Dislocations

Dislocation Evaluation Services

Elbow dislocation is the most common dislocation in children; in adults, it is the second most common dislocation after that of the shoulder. The elbow is amazingly stable, relying more on bony anatomy configuration for stability rather than ligaments. Considerable force is necessary to dislocate the elbow; sports activities account for up to 50% of elbow dislocations, and this type of injury is more commonly seen in adolescent and young adult populations.

Posterior elbow dislocations comprise over 90% of elbow injuries. Early recognition of this injury is required due to the need for early reduction, given a higher likelihood for poor function and possible neurovascular compromise with delays in reduction. Associated fractures are not infrequent with elbow dislocations, given the force that is required to dislocate the elbow.

Anterior dislocations are seen much less commonly than posterior dislocations. Divergent dislocations, which result in the ulna and radius dislocating in opposite directions, are even more rare. In the pediatric population, radial head subluxation is the main cause of elbow dislocations.

For excellent patient education resources, visit eMedicine’s Breaks, Fractures, and Dislocations Center. Also, see eMedicine’s patient education articles Elbow Dislocation and Broken Elbow.

Shoulder dislocations account for 50 percent of all major joint dislocations [1-5]. Anterior dislocation is most common, accounting for 95 to 97 percent of cases. Posterior dislocation accounts for 2 to 4 percent and inferior dislocation (ie, luxatio erecta, which means “to place upward”) 0.5 percent [6].

This topic review will discuss the mechanism of injury, evaluation, and reduction of shoulder dislocations. Evaluation of the patient with shoulder pain and other shoulder injuries are discussed elsewhere. (See “Evaluation of the patient with shoulder complaints” and “Acromioclavicular injuries” and “Frozen shoulder (adhesive capsulitis)” and “Glenohumeral osteoarthritis” and “Multidirectional instability of the shoulder” and “Presentation and diagnosis of rotator cuff tears” and “Shoulder impingement syndrome”.)

SHOLDER ANATOMY

The shoulder is an inherently unstable joint . The glenoid is shallow, allowing for a wide range of motion, with only a small portion of the humeral head articulating with the glenoid in any position. The glenoid labrum is a fibrocartilaginous structure that surrounds the glenoid and inserts into the edge of the joint capsule. The distal portion of the joint capsule attaches to the humeral neck. The inferior glenohumeral ligament represents the anterior-inferior portion of the capsule. This ligament is thicker than the rest of the joint capsule and provides the strongest impediment to anterior dislocation.

The rotator cuff muscles provide additional support of the glenohumeral joint. The subscapularis muscle lies anterior to the joint capsule and acts as a secondary support resisting dislocation. Posteriorly the supraspinatus, infraspinatus, and teres minor pull the humeral head into the glenoid and help to prevent it from anterior subluxation.

The axillary nerve, the nerve most often injured with shoulder dislocations, runs inferiorly to the humeral head and wraps around the surgical neck of the humerus. It innervates the deltoid and teres minor muscles and the skin overlying the lateral shoulder (“shoulder badge” distribution). Shoulder anatomy is discussed in greater detail elsewhere.