Patent Publication Number: US-2022211520-A1

Title: Angling inserter tool for expandable vertebral implant

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/664,980, filed on Oct. 28, 2019, which is a continuation of U.S. patent application Ser. No. 15/878,601, filed on Jan. 24, 2018, which is a continuation of U.S. patent application Ser. No. 15/139,684, filed on Apr. 27, 2016 (published as U.S. Patent Publication No. 2016/0235553), which is a continuation of U.S. patent application Ser. No. 14/281,458, filed May 19, 2014 (now U.S. Pat. No. 9,345,588), which is a continuation of U.S. patent application Ser. No. 13/421,411, filed on Mar. 15, 2012 (now U.S. Pat. No. 8,870,880), which is a continuation-in-part of U.S. patent application Ser. No. 13/333,227, filed on Dec. 21, 2011 (now U.S. Pat. No. 8,591,585), which is a continuation-in-part of U.S. patent application Ser. No. 12/758,529, filed on Apr. 12, 2010 (now U.S. Pat. No. 8,282,683), the entire disclosures of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a device to support the spine after removal of at least a part of a vertebra. 
     BACKGROUND OF THE INVENTION 
     When a vertebra is damaged or diseased, surgery may be used to replace the vertebra or a portion thereof with a prosthetic device to restore spinal column support. For example, vertebral body replacement is commonly required in the treatment of vertebral fracture, tumor, or infection. 
     In recent years, several artificial materials and implants have been developed to replace the vertebral body, such as, for example, titanium cages, ceramic, ceramic/glass, plastic or PEEK, and carbon fiber spacers. Recently, various expandable prosthetics or expandable cages have been developed and used for vertebral body replacement. The expandable prosthetic devices are generally adjustable to the size of the cavity created by a corpectomy procedure and typically are at least partially hollow to accommodate bone cement or bone fragments to facilitate fusion in vivo. Some expandable implants may be adjusted prior to insertion into the cavity, while others may be adjusted in situ. Two advantages of the vertebral body replacement using an expandable prosthetic device that is adjustable in situ is that it is easy to place or insert and it permits an optimal, tight fit and correction of the deformity by in vivo expansion of the device. Some other advantages offered by an expandable prosthetic device are that they can facilitate distraction across the resected vertebral defect for correction of the deformity, and allow immediate load bearing after corpectomy. 
     Instrumentation and specialized tools for insertion of a vertebral implant is one important design parameter to consider when designing a vertebral implant. Spinal surgery procedures can present several challenges because of the small clearances around the prosthetic when it is being inserted into position. Another important design consideration includes the ability of the device to accommodate various surgical approaches for insertion of the vertebral implant. 
     SUMMARY OF THE INVENTION 
     The present invention relates to an expandable prosthetic implant device for engagement between vertebrae generally comprising an inner member, outer member, and gear member positioned coaxial with respect to each other such that the inner and outer members are moveable relative to each other along an axis. The inner member has a hollow interior portion and a threaded external portion and includes a first end portion configured to engage an endplate which is capable of engaging a first vertebral body. The outer member has a hollow interior portion configured to receive the inner member and includes a second end portion configured to engage an endplate which is capable of engaging a second vertebral body. The gear member is axially fixed to the outer member and freely rotatable with respect to the outer member and the gear member threadedly engages the threaded portion of the inner member. 
     The implant is configured to engage the vertebrae such that first and second end portions are oriented in a predetermined alignment with respect to the first and second vertebral bodies. The gear member includes teeth extending around the perimeter of the gear member and the teeth are exposed to the exterior and configured to be accessible by a tool member. 
     The present invention further relates to a method of inserting an implant comprising providing an expandable vertebral implant. The method further may comprise providing an angling inserter tool. The angling inserter tool comprises a handle portion, a base portion, and a tip assembly, the base portion being disposed between the handle portion and the tip assembly. The method further may comprise distally advancing a central shaft of the tip assembly with rotation into an opening in the expandable vertebral implant to secure the angling inserter tool to the expandable vertebral implant. The method further may comprise positioning the expandable vertebral implant in a patient&#39;s spine. The method further may comprise distally advancing an internal shaft to cause the tip assembly to angulate with respect to a longitudinal axis of the angling inserter tool, wherein the internal shaft is coaxial with an outer cylinder of the base portion. The method further may comprise rotating a primary drive shaft of the base portion to cause a gear member on the expandable vertebral implant to rotate thereby causing the expandable vertebral implant to expand, wherein the primary drive shaft is coaxial with the internal shaft. The method further may comprise distally advancing an internal shaft, wherein advancing the shaft comprises rotating a knob on an outer cylinder to cause a drive shaft to distally advance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more readily understood with reference to the embodiments thereof illustrated in the attached drawing figures, in which: 
         FIG. 1  is a perspective view of an implant in accordance with an embodiment of the present invention; 
         FIG. 2  is an exploded view of the implant of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of the implant of  FIG. 1  taken along line  3 - 3  of FIG. 1 ; 
         FIG. 4  is perspective view of an embodiment of an inner member of the implant of  FIG. 1 ; 
         FIG. 5  is perspective view of an embodiment of an outer member of the implant of  FIG. 1 ; 
         FIG. 6  is an elevated perspective view of one embodiment of a gear member of the implant of  FIG. 1 ; 
         FIG. 7  is a bottom perspective view of the gear member of  FIG. 6 ; 
         FIG. 8  is a perspective of one embodiment of a tool according to the present invention; 
         FIG. 9  is a cross-sectional view of the tool of  FIG. 8  shown engaging an embodiment of an expandable implant according to the present invention; 
         FIG. 10  is a perspective view of another embodiment of an implant according to the present invention; and 
         FIG. 11  is a perspective view of another embodiment of an endplate of an implant according to the present invention; 
         FIG. 12  is an exploded view of the endplate of  FIG. 11 ; 
         FIG. 13  is a cross-sectional view of the endplate of  FIG. 11 ; 
         FIG. 14  is a perspective view of an angling inserter tool of one embodiment of the present invention; 
         FIG. 15  is an exploded view of the angling inserter tool of  FIG. 14 ; 
         FIG. 16  is a top view of the angling inserter tool of  FIG. 14 ; 
         FIG. 17  is a cross-sectional view of the angling inserter tool of  FIG. 14 ; 
         FIG. 18  is a cross-sectional view of one embodiment of a tip assembly of the angling inserter tool of  FIG. 14 ; 
         FIG. 19  is an exploded view of the tip assembly of  FIG. 18 ; 
         FIG. 20  is an elevated partial exploded view of the tip assembly of  FIG. 18 ; 
         FIG. 21  is another partial exploded view of the tip assembly of  FIG. 18 ; 
         FIGS. 22 and 23  are top views of one embodiment of the angling inserter tool of  FIG. 14  showing angulation of the tip assembly; 
         FIG. 24  is a view of an expandable trial assembly of one embodiment of the present invention in a contracted position; 
         FIG. 25  is a cross-sectional view of the expandable tip assembly of the expandable trial assembly of  FIG. 24  in a contracted position; 
         FIG. 26  is a view of the expandable trial assembly of  FIG. 24  in an expanded position; 
         FIG. 27  is a cross-sectional view of the expandable tip assembly of the expandable trial assembly of  FIG. 24  in an expanded position; 
         FIG. 28  is a cross-sectional view of one embodiment of the proximal end of the expandable trial assembly of  FIG. 25  showing the scale portion; and 
         FIG. 29  is a view of one embodiment of the proximal end of the trial assembly of  FIG. 25  showing the scale portion. 
