed of multiple materials, for example titanium for a proximal, bone screw engaging portion, and UHMWPE for a distal, bone engaging portion. Further, endplates  110 B,  112 B may be provided with teeth or other projections, to positively engage body tissue and reduce a likelihood of undesired migration of implant  100 B. 
     With reference to  FIGS.  33 - 40   , a spacer implant  100 C includes frame  152 C which forms a dovetail engagement with upper and lower endplates  110 C,  112 C. In this manner, endplates  110 C,  112 C are further stabilized throughout a range of expansion of implant  100 C. As may be seen in  FIG.  36   , a cross section of endplate portion  124 C illustrates frame support channel  232  of endplate portion  124 C is shaped to slidingly retain frame extension guide  234  of frame  152 C (also visible in  FIGS.  44 - 45   ). It should be understood that an inverse configuration can be created, wherein a channel is formed in frame  152 C and an extension is formed from endplate portion  124 C. Similar channels and extensions can be formed on opposing sides of frame  152 C, as illustrated, with a frame support channel  232  formed in lower endplate portion  124 C′, as well. In an embodiment, frame  152 C can form an extended region  238  along all or part of the dovetail engagement area of frame support channel  232  and extension guide  234 . For example, frame  152 C can extend in superior and inferior directions to extend from near an outer surface of endplate  110 C to near an outer surface of endplate  112 C, or may extend over a lesser distance. Channel  232  and extension guide  234  are illustrated as transverse to an A-P or longitudinal axis of implant  100 C. In an alternative embodiment, channel  232  and guide  234  are disposed at a non-transverse angle with respect to the longitudinal axis. 
     With reference to  FIGS.  35  and  37   , carriage  156 C includes a graft chamber portal  236 , providing access from an exterior to a proximal end of implant  100 C into graft chamber  204 , after implant  100 C is implanted within the body. Carriage  156 C includes two portals  236  specifically formed to admit the passage of graft or other therapeutic materials, however one or more than two portals  236  can be provided. In the embodiment illustrated, graft chamber portals  236  are formed within a portion of carriage ramp  170 , although other portions of carriage  156 C may be shaped or opened in a like manner. A bone funnel  440  may be used to direct material through one or more of graft chamber portal  236 . 
     As can be seen in  FIG.  35   , actuator screw  154 C includes actuator screw bearing  184 C and lateral screw bearings  240 , provided to promote smooth rotation of actuator screw  154 C. Bearing channels  242  within actuator screw  154 C can be provided to maintain an orientation of lateral screw bearings  240  within screw guide  246  of carriage  156 C. In an embodiment, an interference fit is formed between lateral screw bearings  240  and screw guide  246 , to prevent unintended rotation of actuator screw  154 C. To further stabilize carriage throughout at least a portion of its range of motion, stabilizing posts, screws, or pins  248  can be provided, connected to frame  152 C, for example within frame pin bore  250  by threads, adhesive, or an interference fit, and slideably engageable within pin bores  252  within carriage  156 C. Alternatively, pins  248  can be affixed to carriage  156 C, and can slide within frame pin bores  152 C. In an embodiment, 
     As can be seen in  FIGS.  35  and  38 - 39   , one or more radiographic markers  254  are positioned within implant  100 C, for example within radiotransparent portions of implant  100 C, or any other radiotransparent portion of the various embodiments herein. For example, a radiographic marker can be positioned within polymeric endplate portion  122 ,  122 A, so that an expanded or contracted position thereof may be positively ascertained using imaging. As may be seen in  FIG.  39   , radiographic markers  254 A,  254 B are oriented to be aligned with an end of carriage ramps  168 ,  168 A, which in this embodiment are radiopaque, only when implant  100 C is fully expanded. To indicate an extent of expansion, one or more radiopaque markers  254  can be positioned with respect to frame  152 , carriage  156 , or any other portion of implant  100  which does not move together with an endplate  110 ,  112 , and which is radiopaque, or which is similarly configured with a radiopaque marker  254 . 
