Subacromial impingement

Abstract

The subacromial space is delimited above by the coracoacromial arch, which consists of the anterior part of the acromion, the coracoid process, the coracoacromial ligament (CAL), and the acromioclavicular (AC) joint and below by the humeral head covered by the rotator cuff. In 1972, Neer (J Bone Joint Surg 54A:41–50, 1972) first highlighted the correlation between degenerative changes of the coracoacromial arch and tendinopathy of the rotator cuff and long head of the biceps. He described the “subacromial impingement syndrome” as the main cause of shoulder pain due to a pathological reduction of the subacromial space that results in an attrition between the rotator cuff and the coracoacromial arch during the movements of flexion, abduction, and rotation of the limb, which can cause degenerative lesions of all the structures contained in the subacromial space.