UNICOMPARTMENTAL KNEE ARTHROPLASTY IN MIDDLE-AGED PATIENTS - A 2 TO 6-YEAR FOLLOW-UP EVALUATION

Twenty-eight unicompartmental knee arthroplasties performed as an alte rnative to high tibial osteotomy or tricompartmental knee arthroplasty in patients under 60 years of age were reviewed after 2 to 6 years of follow-up. The patient's age at the time of operation averaged 52 yea rs. Using the Knee Society Score, 90% were rated good or excellent res ults in terms of function and pain relief. The average flexion angle o btained was 124 degrees, and the average postoperative alignment-was 4 degrees of anatomic valgus for varus deformities and 8 degrees for va lgus deformities. The average activity level according to the Tegner a nd Lysholm score slightly improved (preoperative, 2.3; follow-up, 2.7 points). Of the 28 knees, 9 (32%) presented radiolucent lines about th e tibial component and two had incomplete radiolucent lines at the bon e-cement interface on the femoral side. There was no correlation betwe en activity level and tibial radiolucent lines. Two revisions were per formed because of loosening of the femoral component at the prosthesis -cement interface. One was converted to another unicompartmental arthr oplasty and the other to a tricompartmental arthroplasty. One tibial c omponent exhibited an asymptomatic slowly progressive radiolucency. Un icompartmental knee arthroplasty in middle-aged patients yields 2- to 6-year results competitive with osteotomy but inferior to tricompartme ntal arthroplasty in terms of revision. The specific prosthetic design used in this series appeared to be vulnerable to femoral component lo osening possibly because of constrained tibial topography and smooth t apered femoral fixation lugs.