Orientation and Wear of the Acetaular Component In Third Generation Alumina-on-alumina Ceramic Bearings

Lusty PJ, Watson A, Tuke MA, Walter WL, Walter WK, Zicat B.
Joint Surg (Br) 2007; 8-B: 1158-64

Alumina-on alumina bearings are highly resistant to wear, however laboratory simulation of wear is not thought to reproduce wear in vivo. This paper attempted to quantify in vivo wear and its relation to acetabular component orientation in third generation ceramic.

Forty one ceramic bearings were retrieved during the study period of which 33 femoral heads and 28 liners were analysed. The mean time in situ was 26.8 months. Wear was assessed on femoral heads and liners were available. The anteversion of acetabular components was measured from anteroposterior radiographs, inclination was also measured, these radiological values were then converted to operative measurements.

Median wear rate was 0.1mm3/yr for the 33 heads and 0.04mm3/yr for the 28 liners. There was no relation between time in situ and rate of wear or for size of bearing and rate of wear. There was no relationship between inclinatio and acetabular component wear. Rate of wear and anteversion were correlated with a higher rate of wear with lower acetabular anteversion. The majority of high rates of wear were in patients with >15º anteversion.

A review of their patients showed that good outcome had an acetabular inclination of 45º (+/-10º) and an anteversion of 25º (+/-10º ). They consider the rate of wear under severe conditions of edge loading to be low when compared with metal-on-polyethylene bearings and note that in vitro tests have shown ceramic particles to be less destructive than polyethylene particles.