Images in Emergency Medicine

Article Outline

• Diagnosis
  • Posterior shoulder dislocation with reverse Hill-Sachs deformity
• Copyright

A 60-year-old woman presented with left shoulder pain that woke her from sleep. On examination, the patient maintained her shoulder in adduction and internal rotation, with limited range of motion and no obvious asymmetries.

Radiographs were interpreted as inconclusive (Figure 1). Attempts at manual reduction were unsuccessful. The patient was unable to tolerate axillary views. What would be the next step in the treatment of this patient?

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• Figure 1. 

  Anteroposterior radiograph of the shoulder demonstrating slightly increased overlap of the humeral head of the glenoid fossa.

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Diagnosis 

Posterior shoulder dislocation with reverse Hill-Sachs deformity 

Signs of a posterior dislocation are an arm maintained in adduction and internal rotation and inability to supinate the forearm. The normal contour of the anterior shoulder may be lost. The dislocated humeral head may create a posterior fullness. Posterior dislocations are rare and easily overlooked. They are commonly misdiagnosed as adhesive capsulitis. When the diagnosis cannot be confirmed by radiographs, a computed tomographic (CT) scan is indicated. This patient’s CT scan revealed a posterior dislocation and reverse Hill-Sachs deformity (Figure 2). The humeral head was locked on the glenoid at the site of fracture deformity, which is characteristic of most posterior dislocations. In retrospect, our patient’s plain radiograph exhibited overlapping of the humeral head and glenoid, one of several subtle findings on radiograph that are indicative of posterior instability.

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• Figure 2. 

  Computed tomography of the shoulder indicating a posterior dislocation with associated impaction of the humeral head and a resulting groove fracture defect. Used with permission of Barry Hahn, MD, Department of Emergency Medicine, Staten Island University Hospital, Staten Island, NY.

Reduction is performed by traction on an internally rotated and adducted arm, combined with posterior pressure on the humeral head. Countertraction may be applied. Closed reduction is recommended if the dislocation occurred within 6 weeks and the articular defect involves less than 20% of the articular surface on axillary radiograph. Fractures greater than 40% require surgery.