Rotator cuff injury and impingement syndrome have been thought to be related to the structure of acromion, such as subacromial distance, acromial type, acromial spur and acromial angle. Evaluation was done in 90 normal shoulders without impingement or rotator cuff injury, using shoulder X-ray series, composed of AP view, impingement view, and arch view.

As results, 52(52.8%) of them had subacromial spur by the impingement views. The spur size was 12.4⁑4.5 mm and increased with age without statistical significance(p＞0.05). The subacromial distance was 11.1⁑2.2 mm in AP view and 10.4⁑1.9 mm in arch view without statistical difference for age and sex(p＞0.05). Among 90 normal shoulders, the acromion was quite often curved Type II, 51.1%, type I, 22.2%, and type III 26.7%. Mean acromial angle was 29.1^o in arch view and increased with age(p＜0.05). Mean acromial tilt was 31.8⁰ without significant difference for age and sex(p＞0.05).

These results suggest their clinical relevance to the impingement syndrome and the rotator cuff injury.