Abstract:
This invention relates to a porous bone implant ( 10, 110 , and  210 ), a method of manufacturing the implant and a method of orthopedic treatment. The mesh implant can be manufactured using extrusion techniques and a variety of cutting and machining processes to provide the implant with the desired structural features and in the required dimensions to be matingly received within the bone defect or cavity. The implant can be used to strengthen bone structures and support bone tissue adjacent to a defect of cavity. Thus, the implant can be used to provide improved treatment of patients having bone defects or diseases with decreased postoperative pain and a shorter recovery time.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application claims the benefit of U.S. Provisional Application Ser. No. 60/160,506 filed on Oct. 20, 1999, and entitled “Impacted Orthopedic Bone Implant,” which is hereby incorporated by reference in its entirety. 

   BACKGROUND OF THE INVENTION 
   The present invention concerns a device for implantation into bone tissues, a method of manufacturing such a device, and a method of orthopedic treatment. More specifically, this invention is directed to an orthopedic mesh implant for implantation into bone cavities to support bone tissue adjacent to the cavity. The invention is also specifically directed to methods of manufacturing a mesh implant and to methods for treating patients using the mesh implant. 
   The repair and reconstruction of bone structures having a defect, such as a cavity, crack or chip, can be accomplished by directly fixing bone structures adjacent a defect to each other, such as by plate(s) and screw(s). In other instances an osteogenic material, i.e. a bone growth inducing material, can be introduced into the bone defect to promote bone growth to fuse the bone structures together. Implantation of bone growth material can be particularly advantageous where the bone includes a cavity because a portion of the bone structure or adjoining structure is missing. Cavities can be formed naturally, by trauma, or because of intentional harvesting of bone grafts for implantation into other bone structures. 
   While implants are known that may provide stability between adjacent bony structures, the effectiveness, as well as the cost of manufacture and availability of such implants, limits the advantages that may be realized. 
   A cylindrical spacer assembly is described in WO 99/32055. The spacer assembly includes opposite, detachable endcaps that connect with the spacer body with interdigitating teeth. 
   In light of the above-described problems, there is a continuing need for advancements in devices and methods relating to orthopedic treatment of bone defects and diseases to reduce the treatment risks and enhance the patency bone fusion devices. The present invention is such an advancement and provides a wide variety of benefits and advantages. 
   SUMMARY OF THE INVENTION 
   For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated herein 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 processes, systems or devices, 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. 
   According to one form of the invention, there is provided an implant for insertion into bone structures. The implant comprises a hollow body having an interior chamber, a first and second end for bearing against bone tissue and each end having an opening providing communication with the interior chamber. The hollow body is formed to include one or more mesh sides having a grid work of openings into the interior chamber. Thus, the invention provides a device that is implantable into bone structures and provides a depot for deposition of bone growth inducing material to promote bone growth and to provide support for weak bone structures. 
   In another form, the invention provides an implant for supporting weak bone tissue. The implant comprises a mesh body having an interior chamber and a passageway therethrough and defining a longitudinal axis substantially parallel to the passageway; the body includes a first end and a second end, each end positioned substantially transverse to the longitudinal axis and each end having a supporting portion positioned about the perimeter of the respective ends. The mesh body also includes a central portion having a longitudinal wall extending from the first end to the second end and having formed therein a grid work of openings providing communication into the interior chamber. In preferred embodiments, the supporting portions include an uninterrupted support band positioned about the periphery of each of the first and second end. In other preferred embodiments, the implant includes at least one tool-engaging portion provided in the longitudinal wall. In still other preferred embodiments, the implant is formed as a one-piece unitary body. 
   It is one object of the present invention to provide an orthopedic bone support implant to facilitate reconstruction and/or repair of bone structures. 
   Further objects, features, aspects, forms, advantages and benefits shall become apparent from the description and drawings contained herein. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of one embodiment of an implant according to the present invention. 
       FIG. 2  is a top plan view in partial section of the implant depicted in  FIG. 1 . 
       FIG. 3  is an end elevation view in partial section of the implant depicted in  FIG. 1 . 
       FIG. 4A  is a side elevation view in partial section of the implant depicted in  FIG. 1 . 
       FIG. 4B  is a side elevation view in partial section of an implant similar in configuration to the implant depicted in  FIG. 1 , but having a shorter length. 
       FIG. 5  is a perspective view of one embodiment of a cylindrical implant according to the present invention. 
