Polymeric-hydroxyapatite bone composite

Abstract

A method for the fabrication of three-dimensional macroporous polymer matrices for use as bone graft or implant material was developed. The composites are formed from a mixture of biodegradable, biocompatible polymer and hydroxyapatite (HA), a particulate calcium phosphate ceramic. The method leaves irregular pores in the composite between 100 and 250 microns in size. In a preferred embodiment, implants are composed of a 50:50 poly(lactide-co-glycolide) (PLGA) polymer and reinforced by hydroxyapatite. Mechanical and histological analysis showed the matrix fabricated by this method to be structurally and mechanically similar to cancellous bone. Prior to degradation, pure polymer specimens exhibited an elastic modulus of 293 MPa and specimens which were 50% HA by weight exhibited a modulus of 1459 MPa. After six weeks of degradation under physiological conditions, the reinforcing effect of ceramic loading had diminished. Modulus of polymer matrices at all HA load levels had decreased sharply to approximately 10 MPa. Mean macro- and micropore diameters of the polymer specimens were 100 .mu.m and 20 .mu.m respectively and remained constant throughout degradation.

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