     
    
    
     Throughout the drawing figures, it should be understood that like numerals refer to like features and structures. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the invention will now be described with reference to the attached drawing figures. The following detailed description of the invention is not intended to be illustrative of all embodiments. In describing preferred embodiments of the present invention, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected. It is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose. 
     Referring to  FIGS. 1-6 , a preferred embodiment of an expandable vertebral implant  10  is shown. The implant  10  preferably comprises an inner member  12  which may be telescopingly received within an outer member  14 . The implant  10  further comprises a gear member  16  generally configured to effect translation of the inner member  12  with respect to the outer member  14  thereby allowing for expansion and contraction of the implant  10 . The inner member  12 , the outer member  14 , and the gear member  16  are preferably centered along a longitudinal axis  18  and define a hollow interior portion which may be filled with bone material, bone growth factors, bone morphogenic proteins, or other materials for encouraging bone growth, blood vessel growth or growth of other tissue through the many apertures in the device. In one preferred embodiment, members  12 ,  14 , and  16  are made of a polyether ether ketone (PEEK) plastic material. There are several known advantages of PEEK plastic material including being radiolucent, having a mechanical strength that is close to bone, and may be more easily sterilized than other plastics. In alternate preferred embodiments, the members  12 ,  14 , and  16  may be made of a biologically inert metal alloys, such as titanium, or other suitable materials. 
     Referring to  FIGS. 1-5 , the inner member  12  has a generally cylindrical body  24  with a distal end  22  and a proximal end  36 . In a preferred embodiment, the body  24  of the inner member  12  comprises an inner surface  28  and an outer surface  30  and generally defines a hollow interior portion  23  extending axially therethrough. At least part of the outer surface  30  preferably includes external threads  32 . Located proximate to the distal end  22  of the body  24  are a plurality of tabs  38  which assist in connecting and positionally locating an endplate  20 . In a preferred embodiment, the body  24  is configured and dimensioned to be cooperatively received within outer member  14 . 
     The outer member  14  has a generally cylindrical body  40  with a distal end  42  and a proximal end  44 . In a preferred embodiment, the body  40  of the outer member  14  comprises an inner surface  46  and an outer surface  48  and generally defines a hollow interior portion  50  extending axially therethrough. The outer surface  48  preferably has at least one slot  52  and an opening  54  configured and dimensioned to receive a portion of an implantation tool. In a preferred embodiment, the opening  54  extends from the outer surface  48  to the hollow interior portion  50  and at least a portion of the opening  54  is threaded. As best seen in  FIG. 5 , the inner surface  46  includes a channel  57  for receiving a locking member (discussed below). Located proximate to the proximal end  44  of the outer member  14  are a plurality of tabs  60  which assist in connecting and positionally locating an endplate  62 . In a preferred embodiment, a lip  62  is formed around the exterior of the distal end  42  of body  40  and is configured to cooperatively fit with a portion of the gear member  16 . A plurality of relief spaces or slots  63  are radially spaced around lip  62  to facilitate a snapping engagement of the lip  62  with the gear member  16 . In this regard, slots  63  allow the lip  62  to deform slightly and contract in the radial direction to accommodate gear member  16  to snap on to lip  62 . In a preferred embodiment, the interior portion  50  of body  44  is configured and dimensioned to cooperatively receive body  24  of inner member  12  within outer member  14 . In this regard, the dimensions of interior portion  50  of body  44  are greater than dimensions of body  24  of inner member  12 . 
     As best seen in  FIGS. 2-5 , in a preferred embodiment of a prosthetic device  10 , the body  24  of the inner member  12  includes a flattened portion  34  which extends at least in part from the distal end  22  to the proximal end  36  and includes a base member  37  having at least one lobe  39  located proximate to the distal end  36  of the body  24 . Focusing on  FIG. 5 , the body  40  of the outer member  14  includes a flattened area  56  and at least one depression  58  on the inner surface  46 . When the inner member  12  is assembled within the outer member  14 , the flattened area  56  of the outer member  14  cooperatively aligns with the flattened portion  34  of the inner member  12  and the at least one depression  58  of outer member  14  receives the at least one lobe  39  of the inner member  12 . The flattened portion  34  and the flattened area  56  along with the lobes  39  and the depressions  58  cooperate to allow the inner member  12  to linearly move with respect to the outer member  14  but prevent the inner member  12  from rotating with respect to the outer member  14 . In addition, the base member  37  serves as a stop preventing the inner member  12  from rotating to a point of disengagement from outer member  14 . 
     Referring now to  FIGS. 6-7 , a gear member  16  comprises a generally hollow body  64  extending from a distal end  66  to a proximal end  68  with a helical thread  70  along at least part of an inner wall  72  and an array of gear teeth  74  along a portion of the exterior wall  75 . The gear member  16  is generally configured to rotatably connect to the distal end  42  of the outer member  14  and the internal helical thread  70  is configured to engage the external threads  32  of the inner member  12  to cause translation of the inner member  12  with respect to the outer member  14 . In a preferred embodiment, the gear member  16  includes a cylindrical cutout feature  76  extending around the inner wall to cooperatively receive the lip  54  of the outer member  14 . In this regard, the gear member  16  may rotate freely with respect to the outer member  14  while being retained from longitudinal and lateral movement. In a preferred embodiment, the gear member  16  also includes a series of cutouts  73  located proximate to the proximal end  68  for engaging a portion of a locking member. 
