Posterior shoulder dislocation

Revision as of 23:56, 13 May 2019 by SLuckettG (talk | contribs) (Disposition)


  • 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


  1. Adduct the arm
  2. Apply traction along long axis of humerus
  3. Have assistant push humeral head anteriorly into glenoid fossa
  4. Apply shoulder immobilizer
  5. Obtain post-reduction radiographs
  • Note: Do not reduce chronic dislocations (>4 weeks) in the ED due to risk of arterial injury - consult ortho for open reduction


  • Discharge after successful reduction
  • Orthopedic surgery outpatient follow-up
  • Any patient with a chronic dislocation requires orthopedic consult in the ED for consideration of operative reduction due to the risk of arterial injury

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.