Abstract:
An expandable medical implant for supporting bone structures is disclosed. The implant may include an outer member and an inner member receivable in the outer member. One of the outer and inner members includes a tapered surface and the other of the outer and inner members includes a scalloped surface. The implant may also include a locking element disposed between the tapered surface and the scalloped surface. The tapered surface may be movable relative to the locking element to transversely shift the locking element into engagement with the scalloped surface to inhibit a decrease in the overall implant height.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of replacing portions of the human structural anatomy with medical implants, and more particularly relates to an expandable implant and method for replacing bone structures such as one or more vertebrae or long bones. 
     BACKGROUND 
     It is sometimes necessary to remove one or more vertebrae, or a portion of the vertebrae, from the human spine in response to various pathologies. For example, one or more of the vertebrae may become damaged as a result of tumor growth, or may become damaged by a traumatic or other event. Excision of at least a generally anterior portion, or vertebral body, of the vertebra may be referred to as a corpectomy. An implant is usually placed between the remaining vertebrae to provide structural support for the spine as a part of a corpectomy.  FIG. 1  illustrates four vertebrae, V 1 -V 4  of a typical lumbar spine and three spinal discs, D 1 -D 3 . As illustrated, V 3  is a damaged vertebra and all or a part of V 3  could be removed to help stabilize the spine. If removed along with spinal discs D 2  and D 3 , an implant may be placed between vertebrae V 2  and V 4 . Most commonly, the implant inserted between the vertebrae is designed to facilitate fusion between remaining vertebrae. Sometimes the implant is designed to replace the function of the excised vertebra and discs. All or part of more than one vertebrae may be damaged and require removal and replacement in some circumstances. 
     Many implants are known in the art for use in a corpectomy procedure. One class of implants is sized to directly replace the vertebra or vertebrae that are being replaced. Another class of implants is inserted into the body in a collapsed state and then expanded once properly positioned. Expandable implants may be advantageous because they allow for a smaller incision when properly positioning an implant. Additionally, expandable implants may assist with restoring proper loading to the anatomy and achieving more secure fixation of the implant. Implants that include insertion and expansion members that are narrowly configured may also provide clinical advantages. In some circumstances, it is desirable to have vertebral endplate contacting surfaces that effectively spread loading across the vertebral endplates. Effective implants should also include a member for maintaining the desired positions, and in some situations, being capable of collapsing. Fusion implants with an opening may also be advantageous because they allow for vascularization and bone growth through all or a portion of the entire implant. 
     Expandable implants may also be useful in replacing long bones or portions of appendages such as the legs and arms, or a rib or other bone that is generally longer than it is wide. Examples include, but are not limited to, a femur, tibia, fibula, humerus, radius, ulna, phalanges, clavicle, and any of the ribs. 
     SUMMARY 
     In one exemplary aspect, an expandable medical implant for supporting bone structures is disclosed. The implant has an overall implant height adjustable along a longitudinal axis. The implant may include an outer member configured to cooperatively engage a first bone structure and an inner member receivable in the outer member. The inner member may be movable relative to the outer member to increase and decrease the overall implant height. The inner member may be configured to cooperatively engage a second bone structure. One of the outer and inner members includes a tapered surface and the other of the outer and inner members includes a scalloped surface. The implant may also include a locking element disposed between the tapered surface and the scalloped surface. The tapered surface may be movable relative to the locking element to transversely shift the locking element into engagement with the scalloped surface to inhibit a decrease in the overall implant height. 
     In another exemplary aspect, a locker member may be disposed between the inner and outer member. The locker member may include a receiving aperture containing the locking element, and may be configured to act on the locking element to affect the position of the locking element relative to the outer member. The tapered surface of the outer member may be configured to affect the position of the locking element relative to the scalloped surface of the inner member. 
     In another exemplary aspect, an expandable medical implant for supporting bone structures may include an outer member having an inner surface configured to cooperatively engage a first bone structure. The implant also may include an inner member receivable in the outer member and movable relative to the outer member to increase and decrease the overall implant height. The inner member may have a scalloped surface and may be configured to cooperatively engage a second bone structure. A locking element may be disposed between the inner surface of the outer member and the scalloped surface of the inner member. The locking element may be movable between a locked condition and an unlocked condition and may be biased toward the locked condition. The locking element may be disposed to selectively engage the scalloped surfaces to inhibit a decrease in the overall implant height. 
