Synthetic reinforced interbody fusion implants

Abstract

Interbody fusion implants that include a load bearing body composed of a calcium phosphate material hardened around one or more structural reinforcing members are provided. The reinforcing members aid the load bearing body in resisting bending forces and, in certain forms of the invention, aid in preventing expulsion of the implant after implantation. Methods for promoting fusion bone growth in the space between adjacent vertebrae and methods for making the inventive implants are also provided.

What is claimed is:  
     
         1 . An interbody fusion implant, comprising: 
 a biocompatible load bearing body, said body comprised of a synthetic calcium phosphate material hardened around at least one structural reinforcing member for resisting bending forces when implanted, said body sized and configured for engagement between two vertebrae and having a superior surface configured to contact one of said vertebrae, and an inferior surface configured to contact the other of said vertebrae, said structural reinforcing member disposed between said superior surface and said inferior surface and extending along a length of said body.    
     
     
         2 . The interbody fusion implant of  claim 1 , wherein said calcium phosphate ceramic is a calcium phosphate apatite.  
     
     
         3 . The interbody fusion implant of  claim 2 , wherein said calcium phosphate apatite is a low crystallinity apatite.  
     
     
         4 . The interbody fusion implant of  claim 1 , wherein said reinforcement member is comprised of a metal.  
     
     
         5 . The interbody fusion implant of  claim 4 , wherein said metal is titanium.  
     
     
         6 . The interbody fusion implant of  claim 5 , wherein said titanium is a titanium mesh.  
     
     
         7 . The interbody fusion implant of  claim 5 , wherein said metal is selected from the group consisting of titanium, stainless steel, cobalt-chromium, tantalum, mixtures thereof and alloys thereof.  
     
     
         8 . The interbody fusion implant of  claim 1 , wherein said implant has a compressive strength of at least about 40 MPa.  
     
     
         9 . The interbody fusion implant of  claim 1 , wherein said body further comprises a tool engaging end defining a tool engaging hole for receiving a driving tool for implanting the spacer.  
     
     
         10 . The interbody fusion implant of  claim 1 , wherein said body has an outer surface that defines threaded bone-engaging portions.  
     
     
         11 . The interbody fusion implant of  claim 1 , wherein said implant is a dowel.  
     
     
         12 . The interbody fusion implant of  claim 1 , wherein said implant is a wedge.  
     
     
         13 . The interbody fusion implant of  claim 1 , wherein said body further includes a wall connecting said superior surface and said inferior surface.  
     
     
         14 . The interbody fusion implant of  claim 13 , wherein said body is elliptical.  
     
     
         15 . The interbody fusion implant of  claim 1 , wherein said body further defines at least one thru-hole.  
     
     
         16 . The interbody fusion implant of  claim 15 , wherein said body has a longitudinal axis and said thru-hole extends perpendicular to said longitudinal axis.  
     
     
         17 . The interbody fusion implant of  claim 16 , wherein said body further includes an osteogenic material disposed within said thru-hole.  
     
     
         18 . The interbody fusion implant of  claim 17 , wherein said osteogenic material comprises natural bone, demineralized bone, a calcium phosphate material, a bioceramic, bioglass, an osteoinductive factor and mixtures thereof.  
     
     
         19 . The interbody fusion implant of  claim 18 , wherein said osteoinductive factor comprises a bone morphogenetic protein.  
     
     
         20 . The interbody fusion implant of  claim 19 , wherein said bone morphogenetic protein comprises a recombinant protein.  
     
     
         21 . The interbody fusion implant of  claim 20 , wherein said recombinant bone morphogenetic protein comprises a human protein.  
     
     
         22 . The interbody fusion implant of  claim 21 , wherein said recombinant human protein comprises BMP-2, BMP-4, BMP-7, or heterodimers thereof.  
     
     
         23 . The interbody fusion implant of  claim 1 , wherein said reinforcing member extends parallel to said superior and inferior surfaces.  
     
     
         24 . An interbody fusion implant, comprising: 
 a) a biocompatible load bearing body, said body comprised of a hardened synthetic calcium phosphate material, said body sized and configured for engagement between two vertebrae and having a superior surface and an inferior surface; and    b) at least one structural reinforcing member for resisting expulsion after implantation, said structural reinforcing member at least partially embedded in said load bearing body and configured to contact adjacent vertebrae.    
     
     
         25 . An interbody fusion implant, comprising: 
 a load bearing body formed of a hardened synthetic calcium phosphate material, said body containing at least one internal reinforcing member adapted to resist bending or tensile forces along a length of said body, said body sized and configured for engagement between two vertebrae and having a first surface for contacting a first of said vertebrae and a second surface for contacting another of said vertebrae.    
     
     
         26 . A method of promoting fusion bone growth between adjacent vertebrae, comprising: 
 (a) providing an interbody fusion implant comprising: 
 (i) a porous, biocompatible load bearing body, said body composed of a synthetic calcium phosphate material hardened around at least one structural reinforcing member for resisting bending forces when implanted, said body sized and configured for engagement between two vertebrae and having a superior surface configured to contact one of said vertebrae, and an inferior surface configured to contact the other of said vertebrae, said structural reinforcing member disposed between said superior surface and said inferior surface and extending along a length of said body.  
   (b) preparing said adjacent vertebrae to receive the implant in an intervertebral space between adjacent vertebrae; and    (c) placing the implant into the intervertebral space.    
     
     
         27 . The method of  claim 26 , wherein said body defines a thru-hole extending therethrough.  
     
     
         28 . The method of  claim 27 , further comprising filling said thru-hole with an osteogenic material prior to said placing the implant into the intervertebral space.  
     
     
         29 . A method of making an interbody fusion implant, said method comprising: 
 (a) providing a mold having positioned therein a structural reinforcing member;    (b) passing a hardenable synthetic calcium phosphate material into the mold; and    (c) causing said material to harden to form a load bearing interbody fusion implant, said implant sized and configured for engagement between two vertebrae and having a superior surface configured to contact one of said vertebrae, and an inferior surface configured to contact the other of said vertebrae.    
     
     
         30 . The method of  claim 29 , wherein said implant is a dowel.  
     
     
         31 . The method of  claim 29 , wherein said implant is a wedge.