ANTERIOR DISLOCATION OF GLENOHUMERAL JOINT
About 95% of shoulder dislocations are anterior and are chiefly due to an indirect mechanism. The most common anterior dislocation type is a subcoracoid dislocation; the most uncommon is a subclavicular dislocation. Anterior dislocations are seen in all age groups and are most commonly seen in adolescents and young adults. They are often due to athletic injuries in which there is trauma to the shoulder generally from a fall or contact to the more distal aspect of the shoulder where the arm is placed into abduction and external rotation (i.e., a cocked arm position for overhead throwing). It is also in this position that patients are most likely to have a recurrent dislocation of the shoulder or have a sense of instability of the shoulder.
The clinical appearance of anterior dislocation demonstrates a prominent acromion and a flattened area of the lateral deltoid region with a prominence of the humeral head anteriorly. The arm is often in an abducted and internally rotated position with loss of passive external rotation. The axillary nerve is located anteriorly immediately outside the anterior inferior axillary portion of the capsular ligaments. With a traumatic anterior dislocation of the shoulder there is often a traction-type injury to the axillary nerve. This will result in an area of decreased sensation in the lateral aspect of the arm as well as a weakness of deltoid function. In addition, the musculocutaneous nerve is located 5 to 7 cm distal to the tip of the corticoid and can be injured by compression or traction in the anterior shoulder dislocation. This will often result in decreased sensation in the preaxial border of the forearm and will result in weakness of elbow flexion.
Closed reduction of the shoulder is most commonly performed at the location of the dislocation if a trained person is available or in an emergency department setting. First-time dislocations are often the most difficult to reduce. The sooner a dislocation can be safely reduced, the least likely further damage could occur to the cartilage of the joint, to the posterior aspect of the humeral head (Hill-Sachs lesion), or to axillary and/or musculocutaneous nerves. In all methods of closed reduction, relaxation of the patient and the muscles around the shoulder and axial traction are components of the successful reduction. The less rotational manipulation, the less likely it is to create further trauma as a result of the reduction. A commonly used method of reduction is the Stimson maneuver. The patient is placed prone and given conscious sedation or pain medication. The arm is gently placed over the edge of the bed and traction applied either manually or by a static weight, as shown in Plate 1-26. In most cases, when the patient becomes relaxed the humeral head becomes disengaged from the anterior g enoid and the shoulder reduces into the glenoid fossa.