Mechanical Properties and Tribological Behaviour of Retrieved UHMWPE Tibial Insert in Total Knee Replacement after Implantation 30 Months

Ultra high molecular weight polyethylene (UHMWPE) has been used as a load bearing and articulating counter face in total knee replacement (TKR) for over forty years1. However, wear debris generation of UHMWPE materials after their implantation in the human body has been proven to induce osteolysis and aseptic loosening, which is the main cause of long-term failure of TKR composed of UHMWPE and hard patella balls2-4. The relationships between the mechanical behaviour of UHMWPE and the long-term clinical performance of TKR component bearings remain poorly understood; therefore the reliable prediction of the wear performance of UHMWPE in human body has been a challenge for artificial joint materials study5. After implantation, the UHMWPE material will bear the multi-directional sliding friction and dynamic load in body fluid immersion; this is a black box of biotribology of joint implants in physiological environments which results in the reduction of the wear resistance of UHMWPE liners associated with mechanical failure6-8 and chemical degradation9-11. For this reason, previous studies focused their attention on the degradation mechanism of UHMWPE12-14, accelerated aging for degradation simulation15-19, the correlation between the mechanical behaviour of polymeric biomaterials and their wear performance in a knee simulator20-24.