Patent ID: 8366780

Claim:
An implant for providing a replacement articulating surface for a head of one bone member of an orthopedic joint, which implant comprises: a pyrocarbon shell having an outer convex surface which is a section of a sphere that will serve as an articulating surface, a concave domed interior surface and an open proximal base that is formed to terminate at an inward-extending rim, a metal substructure having a convex distal surface and means at a proximal end thereof for securing the implant in a cavity formed at an end of the bone member, an intermediate element of flexible polymeric material which has a radially outer surface near a base thereof, which radially outer surface is of greater diameter than an interior diameter of said inward-extending rim, and which is sufficiently flexible to allow insertion of said intermediate element axially into said open proximal base of said pyrocarbon shell to create a fit where there is nonadhesive physical interference between said intermediate element radially outer surface and said inward-extending rim at the base of said pyrocarbon shell that prevents withdrawal of said intermediate element from said pyrocarbon shell, creating a subassembly of said shell and said intermediate element, said intermediate element having a cylindrical interior surface section and said metal substructure having a cylindrical surface section, and said metal substructure and said intermediate element being mated with each other so that said cylindrical surfaces juxtapose, and interengaging means at a specific location along said juxtaposed cylindrical surfaces which allows said metal substructure to be inserted fully into said subassembly but physically prevents subsequent disassembly by withdrawal of said metal substructure therefrom, whereby forces at said joint are transferred compressively through said pyrocarbon shell to said convex distal surface of said metal substructure when the implant is in place at said joint.