       FIG.  40    illustrates a bone funnel  440  useable with implants  100 ,  100 B,  100 C,  100 D,  100 E (collectively, herein,  100 ) of the invention. An output aperture  442  is placed proximate an opening into an open area within implant  100 , for example graft chamber  204 . Bone graft material, and or other therapeutic agents, are collected within including for example bone growth factors, antimicrobial agents, or other therapeutic is placed into widened input chamber  444 , and then pushed down pipe  446  with a driver, for example a rod (not shown). A pipe connector  448  can be provided, sized to correspond to graft chamber portal  236 . Driven bone graft material is passed into an interior of implant  100 , where it may have its intended therapeutic benefit upon contacting body tissue of at least one vertebra. 
     In an embodiment, carriage ramps  168 ,  168 A,  170 ,  170 A can have differing ramp angles and or sizes, wherein endplate ramps  166 ,  166 A have corresponding profiles and sizes. For example, if ramps  168 ,  168 A are shorter than ramps  170 ,  170 A, expansion will occur at a greater rate along a proximal side of implant  100 , and in this manner an angular orientation of the spine, for example lordosis, may be corrected. Similarly, ramps  170 ,  170 A can be shorter than ramps  168 ,  168 A. Alternatively, one side of ramp  168 ,  168 A can be shorter than another side of ramp  168 ,  168 A, with a corresponding difference along ramps  170 ,  170 A. In this manner, a sideways orientation of the spine, for example Scoliosis, may be corrected. 
       FIGS.  41 - 43    illustrate an alternative implant  100 D of the disclosure, which pivots proximate ends of endplates  110 D,  112 D, providing both axial translation, as indicated by arrows “A”, and pivoting, as indicated by arrows “B”. Axial translation is maintained using frame  152 C, together with frame extension guide  234  and frame support channel  232 , as described with respect to implant  100 C. However, an endplate pivot  256  is formed between endplate portions  122 D and  124 D, and between endplate portions  122 D′ and  124 D′.  FIG.  43    illustrates implant  100 D with frame  152 C removed, illustrating an endplate hinge  258  formed between endplate portions  122 D and  122 D′. Connected in this manner, endplate portions  122 D and  122 D′ pivot about endplate hinge  258 , as well as endplate pivots  256 . Accordingly, a height of implant  100 D at a distal end of implant portions  122 D and  122 D′ is held constant, while a proximate end of implant portions  122 D and  122 D′ translates axially with endplate portions  124 D and  124 D′ to increase a height of implant  100 D. 
     Implant  100 D can be inserted into the intervertebral disc space at a collapsed height, and then expanded into lordosis to restore sagittal balance and height loss in the disc space. Implant  100 D provides distraction as well as achieving optimal sagittal balance. Further, implant  100 D reduces impaction to body tissue during insertion at a collapsed height, and gives a medical practitioner the capability to continuously adjust the lordotic angle of the supporting endplates to best fit the patient&#39;s anatomy and therapeutic needs. 
     Endplate pivot  256  is formed as mating circular portions of endplate portions  122 D and  124 D, and of endplate portions  122 D′ and  124 D′. While one endplate portion forms an extension, and the other a receptacle, it should be understood that this configuration may be reversed. 
     Endplate hinge  258  is formed as a flexible connector  260  extending between endplate portions  122 D and  122 D′. In an embodiment, endplate portions  122 D and  122 D′ are molded as a single part from a polymeric or other flexible material, thus forming a living hinge. In a further embodiment, a hinge is formed between endplate portions  122 D and  122 D′ by any known means, including a barrel or flag hinge, or a hinge similar in style to endplate pivots  256 . In an alternative embodiment, endplate hinge  258  is formed in connection with frame  152 C. 
     By providing both axial and pivoting movement of endplate portions, implant  100 D enables the formation of an alternative supporting structure, and in particular, a supporting structure with a convex conformity. This can be useful to correct particular spinal problems, including lordosis, for example. 
