Comparison of wear of ultra high molecular weight polyethylene acetabular cups against alumina ceramic and chromium nitride coated femoral heads

Three 28-mm diameter Biolox™ Forte alumina ceramic heads and three CrN coated CoCr heads were articulated against UHMWPE GUR 1020 GVF (gamma irradiated in a vacuum foil pack), acetabular cups in the Leeds II hip joint simulator. The CrN heads were coated at Ionbond Limited using arc evaporative physical vapour deposition. The wear of polyethylene against alumina ceramic was 17 mm3/million cycles and against CrN was 23 mm3/million cycles. The difference was not statistically significant. Deliberate scratching of the femoral heads after 5 million cycles did not alter the wear rate. The coated heads had a slightly higher surface roughness and a higher contact angle than the ceramic heads. The contribution of both factors to the wear rate is currently being investigated.