Survival analysis and predictors of failure in unicompartmental knee replacement using a PCA prosthesis

We evaluated 109 unicompartmental Porous Coated Anatomic arthroplasties after a mean follow up of 2.7 (range 0.25–5.9) years. In 91 medial arthroplasties the mean preoperative tibiofemoral varus angle of 1.3° (±4.2°) was corrected to 6° valgus (P < 0.001). Correspondingly, in 18 lateral arthroplasties, 16.2° (±4.8°) valgus was realigned to 7.7° valgus (P < 0.001) after operation. There were indications for revision in 27 cases. Conversion to total arthroplasty has been performed in 16 knees, and in four knees tibial and/or femoral components have been exchanged. The main reason for revision was polyethylene wear which had resulted in increasing varus or valgus deformity. According to statistical analysis, clinical findings at follow up (first step pain and contracompartmental pain) and lateral knee replacement predicted the risk of revision. Estimated cumulative survival at 3.7 years was 77% for the medial, and 45% for the lateral replacements, respectively (P = 0.3159).