Skin puckering of the upper arm

A teenage boy presented to the emergency department three hours after he injured his left shoulder when he fell while running. He had persistent pain and was unable to move his left shoulder. There was noticeable skin puckering at the proximal end of the humerus near the shoulder, accompanied by subcutaneous bruising (fig 1). On examination there was tenderness in the shoulder joint, limited shoulder movement, weakness in forearm flexion, normal distal arterial pulse, and no sensory abnormalities. No emptiness in the shoulder socket was detected on palpation, and the humeral head could not be felt beneath the anterior-inferior aspect of the coracoid process. The patient’s temperature and other vital signs were normal, as was sensation in other areas. A radiograph of the left shoulder joint was taken on initial examination (fig 2).