Reinforced molded implant formed of cortical bone

Abstract

This invention relates to arthodesis for stabilizing the spine. More specifically, the present invention is directed to an intervertebral spacer formed of a bone material and to methods of treating patients having spinal deformities. The invention provides a spinal implant assembly comprising bone-derived components. The bone-derived components can be formed into modular units that can be assembled to provide a wide variety of implant configurations. In addition, the bone-derived components can form scaffold that can withstand the shear and impact forces necessary to insert the assembled implant into a disc space between adjacent vertebrae. In preferred forms the implants define an open spacer that serves as a depot for receipt of an osteoconductive material. The ostoegenic material is preferably a moldable filler that can form a molded reinforced implant.

1 .- 44 . (canceled) 
     
     
         45 . An implant for promoting bone fusion between adjacent vertebral bodies, comprising:
 an assembly of cortical bone-derived components extending along a longitudinal axis, said cortical bone-derived components including:
 a first strut having a first bone-engaging portion and an opposite second bone-engaging portion; 
 a second strut laterally spaced from said first strut and defining an interior space therebetween, said second strut having a third bone-engaging portion and an opposite fourth bone-engaging portion; and 
 at least one cross member positioned within said interior space and interconnected with said first strut and said second strut; and 
   an osteogenic material positioned within said interior space between said first and second struts.   
     
     
         46 . The implant of  claim 45  wherein said first strut includes a first end defining a first impact surface extending along a plane substantially orthogonal to said longitudinal axis, and a second end opposite said first end and defining a first curved end surface to facilitate impaction between the adjacent vertebral bodies; and
 wherein said second strut includes a third end defining a second impact surface extending along a plane substantially orthogonal to said longitudinal axis, and a fourth end opposite said third end and defining a second curved end surface to facilitate impaction between the adjacent vertebral bodies.   
     
     
         47 . The implant of  claim 46  wherein each of said first and second impact surfaces includes a tool engaging aperture. 
     
     
         48 . The implant of  claim 45  wherein said first, second, third and fourth bone-engaging portions each include anti-expulsion structures. 
     
     
         49 . The implant of  claim 48  wherein said anti-expulsion structures comprise a plurality of notches spaced axially along each of said first, second, third and fourth bone engaging portions. 
     
     
         50 . The implant of  claim 48  wherein said anti-expulsion structures comprise pointed edges extending axially along each of said first, second, third and fourth bone engaging portions. 
     
     
         51 . The implant of  claim 50  wherein said anti-expulsion structures further comprise a plurality of notches spaced axially along each of said pointed edges. 
     
     
         52 . The implant of  claim 45  wherein said first and second struts each have a first end portion and an opposite second end portion spaced apart along said longitudinal axis, said first end portions of said struts each having a first height D 1  transverse to said longitudinal axis, said second end portions of said struts each having a second height D 2  transverse to said longitudinal axis, and wherein said first height D 1  is greater than said second height D 2 . 
     
     
         53 . The implant of  claim 45  wherein said first strut has a first end portion and an opposite second end portion spaced apart along said longitudinal axis, said first strut defining a substantially uniform first height D 1  transverse to said longitudinal axis between said first and second end portions, wherein said second strut has a third end portion and an opposite fourth end portion spaced apart along said longitudinal axis, said second strut defining a substantially uniform second height D 2  transverse to said longitudinal axis between said third and fourth end portions, and wherein said first height D 1  is greater than said second height D 2 . 
     
     
         54 . The implant of  claim 45  further comprising at least one additional cross member positioned within said interior space and interconnected with said first strut and said second strut. 
     
     
         55 . The implant of  claim 45  wherein said cross member comprises a cylindrical shaft extending from said first strut to said second strut. 
     
     
         56 . The implant of  claim 45  wherein said first strut comprises a substantially planar first wall portion and said second strut comprises a substantially planar second wall portion positioned to lie substantially parallel to said first wall portion, and wherein said cross member comprises a substantially planar member extending from said first strut to said second strut. 
     
     
         57 . The implant of  claim 45  wherein said first strut defines a first curved wall portion having a concave first surface and an opposite convex second surface, wherein said second strut defines a second curved wall portion having a concave third surface and an opposite convex fourth surface, and wherein said concave first surface of said first strut opposes said concave third surface of said second strut and defines said interior space therebetween. 
     
