Polyethylene failure of metal-backed patellar components. 111 AGC total knees followed for 7-22 months.

In a series of 111 AGC total knee arthroplasties, eight failures of the polyethylene part of the metal-backed patellar component were seen after a period of 7-22 months. All of these patients experienced a characteristic grating sound as the knee was bent, and skyline radiographs revealed direct metal-on-metal contact. At revision, fracture and separation of the polyethylene part were found together with an extensive, black, thickened synovium and abrasive wear of the naked metal backing of the patellar component. The cemented metal backings were all solidly anchored in the patella. Based on this high failure rate, we have abandoned the metal-backed patellar component in favor of an all-polyethylene component.