Biotribological study of large diameter ceramic-on-CFR-PEEK hip joint including fluid uptake, wear and frictional heating.

A novel material combination of a large diameter Biolox(®) Delta zirconia-toughened-alumina (ZTA) head and a pitch-based carbon fibre reinforced poly ether-ether-ketone (CFR-PEEK) MOTIS(®) cup has been studied. The acetabular cups were inclined at three angles and tested using Durham Hip Simulators. The different inclination angles used did not have a significant effect on the wear rates (ANOVA, p = 0.646). Averaged over all cups, the wear rates were calculated to be 0.551 ± 0.115 mm(3)/10(6) cycles and 0.493 ± 0.107 mm(3)/10(6) cycles taking into account two types of soak controls; loaded at room temperature and unloaded at 37 °C respectively. Averaged across all femoral heads, the wear rate was 0.243 ± 0.031 mm(3)/10(6) cycles. The temperature change of the lubricant caused by the frictional heat was measured in situ. Friction factors measured using the Durham Friction Simulator were lower for the worn CFR-PEEK cups compared with unworn. This correlated with the decreased surface roughness. Even though relatively high friction was observed in these hemispherical hard-on-soft bearings, the wear rate is encouragingly low.