     In another exemplary aspect, the implant may include a locker member disposed between the inner and outer member, the locker member including a receiving aperture containing the locking element. 
     In yet another exemplary aspect, an expandable medical implant for supporting bone structures may include an outer member having a tapered inner surface and being configured to cooperatively engage a first bone structure. The implant also may include a locker member receivable in the outer member and movable relative to the outer member. The locker member may include a receiving aperture. An inner member may be receivable in the locker member and movable relative to the locker member and the outer member to increase and decrease the overall implant height. The inner member may have a scalloped surface and may be configured to cooperatively engage a second bone structure. A locking element may be disposed within the receiving aperture of the locker member. The locking element may be associated with the tapered inner surface of the outer member and the scalloped surface of the inner member. The tapered surface may be movable relative to the locking element to transversely shift the locking element into engagement with the scalloped surface to inhibit a decrease in the overall implant height. 
     In yet another exemplary aspect, a method of supporting bone structures with an expandable medical implant is disclosed. The implant may have an overall implant height adjustable along a longitudinal axis. The method may include placing the implant between bone structures to be supported and displacing an inner member having a scalloped surface relative to an outer member having a tapered inner surface in order to increase the overall implant height. The outer member may be configured to cooperatively engage a first bone structure and the inner member may be configured to cooperatively engage a second bone structure. Displacing the inner member may allow a locking element to disengage the scalloped surface. A compressive load may be supported from the bone structures on the inner and outer members, and the compressive load may cause the tapered surface to shift the locking element into engagement with the scalloped surface and to inhibit a decrease in the overall implant height. 
     In yet another exemplary aspect, an expandable medical implant for supporting bone structures includes an outer member being configured to cooperatively engage a first bone structure and an inner member receivable in the outer member. The inner member may be movable relative to the outer member to increase and decrease the overall implant height and may be configured to cooperatively engage a second bone structure. At least one of the inner and outer members includes vascularization openings formed on first and second opposing sides of the implant. The vascularization openings on the first opposing side may be larger than the vascularization openings on the second opposing side. 
     Further aspects, forms, embodiments, objects, features, benefits, and advantages of the present invention shall become apparent from the detailed drawings and descriptions provided herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevation view of a segment of a lumbar spine. 
         FIG. 2  is a pictorial illustration of an exemplary expandable implant according to one embodiment of the present invention. 
         FIGS. 3   a - 3   c  are pictorial illustrations of exploded views of the implant of  FIG. 2 . 
         FIG. 4  is an isometric pictorial illustration of a base component of the implant of  FIG. 2 . 
         FIG. 5  is a top pictorial illustration of the base component of  FIG. 4 . 
         FIG. 6  is a sectional pictorial illustration of the base component of  FIG. 5 , taken along line  6 - 6 . 
         FIG. 7  is an isometric pictorial illustration of a locker component of the implant of  FIG. 2 . 
         FIG. 8  is an isometric pictorial illustration of a post component of the implant of  FIG. 2 . 
         FIG. 9  is a side pictorial illustration of the implant of  FIG. 2 . 
         FIG. 10  is a sectional pictorial illustration taken along line  10 - 10  in  FIG. 9 . 
         FIG. 11  is a sectional pictorial illustration taken along line  11 - 11  in  FIG. 9 . 
         FIG. 12  is a sectional pictorial illustration of an exemplary locking arrangement usable with the implant of  FIG. 2 . 
         FIG. 13  is an elevation view of another exemplary embodiment of the present invention. 
         FIG. 14  is another elevation view of the exemplary embodiment of  FIG. 13 . 
         FIG. 15  is an elevation view of another exemplary embodiment of the present invention. 
         FIG. 16  is another elevation view of the exemplary embodiment of  FIG. 15 . 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments, or examples, illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates. 
       FIGS. 2 and 3   a - 3   c  show an exemplary expandable implant  100  usable to secure and space adjacent bone structures. In  FIG. 2 , the implant  100  is shown fully assembled, while  FIGS. 3   a - 3   c  show the implant  100  in an exploded condition, along a longitudinal axis L. Referring to these figures, the implant  100  includes three main components, including a base  102 , a locker  104 , and a post  106 . These main components operate together to provide the support and spacing between the adjacent bone structures. In addition to these components, the exemplary implant  100  includes locking elements  108 , pegs  110 , and biasing elements  112 . 
