OSTEONECROSIS IN THE RHEUMATOID FEMORAL-HEAD

Objective. To define the prevalence and pathological spectrum of femor al head osteonecrosis in patients with rheumatoid arthritis (RA) and t o correlate its presence with disease related clinical and therapeutic factors. Methods. A total of 545 primary total hip arthroplasties per formed in 507 patients with RA were identified. A historical review of each patient's rheumatoid disease and treatment as well as pathologic al review of each femoral head specimen was performed. Results. Osteon ecrosis was identified in 66 specimens (12.1%) in one of 2 discrete fo rms. Thirty-two specimens (5.9%) contained classic subchondral avascul ar necrosis. Thirty-four specimens (6.2%) contained osteonecrosis in a ssociation with degenerative changes (within regions of sclerotic and eburnated subchondral bone), but not classic avascular necrosis. Remai ning femoral head specimens were characterized by inflammatory arthrit is (431 specimens) or degenerative joint disease (48 specimens). Corti costeroid therapy was used in 81% of patients with avascular necrosis and 68% with degenerative osteonecrosis. This was significantly greate r prevalence than in patients without osteonecrosis (33%), Average dai ly prednisone dosage was 8 mg and no association between dosage and th e presence of osteonecrosis was identified. No correlation between pat hological findings and clinical disease severity was identified. In 5 of 27 specimens showing classic avascular necrosis and 11 of 34 contai ning degenerative osteonecrosis, no steroid treatment had been adminis tered. Conclusion. Femoral head osteonecrosis is present in about 12% of patients with RA at hip arthroplasty, and occurs in 2 forms - class ic avascular necrosis and degenerative necrosis, Both forms are signif icantly associated with corticosteroid use. ''Low dose'' therapy does not protect patients against the development of osteonecrosis. Additio nally, baseline prevalence of osteonecrosis of about 3% occurs in the absence of steroid use and may be related to the underlying inflammato ry diseases, Despite its association with osteonecrosis the net effect of corticosteroid therapy on the natural history of rheumatoid hip di sease remains unclear.