Last Updated on July 1, 2022
Introduction
• Rare, only 4% of all shoulder dislocation
• Can be difficult to diagnose[1]
• Chronic dislocation if >1 week [2]
Clinical Features
Mechanism of injury
• Direct blow from the front of affected shoulder
• 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, ask for any previous episode of posterior shoulder dislocation e.g. MVA
• 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
• Axillary nerve injury
• Brachial plexus injury
• Bankart lesion
• Recurrence [1]
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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 and scapular Y-view of affected side, to look for type of dislocation and presence of fracture PRIOR to CMR
Management
• Depends on chronicity of dislocation
• 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 [video 1] [video 2]
• Recheck neurovascular status of affected upper limb
• Check X-ray post CMR
• Documentation
• Referral letter to Orthopaedic Clinic in 2 weeks with XOA of affected shoulder (AP and Y view)
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