     In the exemplary embodiment shown in  FIGS. 2 and 3   a - 3   c , the base  102  is configured and shaped to receive and house the locker  104 , which, in turn, is configured and shaped to receive and house the post  106 . The locking elements  108  cooperate with the locker  104  to control displacement of the post  106  relative to the base  102 , thereby controlling the overall height of the implant  100 . In this embodiment, the pegs  110  connect the base  102 , the locker  104 , and the post  106  into a unitary mechanism. The biasing elements  112  cooperate with the base  102  and the locker  104  to bias the locker  104 , and likewise the locking element  108 , into a position that selectively locks or secures the post  106  relative to the base  102 , thereby hindering the ability of the implant  100  to collapse after implantation. In the embodiments shown, the biasing element  112  is a leaf spring. However, the biasing element could be any type of spring, including a coil spring, or a material, such as a silicone or elastomeric bumper, or an elastic member, such as a stretchable band that may act in compression or tension. 
     The components of the exemplary implant  100  will be described in further detail with reference to  FIGS. 4-12 . The base  102  will be described first, with reference to  FIGS. 4-6 , as well as  FIGS. 3   a - 3   c .  FIG. 4  shows an isometric view of the base  102 ;  FIG. 5  shows a top view; and  FIG. 6  shows a cross-sectional view. 
     The base  102  includes a top surface  114 , a bottom surface  116 , an outer wall  118 , and an inner wall  120 , defining a bore  122 . The top and bottom surfaces  114 ,  116  may be relatively flat surfaces having the bore  122  formed therein. The top surface  114  may be configured to cooperate with locker  104 , and the bottom surface  116  may be configured to cooperatively engage a bone structure, either directly or through additional components, such as endplates. The bottom surface  116  may include features for attachment to endplates or other components. Some exemplary features are described below with respect to the post  106 . 
     In the exemplary embodiment shown, the outer wall  118  may include instrument receiving features  124  that cooperate with surgical instruments for placement of the implant  100  between desired bone structures. In the embodiment shown, the instrument receiving features  124  are indentations on opposite sides of the base outer wall  118 , however, it is contemplated that many other features could be used to cooperate with instruments that would allow the instruments to grip, support, or otherwise place the implant  100  in a desired location. Further, some embodiments lack any instrument receiving features. 
     In the exemplary embodiment shown, in addition to the instrument receiving features  124 , the outer wall  118  includes additional cut outs and features that function to reduce the mass of the implant  100  while maintaining sufficient strength to properly support the bone structures and weight of a patient. In addition, these additional cutouts and features may simplify additional processing, such as, for example, when using a wire EDM to cut features at the bottom surface  116 . 
     Referring now to  FIGS. 5 and 6 , the base  102  includes the inner wall  120 , forming the bore  122 . In this exemplary embodiment, the bore  122  extends longitudinally from the top surface  114  through the base  102 , to the bottom surface  116 , as best seen in  FIG. 6 . As best seen in  FIG. 5 , the bore  122  in this exemplary embodiment is substantially rectangular. Accordingly, the inner wall  120  may be formed of substantially planar surfaces that form the rectangular shape. It should be noted that in other embodiments, the bore  122  is formed of other polygon shapes, such as, for example, triangular, square, or pentagon. Still other embodiments have bores that are oval or circular shaped. As illustrated in  FIG. 2 , the bore  122  is configured to receive the locker  104  of the implant  100 . 
     The inner wall  120  has a tapered section  128  and a non-tapered section  130 . In the exemplary embodiment shown, the tapered section  128  is adjacent the top surface  114  of the base  102 , while the non-tapered section  130  is adjacent the bottom surface  116  of the base  102 . However, the tapered section  128  may be otherwise arranged or placed. As discussed further below, the tapered section  128  cooperates with the locking element  108  to secure the height of the implant  100  at a desired level. Also, in the exemplary embodiment shown, the inner wall  120  includes two tapered sections  128 , disposed on opposite sides of the bore  122 . Other embodiments include one or more than two tapered sections, and for the reasons described below, symmetry may provide advantages when expanding the implant  100 . 