     With reference to  FIGS.  44 - 45   , which are cross-sections of an alternative implant  100 E of the disclosure, it may be seen that actuator screw  154 E is rotatably connected to frame  152 E, for example using C-clip  262 , as illustrated. An alternative method of rotatably securing actuator screw to frame  152 E can include, for example, a leading set screw  178  (see, e.g.  FIGS.  6 ,  6 A ) that freely spins relative to frame  152 E, but is affixed to actuator screw  154 E. An alternative method includes forming mating portions (not shown) upon frame  152 E and screw  154 E. 
     Further stability can be provided for carriage  156 C through the use of stabilizing pins  248 , frame pin bores  250 , and pin bores in carriage  152 C, as described with respect to implant  100 C herein. 
     In a further embodiment, actuator screw  154 E′ is shorter than actuator screw  154 E, and thereby reduces an obstruction of graft chamber  204 . A tool can be passed through screw guide  246 , and then through graft chamber  204 , to engage actuator screw proximal end  182 . Graft material can additionally be passed through screw guide  246 , and placed within graft chamber  204 . Bone funnel  140  can be used to pass materials through screw guide  246 , and pipe connector can be adapted or replaced to best fit the dimensions of screw guide  246 . 
       FIG.  46    depicts an alternative expandable implant including guide pins in accordance with embodiments of the present application. The expandable implant  100  includes many features disclosed in prior embodiments, including a first endplate  110 , a second endplate  112 , a frame  152  for receiving an actuator  150  therein, and an actuator screw  154 . In addition, the expandable implant  100  in  FIG.  46    includes additional features, including guide pins  359 , first and second compressible clips  380 ,  382  and a blocking mechanism  382 . 
     As shown in  FIG.  46   , the expandable implant includes an upper or first endplate  110  and a lower or second endplate  112 . The upper endplate  110  can be comprised of a first portion  122 A and a second portion  124 A that are operatively coupled together (e.g., via a fastener). In some embodiments, the first portion  122 A comprises a polymeric portion, while the second portion  124 A comprises a metallic portion. By having an endplate formed of a polymeric portion and a metallic portion, this advantageously provides an endplate that is both radiolucent and strong. The lower endplate  112  can be comprised of a first portion  122 B and a second portion  124 B that are operatively coupled together (e.g., via a fastener). In some embodiments, the first portion  122 B comprises a polymeric portion, while the second portion  124 B comprises a metallic portion. In other embodiments, the endplates  110 ,  112  can be formed of a single piece that is formed of either a polymer, such as PEEK, or a metal, such as titanium or cobalt-chrome. As in prior embodiments, the upper endplate  110  and the lower endplate  112  can include one or more bore holes for receiving bone screws therein. For example, as shown in  FIG.  46   , lower endplate  112  includes at least one bore hole  189  for receiving a bone screw therethrough for securing the implant  100  to an adjacent bone member. 
     A frame  152  for receiving an actuator  150  is positioned between the first endplate  110  and the second endplate  112 . The frame  152  is configured to receive side support screws  174  through channels to secure the frame  152  to the actuator  150 . In addition, one or more guide pins  359  are provided at a distal or leading end of the frame  152 . The guide pins  359  are inserted through openings in the frame  152  and contact a surface of the actuator  150 . By engaging the actuator  150 , the guide pins  359  advantageously stabilize the actuator  150  such that it is not tilted during use. 
     The actuator  150  comprises a moveable carriage  156  having a first pair of upper ramped surfaces  170  connected to a second pair of upper ramped surfaces  168  via a bridge member  199 . In some embodiments, the first pair of upper ramped surfaces  170  and the second pair of upper ramped surfaces  168  are inclined in the same direction (e.g., toward the distal or leading end of the actuator  150 ). The first and second pair of upper ramped surfaces  170 ,  168  are configured to engage corresponding angled or ramped surfaces of the first endplate  110 , such that movement of the carriage  156  causes expansion of the implant  100 . In some embodiments, a first pair of lower ramped surfaces extends downwardly from the first pair of upper ramped surfaces  170 , while a second pair of lower ramped surfaces extends downwardly from the second pair of upper ramped surfaces. The first and second pair of lower ramped surfaces are configured engage corresponding angled or ramped surfaces of the second endplate  112 , such that movement of the carriage  156  causes expansion of the implant  100 . 
