Wear simulation of metal on metal hip replacements: an analytical approach

Hip replacement failure is mainly attributable to the implant wear. Consequently preclinical wear evaluations are extremely important. As experimental tests are attractive but highly cost/time demanding, several predictive models have been proposed mainly based on finite element simulations and for metal on plastic (MoP) implants. The aim of this study is to develop a mathematical wear model of metal on metal prostheses, revision of the previous one for MoP implants, developed by the same authors. The model, based on the Archard wear law and on the Hertzian theory, was applied to compare a total (THR) and a resurfacing (RHR) hip replacement under both in vivo and in vitro gait conditions. The results were in agreement with the literature predicting wear rates significantly higher for the RHR than for the THR. The effect of the boundary conditions on wear rates/maps was also investigated and the model limitations discussed.