What is the diagnosis?

Posterior shoulder dislocation.

• Pearl: Seizures and electrocutions are the “classic” mechanisms of action as a high degree of force is required to dislocate posteriorly. 

• Pearl: Posterior dislocations can be missed up to 50% of the time on AP radiographs, especially in the elderly, who can go weeks before presentation [1]. Axillary or scapular Y views can help clarify (see Image 2).

Image 2. Case courtesy of Andrew Murphy, Radiopaedia.org, rID: 53737

What additional subtle radiographic findings are there on Image 1?

Reverse Hill-Sachs of the humerus and bony Bankart lesion of the glenoid. Read more about their counterparts in anterior dislocations here.

Image 3. Annotation and image by author

What is your management in the ED?

Closed reduction and placement in sling or shoulder immobilizer. This should be performed in consultation with orthopedics as these reductions are generally more difficult and may need to go to the operating room [1].

• Pearl: Reduction can be attempted using traction-countertraction method with anterior pressure on the humeral head. Additional methods may be reviewed here [2].

• Pearl: Relative contraindications to closed reduction are a delay in presentation and a large Hill-Sachs lesion or humeral head fracture [1]. Be sure to speak with your orthopedic surgeon prior to attempting reduction.

When does this patient need orthopedics?

If reduction is successful, immobilize the shoulder with a sling or brace and have the patient follow-up outpatient in 1-2 weeks. Eventual operative repair is frequently needed as these injuries are highly traumatic and damaging to the labrum and joint capsule.