METALLOSIS AFTER TOTAL KNEE ARTHROPLASTY USING AGC-S TYPE PROSTHESIS

Abstract

Between 1989 and 1993, 158 patients with a total of 187 damaged knees underwent TKA using AGC-S prosthesis (Biomet). Of these patients, six required revision surgeries due to metallosis. The average period from the first operation to the revision was 68.0 months (range: 41–97 months). In all six cases, the plain X-rays taken immediately before reoperation, showed sinking of the tibial component. The withdrawn implants showed severe abrasion of the polyethylene used in the posteromedial area. The percent share of the tibial component averaged 90.3% (range: 85.3–93.5%) on the anteroposterior view, and on the lateral view averaged 83.1% (range:76.9–94.0%). The tibial components used for AGC-S type TKA can be characterized by the presence of a rim. In some cases, however, the rim cannot be placed on the tibial cortex, and this obliges the surgeon to select smaller components, resulting in a smaller percent share of the tibial component. The tibial component can sink in such cases. The sinking of the tibial component probably leads to malalignment and joint instability. Furthermore the insert with a flat surface was likely to induce articular instability, thus enhancing the abrasion of the polyeth