       FIG. 6  is an end elevation view in partial section of the implant depicted in  FIG. 5 . 
       FIG. 7  is side elevation view in partial section of the implant depicted in  FIG. 5 . 
       FIG. 8  is a side elevation view in partial section of an alternative embodiment of an implant according to the present invention. 
       FIG. 9  is a top elevation view in partial section of the implant depicted in  FIG. 8 . 
       FIG. 10  is an end elevation view in partial section of the implant depicted in  FIG. 8 . 
       FIG. 11  is an illustration of cutting a bone graft from the iliac crest. 
       FIG. 12  is an illustration of harvesting the cut bone graft from the iliac crest. 
       FIG. 13  is a side elevation view of an implant holder and an implant according to the present invention. 
       FIG. 14  is an illustration of impacting an implant of the present invention into bone tissue. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated herein 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 processes, systems or devices, 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. 
   The present invention contemplates an implant for insertion into bone structures. In one aspect of the invention, the implant provides a device for supporting weak bone structures. In other aspects, the implant provides a receptacle for deposition of bone growth material. In still other aspects the implant of this invention is intended to replace current mesh or cage-type devices for engagement with bone structures. The implant of this invention is provided to be implanted into bone structures. The phrase “implanted into bone structures” is not intended to limit this invention to implantation into a single bone structure. Therefore, it is also within the scope of this invention to provide implants that can be implanted between adjacent bone structures, for example, in an intervertebral space between adjacent vertebrae. 
     FIGS. 1-4A  and  4 B illustrate one embodiment of a mesh bone implant  10  according to the present invention. Bone implant  10  includes a body  12  having an interior chamber  11 . Implant  10  also includes a first end  18  and opposite second end  20  and a central portion  22  extending from first end  18  to second end  20 . Central portion  22  includes a first longitudinal wall  13  having a first longitudinal wall portion  30  and a second longitudinal wall portion  32  and passageway  14  therethrough defining a longitudinal axis  16 . 
   First end  18  includes a support portion  24  positioned about its perimeter. In one form, support portion  24  includes an integrally formed support band  26  positioned circumferentially about longitudinal axis  16 . Band  26  is adapted to withstand impaction forces to seat impact implant  10  into a defect or a prepared cavity in the bone structure. In one form, band  26  is an uninterrupted band having an outer peripheral surface flush with the exterior surface of the longitudinal wall  13 , and can be provided as an integrally formed band having a cross section thicker than the cross section of other wall portions, i.e. walls  30  and  32 , of body  10 . Preferably, band  26  does not extend beyond either wall  30  or wall  32  in a direction orthogonal to and away from longitudinal axis  16 . In this form, wall portions  30  and  32  define a substantially planar surface extending from first end  18  to second end  20 . Band  26  can taper uniformly in a direction towards interior chamber  11 ; gradually increasing in width to a maximum width proximate to first end  18 . Extension of band  26  internally serves to provide a thickened portion to enhance the load bearing capabilities of implant  10 . Further, internal projections of band also provide a retaining ring about the perimeter of first end  18 . Ring  27  provides containment of osteogenic material deposited in internal chamber  11  and facilitates greater packing density of the osteogenic material by inhibiting the escape of the packed osteogenic material from the implant. In other forms, band  26  can be provided as a lip or abutment extending from the perimeter of first end  18  toward the interior chamber proximate to first end  18 . 
   Band  26  includes an exterior bearing surface  42 . Preferably, first surface  42  defines a substantially planar surface positioned substantially to lie in a plane generally perpendicular to longitudinal axis  16 . Further, first surface  42  is adapted to engage an adjacent facing surface of a bone defect or bone cavity. In one form, the first surface is a roughened or knurled surface to secure implant  10  to the adjacent bone surfaces. First end  18  also includes an opening  21  into interior chamber  11 . In the preferred form of the illustrated embodiment in  FIG. 14 , interior perimeter of band  26  defines opening  21 . 
   Second end  20  is opposite central portion  22  from first end  18 . Second end  20  includes a second support portion  25 . Second support portion  25  can be provided as is substantially described for first support portion  24  and can include a second support band  27 . Further, second end  20  also includes an opening into interior cavity  11  as described for first end  18 . 
