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Traumatic Dislocation of the Shoulder: Classification
The shoulder is the most mobile major joint and is consequently the most frequently dislocated joint. Traumatic dislocation implies complete loss of congruity between the humeral head and glenoid, usually with capsulolabral, bony or rotator-cuff injury. Classification is clinically useful because the direction of displacement, duration, associated fracture and presence of a locked humeral-head defect determine the imaging strategy and treatment.
1. Classification according to direction
| Type | Direction and characteristic position | Important clinical and management implications |
|---|---|---|
| Anterior dislocation | Humeral head lies anterior to the glenoid, commonly in a subcoracoid position; less commonly subglenoid, subclavicular or intrathoracic. | Usually follows abduction, extension and external rotation. It may produce anteroinferior labral avulsion, greater-tuberosity fracture, Hill–Sachs impaction and axillary-nerve injury. |
| Posterior dislocation | Humeral head lies posterior to the glenoid, usually subacromial or subspinous. | Often missed on a single anteroposterior radiograph. It follows seizures, electrical injury or a direct blow to the anterior shoulder, but may also be caused by trauma. Reverse Hill–Sachs impaction and posterior labral injury are important. |
| Inferior dislocation (luxatio erecta) | Humeral head lies inferior to the glenoid; the arm is fixed in marked abduction, commonly above the head. | High-energy injury with frequent soft-tissue, vascular and… |