Shoulder dislocations

Background/Epidemiology

• One of the most commonly dislocated joints.  Incidence ~12/100,000
  • Can be misdiagnosed/mismanaged
    • Important to manage appropriately to avoid complications (see below)
• More common in young men (‘fighters’ 20-30 years) and older women (‘fallers’ 60-80 years)
• Can be anterior, posterior or inferior
  • Anterior is the most common (95-98%)
    • Almost always associated with injury/trauma, usually when the shoulder is in abduction/hyperextension and external rotation
  • Posterior dislocation is unusual
    • Usually occurs with high-force trauma whilst the shoulder is held in internal rotation and adduction.  Occasionally occurs in states of convulsions/fits or electrical shock.

Risk factors

• Contact sports
• Older patients
• Patients with previous shoulder dislocations
• Disorders of collagen synthesis e.g. Ehlers Danlos

Presentation

• History
  • Patient usually presents with a history of trauma with acute onset severe pain and inability to move the arm/shoulder
    • NB with recurrent dislocations, the trauma may be minimal and, occasionally, the patient may be able to relocate the joint themselves
  • Important to ask about the mechanism of injury
  • Ask about previous shoulder injury, dislocations or surgeries
• Examination
  • In anterior dislocation
    • the arm is usually held in abduction and external rotation and patients will try to minimise any movements, particularly adduction and internal rotation
    • the normal contour of the deltoid may be lost
    • the humeral head may be palpated anteriorly
    • the acromion may be palpated posterolaterally
  • In posterior dislocation
    • the arm is usually held in adduction and internal rotation and abduction/external rotation are resisted (may be impossible to externally rotate to a neutral position); as is supination
    • a posterior bulge may be present and the humeral head may be palpable below the acromion process
    • may resemble frozen shoulder (especially in chronic unreduced dislocation)
  • there may be bruising/signs of injury
  • Neurovascular examination
    • Vascular
      • Check the radial and ulnar pulses
      • Examine for axillary haematoma
      • Measure capillary refill
      • Look for temperature and colour of the arm
    • Nervous
      • Axillary nerve damage
        • Badge patch sensation

Investigations

• X-ray (usually 2 views, one of which AP, the other usually trans-scapular Y view or axillary view)
  • Posterior dislocations can be very difficult to differentiate from normal
  • In a normal AP view, the humeral head should be congruous with the glenoid.  In anterior dislocation, there is usually a loss of congruity
    • Sub-coracoid is the most common appearance for anterior dislocations
  • Axillary views are useful in evaluating the direction of dislocation

Management

• Reduction
  • Before any reduction, appropriate analgesia should be given
  • There are two methods commonly used, both are equally as effective (use whichever the doctor finds most comfortable)
    • Hippocratic method
      • With the patient supine, hold the hand of the affected side and apply a slow, steady traction force to the extended arm whilst someone else provides resistance (or this can be done with your foot if you do not have assistance)

• Kocher method
  • The arm is placed in its anatomical position. Gently support the arm at the wrist and elbow before flexing the elbow to 90°. Then, externally rotate the arm until you encounter resistance. Apply a lateral distraction force to the humerus to unlock it from the glenoid, followed by internal rotation to return the arm to the resting position.
• If reduction is unsuccessful, refer to orthopaedics (possibility of surgical reduction)
• If reduction works, the shoulder should be immobilised in a sling for 4-6 weeks
  • An x-ray should be taken to confirm relocation

Complications

• Soft tissue injury
  • Bankart lesion
  • Hill-sachs lesion
  • Rotator cuff tear
• Neurovascular injury
  • Axillary nerve injury (10%)
  • Axillary artery rupture
• Shoulder instability
  • Recurrent dislocations
  • Fractures (greater tuberosity, scapula, humeral head or shaft)

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