Shoulder impingement syndrome

an abnormality that occurs when the bone and soft tissue structures of the superior aspect of the shoulder in the coracoacromial arch encroach on the rotator cuff during abduction of the arm. Findings in this syndrome include structural factors related to the acromioclavicular joint (congenital anomalies or osteophytes), acromion (alterations in shape, fractures with malunion or nonunion, os acromiale or osteophytes), coracoid process (congenital anomalies or posttraumatic or postsurgical changes), subacromial subdeltoid bursa (inflammation or thickening), rotator cuff (calcification, thickening or irregularity related to tendon tears, or postoperative or posttraumatic scars) or humerus (congenital anomalies, fractures with malunions or altered position of a humeral head prosthesis).

Chronic pain, stiffness and weakness of the shoulder with limited range of motion are common manifestations. In some patients subacromial bursitis and rotator cuff inflammation and rupture may result. Usually diagnosis is possible by physical examination, but routine radiography, fluoroscopy, arthrography, computed arthrotomography, ultrasonography and MR imaging may provide additional information.

On plain films, sclerosis and cysts in the greater tuberosity or osteoarthritis of the acromioclavicular joint may be observed, but these findings are nonspecific. Other features occurring in some patients are bone proliferation and eburnation. A well-defined bone excresence at the site of attachment of the coracoacromial ligament, termed a subacromial enthesophyte, is a relatively specific but insensitive finding on MR imaging.

Treatment depends on the severity of the syndrome; patients in the milder stages may be treated conservatively, whereas those with more severe conditions may require surgery, usually a form of anterior acromioplasty.