Ceramics mostly used in orthopaedics are alumina (Al²O³) and zirconia (ZrO²), the rate of fracture bioceramics hip prostheses being around 0.01% [1]. Some in vivo fractures have been reported and some of them have occurred in overweight patients [2]. One may suggest that prostheses may fail because of important repeated mechanical shocks. Moreover, the microseparation between the head and cup that may occur in vivo [3,4] seems to be another key parameter influencing the lifetime of the prostheses. Only few walking hip simulators have been modified to take into account this phenomenon and it has been shown that microseparation increases the wear and creates the so-called wear bands that have been observed in vivo on ceramic heads [5,6]. The main goal of this work was to use a specially designed shock machine to test bioceramics heads and cups under microseparation.