Unicompartmental knee arthroplasty. Sequential radiographic and scintigraphic imaging with an average five-year follow-up.

Clinical, radiographic, and scintigraphic results of 33 consecutive unicompartmental knee arthroplasties were reviewed after a mean follow-up period of 68 months (range, 24 to 112 months). Clinical grades employing criteria established by the Hospital for Special Surgery showed 74% good to excellent and 11% fair to poor results. Four knees (15%) required revision to a total knee arthroplasty after an average postoperative interval of 7.4 years. Within the subset of surviving medial compartment arthroplasties (23 knees), superior clinical results were associated with a central or slightly medialized mechanical axis (p < 0.05). Periprosthetic radiolucency showed no correlation with clinical scores or failures resulting in revision surgery. There was no radiographic evidence of progressive arthrosis within the unreplaced compartments. Comparative analysis of preoperative and annual postoperative technetium bone scans showed no temporally related changes indicative of impending prosthetic failure or disease progression within the unoperated compartments. The surgically treated compartments maintained uniformly intense femorotibial activity, whereas the unoperated compartments, including the patellofemoral joint, remained scintigraphically quiescent. Disease progression in unreplaced compartments is unusual after contemporary unicompartmental knee arthroplasty. Most failures and poor results arise from mechanical inadequacies amendable to surgical technique and/or future design considerations.