Makindo Medical Notes

Related Subjects: |Shoulder Anterior Dislocations |Shoulder: Posterior Dislocation

Introduction

• Posterior shoulder dislocation is a rare condition, accounting for approximately 1 in 20 shoulder dislocations.

Associations

• It is typically associated with trauma, such as seizures and electrocution.
• Due to its relative rarity, this diagnosis is often overlooked, making a high degree of suspicion necessary for accurate identification and management.

Clinical Features

• Arm held in internal rotation: The arm is typically held in a position of internal rotation, and the patient may be unable to move it freely.
• Reduced active external rotation: External rotation is severely limited, and this is a key clinical sign to differentiate posterior dislocation from other shoulder injuries.
• Axillary nerve function: It is crucial to assess and document axillary nerve function to check for any associated nerve injury, which can occur with dislocations.

X-ray Findings

• AP View: The anteroposterior (AP) X-ray view may appear normal, which can sometimes lead to misdiagnosis. Therefore, it is important to carefully evaluate other signs.
• Light-bulb sign: On the AP view, the humeral head may appear round like a light bulb, which is a hallmark sign of posterior dislocation.
• Y-view: The diagnosis is much easier to make on the "Y" view, a specialized X-ray view that provides better visualization of the shoulder joint.

Management

• Reduction in ED: If posterior dislocation is suspected, the first step is to attempt a reduction in the emergency department (ED). This should be done under appropriate sedation or anesthesia to ensure patient comfort and safety.
• Polysling and analgesia: If the dislocation is successfully reduced, the patient should be placed in a polysling to immobilize the shoulder. Adequate analgesia should be provided to manage pain post-reduction.
• Fracture clinic (VFC): Following reduction, the patient should be referred to a fracture clinic for follow-up to monitor healing and further management.
• Referral to orthopaedics: If reduction is unsuccessful, the patient should be referred to the on-call orthopaedics team for further intervention.

Conclusion

Posterior shoulder dislocation is a rare but important diagnosis to consider, particularly in patients with a history of seizure or electrocution. A thorough clinical examination and appropriate imaging, including the "Y"-view, are crucial in confirming the diagnosis. Early reduction and proper management can prevent complications and improve patient outcomes.