Mechanism of anterior dislocation of shoulder:

Reference: Wat son-Jones, Fractures and Joint Injuries, 7th edition. Page 482- 484.Explanation:Anterior dislocation of the shoulder - Mechanism of injuryIt is a fall on the outstretched hand w ith limb in lateral rotation, so that the head of the humerus is forced against the anterior capsule which is torn or avulsed from the glenoid labrum.It is not just an abduction injury but a lateral rotation injury as well.Thus the mechanism mav be said to be abduction and external rotation.Posterior dislocation of the shoulder - Mechanism of injuryA forceful medial rotation causes posterior dislocation.This is commonly seen in the bizarre position of the shoulder because of muscle spasm during epileptic attacks, severe electric shock and electro- convulsive therapy when muscle relaxants have not been used.Rarely a direct blow on the front of the shoulder can cause the head of the humerus to be pushed out posteriorly.