Posterior shoulder dislocation
Background
- 2-4% of shoulder dislocations[1]
- 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
- Classically associated with seizures and lightning strikes
Shoulder dislocation types
- Anterior shoulder dislocation (~95%)
- Posterior shoulder dislocation (~5%)
- Inferior shoulder dislocation (<1%)
Clinical Features
- Posterior aspect of shoulder unusually prominent
- Anterior aspect of shoulder appears flattened
- Inability to rotate or abduct affected arm
Mechanism
- Forceful internal rotation and adduction
- Usually due to seizure or electric shock
- Consider in alcohol withdrawal, even without clear history of shoulder injury
- Usually due to seizure or electric shock
- Blow to anterior shoulder
Differential Diagnosis
Shoulder and Upper Arm Diagnoses
Traumatic/Acute:
- Shoulder Dislocation
- Clavicle fracture
- Humerus fracture
- Scapula fracture
- Acromioclavicular joint 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
- Cervical radiculopathy
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
- 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
- Consider CT for occult dislocations of evaluation of fractures
- 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
Indications for Surgery
- Lesser tuberosity displacement not reduced with reduction
- Articular defect >25%
- Dislocation >3 weeks
- Do not reduce chronic dislocations in the ED due to risk of arterial injury; consult ortho for open reduction
Disposition
- Discharge after successful reduction
- Maintain sling +/- swath or shoulder immobilizer (shoulder in adduction and internal rotation) until seen in follow-up by orthopedic surgery
- Any patient with a chronic dislocation requires orthopedic consult in the ED for consideration of operative reduction due to the risk of arterial injury
Complications
- Humerus fracture plus fracture of the posterior glenoid rim
- Isolate fracture of lesser tuberosity
- Reverse Hill-Sachs deformity
- Impaction fracture of anteromedial humeral head
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.