Posterior shoulder dislocation

Case contributed by Dr Balint Botz


Persistent pain in the left shoulder region following gardening three days before. No precise injury mechanism reported.

Patient Data

Age: 45 years
Gender: Male

The AP radiograph demonstrated a marked loss of the normal half moon overlap sign, while the transthoracic lateral view confirmed a posterior dislocation of the humeral head. In the AP view a subtle sclerotic shadowing could be observed overlying the humeral head, however no cortical irregularity could be discerned. Therefore, a non-contrast CT was requested.

CT demonstrated a compression fracture of the lesser tuberosity, characteristic for the reverse Hill-Sachs lesion, caused by the impaction of the anteromedial part of the humeral head against the glenoid rim. 

Case Discussion

Posterior dislocations of the shoulder, are relatively uncommon, and usually, arise due to convulsive disorders. However, occasionally strength imbalance of the rotator cuff muscles may result in it without direct trauma, as demonstrated by the current case. The reverse Hill-Sachs lesion is a commonly associated fracture of posterior dislocation, and radiographic signs might be subtle. Careful scrutiny of the humeral head is therefore always mandated when posterior dislocation is found while reporting radiographs.

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