An evaluation of the tribological performance of zirconia and CoCrMo femoral heads

摘要

Five new zirconia; five new CoCrMo and threeexplanted CoCrMo femoral heads were wear-tested in bovineserum for five million cycles using the Durham Hip Joint WearSimulator. Wear was measured gravimetrically and surfacetopography with a 3D non-contacting profilometer. This allowedan evaluation of the different head types on UHMWPE acetabularcup wear rates and the effect of roughening of the femoral head onacetabular cup wear. The mean acetabular cup wear rate against thefive CoCrMo femoral heads was 40.8 mm3/106 cycles which wassignificantly higher (p=0.03) than against zirconia (33.3 mm3/106cycles).The initial surface roughness of the CoCrMo femoralheads (Ra=4.6 nm) was statistically significantly higher than for thezirconia heads (Ra=3.1nm). Over the wear test the CoCrMo headsgot statistically significantly rougher (Ra=10.5nm) whilst thezirconia heads showed no statistically significant change. The threeexplanted CoCrMo femoral heads had initial mean surfaceroughness, Ra, values of 19,24 and 55 nm with corresponding cupwear rates of 97.6, 131.2 and 148.4 mm3/106 cycles respectively.The very high wear rates against the explanted heads highlight theneed for scratch resistant femoral head surfaces.