[A bilateral posterior shoulder dislocation caused by humeral head osteonecrosis]

We report a case of simultaneous bilateral posterior shoulders dislocations in a 46-year-old male with antecedent of high-dose corticotherapy. The mechanism was non-traumatic after a contraction of the sub scapularis muscle in internal rotation. The interscapular pain was not initially diagnosed although a tomodensitometry was realized to eliminate a cardiovascular emergency. After reduction, the shoulders were unstable and the MRI showed an osteonecrosis of the humeral heads. The patient underwent surgery with an iliac spongy bone graft in the humeral nick. At 3 months, there was no recurrence and mobilities were good. Bilateral posterior shoulders dislocations are unusual and it is the first case of non-traumatic dislocation. Aetiology are often epilepsy, electrocution, and extreme traumatism. Diagnosis is often misrecognized and the treatment is not well codified.