Correct Answer:

posterior dislocation of the elbow

Educational Objective:

Describe the clinical presentation associated with posterior elbow dislocation.

Key Point:

The classic mechanism of injury for posterior elbow dislocation is a fall on the outstretched hand or wrist, with the elbow either extended or hyperextended. The patient will present with the elbow in flexion at ~45 degrees and with prominence of the olecranon process.

Explanation:

The patient’s x-ray shows posterior elbow dislocation with a slightly displaced, avulsed fragment of the coronoid process. Compare the Figures to notice how relatively unimpressive the clinical presentation of a dislocated elbow looks in comparison with the more dramatic-looking x-ray.

The elbow is the second most commonly dislocated joint (after the shoulder) in the upper extremity. The classic mechanism of injury for posterior elbow dislocation is a fall on the outstretched hand or wrist, with the elbow either extended or hyperextended. The patient will present with the elbow in flexion at about 45 degrees and with prominence of the olecranon process. Dislocations of the elbow require considerable forces, so associated fractures of adjacent bony structures are common.

Immediate reduction of these dislocations is imperative to relieve the frequently associated neurovascular compromise and to prevent compartment syndrome. Posterior elbow dislocations can be reduced with a partner by bringing the elbow into flexion while steady countertraction is applied to the anterior surface of the distal humerus.

Anterior elbow dislocations are rare and usually the result of a direct blow to the olecranon with the elbow in a flexed position.

Nursemaids elbow is usually diagnosed clinically.

In children, the same mechanism of injury results in an extension supracondylar fracture rather than a dislocated elbow.

Reference:

Bookman K. Humerus and elbow. In: Walls R, et al. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 9th ed., 2018: 530-548.e1.