LONG-TERM COMPRESSIVE CREEP DEFORMATION AND DAMAGE IN ACRYLIC BONE CEMENTS

Compressive creep tests were performed on five commercially available acrylic bone cements under conditions simulating in vivo usage. All five cements were two-component systems, intended for mixing at the time of implantation, and consisted primarily of a poly(methyl methacrylate) polymer powder and a methyl methacrylate monomer liquid. Measured creep strains are quite large, generally exceeding elastic strains. Large variations in creep response were noted among the various cements, with a carbon-reinforced cement by far the most resistant to creep. The empirical model epsilon equals alpha exp(b sigma )t**n was found to predict creep strains within about 10% of the measured values. Microscopic examination of some specimens after testing revealed significant cracking, resulting from long-term loading, that could be a contributing cause of time-dependent failure.