Wear of ultra-high-molecular-weight polyethylene components of 90 retrieved knee prostheses

Wear of the ultra-high-molecular-weight polyethylene (UHMWPE) components in total knee arthroplasties is a potential long-term problem. Ninety total knees of various designs with implant times up to 10 years were retrieved. The wear noted in the majority of components was much greater than that noted in wear studies of acetabular components in total hip prostheses. Abrasion from cement or bone and delamination wear were particularly pronounced in the knee. Delamination, consisting of complete breakup of material in flakes and particles, appeared to be initiated by intergranular material defects and propagated by the excessive subsurface stresses beneath the contact zone. Material that was free of defects did not show delamination wear even after long time periods in a highly stressed, low-conformity design. Wear particles of UHMWPE can result in adverse tissue reaction with cellulitis, giant cell reaction, and necrotic tissue, and these effects could be cumulative with time. There is some evidence that particles can lead to bone resorption, including at the implant-bone interface, which could accelerate loosening. There is cause for concern as to the long-term effects of UHMWPE in total knee arthroplasty. This suggests the need for improved processing methods or more wear-resistant materials.