Wear of ultra-high molecular weight polyethylene and polytetrafluoroethylene in a hip simulator - A dose-response study of protein concentration

Charnley's laboratory wear studies of non-gamma sterilized polyletrafluoroe thylene (PTFE) and polyethylene (PE) found that the PTFE to PE wear-rate ra tio of 250:1 was much higher than the in-vivo wear ratio of 20:1. Tests of PTFE and PE in our laboratory showed a wear ratio of 150:1, using bovine se rum as the lubricant and 190:1 with water as the lubricant. Our hypothesis was that the wear-rates of PTFE and PE cup materials were re lated to the concentration of protein in the serum. We studied the wear beh avior of PTFE and PE cups in varied protein concentrations, using 4 femoral head sizes to validate the clinical range reported by Charnley, The PTFE wear-rates increased with increasing protein concentration and con versely, PE wear-rates decreased with increasing protein concentration. Thi s inverse relationship made it possible to bring the wear ratio closer to t he desired clinical wear ratio. We found that the clinically relevant PTFE/ PE wear ratio corresponded to 3-10 mg/mL of protein in bovine serum.