One of the areas of research for reducing the generation of wear debris from total joint replacements is the utilization of cobalt alloys that meet ASTM F 1537 for the production of metal on metal bearing pairs. The standard currently allows carbon contents to range between 0% and 0.35%. Some research on metal-on-metal hip bearings indicates that alloys with carbon content at the upper end of this range will yield bearing pairs with superior resistance to wear. The purpose of this study was to compare the wear resistance of components manufactured from high carbon (0.24%) and low carbon (0.06%) alloys when tested in a hip simulator.
Wear of the metal cups was measured by a gravimetric (weight loss) technique every 500 000 cycles to a total of 5 000 000 cycles. Wear of the metal heads was evaluated approximately every 1 500 000 cycles, to 5 000 000 cycles. Results of the study show a small difference in wear between the two alloys. After the initial wear-in period, the samples with the higher carbon content exhibited a significantly lower wear rate than those with the lower carbon content.