   In one embodiment, first end  18  and second end  20  are separated by a distance, d 1 . Distance d 1  is selected so that implant  10  is matingly received within a cavity or other defect in a bone structure. When d 1  is properly selected, first end  18  and second end  20  each can bear against respective facing bone tissue of a cavity or other defect and provide support and strength to the bone structure. As an example of implants having varying d 1  distances, an implant similar in configuration to implant  10  is illustrated in  FIG. 4B . Implant  10 ′ is selected to have a shorter longitudinal length, d 1 , implant  10 . 
   It is also intended to include within the scope of this invention a series of implants, each having a configuration as described for implant  10 , but differing in length d 1 . 
   Central portion  22  extends from first end  18  to second end  20  and includes a longitudinal wall  13 . Longitudinal wall  13  includes a plurality of openings  31  providing communication with the interior chamber  11 . In one form, the plurality of openings  31  define a grid pattern or grid work on first wall  30 . Each of the plurality of openings  31  can be formed in a variety of configurations, including triangular, square, rectangular, and polyhedron. In a preferred form, the intersecting bars define a pattern of equilateral triangles or isosceles triangles. In another form, the gridwork or grid pattern is formed by a plurality of intersecting elongate bars. In a preferred form, the plurality of intersecting elongate bars include a first group of elongate bars have a longitudinal bar axis arranged perpendicular to longitudinal axis  16  and a second group of elongate bars having a longitudinal bar axis arranged non-perpendicular relative to longitudinal axis  16 . A plurality of joints are formed by the intersections of the elongate bars, each joint defining a corner of an opening into interior chamber  11 . 
   The elongate bars can define a repeating pattern of triangles on wall sections  30  and  32 , preferably isosceles triangles; more preferably, equilateral triangles. When equilateral triangles are used, the wall portions can have a maximum amount of open areas, while still retaining the requisite strength to support adjacent bone structures. The trim open area is intended to mean the sum of the area of the plurality of open portions  31  in walls portions  30  and  32 , respectively. 
   Preferably, the ratio of open area to the total surface area defined by either wall portion  30  (or wall portions  32 ) is greater than about 1:2; more preferably greater than about 3:4. That is, at least 50% of the exterior surface area of either wall portion  30  or  32  is open area 
   Longitudinal wall  13  can include a first wall section  30  and an opposing second wall section  32 . First wall  30  extends from first end  18  to second end  20  and defines a plane that is substantially parallel with longitudinal axis  16 . Second wall  32 , similar to first wall  30 , extends from first end  18  to second end  20  and defines a plane that is also substantially parallel with longitudinal axis  16 . Thus in one form, first wall portion  30  and second wall portion  32  are positioned to lie substantial parallel to each other. 
   Longitudinal wall  13  also includes a tool insertion end  28 . Tool insertion end  28  is positioned substantially orthogonal to first wall portion  30  and extends in a direction substantially parallel to longitudinal axis  16 . Tool insertion end  28  includes the tool-engaging portion  34 . Tool-engaging portion  34  can be provided in a variety of features adapted to engage an insertion tool for insertion of implant  10  into a prepared bone tissue. For example, tool-engaging portion  34  can include a variety of indents and openings, which may or may not be threaded, to engage corresponding configured features on an insertion manipulation accessory (not shown) to facilitate implantation of implant  10  into bone tissue. In a preferred embodiment of  FIG. 14 , tool-engaging portion  34  includes a longitudinally extending threaded bore  35  and a driving indent  36 . 
   Tool insertion end  28  defines an exterior surface  37 . In one form, surface  35  is curved in a direction transverse to longitudinal axis  16  from wall portion  30  to wall portion  32 . In another form, the exterior surface defines an arcuate surface in a direction along axis  16  and extending from the first end. 
   Referring now to  FIGS. 5-7 , there is depicted another embodiment of a mesh bone implant according to the present invention for supporting bone structures. In the preferred form of the illustrated embodiment, mesh implant  110  includes a cylindrical body  112  having a mesh wall  113  defining an interior chamber  111  therein. Body  112  includes a passageway  114  therethrough defining a longitudinal axis  116 . Preferably, cylindrical wall  113  extends circumferentally about longitudinal axis  116 . In the illustrated embodiment, cylindrical wall  113  is formed in the shape of a cylinder. However, it is understood that the mesh wall  113  can define a variety of shapes, including shapes having at least one flat surface. 
