Posterior shoulder dislocation

Case contributed by Akos Jaray


Unexplained left shoulder pain since hypoglycemic episode. Previous instability of joint. No obvious deformity, no swelling, no bruising. Minimal range of motion.

Patient Data

Age: 60 years
Gender: Female

The X-ray study is less reliable to confirm the posterior shoulder dislocation, but knowing the lightbulb sign (AP view due to the internal rotation of the shoulder) might help.

There is posterior subluxation of the left humerus with cortical depression of the anteromedial aspect of the sphericity in keeping with an impression fracture.
Tiny bony flake is noted in the dorsal aspect of the glenoid process without significant bony injury of the glenoid process itself.
No further fractures detected.

NB: the volume rendered images demonstrate well the internal rotation of the humerus.


Case Discussion

Reverse Hill-Sachs lesion is an impaction fracture of anteromedial aspect of the humeral sphericity following posterior dislocation of the humerus. Surgical management might prevent avascular necrosis. While anterior dislocation is often easy to assess on X-ray, CT is highly recommended in case there is a suspicion of dorsal shoulder dislocation.

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