     In addition to the elements described, the base  102  also includes a peg aperture  132 , a biasing member aperture  134 , and a vascularization aperture  136 . During assembly, the peg  110  may be inserted into the peg aperture  132 , and the biasing element  112  may be inserted through the biasing member aperture  134 . The vascularization aperture  136  provides access to the bore  122  and may be used to introduce bone graft, tissue, or other material into the bore  122  after implantation. In addition, it allows fluid into the interior of the base  102  thereby, encouraging bone growth. Because of the cutouts, the outer wall  118  of the base  102  also forms a flange  138 , as best seen in  FIGS. 2 ,  3   a , and  4 . 
     As shown in  FIG. 2 , the base  102  receives the locker  104 , which is described with reference to  FIGS. 2 ,  3   a - 3   c , and  FIG. 7 . The locker  104  includes an upper end  150 , a lower end  152 , an inner surface  154 , an outer surface  156 , and a flange  157 . 
     In this exemplary embodiment and as shown in  FIG. 2  in an assembled condition, the upper end  150  is disposed outside the base  102 , and the lower end  152  is disposed within the bore  122  of the base  102 . At the upper end  150 , the flange  157  radially extends to have an outer perimeter substantially matching that of the base  102 . As described below, the flange  157  may be used to displace the locker  104  relative to the base  102  in order to change the overall height of the implant  100 . 
     In the embodiment shown, the outer surface  156  of the locker  104  is sized and formed to be received within the bore  122  of the base  102 . In this embodiment, like the bore  122  of the base  102 , the outer surface  156  is substantially rectangular. However, the outer surface may be in the form of other shapes, as described above with reference to the base  102 . 
     The outer surface  156  includes a locking element receiver  158 , which in this embodiment is an aperture from the outer surface  156  to the inner surface  154 . In addition, the outer surface includes a biasing member support  160 , a vascularization aperture  162 , and a peg slot  164 . 
     As described further below, the locking element  108  fits within and extends through the locking element receiver  158  to engage and disengage the base  102  and the post  106 , restricting movement of the post  106  relative to the base  102 . The biasing member support  160  cooperates with the biasing member  112  to provide a biasing force on the locker  104  to maintain it within the base  102 . The peg slot  164  receives the peg  110 , which also extends through the base  102 . This allows the locker  104  to move relative to the peg  110 , but the peg  110  blocks removal of the locker  104  from the base  102 . Accordingly, the peg slot  164  cooperates with the peg  110  to slidably maintain the locker  104  within the base  102 . 
     The inner surface  154  of the locker  104  forms a locker bore  166 . The locker bore  166  in this exemplary embodiment is rectangular, as is the outer surface  156 . However, the locker bore  166  need not be rectangular but could be formed into some other shape. As will be described below, the locker bore  166  is configured and sized to receive the post  106 . 
     The post  106  will be described with reference to  FIGS. 8 and 3   a - 3   c . The post  106  includes a top end  180 , a bottom end  182 , and a main body  184  extending therebetween. The top end  180  includes a top surface  181  having end plate connectors  186  formed therein. In the embodiment shown, the end plate connectors  186  are configured for attachment to an end plate (not shown). In the embodiment shown, the end plate connectors  186  are a series of holes configured to attach to endplates. In some embodiments, instead of attaching to separate endplates, the post  106  is configured to cooperatively attach directly to bone structure. In this exemplary embodiment, one end plate connector  186  may include an attachment aid  188  that cooperates with an end plate to secure the end plate onto the top surface  180  of the post  106 . In this embodiment, the attachment aid  188  is a spring feature that is deformable to receive an endplate post and frictionally grip it to hold the endplate in place during implantation. In addition, the bottom surface  116  of the base  102  may include similar features, including the end plate connectors and the attachment aid, such as the spring feature. In some embodiments, the end plate connectors are cylindrical posts that extend from an endplate and are configured to be received by the end plate connectors  186 . The end plates could be at any angle or of various types. Alternatively, the end plate connectors may be used with an intermediate spacer to connect and stack two implants. 
     The bottom end  182  of the post  106  includes a bottom surface  183  having a vascularization aperture  190  formed therein. The bottom end  182  fits within the locker bore  166 , and is slidable relative to the locker  104  and the base  102  to increase and decrease the overall height of the implant  100 . In the embodiment shown, the bottom end  182  of the post  106  is sized and formed to be received within the locker bore  166 . In this embodiment, like the locker bore  166 , the bottom end  182  is substantially rectangular. However, the bottom end may be in the form of other shapes, as described above with reference to the base  102 . 
