Polyethylene exchange only for prosthetic knee instability.

From 1987 to 1996, 47 revision total knee arthroplasties were done for tibiofemoral instability. Sixteen of these patients had polyethylene exchange only to treat their instability. Fourteen of these patients were available for review. The mean followup was 56 months. The mean Hospital for Special Surgery Knee Score increased from 50 points preoperatively to 73 points at the most recent followup. Clinically, stable knees were produced in 71% of patients (10 of 14). The results of the current study suggest that polyethylene exchange can be an effective, low morbidity procedure to treat certain types of prosthetic knee instability. A failure rate of 29% (four of 14) however, is concerning. Alternative methods of stabilization should be used, if there is any question concerning the stability of a construct where a polyethylene exchange only is used.