Posterior shoulder dislocation

Revision as of 23:53, 13 May 2019 by SLuckettG (talk | contribs) (Clinical Features)


  • 2-4% of shoulder dislocations[1]
  • Causes:
    • Forceful internal rotation and adduction
      • Usually due to seizure or electric shock
        • Consider in alcohol withdrawal, even without clear history of shoulder
    • Blow to anterior shoulder
  • Complications (neurovascular injuries and rotator cuff tears) less common than in anterior dislocation
  • May go undetected for extended period as often missed on physical exam and imaging

Clinical Features

  • Posterior aspect of shoulder unusually prominent
  • Anterior aspect of shoulder appears flattened
  • Inability to rotate or abduct affected arm

Differential Diagnosis

Shoulder and Upper Arm Diagnoses



Refered pain & non-orthopedic causes:


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


  • 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


  • Discharge after reduction
  • Ortho follow-up

See Also

External Links


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