Total knee arthroplasty in patients with ankylosing spondylitis.

BACKGROUND: Ankylosing spondylitis is a seronegative spondyloarthropathy that primarily affects the sacroiliac joints, spine, hips, and, less commonly, the knee joints. The purpose of this study was to evaluate the results in a consecutive group of patients with ankylosing spondylitis who underwent total knee arthroplasty.
METHODS: The results of thirty total knee arthroplasties in twenty patients with ankylosing spondylitis were reviewed. There were seventeen men and three women, with an average age of fifty-five years (range, twenty-eight to sixty-seven years) at the time of the arthroplasty. The diagnosis of ankylosing spondylitis was established preoperatively with use of the New York criteria. All patients received a cemented condylar-type implant. The average duration of follow-up was 11.2 years (range, three to sixteen years).
RESULTS: The average Knee Society pain score improved from 14 points preoperatively to 76.3 points at the time of the latest follow-up. The improvement in the average Knee Society function score was less impressive, with an increase from 16.3 points preoperatively to 58.7 points at the time of the latest follow-up. The average arc of motion was 84.8 degrees prior to the arthroplasty and 86.7 degrees at the time of the final follow-up. Six knees (20%) had heterotopic bone formation. Three knees required manipulation under anesthesia because of poor motion postoperatively. There was one revision, due to loosening of a patellar component. All other components were radiographically stable at the time of the latest follow-up.
CONCLUSIONS: Total knee arthroplasty with cement in patients with ankylosing spondylitis provided excellent pain relief and durable fixation at an average of 11.2 years postoperatively. However, patients with ankylosing spondylitis are at increased risk for the development of stiffness and heterotopic bone formation.