Fig. 128.2 (A) Anterior glenohumeral dislocation. Anteroposterior (AP) radiograph in a patient with shoulder pain after trauma shows inferior and medial displacement of the humeral head (black arrow) relative to the glenoid fossa (white arrow). The humeral head in anterior dislocation is usually pulled medially by muscles and is displaced inferiorly under the coracoid process. (B) Posterior glenohumeral dislocation. AP radiograph shows a patient with shoulder pain after a motorcycle accident. Note the wide glenohumeral joint (white arrows), the so-called rim sign, and loss of the normal half-moon overlap. The humerus is also internally rotated, causing the light bulb sign, where the lesser tuberosity (black arrow) projects medially. (C) Inferior glenohumeral dislocation (luxatio erecta humeri). AP radiograph of right shoulder showing inferior dislocation of glenohumeral joint.