The influence of the acromioclavicular joint degeneration on supraspinatus outlet impingement and the acromion shape.

PURPOSE To assess the anatomic association of acromioclavicular joint degeneration to supraspinatus outlet impingement and the acromion shape. METHODS Sagittal oblique magnetic resonance images of 49 shoulders in 49 patients were reviewed. 29 of them (mean age, 59 years) underwent surgery for impingement with or without rotator cuff tear (group 1), whereas the 20 controls (mean age, 27 years) were treated for shoulder instability without rotator cuff disease or acromioclavicular joint derangement (group 2). The supraspinatus outlet and the acromion shape of the 2 groups were compared. RESULTS The difference in the mean supraspinatus outlet between groups 1 and 2 was 11% (514 vs 577 mm[2], p=0.095) and between the subgroup (of group 1) with full thickness rotator cuff tears and group 2 was 17% (481 vs 577 mm[2], p=0.036). Six of the acromions in group 1 were type III (hooked) compared to none in group 2. CONCLUSION In severe acromioclavicular degeneration, distal clavicular excision is recommended, even in cases with an asymptomatic acromioclavicular joint, so as to prevent further osteophyte formation.