     An actuator screw  154  can be provided to actuate the actuator  150 . The actuator screw  154  comprises a head portion  197  and a shaft portion  198 . The shaft portion  198  comprises threads for engaging a corresponding threaded portion of the actuator  150 . Rotational movement of the actuator screw  154  in a first direction causes linear translation of the moveable carriage  156  of the actuator  150 , thereby causing separation of the endplates  110 ,  112  and expansion of the implant. Rotational movement of the actuator screw  154  in a second direction opposite the first direction causes linear translation of the moveable carriage  156  of the actuator  150  in an opposite direction, thereby causing contraction of the endplates  110 ,  112 . 
     To retain the actuator screw  154  in the implant  100 , an actuator frame  212  can be provided. The actuator frame comprises an upper tab portion  214  and a lower tab portion  216 , and an opening  213  therebetween for receiving the actuator  150  therethrough. The upper tab portion  214  can be received in a slot in the first endplate  110 , while the lower tab portion  216  can be received in a slot in the second endplate  112 . To maintain the actuator  150  in the actuator frame  212 , a first compression clip or “C-clip” locking mechanism  380  can be provided to secure the actuator  150  to the actuator frame  212 . The C-clip  380  is configured to fit around a portion of the actuator  150 , such as the head portion  197 . In some embodiments, the C-clip  380  is retained within a recess or groove formed around the circumference of the actuator head portion. The C-clip  380  is advantageously configured to compress such that it can be trapped in a recess  288  in the actuator frame  212  (as shown in  FIGS.  47 A and  47 B ). This advantageously secures the actuator  154  within the actuator frame  212 . 
     To prevent the bone screws from inadvertently backing out, a blocking mechanism  390  can be provided and attached via a C-clip  382 . The blocking mechanism  390  comprises a body  391  having an opening  392  for receiving at least a portion of the head portion  197  of the actuator screw  154  therethrough. In some embodiments, a second compression clip or “C-clip” locking mechanism  382  can be provided to secure the blocking mechanism  390  to the actuator screw  154 . As shown in  FIGS.  47 A and  47 B , the C-clip  382  is configured to fit around the head portion  197  of the actuator screw  154 . In some embodiments, the C-clip  382  can be received within a recess or groove formed in the head portion  197  of the actuator screw  154 . The C-clip  382  is configured to compress until it reaches a recess  289  (shown in  FIGS.  47 A and  47 B ) in the blocking mechanism  390 , thereby securing the C-clip  382  to the blocking mechanism  390 . 
       FIGS.  47 A and  47 B  show the implant  100  of  FIG.  46    in unexpanded and expanded configurations, respectively. From these views, one can see the additional novel features, such as the first C-clip  380  and the second C-clip  382  retained in recesses  288 ,  289 , thereby maintaining the components of the implant  100  in a secure connection. 
     In some embodiments, the implant  100  of  FIG.  46    is sized and configured to be used in an anterior approach. In some embodiments, when assembled, the leading end of the implant  100  comprises a convex surface, while the trailing end of the implant  100  comprises a substantially flat surface. The leading end and the trailing end can be separated by curved arms, formed by side arms of the frame  152 . 
     A method of insertion is now provided. After forming an incision in a patient and removing tissue from a disc space, a surgeon can insert the implant  100  through an anterior approach. The implant  100  can be inserted in an unexpanded configuration, as shown in  FIG.  47 A . Once the implant  100  has been inserted into the disc space, the implant  100  can be expanded by rotating or actuating the actuator screw  154  (e.g., via a driver). This causes translational movement of the carriage  156  with the ramps, thereby causing expansion of the implant  100 . In some embodiments, prior to inserting and expanding the implant  100 , bone graft material can be provided in a graft opening of the implant. In other embodiments, the implant  100  can include an opening that can receive bone graft therethrough after inserting the implant  100  in a disc space. In some embodiments, bone graft material can be inserted through the screw opening  189  (shown in  FIG.  46   ) after the implant  100  is inserted into a disc space. In other embodiments, the implant  100  can be used in different approaches, including posteriorly or laterally. 
