Radiographic joint space in rheumatoid acromioclavicular joints: a 15 year prospective follow-up study in 74 patients

Objective. To evaluate radiographically the acromioclavicular joint space in patients with long-term rheumatoid arthritis (RA). Methods. A cohort of 74 patients with RA was followed prospectively for 15 yr. At the end point, 148 shoulders were radiographed with a standard method. The acromioclavicular (AC) joint space was examined from the radiographs with a method developed previously for population studies; the joint space was measured at its superior and inferior border, and the average of the two measurements, the integral space, calculated. Results. Mean AC joint space in RA patients was 4.9 (S.D. 3.7), range 0-20.5 mm; 6.2 mm (S.D. 5.1) in men and 4.5 mm (S.D. 3.0) in women. An AC joint space wider than 7 mm in men was found in 11 (31%) out of 36 joints and wider than 6 mm in women in 17 (15%) out of 112 joints. Joint space widening was associated (r = 0.87, 95% CI 0.82-0.90) with increasing destruction (Larsen grading) of the joint and it seems to be an inevitable consequence of AC joint affection in RA. Joint space widening is more progressive on the caudal side because of the nature of the erosive destruction. Degeneration with joint space narrowing was observed in 8 (11%) patients(11 joints, 7%; three bilateral). Conclusions. The largest value of the joint space may be used when evaluating rheumatoid AC joint space. In RA patients, a joint space of > 7 mm in men and > 5 mm in women is a sign of destructive AC joint affection.