ANATOMIC RELATIONSHIPS IN THE SHOULDER IMPINGEMENT SYNDROME

Impingement syndrome of the shoulder may be produced by compression of the subacromial structures against the coracoacromial arch. The anter ior tip of the acromion, the coracoacromial ligament, and the coracoid process have been implicated as sources of impingement. Anatomic spec imens were examined to determine the anatomic sites on the coracoacrom ial arch that result in compression of the subacromial structures duri ng specific shoulder motions that are known to produce impingement pai n. The relationships of the supraspinatus tendon, the biceps tendon, a nd the greater tuberosity of the humerus with the coracoacromial arch were demonstrated through various arcs of shoulder motion in autopsy s ubjects. Biceps tendon impingement occurred predominantly against the lateral free edge of the coracoacromial ligament. Impingement of the s upraspinatus tendon and greater tuberosity was demonstrated primarily against the acromial end of the coracoacromial ligament and the anteri or tip of the acromion during arcs of flexion and internal rotation. T he coracoacromial ligament was stretched by the greater tuberosity pas sing beneath it. This may explain the formation of traction osteophyte s on the anterior acromion in patients with chronic impingement sympto ms.