Wear of composite ceramics in mixed‐material combinations in total hip replacement under adverse edge loading conditions

Ceramic composites have performed very well under adverse edge loading conditions when used in like‐on‐like configurations, where the femoral head and acetabular cup are of the same material. The aim of this study was to determine the wear of pure alumina (Al 2 O 3 ), alumina toughened zirconia (ATZ) and zirconia toughened alumina (ZTA) when used in mixed bearing combinations, under edge loading conditions due to translational mal‐positioning. The head‐on‐cup configurations of three ceramic materials were ATZ‐on‐ZTA, ZTA‐on‐ATZ, Al 2 O 3 ‐on‐ATZ, ATZ‐on‐Al 2 O 3 , Al 2 O 3 ‐on‐ZTA, and ZTA‐on‐Al 2 O 3 . They were tested on the Leeds II hip simulator under microseparation conditions. The bedding in and steady state wear rates of ATZ‐on‐ZTA were 1.16mm 3 /million cycles and 0.18mm 3 /million, respectively, and for ATZ‐on‐Al 2 O 3 were 0.66 mm 3 /million cycles and 0.20 mm 3 /million, respectively. The wear rates of the other bearing combinations under these adverse microseparation conditions, Al 2 O 3 ‐on‐ATZ, Al 2 O 3 ‐on‐ZTA, ZTA‐on‐ATZ and ZTA‐on‐Al 2 O 3 were very low with no clear bedding in and steady state phases, and with steady state wear rates lower than 0.11 mm 3 /million. The mixed material combinations tested in this study have shown slightly higher wear rates when compared to ATZ in like‐on‐like configuration reported previously, but superior wear resistance when compared to alumina‐on‐alumina bearings tested previously under the same adverse microseparation conditions.