Locked posterior shoulder dislocation: treatment options and clinical outcomes

Posterior dislocation of the shoulder is a rare injury and often misdiagnosed during the initial presentation to a physician. Misdiagnosis is due to a lack of clear clinical signs compared to anterior dislocation and inappropriate radiographs. In contrast to anterior dislocations, the humeral head defect accounts for recurrent instability. Depending on the size of the defect and the duration of dislocation, different treatment options include elevation of the defect, bone grafting, McLaughlin procedure, rotation osteotomy or arthroplasty.

We reviewed 35 patients who presented to our institution with a locked posterior dislocation of the shoulder between January 1999 and August 2009. In 6 patients, the shoulder remained stable after closed reduction, so the treatment was conservative; 29 patients underwent surgery.

The mean follow-up was 55 months (range 11-132 months). The interval between trauma and the diagnosis of posterior shoulder dislocation was 66 days (min. 0, max. 365). Patients treated conservatively achieved a Constant Score of 85 points; patients who underwent operative treatment had a slightly worse outcome with an average Constant Score of 79 points. There was a high correlation between the time to the correct diagnosis and the outcome.

Although locked posterior shoulder dislocation is uncommon and often initially misdiagnosed, satisfying results can be achieved by different surgical treatment options. Early diagnosis by detailed clinical examination and sufficient radiographic evaluation with true anterior-posterior and axillary views is essential to improve clinical results. Levl of evidence: IV.