Ultra high molecular weight polyethylene (UHMWPE) metal backed acetabular cups were articulated against Cr-Co-Mo alloy, ion implanted Cr-Co-Mo and zirconiaceramic femoral heads in a five station hip joint simulator, running three tests of three millions walking cycles with each one of the five different head-cup combinations. The wear rate of the acetabular cups was measured gravimetrically. When the thickness of the cup was 10.9 mm, the mean wear rate against 28 mm diameter Cr-Co-Mo femoral heads was 0.14 mm/year, and 0.09 mm/year ''when the cup was articulated against 28 mm ion implanted Cr-Co-Mo femoral heads. When the thickness of the cup was 7 mm the mean wear rate was 0.04 mm/year against 28 mm zirconia heads. The results indicate that significant reduction in the wear of the UHMWPE cup can be achieved when zirconia femoral head is used and that the diameter of the zirconia femoral head, 28 vs 32 mm, seems unimportant as wear factor. A cup thickness below 10 mm may result disadvantageous.

Ultra high molecular weight polyethylene (UHMWPE) metal backed acetabular cups were articulated against Cr-Co-Mo alloy, ion implanted Cr-Co-Mo and zirconiaceramic femoral heads in a five station hip joint simulator, running three tests of three millions walking cycles with each one of the five different head-cup combinations. The wear rate of the acetabular cups was measured gravimetrically. When the thickness of the cup was 10.9 mm, the mean wear rate against 28 mm diameter Cr-Co-Mo femoral heads was 0.14 mm/year, and 0.09 mm/year ''when the cup was articulated against 28 mm ion implanted Cr-Co-Mo femoral heads. When the thickness of the cup was 7 mm the mean wear rate was 0.04 mm/year against 28 mm zirconia heads. The results indicate that significant reduction in the wear of the UHMWPE cup can be achieved when zirconia femoral head is used and that the diameter of the zirconia femoral head, 28 vs 32 mm, seems unimportant as wear factor. A cup thickness below 10 mm may result disadvantageous.