Inferior dislocation may be produced by a hyperabduction force that causes abutment of the neck of the humerus against the acromion process, which levers the head out inferiorly. The humerus is then locked with the head below the glenoid fossa and the humeral shaft pointing overhead, a condition called luxatio erecta. The clinical picture of a patient with luxatio erecta is so clear that it can hardly be mistaken for any other condition. Severe soft tissue injury or fractures about the proximal humerus occur with this dislocation. At the time of surgery or autopsy, various authors have found avulsion of the supraspinatus, pectoralis major, or teres minor muscles and fractures of the greater tuberosity.
Neurovascular involvement is common.
Rockwood and Wirth found that in 19 patients with this condition, all 19 had a brachial plexus injury and some vascular compromise before reduction. The force may be so great as to force the head out through the soft tissues and the skin. Reduction of an inferior dislocation can often be accomplished by traction and countertraction maneuvers. When closed reduction cannot be accomplished, the buttonhole rent in the inferior capsule must be surgically enlarged before reduction can occur. In current literature little is mentioned about this type of dislocation, but undoubtedly occasional cases do occur.