Posterior shoulder dislocation

Case contributed by Dr Talal F M Abdullah

Presentation

Motor vehicle accident, complaint of left shoulder pain and limited mobility.

Patient Data

Age: 65 years
Gender: Male
x_ray

Suspected left posterior shoulder dislocation due to the patient abnormal posture from the visualized dorsal spine scoliosis with the convexity to the left, rendered a difficult interpretation of the frontal projection.  Suspected light bulb sign appearance. 

The patient could not do the axillary view because of pain.

Posterior dislocation of the left shoulder joint noted, lipohemarthrosis and a tiny chip fracture of the posterior glenoid rim.

Sclerotic focus noted at the part of the humeral head behind the posterior glenoid margin; this is seen in the frontal radiographs as the rim sign and trough line sign.

Simple/pseudocyst noted in the proximal humeral metaphysis.

Spondylarthritic changes in the visualized dorsal spine and scoliosis.

Left pulmonary apical fibrosis with cystic changes.

The rest of the bones are unremarkable.

The selected image demonstrates the layering of fat and blood in keeping with a lipohemarthrosis.

Case Discussion

Posterior shoulder dislocation is an unusual presentation in the setting of a motor vehicle accident.  In suspected cases or when there is concomitant advanced bony changes/dysplasia; assessment with computed tomography makes it easier for the diagnosis.

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