Incidence of radiographic unicompartmental arthritis in patients undergoing knee arthroplasty

Unicompartmental knee arthroplasty is increasing in popularity with the advent of less invasive procedures for knee arthritis. The percentage of patients undergoing knee arthroplasty who could be candidates for unicompartmental knee arthroplasty depends on the surgeon's evaluation of the radiographs, and this evaluation may depend on the surgeon's bias regarding partial knee arthroplasty. A retrospective radiographic and chart review was performed on a consecutive series of patients who had undergone tricompartmental knee arthroplasty to determine the percentage of those patients who could have been candidates for unicompartmental knee arthroplasty. Two hundred eighty-eight patients who underwent 308 tricompartmental knee arthroplasties over a 3-year period at a Veteran's Administration Hospital comprised the study group. Assessment of preoperative radiographs was done by 2 surgeons, 1 who favored unicompartmental knee arthroplasty and the other who preferred tricompartmental knee arthroplasty, to determine the percentage of these patients, from each surgeon's viewpoint, who had unicompartmental arthritis. Patients who had radiographic unicompartmental arthritis were then eliminated as candidates for unicompartmental knee arthroplasty, if, on chart review, they had a flexion contracture >10°, an arc of motion <100°, or inflammatory arthritis. The surgeon who was a proponent of unicompartmental knee arthroplasty found that 26% of these patients had acceptable radiologic and clinical indications for unicompartmental knee arthroplasty, whereas the surgeon who had a bias against the procedure felt that only 12% of these patients were unicompartmental knee arthroplasty candidates. A considerable percentage of Veteran's Administration patients undergoing arthroplasty for knee arthritis may be potential candidates for unicompartmental knee arthroplasty, despite the surgeon's bias for or against the procedure.