Shoulder Dislocation

Basics

Description

Shoulder is a very dynamic joint, prone to injury
Anterior dislocation (90–96%):
- Injury is from direct or indirect forces on the abducted and externally rotated arm
- Injury may also result from a direct blow to posterolateral aspect of shoulder
Posterior dislocation:
- Often missed
- Forces on the adducted and internally rotated arm result in posterior dislocation of humeral head in relation to glenoid fossa
- Common mechanism is seizure and sudden contraction of all the posterior muscle groups
- Other mechanisms include electrocution and direct blow to anterior shoulder
Inferior dislocation (rare):
- Luxatio erecta
- Hyperabduction of arm, tear of rotator cuff, and rotation of arm 180° above head; humeral head trapped underneath the coracoid and glenoid
- Commonly seen after a fall from a height:
  - Arm has struck object on descent and is thrust above the head
- Often accompanied by neurovascular injury and fracture

Pediatric Considerations
Dislocation is rare in children: Epiphyseal fractures must be suspected

Geriatric Considerations
Dislocation is often accompanied by fracture

Etiology

Falls from height
Impact injuries
Distraction injuries of upper arm
Seizures
Electrocution

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