     
         58 . The implant of  claim 45  wherein said first strut includes a first channel formed therein and extending substantially parallel to said longitudinal axis, said second strut including a second channel formed therein and extending substantially parallel to said longitudinal axis, said cross member including opposite end portions defining first and second tongue portions, said first and second tongue portions engaged within respective ones of said first and second channels to interconnect said first and second struts. 
     
     
         59 . The implant of  claim 58  wherein said first and second channels and said first and second tongue portions each have a dovetail configuration. 
     
     
         60 . The implant of  claim 45  wherein said first and second struts each include an aperture and said cross member includes opposite end portions positioned within said apertures in said first and second struts. 
     
     
         61 . The implant of  claim 60  wherein said apertures each include an internally threaded portion and said opposite end portions of said cross member each define external threads that are threadedly engaged with respective ones of said internally threaded portions of said apertures in said first and second struts. 
     
     
         62 . The implant of  claim 60  wherein said first and second struts each include an inner surface and an opposite outer surface with said aperture extending from said inner surface to said outer surface, wherein a portion of said opposite end portions of said cross member extends beyond said outer surface of each of said first and second struts, and wherein a retaining element is engaged with said opposite end portions of said cross member to inhibit withdrawal of said cross member from said apertures in said first and second struts. 
     
     
         63 . The implant of  claim 45  further comprising:
 a first of said assembly of cortical bone-derived components;   a second of said assembly of cortical bone-derived components, said first and second assemblies positioned bilaterally relative to one another with said longitudinal axis of said first assembly substantially parallel with said longitudinal axis of said second assembly; and   an interior region defined between an inner strut of said first assembly and an inner strut of said second assembly.   
     
     
         64 . The implant of  claim 63  further comprising an osteogenic filler material positioned within said interior region between said first and second assemblies. 
     
     
         65 . The implant of  claim 63  wherein said inner struts of said first and second assemblies each define a substantially uniform first height D 1 , wherein outer struts of said first and second assemblies each define a substantially uniform second height D 2 , and wherein said first height D 1  is greater than said second height D 2 . 
     
     
         66 . The implant of  claim 45  wherein said assembly of cortical bone-derived components further comprises:
 a third strut laterally spaced from said second strut and defining another of said interior space therebetween; and   a cross member segment positioned within said another of said interior space and interconnected with said second strut and said third strut; and   said osteogenic material positioned within said another of said interior space between said second and third struts.   
     
     
         67 . The implant of  claim 66  wherein said first, second and third struts each have a first end portion and an opposite second end portion spaced apart along said longitudinal axis, said first end portions of said struts each having a first height D 1  transverse to said longitudinal axis, said second end portions of said struts each having a second height D 2  transverse to said longitudinal axis, and wherein said first height D 1  is greater than said second height D 2 . 
     
     
         68 . The implant of  claim 66  wherein said first and third struts each have opposite end portions spaced apart along said longitudinal axis, said first and third struts each defining a substantially uniform first height D 1  transverse to said longitudinal axis between said opposite end portions, wherein said second strut has opposite end portions spaced apart along said longitudinal axis, said second strut defining a substantially uniform second height D 2  transverse to said longitudinal axis between said opposite end portions, and wherein said second height D 2  is greater than said first height D 1 . 
     
     
         69 . An implant for promoting bone fusion between adjacent vertebral bodies, comprising:
 an assembly of cortical bone-derived components including:
 a first strut having a first bone-engaging surface and an opposite second bone-engaging surface, said first strut having a first slot formed therein extending from said first bone-engaging surface toward said second bone-engaging surface; and 
 a second strut having a third bone-engaging surface and an opposite fourth bone-engaging surface, said second strut having a second slot formed therein extending from said fourth bone-engaging surface toward said third bone-engaging surface; and 
 wherein a portion of said first strut is positioned within said second slot of said second strut and a portion of said second strut is positioned within said first slot of said first strut to interengage said first and second struts and with said first strut arranged substantially orthogonal to said second strut; and 
   an osteogenic material positioned within spaces between said first and second struts.