Long-term outcomes and duration of outdoor ambulation following primary total knee arthroplasty in patients with rheumatoid arthritis.

Abstract

The medical treatment of rheumatoid arthritis (RA) has made remarkable progress with the introduction of methotrexate and biological agents. However, there have been few reports of long-term results of total knee arthroplasty (TKA) for RA since the introduction of these drugs. Ambulation is an important form of exercise for maintaining health. We investigated the long-term outcomes and the ability to walk outdoors following TKA in patients with RA. We retrospectively reviewed 142 patients with RA (201 knees) who had undergone primary TKA. The mean follow-up was 10.6 years. Markers of RA disease activity all improved significantly postoperatively. Mean Japanese Orthopedic Association scores improved from 49.3 points before surgery to 81.8 at follow-up. The mean maximum flexion angle improved from 107.8° to 112.9°. The causes of TKA revision comprised 2 mechanical loosening, 1 late infection, and 1 fracture of the femoral condyle. The survival rate of TKA was 96.6% at 15 years. Fifty-five patients were not able to walk outdoors. The rate of inability to ambulate outdoors was 38.3 per 1000 person-years. The survival rate of ability to ambulate outdoors were 48.8% at 15 years. Preoperative advanced age, low body weight, steroid use and non-use of biologics were identified as risk factors for inability to ambulate outdoors. Although the cumulative survival rate of TKA implants was as good as 96.6% in 15 years, the cumulative rate of ability to ambulate outdoors was only 48.8%. The reason for the inability to walk outdoors was thought to be mainly due to deterioration of RA, comorbidity or muscular weakness associated with aging, rather than knee dysfunction.