       FIG.  48    depicts an alternative expandable implant including endplates that are formed primarily of metal in accordance with embodiments of the present application. The expandable implant  100  includes many features disclosed in prior embodiments, including a first endplate  110 , a second endplate  112 , a frame  152  for receiving an actuator  150  therein, and an actuator screw  154 . The expandable implant also includes guide pins  359  and compression C-clips  380 ,  382  as discussed with respect to prior embodiments. 
     As shown in  FIG.  48   , the first endplate  110  is a single-piece member formed of a metal. Likewise, the second endplate  112  is a single-piece member formed of a metal. In some embodiments, the first and second endplates  110 ,  112  are formed completely of a metal, as shown in  FIG.  48   . In other embodiments, the first and second endplates  110 ,  112  are formed primarily of a metal, but may have traces of other materials. Advantageously, by providing endplates that are formed primarily or completely of metal, this advantageously creates an implant having increased strength. 
     In some embodiments, the expandable implant  100  in  FIG.  48    is sized and configured to be implanted anteriorly. In other embodiments, the expandable implant  100  can be inserted posteriorly or laterally. 
       FIGS.  50 A and  50 B  illustrate unexpanded and expanded configurations of an alternative expandable implant having an alternative means to capture the blocking mechanism in accordance with embodiments of the present application. The expandable implant  100  includes many similar features as prior embodiments, including a first endplate  110 , a second endplate  112 , a frame  152  for receiving an actuator  150 , and an actuator screw  154 . The implant  100  in the current embodiment, however, has a distinct blocking mechanism  390  that is not attached to the actuator screw  154  by a C-ring. Rather, the blocking mechanism  390  is captured between the actuator screw  154  and the actuator plate  212 . The blocking mechanism  390  includes an extension portion  394  that can fit in a recess, groove or track formed in the actuator plate  212 . As the actuator screw  154  is rotated and linearly translated, the actuator screw  154  pushed in the blocking mechanism  390  such that the extension portion  394  of the blocking mechanism  390  engages the track of the actuator plate  212 , thereby securely capturing the blocking mechanism  390  within the assembly. In other embodiments, a compression C-ring can be optionally provided to retain the blocking mechanism  390  on the actuator screw  154 , in addition to the engagement mechanism discussed herein. 
     With reference to  FIGS.  51 A through  52 D , implant  500  may be operative and contain the same components as with previously described implants including but not limited to any of the implants described herein. Implant  500  is operative, when positioned between adjacent bones of a joint, such as for example vertebrae  10 ,  12  (shown in  FIG.  11   ), to stabilize a joint formed by adjacent vertebrae. Implant  500  may have a collapsed state or height, and an expanded state or height as previously described. Implants  500  of the disclosure may be inserted into the intervertebral disc space at a collapsed height, and then expand axially (superior/inferior) to restore height loss in the disc space. The implant provides distraction as well as achieves optimal height restoration. When inserted in a collapsed state, implant  500  may reduce impaction to tissue in the joint space during insertion, and form the least visually blocking or obstructing profile. 
     Implant  500  includes two separable endplates  502 ,  504 . A surface  506  of an endplate  502 ,  504  can be provided with projections  508  which can penetrate body tissue to reduce a likelihood of migration of implant  500  after implantation. Implant  500  is further secured with one or more fasteners or anchors  510 , which pass through socket  512  within implant  500 , and into body tissue of the patient. In the embodiment illustrated in  FIGS.  51 A-D , two sockets  512  for two anchors  510  are provided, anchors  510  may be further retained in connection with implant  500  by blocking fasteners. Anchor  510  can be a curved, t-shaped shim type of structure with sharp edges to penetrate bone tissue. Sockets  512  may be correspondingly shaped, whereby anchor  510  may be inserted into body tissue at an optimal angle with respect to implant  500 , whereby optimal penetration may be obtained, or certain body tissue may be avoided. 
