Rotator cuff function in the impingement syndrome.

Thirty-three patients with impingement syndrome of the rotator cuff were studied before and at operation. It was shown that the rotator cuff lengthens and twists during elevation of the arm. Elevation is achieved by early glenohumeral abduction and continuous flexion and external rotation. The range of free rotation at the glenohumeral joint diminishes progressively during elevation. Rotator cuff impingement occurs towards the end of the early glenohumeral abduction. Excision arthroplasty of the acromioclavicular joint and anterior acromioplasty is highly effective for impingement under the acromion, but only moderately effective where impingement is under the acromioclavicular joint.