An investigation into the fixation of hip replacements

This paper describes an experimental study of hip prosthesis stems fixed with bone cement in model femora and subjected to cyclic loading. Loosening of the stems did not occur due to fatigue of the bone cement, even when reduction of medial support from the calcar had been simulated. Measurement of stresses in the cement layer and comparison with published properties of bone cement indicated that fatigue failure was not likely under the experimental conditions. Fatigue failure of cement could not be solely regarded as initiating loosening. It is concluded that the results uphold theories that biological factors must also contribute to the initiation of loosening, rather than being a response to mechanical failure.