Shoulder Dislocation

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | References

Definition

Shoulder dislocation refers to the displacement of the humeral head from the glenoid cavity of the scapula. It is one of the most common joint dislocations, with anterior dislocations accounting for the vast majority of cases.

Aetiology

Shoulder dislocation can occur due to various causes:

• Trauma: The most common cause, particularly in younger individuals involved in contact sports or accidents. This often results in an anterior dislocation.
• Recurrent dislocations: Previous dislocations increase the risk of subsequent episodes due to damage to the stabilising structures of the shoulder.
• Congenital or acquired ligamentous laxity: Conditions such as Ehlers-Danlos syndrome can predispose individuals to dislocations.
• Seizures or electric shocks: These can cause posterior shoulder dislocations due to violent muscle contractions.

Pathophysiology

The pathophysiology of shoulder dislocation involves:

• Anterior dislocation: The humeral head is displaced anteriorly, typically following a forceful external rotation and abduction of the arm. This can result in injury to the glenoid labrum (Bankart lesion) and the humeral head (Hill-Sachs lesion).
• Posterior dislocation: Less common, often resulting from direct trauma or seizures. The humeral head is displaced posteriorly, which can be missed on standard X-rays.
• Inferior dislocation: Rare and often results from hyperabduction, where the humeral head is displaced inferiorly.
• Damage to the rotator cuff, ligaments, and labrum during dislocation, which compromises the stability of the shoulder joint and increases the risk of recurrence.

Risk Factors

• Participation in contact sports or activities with a high risk of falls
• Previous history of shoulder dislocation
• Congenital or acquired ligamentous laxity
• Age, with younger individuals more likely to experience traumatic dislocations and older individuals more prone to recurrent dislocations
• Conditions such as seizures or electric shocks, which can cause violent muscle contractions

Signs and Symptoms

The signs and symptoms of shoulder dislocation include:

• Severe pain in the shoulder, particularly after trauma
• Visible deformity of the shoulder, often with a squared-off appearance due to displacement of the humeral head
• Inability to move the arm or shoulder
• Numbness or tingling in the arm, which may indicate nerve involvement (e.g., axillary nerve injury)
• Swelling and bruising around the shoulder

Investigations

Specific investigations to assess shoulder dislocation include:

• Physical examination: Assessment of shoulder deformity, range of motion, and neurovascular status. Specific tests, such as the apprehension test, may indicate instability.
• X-rays: Anteroposterior (AP) and lateral views are standard to confirm the dislocation and identify any associated fractures. For suspected posterior dislocations, a specialised view (e.g., axillary or scapular Y view) may be required.
• MRI: Used to assess soft tissue damage, such as rotator cuff tears, labral injuries, or Hill-Sachs lesions, particularly in recurrent dislocations.
• CT scan: May be used to assess complex fractures or when X-ray findings are inconclusive.

Management

Initial Management

• Reduction: Immediate reduction of the dislocated shoulder is essential to relieve pain and prevent further damage. Various techniques, such as the Hippocratic or Kocher manoeuvre, can be used depending on the clinician’s expertise and the patient’s condition.
• Immobilisation: Following reduction, the shoulder should be immobilised using a sling or shoulder immobiliser for 1-3 weeks, depending on the patient's age and the risk of recurrence.
• Pain management: NSAIDs or analgesics should be administered to manage pain following the reduction.

Specialist Management

• Referral to orthopaedics: Referral is recommended for patients with recurrent dislocations, associated fractures, or significant soft tissue damage identified on imaging.
• Rehabilitation: Physical therapy is crucial to restore range of motion, strengthen the rotator cuff, and prevent future dislocations. This typically begins with gentle exercises and progresses to more intensive rehabilitation over several weeks.
• Surgical intervention: Indicated for patients with recurrent dislocations, significant soft tissue injuries (e.g., Bankart or Hill-Sachs lesions), or fractures. Surgical options may include arthroscopic or open repair of the labrum, rotator cuff, or other stabilising structures.

References

1. NHS (2024) Shoulder Dislocation. Available at: https://www.nhs.uk/conditions/shoulder-dislocation/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Shoulder Instability. Available at: https://cks.nice.org.uk/topics/shoulder-instability/ (Accessed: 24 June 2024).
3. British Medical Journal (2024) Shoulder Dislocation: Clinical Features, Diagnosis, and Management. Available at: https://www.bmj.com/content/350/bmj.h3800 (Accessed: 24 June 2024).
4. American Academy of Orthopaedic Surgeons (2024) Shoulder Dislocation. Available at: https://orthoinfo.aaos.org/en/diseases--conditions/shoulder-dislocation/ (Accessed: 24 June 2024).

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