Dislocation

• Shoulder is the most regularly dislocated joint in the body

  Of these dislocations the majority are anterior - the rest are posterior or inferior
• An anterior dislocation is classically caused by force being applied to an extended, abducted, and externally rotated humerus
• Shoulder dislocation is where the ball of the shoulder (head of the humerus) comes entirely out of the socket (glenoid cavity of the scapula). 
• Subluxation refers to a partial dislocation of the shoulder. The ball does not come fully out of the socket and naturally pops back into place shortly afterwards.
• Posterior dislocations are associated with electric shocks and seizures. - classic sign on x-ray is the lightbulb sign - due to humerus being fixed in internal rotation
• Associated damage:

  • Glenoid labrum tear
  • Bankart lesions - tears to anterior portion of the labrum occurring due to repeated anterior dislocations
  • Hill-sachs lesions - compression fractures of the posterolateral part of the head of the humerus
  • Axillary nerve damage - comes from C5 and C6 nerve roots - loss of sensation in the regimental badge area over the lateral deltoid. Motor weakness in the deltoid and teres minor - cannot complete abduction
• Fractures can occur alongside shoulder dislocations, affecting the:

  • Humeral head
  • Greater tuberosity of the humerus
  • Acromion of the scapula
  • Clavicle
• Rotator cuff tears may occur with shoulder dislocations, particularly in older patients. 
• Presentation:

  • Pain
  • Acutely reduced mobility
  • Feeling of instability
  • Usually present with a flexed elbow, adducted and internally rotated arm
  • Shortly after the dislocation the muscles will go into spasm
  • On exam - flattened deltoid, humerus will cause a bulge and be palpable at the front of the shoulder
• It is important to assess patients with a shoulder dislocation for:

  • Fractures
  • Vascular damage (e.g., absent pulses, prolonged capillary refill time and pallor)
  • Nerve damage (e.g., loss of sensation in the “regimental patch” area)
• Apprehension test:

  • Special test to assess for shoulder instability specifically in the anterior direction
  • Patient lies supine
  • Shoulder is abducted to 90 degrees, and the elbow flexed to 90 degrees
  • Shoulder is slowly externally rotated
  • As the arm approaches 90 degrees of external rotation, patients with shoulder instability will become anxious and apprehensive
• Investigation:

  • X-rays can be used to confirm dislocation - needed if fracture suspected (reduction with fracture could damage axillary nerve)
  • X-ray after reduction to confirm relocation
  • Magnetic resonance arthrography - MRI with contrast injected into shoulder joint - assess for damage e.g. Bankart and Hill-Sachs lesions
  • Arthroscopy - inserting a camera into the shoulder joint
• Acute management:

  • Analgesia, muscle relaxants and sedation
  • Gas and air may be used
  • Broad arm sling can be applied to support the arm
  • Closed reduction of the shoulder (after excluding fractures)
  • Dislocations associated with a fracture may require surgery
  • Post-reduction X-rays
  • Immobilisation for a period after relocation
• Ongoing management:

  • High risk of recurrent dislocations - particularly in younger patients
  • Physiotherapy
  • Shoulder stabilisation surgery may be needed to prevent recurrent dislocations