     With continued reference to  FIGS. 6-7 , the gear teeth  74  extend substantially from the proximal end  68  to the distal end  66  and extend around the entire periphery of at least a portion of the exterior wall  75 . The outer-most external diameter  78  of the gear member  16  is sized to be the same as or slightly smaller than the smallest outer diameter of the endplates  20 ,  62  and the outer member  14 . In this regard, when the implant  10  is viewed from the end in a plane perpendicular to the longitudinal axis  18 , the gear member  16  does not protrude radially outward from beyond the perimeter of the endplates  20 ,  62 . 
     As shown in  FIG. 7 , in a preferred embodiment, the gear teeth  74  extend a width  580  in a generally radial direction and generally extend radially outward to the outer diameter of the gear member  16 . In this regard, the teeth  74  may be designed to have a width  580  to accommodate the expected gear forces given the particular gear ratio, types of material used, and desired overall diameter of prosthetic device  10 . One skilled in the art will appreciate that the larger the outer diameter to which the teeth  74  radially extend, the larger the teeth  74  may be designed while still maintaining the same gear ratio. In this regard, when the teeth  74  are made larger, they generally have a better mechanical strength. Also, the ability to design larger, wider, and stronger teeth  74  is advantageous for embodiments where the implant  10  is made of PEEK, other plastic, or other non-metallic materials that may have less mechanical strength than, for instance, titanium. 
     Furthermore, as described in one embodiment, because the outer-most diameter of the gear member  16  may be as large as the outer diameter of the endplates  20 ,  62 , and the teeth  74  extend radially to the outer-most diameter of the gear member  16 , a larger inner diameter of the gear member  16  may be manufactured without compromising mechanical gear strength. As a result, a larger overall inner diameter of the implant  10  may be accommodated which allows the packing of more bone material therein and facilitates bone fusion once the implant  10  is implanted. 
     As seen in  FIGS. 1-3 , in a preferred embodiment, the teeth  74  are exposed to the exterior of prosthetic device  10 . Because the teeth  74  are exposed around the periphery, little to no material is needed to cover up the exposed teeth, which generally makes the implant  10  lighter and easier to manufacture than prior art devices that require covering the gear teeth. In addition, the gear member  16  is more easily visible by a surgeon and more readily accessible by a rotation tool than devices that hide or cover gear teeth. 
     Referring to  FIGS. 2, 5, and 7 , in a preferred embodiment, the implant  10  also includes a locking member  80 . The locking member  80  may be provided to substantially restrict all relative movement between inner member  12  and outer member  14 , when, for example, the desired expansion of the prosthetic device  10  has been obtained. The locking member  80  has a body portion  82  with a through-hole  84 . In a preferred embodiment, the body portion  82  has at least one, but preferably two, outwardly extending, flexible arms  86 ,  88  and at least one engagement member  90 . In other preferred embodiments, instead of flexible arms  86 ,  88 , it is contemplated that the locking member  80  may include an alternate biasing member, such as a leaf spring. The locking member  80  is configured and dimensioned to be received in the channel  57  of the outer member  14  in such a manner that the arms  86 , 88  rest against a shelf portion in the channel  57  and the through-hole  84  partially aligns with opening  54 . The engagement member  90  preferably protrudes upwardly and is configured and dimensioned to engage the cutouts  73  of the gear member  16  to prevent the gear member  16  from rotating. 
     Referring now to  FIGS. 1-3 , in a preferred embodiment, the endplates  20 ,  62  are shown wherein the endplate  20  connects to the inner member  12  and endplate  62  connects to the outer member  14 . In a preferred embodiment, endplate  20  includes an extension portion  91  which is received in the interior portion  23  of inner member  12 , for example, in an interference or snap fit and includes a plurality of tabs  93  which interdigitate with tabs  38  to connect and position endplate  20  with respect to the inner member  12 . Endplate  62  includes an extension portion  95  which engages the proximal end  44  of the outer member  14 , for example, in an interference or snap fit and includes a plurality of tabs  97  which interdigitate with tabs  60  to connect and position endplate  62  with respect to the outer member  14 . The endplates  20 ,  62  also preferably include hollow interior portions  99 ,  101  which are in fluid communication with the hollow interior portions  23 ,  50  of inner member  12  and outer member  14 , respectively. 
     In a preferred embodiment, each endplate  20 ,  62  is generally annular in shape when viewed from the end or perpendicular to the longitudinal axis  18 . It is, however, contemplated that the endplates  20 ,  62  can be other shapes including oblong, elliptical, kidney bean, polygonal, or geometric. Preferably, the endplates  20 ,  62  are designed to resemble or mimic the footprint of the vertebral body to which the endplates will engage. In this regard, endplates  20 ,  62  are configured to engage portions of the vertebrae in a predetermined orientation to maximize contact of the superior surface of the endplates  20 ,  62  with bone. 
     The dimensions of endplates  20 ,  62  can be varied to accommodate a patient&#39;s anatomy. In some embodiments, the endplates  20 ,  62  have a wedge-shaped profile to accommodate the natural curvature of the spine. In anatomical terms, the natural curvature of the lumbar spine is referred to as lordosis. When implant  10  is to be used in the lumbar region, the angle formed by the wedge should be approximately between 3.5 degrees and 16 degrees so that the wedge shape is a lordotic shape which mimics the anatomy of the lumbar spine. In alternate embodiments, the wedge shape profile may result from a gradual increase in height from an anterior side to a posterior side to mimic the natural curvature, kyphosis, in other regions of the spine. Thus, in other embodiments, the angle may be between about −4 degrees and −16 degrees. 
     As shown in  FIGS. 1-3 , in a preferred embodiment, the endplates  20 ,  40  include a plurality of mounting holes  92  spaced around the perimeter of each endplate  20 ,  40  for receiving insertable bone engaging members  94 . In one embodiment, bone engaging members  94 , comprise conical spikes  96  each having a cylindrical base portion  98  configured to fit within holes  92 , for instance, by press-fit or by threaded engagement. In alternate embodiments, differently shaped bone engaging members  100  may be used, or in other embodiments no bone engaging members may be used. Referring again to  FIG. 2 , according to one embodiment, endplates  20 ,  62  have chamfered edges  100  around the perimeter to facilitate insertion and/or accommodate the shape of the vertebral bodies which they engage. The superior or bone engaging surfaces  102 ,  104  of endplates  20 ,  62  may also include numerous types of texturing to provide better initial stability and/or grasping contact between the end plate and the respective vertebrae. In a preferred embodiment, the texturing is a plurality of teeth  106 . In preferred embodiments where the implant  10  is manufactured from PEEK or other plastic materials, the endplates  20 ,  62  may also include radio-opaque material, such as tantalum markers  108 , which aid in providing location markers in radiographic images. 
