Subacromial osteochondroma.

The most common cause of impingement syndrome is mechanical irritation of the subacromial bursa and rotator cuff by the coracoacromial arch. Offending structures include the undersurface of the anterolateral acromion, coracoacromial ligament, and the undersurface of the distal clavicle. We present a case of impingement syndrome caused by mechanical irritation of the rotator cuff by a subacromial osteochondroma that was successfully treated with arthroscopic resection. Osteochondroma is the second most common benign bone tumor following nonossifying fibroma. These lesions are thought to arise from aberrant growth of normal epiphyseal growth plate cartilage. Ninety percent of osteochondromas arise from the metaphyseal regions of long bones (eg, distal femur, proximal tibia, or proximal humerus). Scapular involvement accounts for 3.0% to 4.6% of all reported osteochondromas. These lesions represent 14.4% of all tumors of the scapula and 49% of benign scapular tumors, making them the most common benign bone tumors of the scapula. Our patient failed nonoperative management of his subacromial osteochondroma. The concern for malignant transformation was low, as the patient's pain had been consistent for the past 15 years. Although his pain had been largely unchanged for more than a decade, he elected to undergo resection so that he could resume the hobbies that his pain had forced him to abandon. He reported substantial pain relief and restoration of function following arthroscopic resection and subacromial decompression, reinforcing mechanical irritation of the rotator cuff as the source of his shoulder pain and dysfunction. To our knowledge, this is the first report of arthroscopic resection of a subacromial osteochondroma.