Case 34 Answer

I could have given you the other rotation. Harder? Confirm your suspicion?

Answer: posterior shoulder dislocation

Relatively fixed internal rotation (lightbulb sign), trace overlap of the humeral head with the glenoid (absent half-moon sign), and suggestion of a trough defect (aka reverse Hill Sachs deformity) on the prior image.

Reference: http://radiopaedia.org/articles/posterior-shoulder-dislocation

Remember:

anterior dislocation = Hill Sachs (both WAAAYY more common), and sometimes a Bankart injury (technically ONLY the labrum - vs anterior glenoid fracture which includes the bone and termed by some a “bony Bankart”)

posterior dislocation = trough sign (aka reverse Hill Sachs) and sometimes a posterior glenoid injury