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

This study was performed to investigate the performance changing of an ultra high molecular weight polyethylene (UHMWPE) tibial insert, which was removed from a 56 years old male patient after 30 months of service. The tibial insert was investigated by using a contact angle goniometer, UMT-2 friction tester and MicroXAM three-dimensional profilometer to characterize the wettability, ball indentation hardness, creep resistance, friction and wear performance. Scanning electron microscopy (SEM) was employed to describe the morphology of the sample surface of unused and retrieved UHMWPE after friction and wear test. Surface differential scanning calorimetry (DSC) was used to calculate the surface crystallinity of UHMWPE. The results showed that the contact angle of retrieved UHMWPE with bovine calf serum was obviously decreased by about 15% compared with unused UHMWPE. The surface crystallinity of retrieved UHMWPE increased 9.6% compared with unused UHMWPE. All of these induced the ball indentation hardness and creep resistance decreased 18% and 31%, the wear loss of retrieved UHMWPE increased 24% compared with unused UHMWPE.