Shoulder dislocation

• The gleno-humeral joint is the commonest joint in the body to dislocate.
• Related to lack of bony stability.
• Bimodal age distribution – men aged 20–30 and women aged 60–80.
• Anterior, posterior and inferior seen in decreasing order of frequency.
• Anterior dislocations usually secondary to a fall. The labrum detaches allowing the humeral head to dislocate anteriorly.
• With posterior dislocations, the head is displaced directly backwards and is usually secondary to a direct blow or fall onto an internally rotated hand. It can be missed following a difficult obstetric delivery.
• Anterior shoulder dislocation : Majority seen well on the standard AP view.An axial or apical view may be obtained if in doubt.The greater tuberosity may be fractured. Hill–Sachs lesion: A depression of the postero-lateral aspect of humeral head; common with recurrent dislocations, as the humeral head hits the glenoid. Bankart lesion: Anterior glenoid labrum defect best seen on MRI. Bulbous distortion of the scapulo-humeral arch.
• Posterior shoulder dislocation : Best seen on the axillary view. Light-bulb sign on AP view and widened gleno-humeral space ( 6 mm). The scapulo-humeral arch may have an abnormally sharp angle. Trough sign, an associated compression fracture of the antero-medial humeral surface, seen as a sclerotic line parallel to the articular surface.

Anterior and posterior shoulder dislocation.