     In preferred embodiments, the length, diameter, and shape of prosthetic device  10  may vary to accommodate different applications, different procedures, implantation into different regions of the spine, or size of vertebral body or bodies being replaced or repaired. For example, implant  10  may be expandable to a longer distance to replace multiple vertebral bodies. Also endplates  20 ,  62  can be sized and shaped as well as positioned to accommodate different procedures and approached to the spine. For example, endplates  20 ,  62  may be made smaller for smaller statured patients or for smaller regions of the cervical spine. In addition, it is not required that endplates  20 ,  62  be shaped and sized identically and in alternate embodiments they can be shaped or sized differently than each other and/or include different bone engaging members or texturing. 
     Turning now to  FIGS. 8-9 , the implant  10  may be expanded by a tool  110  that includes a gear member  112  at its distal end  114 . The tool  110  extends along a tool axis  514  and in operation the tool  110  is configured to engage the implant  10  such that the tool axis  514  is generally perpendicular to the longitudinal axis  18 . The gear member  112  is configured to engage teeth  74  of the gear member  16  such that when the gear member  112  is rotated about the axis of the tool  110 , the gear member  16  of the implant  10  is rotated about the longitudinal axis  18  and the inner member  12  translates along the longitudinal axis  18  to either expand or contract the implant  10 . In a preferred embodiment, the tool  110  may include a central shaft  116  having a threaded distal tip portion  118  that extends distally beyond gear member  112  to facilitate location and mounting of tool  110  with the implant  10 . The threaded distal tip portion  118  preferably includes a generally conical end portion and may be configured to extend radially through the opening  54  and threadably engage opening  54  in the outer member  14 . 
     With continued reference to  FIGS. 8-9 , in one embodiment of prosthetic device  10  at least one, but preferably a plurality of mounting features or slots  52  are provided along the outer surface  48  of outer member  14 . The tool  110  includes at least one, but preferably two, articulating arms  120 ,  122  that engage slots  52  for better engagement of the tool  110  with the implant  10  during insertion of the implant  10 . In another preferred embodiment, the tool  110  may include arms  120 ,  122  that do not articulate. 
     In an exemplary use of the tool  110  with the implant  10 , the tool  110  initially engages the slots  52  of the implant  10  via the arms  120 ,  122  and gear member  112  engages gear member  16  via their respective interdigitating teeth. A control member on the proximal end of the tool  110  (not shown) is manipulated to advance the central shaft  116  toward opening  54 . The threaded tip portion  118  enters into opening  54  engaging the threads in opening  54  as well as engaging the through-hole  84  of locking member  80 . It is also contemplated that the central shaft  116  is not movable with respect to the tool  110 . In that embodiment, the entire tool  110  is moved so that the central shaft can enter and engage the opening  54  and the through-hole  84 . As discussed earlier, the though-hole  84  is offset from opening  54 , thus, when threaded tip  118  engages and advances into the opening  54  and the through-hole  84 , the locking member  80  is pulled downwardly, riding along the conical edge of the tip  118  until the through-hole  84  is aligned with the opening  54 . As the locking member  80  is pulled downwardly, the arms  82 ,  84  are flexed and the engagement member  90  disengages from the cutout  73  of the gear member  16  allowing the gear member  16  to rotate freely. The gear member  112  of tool  110  is then rotated via opening  114  which, in turn, rotates gear member  16 . As discussed above, the rotation of gear member  16  results in the movement of inner member  12  causing the implant  10  to either expand or contract, depending on the direction the gear member  16  is rotated. Once the desired height for implant  10  is achieved, the tool member  110  is disengaged from implant  10 . When the tool  110  is removed, the locking member  80  returns to the back to its initial position because of the arms  82 ,  84  returning back to their unflexed, at-rest state. The initial position of locking member  80  prevents the gear member  16  from turning because of the engagement of engagement member  90  with the cutouts  73 . In that regard, implant  10  is locked from movement when the locking member  80  is in its initial position. 
     The benefit provided by the present locking mechanism is that it allows for a positive lock that engages and disengages automatically with the engagement and disengagement of the tool  110  with the implant  10 , which minimizes the steps the surgeon must perform during the procedure. 
     Referring now to  FIGS. 10-13 , alternate preferred embodiments of endplates for the expandable implant  10  are shown. Looking at  FIG. 10 , in one variation, the endplates  202  and outer member  204  each include at least one screw hole  206 ,  208 , but, preferably, each include two screw holes. The screw holes  206 ,  208  are configured and dimensioned to receive screws  210 ,  212 . In a preferred embodiment, the screw holes  206 ,  208  are angled such that when the screws  210 ,  212  are seated in the screw holes  206 ,  208 , the screws  210 ,  212  will extend outwardly from the superior surface  214  of endplate  202  and inferior surface  216  of outer member  204 . Endplate  202  and outer member  204  also preferably include a locking element  218 ,  220  which, in a first position, allow the screws  210 ,  212  to back out from the seated position and, in a second position, block the screws  210 ,  212  from backing out of the seated position. In an exemplary use, once the implant  200  is installed and expanded to the desired position, the screws  210 ,  212  can be installed through the screw holes  206 ,  208  in such a manner as to purchase into the adjacent vertebral bodies. Once the screws  210 ,  212  are properly installed, including being engaged with the adjacent vertebral bodies, the locking elements  218 ,  220  can be actuated to block the screws  210 ,  212  from backing out of their installed position. The inclusion of screws  210 ,  212  in the endplate  202  and the outer member  204  provides for additional fixation of the implant  200  in the intervertebral space. 
     Turning to  FIGS. 11-13 , another preferred embodiment of an endplate  250  is shown. The endplate  250  is similar to endplate  20  but includes the additional functionality of being poly-axially rotatable with respect to an implant. In a preferred embodiment, endplate  250  includes a generally arcuate extension portion  252  which is received in an interior portion  253  of a receiving member  254  in such a manner as to allow the endplate  250  to move poly-axially with respect to the receiving member  254 . 
