Posterior shoulder dislocation

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Background

  • Accounts for 2-4% of shoulder dislocations[1]
  • Mechanism of injury - forceful internal rotation/adduction (secondary to e.g. seizure, electric shock) or blow to anterior shoulder
  • Neurovascular and rotator cuff tears are less common than in anterior dislocations

Clinical Features

  • Prominence of posterior shoulder and anterior flattening of normal shoulder contour
  • Patient unable to rotate or abduct affected arm

Differential Diagnosis

Shoulder and Upper Arm Diagnoses

Traumatic/Acute:

Nontraumatic/Chronic:

Refered pain & non-orthopedic causes:

Evaluation

Light bulb sign (right picture) with post-reduction comparison (left picture)
  • Plain film X-ray
    • Scapular "Y" view shows humeral head in posterior position
    • Lack of normal overlap of humeral head and glenoid fossa
    • "Light bulb sign" - fixed internal rotation makes for light bulb appearance of humeral head on AP
  • Bedside ultrasound can be used to assess for both dislocation and successful reduction

Management

  • Reduce
    • Consider procedural sedation
    • Traction applied to adducted arm in long axis of humerus
    • Assistant pushes humeral head anteriorly into glenoid fossa
  • Post-reduction X-ray
  • Apply sling
  • Note: Do not reduce chronic dislocations (>4 weeks) in the ED due to risk of arterial injury - consult ortho for open reduction

Disposition

  • Discharge after reduction
  • Ortho follow-up

See Also

External Links

References

  1. Grate I Jr. Luxatio erecta: a rarely seen, but often missed shoulder dislocation. Am J Emerg Med. 2000 May;18(3):317-21.