     The main body  184  includes a peg slot  192 , additional vascularization holes  194 , and a locking surface  196 . The peg slot  192  is configured to receive the peg  110 , which also extends through the base  102  and locker  104 . Because of the length of the peg slot  192 , the post  106  may be raised or lowered relative to the peg  110  to increase or decrease the overall height of the implant  100 . The vascularization holes  194  and the vascularization aperture  190  provides access for placement of bone graft or other material and allows fluid flow to promote bone growth and attachment to the bone structures. 
     The locking surface  196  is the area configured to contact the locking element  108 , and in this exemplary embodiment, may include roughened features, such as, for example, a series of roughening scallops aligned transverse to a longitudinal axis of the implant  100 , as shown in the figures. As will be described below, the roughened features, such as the scallops cooperate with the locking element  108  to secure the post at a desired height relative to the locker  104  and the base  102 . In this embodiment, the scallops of the locking surface  196  are spaced less than 1 mm apart and enable an incremental increase and decrease in the height of the implant  100 . A scallop radius may substantially correspond with a radius of the locking element  108 , providing a relatively tight fit when the locking element is engaged with the locking surface  196 . In some embodiments, the locking surface  196  is not scalloped, but includes other roughening features. For example, in some embodiments the roughened features of the locking surface includes protruding triangular features or block-like features forming teeth. Still other surface features may be simply rough surfaces, such as those formed by shot peening, blasting, etching, or machining to increase the frictional properties of the locking surface  196 . Still other roughened surface features are contemplated. In yet other embodiments, the locking surface  196  is relatively smooth, thereby allowing for an infinite number of expansion increments. 
     In addition to the features described above, the post  106  includes a flange  198 . In the exemplary embodiment shown, the flange  198  includes instrument receiving grips  200  along its outer edges, formed to fit instruments during implantation or expansion. 
     Operability of the implant  100  will be described with reference to  FIGS. 9 through 12 .  FIG. 9  shows the implant  100  in an assembled condition.  FIGS. 10 and 11  show cross-sectional views of the implant  100 .  FIG. 12  shows one model of components used to illustrate the functionality of the locking mechanism of the implant  100 . 
     Referring now to the cross-sectional view in  FIG. 10 , the peg  110  is shown extending through the base  102 , the locker  104 , and into the post  106 . As can be seen, the peg slot  164  in the locker  104  allows the locker  104  to move along the longitudinal axis L of the implant  100  relative to the base  102 . Likewise, the peg slot  192  in the post  106  allows additional movement of the post  106  relative to the base  102 . In this manner, the peg  110  may maintain the components of the implant  100  together, while at the same time allowing them to expand longitudinally to increase and decrease the overall implant height. 
       FIG. 11  is a cross-sectional view through the biasing element  112  and through the locking element  108 . The locking element  108  is maintained in its location by the locking element receiver  158  of the locker  104 . As shown in  FIG. 11 , the biasing element  112  cooperates with the base  102  and the biasing member support  160  of the locker  104  to limit the axial movement of the locker  104  relative to the base  102 . The biasing element  112  provides a continuous biasing force against the locker  104  to maintain the locker  104  in a position that locks the height of the implant. 
       FIG. 12  shows the relationship of the locking element  108  with the base  102 , the locker  104 , and the post  106 , according to one embodiment of the implant. The locking element  108  is disposed in the locking element receiver  158 , and protrudes through the receiver  158  such that the locking element  108  is selectively in contact with both the base  102  and the post  106 . 
     In use, when the locker  104  is raised relative to the base  102 , the locking element  108  also raised relative to the base  102 . Because the base  102  has a tapered section  128 , upward movement of the locking element  108  relative to the base may provide free space for the locking element  108  to move away from the post  214 . This may be referred to as an unlocked condition, allowing the post  214  to slide freely to either increase or decrease the overall height of the implant  100 . Once the desired height is achieved, the locker  104  may be moved downward relative to the base  102 , wedging the locking element  108  between the tapered surface  128  of the base  102  and the post  106 . So doing locks the overall height of the implant at its desired height. This may be referred to as a locked condition. The roughened surface features, such as the scallops, of the post  106  may provide a locking location for the locking element  108  and may reduce slippage between the locking element  108  and the post  106 . 
