Last Updated on August 19, 2026
Introduction
• Rare, only 4% of all shoulder dislocation Sometimes it requires high index of suspicion from typical history + physical examination findings
• Can be
difficult to diagnose
• Chronic dislocation if >1 week [2]
Clinical Features
Mechanism of injury
• Direct blow from the front of affected shoulder e.g. change in body position, wearing clothes etc.
• Fall on outstretched internally rotated hand
• Seizure
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💡Notes
• If the patient presented with features of posterior dislocation but due to
trivial trauma
• The force required to cause posterior shoulder dislocation is usually stronger than that causes anterior shoulder dislocation
Presentation
• Patient complained of extreme pain over affected shoulder + mechanism of injury for posterior shoulder dislocation
Physical examination
• Arm in internal rotation & adduction
• Pain and reduced ROM of affected shoulder
Complications
• Fracture together with dislocation Anterior inferior glenoid labrum tear • 30% of cases
• Axillary nerve injury
• Brachial plexus injury
•
Bankart lesion
•
Recurrence
• Predisposes to joint degenerative changes
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Notes:
Neurovascular injury in posterior shoulder dislocation is less common in compared to anterior shoulder dislocation [further reading]
Investigations
X-rays
• Shoulder X-ray:
AP view
Findings: • Light bulb sign due to internal rotation of shoulder and lack of overlap between head of humerus and glenoid labrum • Rim sign: distance between medial border of humeral head and anterior glenoid rim more than 6 mm
Management
• Depends on
chronicity of dislocation
If dislocation is more than 1 week, open reduction is more preferable; CMR may be difficult
• Open reduction may include repair of soft tissue e.g. rotator cuff muscles
Management — CMR Under PSA
• Golden hours of CMR — best done before oedema worsens
Prior to procedure
• Consent
• Examination and documentation of axillary nerve, radial nerve and pulses at wrist
• Preparation for procedural sedation analgesia
Technique
• Apply traction to the arm in a position of 90% abduction
• May require counter-traction by an assistant using a rolled sheet under axilla
• Gently externally rotate affected arm
Post-procedure
• Immobilization – Apply
collar and cuff and strappings
• Keep for at least 2 weeks (if severe, the duration of immobilization could be longer e.g. up to 6 weeks) e.g. Left shoulder AP and scapular Y-view • Method used Abbreviation: XOA e.g. For assessment of fracture healing during appointment in a previously reduced fracture
• Strappings – keep the affected shoulder in adduction e.g. by using Hypafix®
• For soft tissues to heal / oedema to subside, to prevent recurrence
• Recheck neurovascular status of affected upper limb
•
Check X-ray post CMR
•
Documentation
• Type of PSA given
• Post-procedure examination findings especially axillary nerve, radial nerve and pulses at wrist
• Check X-ray finding
• Referral letter to Orthopaedic Clinic in 2 weeks with
XOA
X-ray on arrival
Related Posts
• Anterior shoulder dislocation [open]
• Procedural sedation [open]
Anterior Shoulder Dislocation VS Posterior Shoulder Dislocation
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Q&A
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Further Reading
Take Home Message
1. Posterior shoulder dislocation associated with high velocity injury (greater force compared to anterior shoulder dislocation)
2. Posterior shoulder dislocation could be more severe, involving soft tissue (ligament, rotator cuff, cartilage) injury
3. CMR of posterior shoulder dislocation requires adequate muscle relaxant and good sedation