Posterior Shoulder Dislocation

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The scapular Y view demonstrates the humeral head lies posterior to the glenoid and beneath the acromion.

Posterior Shoulder Dislocation

lightbulb sign

Frontal radiograph of shoulder shows a humeral head in internal rotation (lightbulb sign), decreased distance between humeral head and glenoid and a “trough fracture” or “reverse Hill-Sachs” deformity of the medial humeral head.

• Causes: electrocution and seizures
• Findings

–Trough sign: vertical compression fx of anteromedial humeral head

–Rim sign: widening of glenohumeral joint > 6 mm

–Absent crescent sign: separation of humerus from glenoid such that normal overlap is lost

–Humerus fixed in internal rotation

• If suspected, get transscapular Y view (axillary view OK, but painful and may dislocate a spontaneously relocated shoulder)

–Humeral head lies posterior to glenoid, center of the “Y”

• CT: evaluate complications such as reverse Hill Sachs or reverse Bankart, stripping of posterior periosteum, tear of posterior labrum

Anterior Shoulder Dislocation

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Anterior Shoulder Dislocation

Anterior Shoulder Dislocation