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Case of the Month 09/09

Q1: This 24 year old male presented to the Emergency department complaining of left shoulder pain and difficulty moving his shoulder due to pain after an altercation.

What's wrong with this picture?

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A1:

The AP view is suggestive of a posterior shoulder dislocation. The humeral head is much more symmetrical than it would be in a normal film (thus the classic “light bulb” appearance) and the space between the glenoid fossa and the humeral head are abnormally wide. Compare the pre and post-reduction films below.

Q2: What further imaging could be done to confirm suspicion of this diagnosis?

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A2:

Making the diagnosis of posterior shoulder dislocation based on AP and/or lateral views alone can be extremely difficult. Other options which can help confirm this diagnosis are the scapular Y, axillary and Velpeau view. Compare the appearance of the pre and post-reduction axillary views below. The fact that the humerus is located away from the direction of the coracoid process clinches the diagnosis of posterior dislocation.