To evaluate the incidence of involvement and nature of destruction of acromioclavicular joints (AC) in a prospectively followed cohort of 74 patients with rheumatoid factor positive and erosive rheumatoid arthritis (RA).
At the 15 year followup, radiographs of 148 AC joints were evaluated, and the grade of destruction was assessed by the Larsen method.
No surgical procedures had been performed on the AC joints. Rheumatoid involvement (Larsen Grade > or = 2) was observed in 87/148 (59%) of the AC joints in 50/74 (68%) patients: 37 bilaterally and 13 unilaterally. Incidence of mild erosions (Larsen Grade 2) was 39%, and of severe (Larsen 3-5) 20%. Erosions were most often observed on the inferior edge of the clavicular joint margin. Degenerative features without rheumatoid changes were present in 11 joints. Larsen score (0-100) of peripheral joints correlated well with the AC joint Larsen Grade in both sides: right, r = 0.56 (95% CI 0.38 to 0.70), left, r = 0.49 (95% CI 0.30 to 0.65).
After 15 years two-thirds of the patients with RA showed involvement of the AC joints. Erosions were located most often on the inferior margin of the joint.