Abstract
The wear phenomenon of ultra-high molecular weight polyethylene (UHMWPE) in the knee and hip prostheses is one of the major restriction factors on the longevity of these implants. Especially in retrieved knee prostheses with screw holes in the tibial tray, the cold flow into the screw holes is frequently observed on the undersurface of the UHMWPE tibial components. In most retrieved cases, the protruded areas of cold flow on the undersurface were located at the reverse side of the severely worn surface of the UHMWPE tibial component. It appears that the cold flow into screw holes contributes to increase of wear of the UHMWPE tibial components. In this study, knee joint simulator tests were performed to investigate the influence of the cold flow into screw holes on the wear of UHMWPE. Significant cold flow into screw hole was identified in the undersurface of the UHMWPE specimen, and was associated with delamination in the contact area on the opposite side of the specimen.