     In a preferred embodiment, the receiving member  254  is received in an interior portion  255  of a locking ring  256 . The receiving member  254  preferably includes a neck portion  258  as well as a plurality of tabs  260 . The neck portion  258  is configured and dimensioned to be received within a hollow interior of an inner member, for example, in an interference or snap fit, and the plurality of tabs  260  interdigitate with tabs to connect and position the receiving member  254  with respect to an inner member. The receiving member  254  further includes a plurality of fingers  262  configured to cooperatively receive the extension portion  252  of endplate  250 . A plurality of relief spaces or slots  264  are radially spaced between fingers  262  to allow fingers  262  to bend or flex radially. 
     In a preferred embodiment, the locking ring  256  has a generally annular, c-shape and includes an exterior wall  266 , an interior wall  268 , and ends  277 ,  279 . The interior wall  268  preferably defines and interior portion  255 . In a preferred embodiment, the interior wall  268  includes a plurality of channel  270  which are spaced radially along the locking ring  256 . The channels  270  allow the locking ring  256  to bend or flex radially. The ends  277 ,  279  each include openings  280 ,  282  which may be partially threaded. A locking element  284  is configured and dimensioned to be threadingly received in the openings  280 ,  282 . It also contemplated that that locking element  284  can engage the ends  277 ,  279  by other non-threaded means, such as a sliding fit. 
     With continued reference to  FIGS. 11-13 , in a preferred embodiment, the endplate  250  includes a plurality of mounting holes  286  spaced around the perimeter of the endplate  250  for receiving insertable bone engaging members. In one embodiment, bone engaging members, comprise conical spikes each having a cylindrical base portion configured to fit within holes  286 , for instance, by press-fit or by threaded engagement. In alternate embodiments, differently shaped bone engaging members may be used, or in other embodiments no bone engaging members may be used. According to one preferred embodiment, endplate  250  has chamfered edges  288  around the perimeter to facilitate insertion and/or accommodate the shape of the vertebral bodies which they engage. The superior or bone engaging surfaces  290  of endplate  250  may also include numerous types of texturing to provide better initial stability and/or grasping contact between the end plate and the respective vertebrae. In a preferred embodiment, the texturing is a plurality of teeth  292 . In preferred embodiments where the implant is manufactured from PEEK or other plastic materials, the endplate  250  may also include radio-opaque material, such as tantalum markers  294 , which aid in providing location markers in radiographic images. 
     In an exemplary use, during the implant installation and expansion to the desired position, the endplate  250  can move in poly-axial fashion with respect to the implant to accommodate the anatomy of the adjacent vertebral body as well as accommodate the natural curvature of the spine, such as kyphosis and lordosis. More specifically, the arcuate extension portion  252  is free to move in the interior portion  253  of the receiving portion  254 . The fingers  262  are generally compliant and can flex to accommodate the movement of the arcuate extension portion  252 . Once the desired positioning of the endplate  250  is achieved, the endplate  250  can be locked in place. The endplate  250  is locked in place by actuating the locking element  284 . As the element  284  engages the threading in opening  280 , 282  the ends  277 ,  279  of the locking ring  256  are brought closer together contracting the ring  254  and reducing the size of the interior portion  255 . As the ring  254  contracts, the fingers  262  of the receiving member  254 , abutting against the inner wall  268 , are flexed radially inwardly pushing against the extension portion  252 . As a result, the endplate  250  is locked in place. 
     Referring now to  FIGS. 14-19 , an angling inserter tool  300  is shown that may be used to expand the implant  10  in accordance with embodiments of the present invention. The tool  300  is configured to hold the implant  10 . As illustrated, the angling inserter tool  300  may comprise a handle portion  302 , a cylindrical base portion  304 , and a tip assembly  306 . In preferred embodiments, the cylindrical base portion  304  is disposed between the handle portion  302  and the tip assembly  306 . As best seen in  FIG. 14 , the angling inserter tool  300  has a longitudinal or tool axis  308  that passes through the tool  300  from proximal end  310  to distal end  312 . The tip assembly  306  can be angled relative to the tool axis  308 , for example, allowing the implant to be placed around or behind certain anatomical structures. As best seen in  FIGS. 18 and 19 , the tool  300  includes a primary gear mechanism (e.g., gears  356 , 412 , 414 , 416 , 410 ), for example, configured to drive gear member  16  on the implant  10  it holds, and the tool  300  also includes a second gear mechanism (e.g., distal gear  368 , central gear  402 , proximal gear portion  398 ), for example, configured to attached or release the implant  10  from the tool  300 . 
     In some embodiments, the cylindrical base portion  304  includes an outer cylinder  314 . At distal end  312 , the outer cylinder  314  preferably includes arms  316  that extend distally from the outer cylinder  314 , as best seen in  FIGS. 18 and 19 . One of the arms  316  may include a bent portion  317  at least a portion of which extends radially outward from the outer cylinder  314 . Each of the arms may include an opening  318 . The openings  318  in each of the arms  316  may be axially aligned and configured to receive a pin  376 , as best seen in  FIGS. 18 and 19 . The pin  376  may rotatably secure the tip assembly  306  to the cylindrical base portion  304  allowing the tip assembly  306  to angulate with respect to the tool axis  308 . 
     Referring to  FIGS. 15-19 , in some embodiments, the cylindrical base portion  304  also includes an internal shaft  320 . As illustrated, the internal shaft  320  may be coaxial with the outer cylinder  314  wherein the internal shaft  320  is received within the outer cylinder  314 . In preferred embodiments, the internal shaft  320  is a generally cylindrical body. In present embodiments, the internal shaft  320  can translate longitudinally with respect to the outer cylinder  314 . In a preferred embodiment, the internal shaft  320  has an angulated distal end  322 , which may be offset from tool axis  308 . As best seen in  FIG. 19 , the angulated distal end  322  may include tabs  324  which may each include an opening  326 . The openings  326  in each of the tabs  324  may be axially aligned and configured to receive a pin  328  as shown on  FIG. 19 . The pin  328  may secure the internal shaft  320  to a linking arm  330  coupling the tip assembly  306  to the internal shaft  320 . 