   Body  112  includes a first end  118  and an opposite second end  120 . First end  118  and second end  120  each include a support portion  124  and  125 , respectively. In one form, support portions  124  and  125  each include a support band,  126  and  127  respectively, positioned circumferentially about longitudinal axis  116 . Support bands  126  and  127  can be provided as an uninterrupted band about the perimeter of first end  118  and second end  120 , respectively. Support band  126  includes an exterior surface  142  that is provided as a substantially smooth surface and defining a plane generally transverse to longitudinal axis  116 . Similarly, support band  127  includes an exterior surface  144  that is provided as a substantially smooth surface and defining a plane generally transverse to longitudinal axis  116 . The substantially smooth planar surfaces  142  and  144  of support band  126  and  127 , respectively, facilitate implantation of implant  110  into bone structures. These surfaces provide particular advantages when implant  110  is inserted into a prepared cavity in a bone structure and engage the walls of the cavity to provide additional support to the bone structure. 
   Support portions  124  and  125  are provided to withstand the requisite impulsion force to seat implant  110  into a bone defect or a prepared cavity. The support portions  124 ,  125  can be formed from wall section having a thicker cross section then other wall sections of body  112 . Thus, the support bands  124  and  125  can be provided in a form as described above for support portions  24  and  25 . 
   First end  118  and second end  120  are separated by a distance, d 2 . Distance d 2  is selected so that implant  110  is matingly received within a prepared cavity or other defect in a bone structure. When d 2  is properly selected, first end  118  and second end  120  each can bear against respective facing bone tissue of a cavity, bone defect or opposing faces of adjacent bone structures and provide additional strength to the bone structure(s). 
   First end  118  and second end  120  each include an opening,  121  into the interior chamber  111 . Opening  121  provides communication with passageway  114  through body  112 . In the preferred form of the illustrated embodiment in  FIGS. 5-7 , the interior perimeter of bands  126  and  127  each define an opening  121 . 
   Mesh implant  110 , similar to mesh implant  10 , includes a central portion  122  extending from first end  118  to second end  120 . In one aspect, cylindrical mesh wall  113  defines central portion  122 . Cylindrical mesh wall  113  also includes a plurality of openings  131 . Openings  131  can be provided in a variety of patterns, including triangular (equilateral or isosceles), square, rectangular, and polyhedron, thereby forming a mesh wall. Preferably, outer peripheral wall  130  includes a uniform grid of a plurality of openings  131 . In another form, cylindrical mesh wall  113  can be formed by a plurality of intersecting elongate bars. The plurality of intersecting elongate bars include a first group of elongate bars have a longitudinal bar axis arranged perpendicular to longitudinal axis  116  and a second group of elongate bars having a longitudinal bar axis arranged non-perpendicular relative to longitudinal axis  116 . A plurality of joints are formed by the intersections of the elongate bars of the first and second groups, each joint forming an apex that defines a corner of one of the openings of the plurality of openings  131  into interior chamber  111 . In another form, cylindrical wall  113  is defined by a plurality of intersecting elongate bars including a first group of bars defining a plane perpendicular to longitudinal axis  116 . A second group of bars having an elongate axis arranged non-perpendicular to longitudinal axis  116  intersects the bars in the first group of bars. Again, a plurality of apexes are formed by the intersection of the first group of bars and the second group of bars. The apexes form one of the corners of the openings  131  in cylindrical wall  113 . Cylindrical wall  113  can be provided substantially as described for wall  13 . 
   Cylindrical wall  113  includes a tool engagement portion  134 . Tool engagement portion  134  can be provided as described for tool engagement portion  34 , and can include a threaded bore  135  and a driving indent  136 . 
   Another form of the invention is illustrated in  FIGS. 8-10 . Mesh implant  210  is depicted generally as a rectangular prism body  212  having a central portion  222  and an interior chamber  211  formed therein. Body  212  includes a passageway  214  therethrough defining a longitudinal axis  216 . Body  212  includes a first transverse wall  240 , an opposite second transverse wall  246 , and a central portion  222  extending from first end  218  to second end  220 . 
   First end  218  includes an opening  221  extending into interior chamber  211 . Similarly, second end  220  includes a second opening extending into interior chamber  211 . First end  218  also includes a support portion  224  extending about the perimeter of first end  218 . Similarly, second end  220  includes support portion  225  extending about its perimeter. Support portions  224  and  225  each include a support band  226  and  227 , respectively, positioned generally circumferentially about longitudinal axis  216 . Bands  226  and  227  are adapted to withstand forces needed to impact implant  210  into a prepared cavity in a bone structure or between adjacent bone structures. In one form, bands  226  and  227  can be provided as integrally formed bands having a cross section thicker than the cross section of other wall portions, particularly mesh walls  230  and  232 , of body  210 . In other forms, band  226  (or  227 ) can be provided as an abutment or a lip extending from the perimeter of first end  218  (or second end  220 ) toward the interior chamber  211  substantially as has been described for bands  26 ,  27 ,  126  and  127 . 
