Frontal film of the right shoulder which reveals a defect of the posterolateral aspect of the humeral head, consistent with a Hill-Sachs deformity. The Hill-Sachs sign represents deformity of the superior, posterior border of the humeral head and is typically a result of impaction of the anterior inferior surface of the glenoid labrum on the posterolateral aspect of the humeral head during dislocation.
Reference
Hill HA, Sachs MD: The grooved defect of the humeral head: A frequently unrecognized complication of dislocation of the shoulder joint. Radiology 1940, 35:690-700.