M´ ecanisme multiphysique de d´ egradation des zircones orthop´ ediques : couplage entre vieillissement hydrothermal et frottement en simulateur de hanche Multi-physics degradation mechanisms of orthoaedic zirconia: Coupling hydrothermal ageing and wear on a hip simulator

The degradation of zirconia-based ceramic components for total hip arthroplasty (head and cup) has been the topic of many works. However, the correlation between what is measured in vivo and what is expected from in vitro simulations on hip simulators may be sometimes feeble, especially where zirconia component are concerned, mainly due to a lack of representativeness of in-vitro experiments. We seek here to explore the combined effects of hydrothermal ageing and wear on zirconia components. We will show that hydrothermal ageing increases the roughness of zirconia components, which in turns might increase the wear rate of the polyethylene counterparts. Moreover, the friction during hip simulation increases the ageing rate of the zirconia components. This auto-accelerating degradation may explain some of the poor long-term in-vivo results of zirconia hip prostheses reported in the literature. Finally, we will show that zirconia-toughened alumina components may be free from this combined degradation.