     With reference now to  FIGS. 14-17 , embodiments of the cylindrical base portion  304  also include a knob  332  generally configured to effect translation of the internal shaft  320  with respect to the outer cylinder  314 . In the illustrated embodiment, the knob  332  is disposed on the outer cylinder  314 . At least a part of the knob  332  may include internal threads  334 , as best seen in  FIG. 15 . In a preferred embodiment, the internal threads  334  engage one or more blocks  336 , as best seen in  FIGS. 15 and 17 . With continued reference to  FIGS. 15 and 17 , the blocks  336  are received in one or more openings  338  in the internal shaft  320  and extend through one or more windows  340  in the outer cylinder  314  to engage the internal threads  334  of the knob  332 . As illustrated, the windows  340  in the outer cylinder  314  may be longer than the blocks  336 , allowing the blocks  336  to move longitudinally in the windows  340 . Accordingly, rotation of the knob  332  on the outer cylinder  314  should cause the blocks  336  to move thereby causing the internal shaft  320  to translate within the outer cylinder  314 . The internal shaft  320  may extend through the outer cylinder  314  or retract into the outer cylinder  314 , depending for example on the direction of the rotation of the knob  332 . Because the linking arm  330  couples the internal shaft  320  to the tip assembly  306 , translation of the internal shaft  320  should move the tip assembly  306  causing rotation of the tip assembly about the pin  376 , as best seen in  FIGS. 22 and 23 . 
     Referring now to  FIGS. 22 and 23 , because the linking arm  330  couples the internal shaft  320  to the tip assembly  306 , translation of the internal shaft  320  should move the tip assembly  306  causing rotation of the tip assembly  306  about the pin  376 . For example, advancement of the internal shaft  320  through the outer cylinder  314  should effect rotation of the tip assembly  306  about the pin  376  in a first direction (as best seen in  FIG. 22 ), while retraction of the internal shaft into the outer cylinder  314  should effect rotation of the tip assembly  306  about the pin  376  in an opposite direction (as best seen in  FIG. 23 ). Rotation of the tip assembly  306  may be monitored using viewing window  342  and visual indicators  344 . As illustrated by  FIGS. 22 and 23 , visual indicators  344  may be disposed on the internal shaft  320 . The visual indicators  344  may be markings, such as numbers, etchings, lines, combinations thereof, or the like, that provide a visual indication of the degree of rotation. The visual indicators  344  on the internal shaft  320  may generally aligned with a viewing window  342  in the outer cylinder  314 . The visual indicators  344  should allow accurate measurement of the angulation of the tip assembly  306  even when the tip assembly  306  itself may be obscured from viewing. 
     With continued to reference to  FIGS. 14-17 , ring  346  may secure the knob  332  on the outer cylinder  314  in accordance with embodiments of the present invention. As illustrated, the ring  346  may be disposed on the outer cylinder  314  proximally to the knob  332 . A set screw  348  disposed through opening  350  in the ring  346  may engage opening  352  in the outer cylinder  314  to secure the ring  346  on the outer cylinder  314 . 
     Referring to  FIGS. 15 and 17-19 , embodiments of the cylindrical base portion  304  also include a primary drive shaft  354 . As illustrated, the primary drive shaft  354  may be coaxial with the internal shaft  320  wherein the primary drive shaft  354  is receiving within the internal shaft  320 . In preferred embodiments, the primary drive shaft  354  may be a generally cylindrical body. As best seen on  FIGS. 18 and 19 , the primary drive shaft  354  includes a distal gear  356 , which may be a bevel gear, for example. In certain embodiments, the distal gear  356  is configured to fixedly engage distal end  358  of the primary drive shaft  354 , as best seen in  FIG. 19 . In present embodiments, the primary drive shaft  354  may be configured to rotate with respect to the internal shaft  320 . A driving instrument (not shown) may be used to rotate the primary drive shaft  354 . The driving instrument may engage the primary drive shaft  354  at proximal end  310  through opening  560  of handle portion  302 , as best seen in  FIG. 15 . As will be discussed in more detail below, the distal gear  356  may be configured to engage one or more corresponding gears (e.g., gears  412 ,  414 ,  416 ) in the tip assembly  306  to cause rotation of implant engagement gear  410  (see, e.g.,  FIGS. 18 and 19 ). 
     In some embodiments, the cylindrical base portion  304  also includes a secondary drive shaft  366 . As illustrated, the secondary drive shaft  366  may be coaxial with the primary drive shaft  354  wherein the secondary drive shaft  366  is received the primary drive shaft  354 . As best seen in  FIGS. 18 and 19 , the secondary drive shaft  366  includes a gear  368  at distal end  312 , which may be a bevel gear, for example. In present embodiments, the secondary drive shaft  366  may be configured to rotate with respect to the outer shaft  314 . A driving instrument (not shown) may be used to rotate the secondary drive shaft  366 . The driving instrument may engage the secondary drive shaft  366  at the proximal end  310  through the opening  560  in the handle portion, as best seen in  FIG. 15 . As will be discussed in more detail below, the gear  368  may be configured to engage one or more corresponding gears (e.g., gear  402 , gear portion  398 ) in the tip assembly  306  to cause extension of central shaft  392  (see, e.g.,  FIGS. 18 and 19 ). 
     Referring to  FIGS. 14-17 , the handle portion  302  includes a cylindrical portion  362  and a handle  364 . As illustrated, the handle  364  may preferably extend downward from the cylindrical portion  362 . Opening  560  may be disposed in the handle portion  302  at the proximal end  310  so that the secondary drive shaft  366  and the primary drive shaft  354  can be accessed. At least a portion of the cylindrical base portion  304  may be disposed in the cylindrical portion  362 . As best seen in  FIG. 17 , a locking member  365  may engage the outer cylinder  314  of the cylindrical base portion  304  to secure the cylindrical base portion  304  to the handle portion  302 . The locking member  365  may extend through an opening in the cylindrical portion  362 . 
     Referring to  FIGS. 18-21 , the tip assembly  306  will now be described in more detail in accordance with embodiments of the present invention. In preferred embodiments, the tip assembly  306  includes an upper plate  372  and a base portion  374 . The upper plate  372  and the base portion  374  may be secured to one another by one or more pins  388 . In the illustrated embodiment, two pins  388  are used to secure the upper plate  372  and the base portion  374 . As illustrated, the pins  388  may be configured to be received in openings  386  in the upper plate  372  and openings  390  in the base portion  374 . 
     As previously described, the tip assembly  306  may be rotatably secured to the cylindrical base portion  304  with the pin  376 . In the illustrated embodiment, the pin  376  is received in an opening  378  in upper tab  380  of the upper plate  372  and in lower tab  384  of opening  382  of the base portion  374 . A bushing  385  may be disposed about at least a portion of the pin  376 . The pin  376  has a pin axis  377  (as shown on  FIG. 18 ) about which the tip assembly  306  may rotate. Referring to  FIGS. 19-21 , the upper plate  372  may further include an outer tab  506  having a corresponding opening  408 . The outer tab  506  may be offset from the tool axis  308  and configured to receive the pin  404 . The pin  404  may secure the tip assembly  306  to the linking arm  330  coupling the tip assembly  306  to the internal shaft  320 . Accordingly, advancement or retraction of the internal shaft  320  should cause rotation of the tip assembly  306  about the pin axis  377 . 