     In the embodiment shown, the overall height of the implant  100  can be increased simply by raising the post  106  relative to the base  104 . So doing may force the locking element  108  to move upwardly along the tapered section  128  to the unlocked condition, thereby allowing the implant height to be increased without requiring any separate attention to the locker  104 . This also allows the locking element  108  to freely engage and disengage the roughened features of the locking surface  196 . Accordingly, in some embodiments such as those shown having the scalloped surface features, during expansion, an audible clicking may be generated as the locking element  108  moves past and falls into each scalloped feature of the locking surface  196 . In some embodiments, the locker  104  and the locking element  108  are configured to require manual or separate displacement of the locker  104  and the locking element  108  to reduce the overall height of the implant  100 . 
     In the embodiment shown, the locking element  108  is a cylindrical rod that distributes its locking force over a wide surface area and in the embodiment shown over the entire width of the post  106 . Accordingly, the locking element  108  contacts the post  106  along a contact line transverse to the longitudinal axis L of the implant  100 , rather than at a single point. Because of this, the implant is less conducive to undesired slipping. It should be noted that the scalloped surface on the post  106  is optional and the post  106  may include other roughened features, indentations or elements that increase the friction between the locking element and the post. 
     In the embodiment shown, the implant  100  includes symmetrically locking features, including opposed tapered surfaces on the base  102 , two locking elements  108  in two opposed receiving apertures  158 , and two opposite locking surfaces  196 . This symmetry may aid expansion and collapse of the implant by substantially equalizing the forces required at each side of the implant to expand or collapse it, providing a better level of control to the physician placing or removing the implant. 
     During implantation, the implant  100  may be gripped with a surgical instrument at instrument receiving features of the base  102  and at the instrument receiving grips  200  of the post  106 . In its smallest condition, the implant may be introduced to a patient through the smallest possible incision. In one exemplary embodiment, the implant  100  may be introduced between two bone structures, such as adjacent vertebral bodies, such as the vertebral bodies V 2  and V 4  in  FIG. 1 , replacing the vertebral body V 3  along with the discs D 2  and D 3 . Once positioned between the adjacent bone structures, the implant  100  may be distracted to increase the overall implant height. Using the instruments, the post  106  is longitudinally displaced relative to the base  102 . In so doing, the post  106  frictionally acts on the locking element  108  to raise it relative to the base  102 , along the tapered section  128 . Once a desired height is achieved, the base  102  and post  106  are released. The continuous biasing force of the biasing member  112  acting on the locker  104  draws the locker  104  and the locking element  108  into a locking condition, where the locking element is wedged between the tapered section  128  and the locking surface  196  of the post  106 . This compressive force locks the implant  100  against further decreases in the overall height. Once expanded, an implanting physician may introduce optional bone growth promoters into the base  102  or post  106  through the vascularization aperture  136  and the vascularization holes  194 , respectively. 
     If it later becomes necessary to remove the implant, the locker flange  157  may be raised relative to the base  102  to remove the locking element  108  from its wedged position. Once the locking element  108  is free to disengage the locking surface  196  of the post  106 , the post  106  may collapse into the locker  104 , and the implant  100  may be removed from the patient. Again, although described with reference to one locking element, it is understood that two or more locking elements may be includes to provide symmetry. 
     In the implantation method described above, some amount of the distraction force is used to overcome the biasing force of the biasing member  112 . In some embodiments, the biasing member may be adjusted to provide a stronger biasing force to resist undesirable actuation of the implant once released. The stronger the biasing member, the greater the force required to deploy the device. However, in other implantation methods, the locker  104  may be separately raised relative to the base  102  to release the locking element prior to distracting the post  106  from the base  102 . In this way, the complete distraction force may be used for distraction, rather than a portion being used to overcome the biasing force acting on the locker  104 . 
     In yet other implantation methods, the implant may also be deployed by raising the center post  106  relative to the base  102  from the bottom end  182 . In these embodiments, deploying instruments may attach to the post bottom end  182 , such as at the bottom surface  183 , or to features on the post  106  such as the vascularization apertures  194 , and in addition, attach to the instrument receiving features  124  on the base  102 . By moving the post  106  from the bottom end  182  (or the vascularization apertures  194 ) relative to the instrument receiving features  124 , the distance between the bottom end  182  (or the vascularization apertures  194 ) and the instrument receiving features  124  decreases, while the overall height of the implant increases. Accordingly, during deployment, the gripping portions of the instrument move closer together (decreasing the instrument size), while the height of the implant increases. Because in this embodiment, the instrument does not grip at the ends of the implant, the implant can be deployed into a space or cavity where both ends of the implant are not directly accessible at the same time. 
