THE POSTERIOR STABILIZED TOTAL KNEE PROSTHESIS - ASSESSMENT OF POLYETHYLENE DAMAGE AND OSTEOLYSIS AFTER A 10-YEAR-MINIMUM FOLLOW-UP

The long-term results of use of the posterior stabilized total knee prosthesis were evaluated with regard to clinical performance, survival of the implant, polyethylene wear, osteolysis, and loosening. One hundred and twenty patients had 165 primary total knee arthroplasties, with insertion of a posterior stabilized total knee prosthesis with a metal-backed tibial component with cement, between March 1981 and March 1983. Thirty-seven patients (fifty-three knees) subsequently died, five patients (six knees) were lost to follow-up, three patients (three knees) refused evaluation, and one patient (two knees) was excluded because of severe medical debilitation. Thus, seventy-four patients (101 knees) were available for analysis. The mean age of the patients at the time of the operation was sixty-four years (range, twenty-two to eighty-one years). The mean duration of follow-up was ten years and eight months (range, ten years to eleven years and ten months). Preoperatively, the mean are of motion was 94 degrees (range, 65 to 130 degrees), compared with 110 degrees (range, 90 to 145 degrees) at the latest follow-up examination. The mean knee score, according to the rating system of The Hospital for Special Surgery, was 51 points (range, 18 to 73 points) preoperatively, compared with 85 points (range, 0 to 100 points) at the latest follow-up examination. When the four knees that had a revision are excluded, the mean knee score, according to the rating system of the Knee Society, was 92 points (range, 67 to 100 points) and the mean functional score was 71 points (range, 0 to 100 points) at the latest follow-up examination. Over-all, seventy-four knees had an excellent result; twenty-three, a good result; and four, a poor result. There were no revisions because of polyethylene wear or osteolysis, and no conclusive evidence of either phenomenon was noted at the clinical or radiographic follow-up examination. No tibial component was loose clinically or radiographically. Minor radiolucent lines were noted in eleven knees (11 per cent), compared with ninety-five (49 per cent) of the 194 knees in a previous study of the same type of prosthesis that had an all-polyethylene instead of a metal-backed tibial component.