     As illustrated by  FIGS. 18-21 , the tip assembly  306  preferably further includes a central shaft  392  disposed in through-bore  394  (as best seen on  FIG. 19 ) in the base portion  374 . The central shaft  392  preferably may include a threaded distal tip portion  396  that extends distally beyond the implant engagement gear  410  to facilitate location and mounting of the angling inserter tool  300  with the implant  10  (see, e.g.,  FIG. 2 ) in accordance with embodiments of the present invention. The central shaft  392  may also include a proximal gear portion  398  that engages corresponding gears to facilitate extension of the central shaft  392  through the through-bore  394 . For example, as best seen on  FIGS. 18 and 19 , the proximal gear portion  398  may engage a secondary central gear  402 , which may be a bevel gear. The secondary central gear  402  may be disposed about the pin  376  and rotate about the pin axis  377 . The secondary central gear  402  may engage gear  368  on the secondary drive shaft  366  of the cylindrical base portion  304 . Accordingly, rotation of the secondary drive shaft  366  about the tool axis  308  should cause rotation of the secondary central gear  402  about the pin axis  377  which should in turn drive the proximal gear portion  398  causing rotation of the central shaft  392  and movement of the central shaft through the through-bore  394 . The central shaft  392  should extend through the base portion  374  or retract into the base portion  374 , depending for example on the direction of rotation of the secondary drive shaft  366 . 
     With continued reference to  FIGS. 18-21 , the tip assembly  306  preferably further includes an implant engagement gear  410 . In preferred embodiments, the implant engagement gear  410  is configured to engage teeth  74  of the gear member  16  of the implant  10  (see, e.g.,  FIG. 2 ) such that when the implant engagement gear  410  is rotated, the gear member  16  of the implant  10  is rotated about the longitudinal axis  18  and the inner member  12  translates along the longitudinal axis to either expand or contract the implant  10 . A series of gears (e.g., gears  412 ,  414 , and  416 ) transfer rotation of the primary drive shaft  354  to the implant engagement gear  410 . For example, rotation of implant engagement gear  410  causes rotation of distal gear  356 . The distal gear  356  may engage a first primary central gear  412  disposed on the pin  376  such that rotation of the distal gear  356  causes rotation of the first primary central gear  412  about the pin axis  377 . The first primary central gear  412  may be a bevel gear, for example. The distal gear  356  and the first primary central gear  412  may have rotational axes that are perpendicular, for example, the tool axis  308  and the pin axis  377 . A second primary central gear  414  may be fixedly engaged to the first primary central gear  412  such that rotation of the central gear  412  causes rotation of the second primary central gear  414 . The second primary central gear  414  may engage secondary transfer gear  416  such that rotation of the second primary central gear  414  causes rotation of the primary transfer gear  416 . The gears  414 ,  416  may each be spur gears, for example. Pin  418  may secure primary transfer gear  416  to upper plate  372 . The primary transfer gear  416  may rotate about the pin  418 . The primary transfer gear  416  may engage the implant engagement gear  410  such that rotation of the primary transfer gear  416  causes rotation of the implant engagement gear  410 . Accordingly, when the primary drive shaft  354  is rotated, the implant engagement gear  410  rotates causing the implant  10  to either expand or contract. 
     In an exemplary use of the angling inserter tool  300  with the implant  10 , the angling inserter tool  300  initially engages the slots  52  of the implant  10  via the arms  400  and implant engagement gear  410  engages gear member  16  via their respective teeth. The secondary drive shaft  366  may then be driven (e.g., rotated) causing the second gear mechanism (e.g., distal gear  368 , central gear  402 , proximal gear portion  398 ) to enable actuation. For example, rotation of the secondary drive shaft  366  rotates the distal gear  368  about the tool axis  308  which rotates the secondary central gear  402  about the pin axis  376  which rotates the proximal gear portion  398  about the tool axis  308  to cause actuation. The threaded tip portion  396  enters into the opening  54  engaging the threads in opening  54  as well as engaging the through-hole  84  of locking member  80 . As discussed previously, the locking member  80  should be engaged such that the gear member  16  may rotate freely. The implant  10  may then be placed in a desired location, for example, in the vertebral space. If desired, the tip assembly  306  can be angled relative to the tool axis  308 , allowing the implant to be placed around or behind certain anatomical structures. As previously described, the knob  332  on the tool  300  may be rotated to cause the tip assembly  306  to angulate. For example, rotation of the knob  332  may cause longitudinal movement of the blocks  336  to cause translation of the internal shaft  320 , thus moving the tip assembly  306  and causing rotation of the tip assembly  306  about the pin  376 . The primary drive shaft  354  may then be driven (e.g., rotated) causing the primary gear mechanism (e.g., gears  356 ,  412 ,  414 ,  416 ), for example, to rotate the gear member  16  on the implant  10 . For example, rotation of the primary drive shaft  354  rotates the distal gear  356  about the tool axis  308  which rotates the first primary central gear  412  about the pin axis  377  which rotates the second primary central gear  414  about the pin axis  377 . Rotation of the second primary central gear  414  rotates the primary transfer gear  416  about an axis generally parallel to the pin axis  377  which rotates the implant engagement gear  410  about an axis generally parallel to pin axis  377 . The implant engagement gear  410  engages the gear member  16  on the implant causing the gear member  16  to rotate about longitudinal axis  18 . As discussed above, the rotation of the gear member  16  results in the movement of the inner member  12  causing the implant  10  to either expand or contract, depending on the direction the gear member  16  is rotated. Once the desired height for the implant  10  is reached, the angling inserter tool  300  may be disengaged from the implant  10 . It should be understood that the angling inserter tool  300  can be disengaged from the implant  10  even with the tip assembly  306  at any angle with respect to the tool axis  308 . When the tool  300  is removed, the locking member  80  returns back to its initial state, thus preventing the gear member  16  from rotating as previously described. 
     While the preceding description of the angling inserter tool  300  is with respect to the implant  10 , it should be understood that embodiments of the angling inserter tool  300  may be used for insertion and expansion of any of a variety of expandable implants for implantation into the spine, including vertebral body spacers for vertebral body replacement and expandable cages for insertion into the disc space. 