   In a preferred form of the illustrated embodiment of implant  210 , first end  218  and second end  220  are provided as arcuate surfaces  252  and  254 , respectively, along a transverse axis  256  positioned to be substantially orthogonal to longitudinal axis  216 . Arcuate surfaces  252  and  254  each have a maximum height positioned between first transverse wall  240  and second transverse wall  246 . In use, at least a portion of arcuate surfaces  252  and  254  can extend into bone tissue, such as cancellous tissue underlying the endplates of vertebral bodies. Arcuate surfaces  252  and  254  inhibit expulsion of the implant from the bone cavity by providing an implant that has a maximum height that is greater than height of a surgically prepared bone cavity, for example, in an intervertebral space between adjacent vertebrae. 
   Central portion  222  also includes first longitudinal wall  230  and second longitudinal wall  232 . At least one, and preferably both, of longitudinal mesh walls  230  and  233  are positioned to define a plane that is generally parallel to longitudinal axis  216 . Further, first wall  230  and second wall  232  are provided with a plurality of openings  231  into interior chamber  211 . Preferably, first wall  230  and second wall  232  are provided with a pattern of substantially uniform apertures forming a mesh. The apertures can be provided in a variety of configurations, including circular, square, rectangular, polyhedron, and the like. A plurality of openings  231 , similar to the openings  11  described for implant  10 , can be formed into walls  230  and  232 . In a preferred form, the apertures are provided in a form of an equilateral or isosceles triangle. Further, first wall  230  and second wall  232  can be defined by a plurality of intersecting elongate bars as described for cylindrical wall  113  for implant  110  and wall  13  of implant  10 . 
   In one form, implant  210  can be inserted in a defect or a prepared cavity between two bone structures to provide support and strengthen the adjacent bone structures. Therefore, body  212  can include a first transverse wall  240  extending between first end  218  and second end  220  and positioned generally orthogonal to longitudinal wall  230 , and an opposing transverse wall  246  also extending between first end  218  and second end  220  and positioned generally orthogonal to longitudinal wall  230 . Transverse wall  240  can include a first bearing surface  242 , an opposite second bearing surface  244 , and a transverse face  247  therebetween. Preferably, first bearing surface  242  and second bearing surface  244  include substantially planar surfaces  243  and  245 , respectively, adapted to engage adjacent surfaces of the prepared bone cavity or bone defect. When inserted into the prepared cavity or bone defect, at least one of first bearing surface  242  or second bearing surface  244  bear against the adjacent bone tissue. 
   In one embodiment, first bearing surface  242  and second bearing surface  244  are separated by a distance d 3  selected to engage first bearing surface  242  and second bearing surface  244  with corresponding opposing adjacent bone structures in the prepared cavity or bone defect. Further, in a preferred aspect, first bearing surface  242  and second bearing surface  244  are substantially planar surfaces extending generally parallel to transverse axis  256 . 
   First transverse wall  240  includes a tool-engaging portion  234 . Tool-engaging portion  234  can be configured as described for tool-engaging portion  34  of implant  10 , including a threaded bore  235  and driving indent  236 . 
   In the preferred embodiments, first and/or second bearing surfaces  242  and  244  include anti-expulsion features  249 , for example, ridges, teeth, and other projections, adapted to inhibit the expulsion of implant  210  from the prepared cavity or bone defect. In the preferred form, the anti-expulsion features are adapted to minimize the force needed to insert implant  210  into the prepared space or bone defect, yet inhibit expulsion of implant  210 . Examples of such preferred forms include: at least one ridge transverse to longitudinal axis  216 , a plurality of ridges, teeth, or spikes. In a preferred form, the anti-expulsion features are adapted to minimize the force needed to insert implant  210  into prepared intervertebral space, yet inhibit expulsion of implant  210 . Examples of such preferred forms include ratchet-shaped ridges or teeth that have an apex pointing toward the first terminal end. When thus configured, the ratchet-shaped ridges or teeth chisel deeper into the cortical bone tissue in response to an expulsive force. 
