Posterior shoulder dislocation
Background
- 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
- Usually due to seizure or electric shock
- Blow to anterior shoulder
- Forceful internal rotation and adduction
- 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
Traumatic/Acute:
- Shoulder Dislocation
- Clavicle fracture
- Humerus fracture
- Scapula fracture
- Acromioclavicular injury
- Glenohumeral instability
- Rotator cuff tear
- Biceps tendon rupture
- Triceps tendon rupture
- Septic joint
Nontraumatic/Chronic:
- Rotator cuff tear
- Impingement syndrome
- Calcific tendinitis
- Adhesive capsulitis
- Biceps tendinitis
- Subacromial bursitis
Refered pain & non-orthopedic causes:
- Referred pain from
- Neck
- Diaphragm (e.g. gallbladder disease)
- Brachial plexus injury
- Axillary artery thrombosis
- Thoracic outlet syndrome
- Subclavian steal syndrome
- Pancoast tumor
- Myocardial infarction
- Pneumonia
- Pulmonary embolism
Evaluation
Light bulb sign (left) with post-reduction comparison (right)
- 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
- Closed reduction
- Most require procedural sedation
- Adduct the arm
- Apply traction along long axis of humerus
- Have assistant push humeral head anteriorly into glenoid fossa
- Apply shoulder immobilizer
- 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
Disposition
- 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
References
- Grate I Jr. Luxatio erecta: a rarely seen, but often missed shoulder dislocation. Am J Emerg Med. 2000 May;18(3):317-21.
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