     Referring to  FIGS. 24-27 , an expandable trial assembly  420  is shown that may be used in the implanting of an expandable implant, such as implant  10  ( FIG. 2 ), in accordance with embodiments of the present invention. In preferred embodiments, the trial assembly  420  may be used to distract adjacent vertebral bodies and to give a measurement of the distraction. In this manner, the trial assembly  420  may give a measurement of the desired height for the subsequent expansion of the implant  10 , for example. As illustrated, the expandable trial assembly  420  may comprise a handle portion  422 , a cylindrical base portion  424 , and an expandable tip assembly  426 . In the illustrated embodiment, the handle portion  422  extends downward from the cylindrical base portion  424 . As illustrated, the expandable tip assembly  426  may be disposed at the distal end  432  of the cylindrical base portion  424 . The expandable trial assembly  420  has a tool axis that extends through the trial assembly  420  from the proximal end  430  to the distal end  432  of the cylindrical base portion  424 . 
     In preferred embodiments, the cylindrical base portion  424  may include an outer cylinder  434  and a drive shaft  436 . The drive shaft  436  may be coaxial with the outer cylinder  434  wherein the drive shaft  435  is inside the outer cylinder  434 . In preferred embodiments, the drive shaft  436  is a generally cylindrical body. In present embodiments, the drive shaft  436  can rotate about the tool axis  428 . A distal gear  438  is located on the drive shaft  436  at the distal end  432 , as best seen in  FIGS. 25 and 27 . Rotation of the drive shaft  436  rotates the distal gear  438 . The teeth of the distal gear  438  are not illustrated for simplicity. 
     Referring to  FIGS. 24, 26, and 28-29 , the cylindrical base portion  424  further includes scale  440  at proximal end  430 . The scale  440  may be in the general form of a cylindrical section. As best seen in  FIGS. 28 and 29 , at least a portion of the scale  440  may be internally threaded with threads  442 . The scale  440  may be keyed to the outer cylinder  434 . For example, locking mechanism  444  may secure the scale  440  to the outer cylinder  434 , as best seen in  FIG. 28 . As seen in  FIGS. 26 and 29 , at least a portion of the drive shaft  436  may be threaded, for example, in the general region of the scale  440 . The threaded portion  446  of the drive shaft  436  may engage the threads  442  of the scale  440 . Accordingly, rotation of the drive shaft  426  should cause the scale  440  to move longitudinally. Visual indicators  448 ,  450  may be placed on the scale and/or the outer cylinder  434  to show, for example, the amount of expansion of the expandable tip assembly  426 . The visual indicators  448 ,  450  may be in the form of numbers, lines, combinations thereof or the like etched or otherwise formed on the scale  440  and/or the outer cylinder  434 . In preferred embodiments, the scale  440  also includes a viewing window  452 . 
     Referring to  FIGS. 24-27 , the expandable tip assembly  426  will now be described in more detail in accordance with embodiments of the present invention. As illustrated, the expandable tip assembly  426  may include a housing  454  which may be in the form of a rounded end. The expandable tip assembly  426  further may include an outer member  456  and an inner member  458  which may be telescopingly received within the outer member  456 . The outer member  456  may generally comprise a generally cylindrical body  460  having external threads  462  on at least a portion thereof. An endplate  464  may be coupled to the outer member  456 . The inner member  458  may comprise a generally cylindrical body  466  having external threads  468  on at least a portion thereof. An endplate  470  may be coupled to the inner member  458 . While trial endplates  464 ,  470  are shown on the tip assembly  426 , it should be appreciated that endplates having a different footprint may be used in accordance with embodiments of the present invention. For example, the endplates  464 ,  470  may be articulating (e.g., ball and socket type joint) to allow for measurement of sagittal alignment/angulation in addition to height. One or more pins  472  may be used to secure the inner and outer members  456 ,  458  from rotational movement. The pins  472  may be disposed in corresponding slots  474  (best seen in  FIG. 26 ) of the inner and outer members  456 ,  458 . 
     In preferred embodiments, the expandable tip assembly  426  may further include upper gear member  476  and lower gear member  478 . While not illustrated, the upper and lower gear members  476 ,  478  may each include outer gear teeth on at least a portion of their exterior surfaces that engage the distal gear  438  of the cylindrical base portion  424 . Accordingly, rotation of the distal gear  438  about the tool axis  430  should cause the upper and lower gear members  476 ,  478  to each rotate about the tip axis  480 , as best seen in  FIGS. 25 and 27 . The upper gear member  476  is engaged with the external threads  462  of the outer gear member  458  and the lower gear member  478  is engaged with the external threads  468  of the inner member  458 . Accordingly, because the outer and inner members  456 ,  458  are locked in rotational position by the one or more pins  472 , rotation of the upper and lower gear members  476 ,  478  should cause the tip assembly  426  to either expand or contract. For example, rotation in one direction should cause the endplates  464 ,  470  to expand (or translate vertically outward) while rotation in the opposite direction should cause the endplates  464 ,  470  to contract (or translate vertically inward). 
     In an exemplary use of the expandable trial assembly  420 , the trial assembly  420  may be inserted into a desired position in a patient&#39;s spine, for example, in a vertebral space, in a contracted position, as shown in  FIGS. 24 and 25 . The drive shaft  436  may then be rotated which causes expansion of the expandable tip assembly  426 .  FIGS. 26 and 27  illustrate the tip assembly  426  in an expanded position. For example, rotation of the drive shaft  436  rotates the distal gear  438  about the tool axis  428  which in turn rotates upper gear member  476  and lower gear member  478  about the tip axis  480 . Rotation of the upper gear member  476  and the lower gear member  478  results in movement of the outer member  456  and the inner member  458  causing the expandable tip assembly  426  to either expand or contract, depending on the direction the drive shaft  436  is rotated. Once the desired height for the tip assembly  426  is reached, the height can be measured using the scale  440  at proximal end  430 . The tip assembly  426  can then be contracted by rotation of the drive shaft  436  and then removed from the patient&#39;s body. An expandable implant, such as implant  10 , can then be positioned in the patient&#39;s body in a manner that will be evident to one of ordinary skill in the art with the benefit of this disclosure. Once positioned in the body, the expandable implant can then be expanded to a desired height based on the measured height of the expandable trial assembly  420 . 
     While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations can be made thereto by those skilled in the art without departing from the scope of the invention as set forth in the claims.