Alumina-on-alumina hip implants: A wear study of retrieved components.

Alumina-alumina bearings are among the most resistant to wear in total hip replacement. Examination of their surfaces is one way of comparing damage caused by wear of hip joints simulated in vitro to that seen in explanted bearings. The aim of this study was to determine whether second-generation ceramic bearings exhibited a better pattern of wear than those reported in the literature for first-generation bearings. We considered both macro- and microscopic findings. We found that long-term alumina wear in association with a loose acetabular component could be categorised into three groups. Of 20 specimens, four had 'low wear', eight 'crescent wear' and eight 'severe wear', which was characterised by a change in the physical shape of the bearing and a loss of volume. This suggests that the wear in alumina-alumina bearings in association with a loose acetabular component may be variable in pattern, and may explain, in part, why the wear of a ceramic head in vivo may be greater than that seen after in vitro testing.