     Although the implant  100  is described as being somewhat porous with vascularization apertures  136 ,  162 ,  190 ,  194 , other embodiments include either more or less vascularization apertures. In some embodiments, the post is substantially solid such that while it is telescopically received within the locker and base, no material may be received within the post, or alternatively, with in the base. 
       FIGS. 13 and 14  show an embodiment of another exemplary expandable implant  300  having additional vascularization openings.  FIG. 13  shows a back side and  FIG. 14  shows a front side. The implant  300  is similar to the implant  100  described above, including a base  302 , a locker  304 , and a post  306 . In this embodiment, the heights of the base  302  and the post  306  are greater than those of the base  102  and post  106  described above. To accommodate grafting, tissue, or other material, the implant  300  includes rear vascularization openings  308 , side vascularization openings  310 , and at least one front access window  312 . The rear and side openings  308 ,  310 , as well as the access window  312 , increase the porosity of the implant, promoting breathability and bone growth. The access window  312  is larger than the rear and side openings  308 ,  310  and provides access to the interior of the base  302 . Accordingly, during implantation, a physician may introduce grafting material through the access window  312  to pack grafting material, tissue, or other material into the base  302 . The larger size of the access window  312  simplifies the packing process, while the smaller size of the rear and side openings  308 ,  310  help reduce the opportunity for the material being packed to extrude from the rear or side openings. This may become important when the implant  300  is placed in a spine and the rear of the implant  100  is facing or located adjacent the spinal cord. Similarly, the larger size of the access window  312  may allow placement of large segments of grafting, tissue, or other material, while the smaller rear and side openings  308 ,  310  help contain the large segments within the base  302 . The post  306  of the implant  300  also includes vascularization holes  314  similar to the vascularization holes  194  described above. 
       FIGS. 15 and 16  show another embodiment of an exemplary expandable implant  400 .  FIG. 15  shows a back side and  FIG. 16  shows a front side. Again, the implant  400  is similar to the implant  100  described above, including a base  402 , a locker  404 , and a post  406 . To accommodate grafting, tissue, or other material, the implant  400  includes rear vascularization openings  408 , side vascularization openings  410 , and front access windows  412  that increase the porosity of the implant, promoting breathability and bone growth. As described above, the access window  412  is larger than the rear and side openings  408 ,  410  and provides access to the interior of the base  402 . In this embodiment, the rear openings  408  are larger than the side openings  410 . Nevertheless, in this embodiment, the rear openings  408  are smaller than the access window  412 . As can be seen, in this embodiment, the base  402  includes three rear openings  408 . 
     The post  406  of the implant  400  also includes vascularization holes  414  similar to the vascularization holes  194  described above. In addition, the post  406  includes post openings  416  in a locking surface  418 . The locking surface  418  may be similar to the locking surface  196  described above. The post openings  416  provide additional vascularization to the implant  400 . 
     In the embodiments shown in  FIGS. 13-16 , the implants include only one access window. However, in other embodiments, the implants include more than one access window on the front side, while the rear and side openings are still maintained smaller than the front access windows. In other embodiments, the rear openings are smaller than the side openings. It also should be noted that the implant may include more or less than three rear openings, and the size of the openings may be determined in part based upon the size of the implant and based upon the size or amount of packing material anticipated. 
     While the post has been shown as telescopically received within the locker and the base, it will be appreciated that in a further embodiment the respective configuration is inverted such that a portion of the base is received within the post. Moreover, while a substantially cylindrical structure having rectangular bores has been shown for the purposes of illustration, in alternative embodiments the tubular and rectangular shapes may take the form of a rectangle, square, ellipse, diamond, oval, D-shape or any shape desired to conform and substantially match the adjacent bone or the bone structure that is being replaced. As a result, the definition of tubular is not intended to be limited to cylindrical but is instead intended to cover all components that may be utilized to reduce the present invention. 
