Posterior dislocations of the humerus account for less than 5 % of shoulder dislocations and are usually due to direct force. Classically, the causes are seizure or electric shock. The axillary view is the best view to demonstrate this type of dislocation.

A	AP radiograph of the right shoulder. A cursory examination reveals no obvious dislocation.
B	Axillary radiograph. Notice the anterior coracoid with the posteriorly dislocated humeral head relative to the glenoid.

Links to online textbooks:

• Wheeless' Orthopedics: discussion of posterior shoulder dislocations

Links to online cases:

• Medical College of Wisconsin
• Bombay Hospital Institute

References:

• Perron AD, Jones RL: Posterior shoulder dislocation: avoiding a missed diagnosis Am J Emerg Med. 2000 Mar;18(2):189-91.           [See related articles]
• Samilson RL, Prieto V: Posterior dislocation of the shoulder in athletes Clin Sports Med. 1983 Jul;2(2):369-78.           [See related articles]