   Body  212  also includes a second transverse wall  246  opposite the first bearing wall  240 . Second transverse wall  246  can include a third bearing surface  248 , an opposing fourth bearing surface  250 , and a face extending therebetween. Third and fourth bearing surfaces  248  and  250 , respectively, are separated by distance d 4 . In one preferred embodiment, distance d 4  is selectively greater than distance d 3  to conform to the desired prepared cavity in the bone structure, for example, in the intervertebral space between adjacent vertebrae. While third and fourth bearing surfaces  248  and  250  are shown as curved surfaces, it is understood that these bearing surfaces can be provided in a variety of shapes, including convex or ogival, in either the horizontal or vertical plane, or both, or substantially planar as depicted with the first and second bearing surfaces  242  and  244 , respectively. Further, third and fourth bearing surfaces  248  and  250  can include anti-expulsion features as described for the first and second bearing surfaces  242  and  246 . 
   Further, transverse wall  246  can include a tool-engaging portion as described for transverse wall  240 , including a threaded bore and a driving indent. 
   Reference will now be made to use of mesh implants  10 ,  110 , and  210  to support adjacent weak bony structures. Typically, mesh implants  10 ,  110 , and  210  can be inserted into a bone structure after preparation of a suitable bone cavity. For example, implants can be inserted into the cavity resulting from harvesting an autograft from the iliac crest. Often, harvesting autografts leads to significant post-operative pain and lengthy recovery time. Use of the implants disclosed in this invention facilitates reconstruction of the cavity and accommodates a quicker recovery time, often with less pain to the patient. 
   Referring now to  FIGS. 11-14 , a selected portion of the iliac crest  260  is removed using a surgical cutting device, such as, for example, a chisel  262 , or a bone saw. After the selected region  264  of the iliac crest has been cut, the cut bone autograft  266  is removed from the residual bone structure  260 ′ of the patient as depicted in  FIG. 12 . An implant as described in the present invention is selected for cavity  268  and to matingly engage in the adjacent bone structures  270  and  272 , respectively. The selected implant  274  is releasably attached to an implant holder  280 , preferably of a known variety. Preferably, implant holder  280  includes an implant insertion portion that is configured to matingly engage in tool-receiving portion  34 ,  134 , and  234  of the selected implants. In preferred embodiments, the insertion portion includes a threaded shaft  284  to readily engage in a threaded bore in the implant. The implant insertion portion can also include a driving blade (not shown) to engage in a driving indent on the implant. In other embodiments, implant tool  280  can include a handle  288 , which may or may not include an impaction tool, such as a slap hammer, to impact the implant into the prepared bone cavity or bone defect. Preferably, implants  10 ,  110 , and  210  are made of a single, integral piece. The implants may be prepared from physiologically acceptable material having a requisite strength to withstand the compressive force exerted on the spinal column during normal activity. Examples of such acceptable material include: titanium, composites (carbon fiber or glass fiber composites), ceramics, bone, stainless steel, and surgical steel. Preferably, implants  10 ,  110 , and  210  are prepared of metal such as titanium or surgical steel. 
   In the preferred manufacturing procedure, implants according to the present invention are made by an extrusion of a tube or hollow construct. The tube or hollow construct may or may not be substantially cylindrical. Preferably, the extruded tube may include end walls with increased thickness compared to sidewalls. After extrusion of the tube, the desired surface features, such as the support bands, anti-expulsion portions, tool-engaging portions, and the mesh configuration, may be defined or cut into the implant using a laser techniques well known in the art or any other suitable method. It will be understood that mesh implants created from extruded tube may be formed faster and with less waste than conventional milling of implants from solid blocks. The extruded implant preferably has already formed therein the cavity for receipt of the bone growth material or osteogenic material. After extrusion and laser cutting of the desired surface features, the implant can be machined to prepare implants having the desired size for uses in a variety of ages of patients and bone structures. 
   The present invention contemplates modifications in the porous bone implant as would occur to those skilled in the art. It is also contemplated that processes embodied in the present invention can be altered, rearranged, substituted, deleted, duplicated, combined, or added to other processes as would occur to those skilled in the art without departing from the spirit of the present invention. In addition, the various stages, steps, procedures, techniques, phases, and operations within these processes may be altered, rearranged, substituted, deleted, duplicated, or combined as would occur to those skilled in the art. Further, any theory of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to make the scope of the present invention dependent upon such theory, proof, or finding. 
   While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is considered to be illustrative and not restrictive in character, it is understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.