     While the present device has been described with respect to insertion between two vertebrae after removal of the intervening vertebrae and intervertebral disc, it is contemplated that the length of the device may be sized appropriate to span multiple vertebrae. Additionally, the device may find application in other orthopedic areas and the size and shape of the device may be made to substantially match the implantation site. For example, while the present embodiment has been illustrated as a substantially cylindrical device, it is contemplated that in certain spinal applications it is desirable that the device have a substantially D shaped cross-section as viewed from top to bottom such that the anterior portion of the device has an exterior convexly curved surface matching the anterior of the vertebral body while the posterior portion of the device is substantially flat or concave allowing it to be positioned closer to the spinal canal without protruding into the spinal canal. 
     Embodiments of the implant in whole or in part may be constructed of biocompatible materials of various types. Examples of implant materials include, but are not limited to, non-reinforced polymers, carbon-reinforced polymer composites, PEEK and PEEK composites, shape-memory alloys, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof. In some embodiments, the locking elements  108  are formed or cobalt chrome and the base  102 , locker  104 , and post  106  are formed of titanium. 
     If the implant is made from radiolucent material, radiographic markers can be located on the implant to provide the ability to monitor and determine radiographically or fluoroscopically the location of the implant in the spinal disc space. In some embodiments, radiographic markers are placed to show the location of the locking elements relative to the post and base. 
     In some embodiments, the implant or individual components of the implant are constructed of solid sections of bone or other tissues. In other embodiments, the implant is constructed of planks of bone that are assembled into a final configuration. The implant may be constructed of planks of bone that are assembled along horizontal or vertical planes through one or more longitudinal axes of the implant. In some embodiments, a cavity is cut or constructed through the implant. The cavity may be useful to contain grafting materials. Tissue materials include, but are not limited to, synthetic or natural autograft, allograft or xenograft, and may be resorbable or non-resorbable in nature. Examples of other tissue materials include, but are not limited to, hard tissues, connective tissues, demineralized bone matrix and combinations thereof. Examples of resorbable materials that may be used include, but are not limited to, polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, and combinations thereof. Implant may be solid, porous, spongy, perforated, drilled, and/or open. 
     In some circumstances, it is advantageous to pack all or a portion of the interior and/or periphery of the implant with a suitable osteogenetic material or therapeutic composition. Osteogenic materials include, without limitation, autograft, allograft, xenograft, demineralized bone, synthetic and natural bone graft substitutes, such as bioceramics and polymers, and osteoinductive factors. A separate carrier to hold materials within the device can also be used. These carriers can include collagen-based carriers, bioceramic materials, such as BIOGLASS®, hydroxyapatite and calcium phosphate compositions. The carrier material may be provided in the form of a sponge, a block, folded sheet, putty, paste, graft material or other suitable form. The osteogenetic compositions may include an effective amount of a bone morphogenetic protein, transforming growth factor β1, insulin-like growth factor 1, platelet-derived growth factor, fibroblast growth factor, LIM mineralization protein (LMP), and combinations thereof or other therapeutic or infection resistant agents, separately or held within a suitable carrier material. A technique of an embodiment of the invention is to first pack the interior of an unexpanded implant with material and then place one or both end members if desired. 
     Access to the surgical site may be through any surgical approach that will allow adequate visualization and/or manipulation of the bone structures. Example surgical approaches include, but are not limited to, any one or combination of anterior, antero-lateral, posterior, postero-lateral, transforaminal, and/or far lateral approaches. Implant insertion can occur through a single pathway or through multiple pathways, or through multiple pathways to multiple levels of the spinal column. Minimally invasive techniques employing instruments and implants are also contemplated. 
     It is understood that all spatial references, such as “top,” “inner,” “outer,” “bottom,” “left,” “right,” “anterior,” “posterior,” “superior,” “inferior,” “medial,” “lateral,” “upper,” and “lower” are for illustrative purposes only and can be varied within the scope of the disclosure. 
       FIG. 1  illustrates four vertebrae, V 1 -V 4 , of a typical lumbar spine and three spinal discs, D 1 -D 3 . While embodiments of the invention may be applied to the lumbar spinal region, embodiments may also be applied to the cervical or thoracic spine or between other bone structures. 
     While embodiments of the invention have been illustrated and described in detail in the disclosure, the disclosure is to be considered as illustrative and not restrictive in character. All changes and modifications that come within the spirit of the invention are to be considered within the scope of the disclosure.