A strut graft substitute consisting of a metal core and a polymer surface

Abstract

In revision hip replacement surgery cortical strut grafts made of allograft bone are used to augment femoral bone stock and to fix periprosthetic femoral fractures. These struts are made from femoral bone as hemicylinders and are fixed to host bone with cerclage wires. We developed an artificial bone substitute for such strut grafts in order to overcome availability restrictions and potential infectious hazards with allograft bone. The partially biodegradable implant consists of a functionallygraded combination of titanium, polylactide, hydroxyapatite, and calcium carbonate. It is made by manual dip-coating of the metal (after chemical surface treatment) into solutions of polylactide with suspended calcium salts. In this way the titanium core is surrounded by an inner layer of slowly biodegradable poly(L-lactide) with calcium carbonate. The part of the implant that is in contact with the bone consists of rapidly biodegradable poly(D,L-lactide), hydroxyapatite and calcium carbonate. This method leads to an implant which is easily adaptable before the implantation to the geometry of the patient’s bone when moderately heated (70 °C), but has a sufficient mechanical strength to serve as support under physiologic temperatures. The implant is mechanically stable, biocompatible, partially biodegradable, and provides a scaffold for growing bone.