     Operation of implant  500  may be the same or substantially similar as previously described herein, including operation of the endplates, actuators, frame, actuator screws, blocking mechanisms, etc. Once the implant  500  has been inserted into the disc space, implant  500  can be expanded by rotating or actuating an actuator screw (like actuator screw  154 ) via a driver. This causes translational movement of a carriage with the ramps, thereby causing expansion of the implant  500 . In some embodiments, prior to inserting and expanding the implant  500 , bone graft material can be provided in a graft opening of the implant. In other embodiments, implant  500  can include an opening that can receive bone graft therethrough after inserting the implant  500  in a disc space. In some embodiments, bone graft material can be inserted through the screw opening (like opening  189  shown in  FIG.  46   ) after the implant  500  is inserted into a disc space. In other embodiments, implant  500  can be used in different approaches, including posteriorly or laterally. 
     As shown in  FIGS.  52 A-C , anchors  510  may be have a spherical head  516 . The portion of anchor  510  that is inserted may be curved and may be t-shaped with sharp edges to cut into the bone of the patient. Anchor  510  may have serrated edges to aid insertion into the bone and may also aid in restriction expulsion of anchor  510 . Anchor  510  is depicted as being curved, however, anchor  510  may be straight or helical and be consistent with the principles of the present disclosure. Anchors  510  can be used with any of the implants as described in the present disclosure. 
     With reference to  FIGS.  53 - 62   , implant  1000  may be operative and contain the same components as with any of the previously described implants. Implant  1000  is operative, when positioned between adjacent bones of a joint, such as for example vertebrae  10 ,  12  (shown in  FIG.  11   ), to stabilize a joint formed by adjacent vertebrae. Implant  1000  has a collapsed state or height, illustrated in  FIGS.  53 - 57   , and an expanded state or height, illustrated in  FIGS.  58 - 62   . Implants  1000  of the disclosure may be inserted into the intervertebral disc space at a collapsed height, and then expand axially (superior/inferior) to restore height loss in the disc space. The implant provides distraction as well as achieves optimal height restoration. When inserted in a collapsed state, implant  1000  may reduce impaction to tissue in the joint space during insertion, and form the least visually blocking or obstructing profile. 
     Implant  1000  includes two separable endplates  1100 ,  1120 . A surface  1140  of an endplate  1100 ,  1120  can be provided with teeth or other projections  1160  which can penetrate body tissue to reduce a likelihood of migration of implant  1000  after implantation. Implant  1000  is further secured with one or more fasteners or anchors  3000 , which pass through socket  1180  within implant  1000 , and into body tissue of the patient. In the embodiment illustrated in  FIGS.  46 - 55   , three sockets  1180  for three anchors are provided, anchors  3000  further retained in connection with implant  1000  by blocking fasteners  1200 . Anchor  3000  can be a curved, t-shaped shim type of structure with sharp edges to penetrate bone tissue. Sockets  1180  may be correspondingly shaped, whereby anchor  3000  may be inserted into body tissue at an optimal angle with respect to implant  1000 , whereby optimal penetration may be obtained, or certain body tissue may be avoided. 
     Operation of implant  1000  may be the same or substantially similar as described herein with respect to previously described implants herein, including operation of the endplates, actuators, frame, and carriage. Endplates  1100 ,  1120  are moveably connectable to an actuator operable to change a relative relationship of endplates  1100  and  1120 . As described previously, the actuator may include a frame rotatably supporting an actuator screw, and a moveable carriage. 
     Anchors  3000  may be the same or similar to anchors  512  and have a spherical head as described in greater detail with respect to FIG. The portion of anchor  3000  that is inserted may be curved and may be t-shaped with sharp edges to cut into the bone of the patient. Anchor  3000  may have serrated edges to aid insertion into the bone and may also aid in restriction expulsion of anchor  3000 . Anchor  3000  is depicted as being curved, however, anchor  3000  may be straight or helical and be consistent with the principles of the present disclosure. 
     All references cited herein are expressly incorporated by reference in their entirety. There are many different features to the present invention and it is contemplated that these features may be used together or separately. Unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Thus, the invention should not be limited to any particular combination of features or to a particular application of the invention. Further, it should be understood that variations and modifications within the spirit and scope of the invention might occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention.