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)
- Can be misdiagnosed/mismanaged
- 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.
- Anterior is the most common (95-98%)
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
- Patient usually presents with a history of trauma with acute onset severe pain and inability to move the arm/shoulder
- 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
- Axillary nerve damage
- Vascular
- In anterior dislocation
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)
- Hippocratic method
- 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)