A Case on Posterior Shoulder Dislocation: The Hidden Injury

Abstract

Introduction: Posterior shoulder dislocation (PSD) is a rare injury, accounting for a small proportion of glenohumeral dislocations, and is frequently missed at initial presentation due to subtle clinical signs and inconclusive standard radiographs. Delayed diagnosis may result in persistent instability, pain, and early degenerative changes, particularly when associated with osseous defects such as the reverse Hill-Sachs lesion (rHSL). Electrocution is a classic but often under-recognized mechanism leading to PSD because injury can occur without direct trauma.

Case Presentation: We report the case of a 21-year-old male who presented with acute pain and restricted external rotation of the right shoulder following accidental electrocution. Clinical examination revealed the arm held in addition and internal rotation with limited external rotation. Plain radiographs demonstrated features suggestive of posterior dislocation, including the lightbulb and trough line signs. Following closed reduction, magnetic resonance imaging revealed an engaging reverse Hill-Sachs lesion involving approximately 30% of the humeral head, with an associated reverse Bankart lesion. Given the size and engagement of the defect, the patient underwent an arthroscopic modified McLaughlin procedure combined with posterior labral repair.

Result: Postoperative rehabilitation resulted in a satisfactory range of motion and return to functional activity, with no evidence of instability at three-month follow-up.

Conclusion: This case highlights the importance of maintaining a high index of suspicion for PSD following electrocution. Advanced imaging is essential for identifying rHSLs and guiding management. Arthroscopic defect-addressing procedures combined with capsulolabral repair provide a reliable, joint-preserving solution in young patients with engaging humeral head defects.