Posterior gleno-humeral instability resulting in posterior locked dislocation .

 The fat-suppressed proton density-weighted axial image reveals alignment of the humeral head posteriorly relative to the glenoid, with an impaction fracture of the humeral head articular surface (red arrow). The posterior labrum is avulsed, and stripped scapular periosteum remains attached to the posterior labrum (arrowhead). An impaction fracture is also present at the posterior glenoid rim (blue arrow). 

The T2-weighted sagittal image confirms posterior displacement of the humeral head (arrow) relative to the glenoid (asterisk). Low signal intensity blood clot (arrowhead) is present within the subscapularis recess.

rough-like defects within both the humeral head (red arrows) and the glenoid (arrowheads) are visible on the fat-suppressed T2-weighted coronal image. Tearing of the inferior glenohumeral ligament at the humeral attachment (blue arrow) is also evident.