Introduction
Background
Elbow dislocation is the most common dislocation in children; in adults, it is the second most common dislocation after that of the shoulder.1,2,3,4 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.1,2,3,4,5 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.
Related eMedicine topics:
Joint Reduction, Elbow Dislocation, Posterior
Joint Reduction, Radial Head Dislocation
Posttraumatic Heterotopic Ossification
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Resource Center Exercise and Sports Medicine
Resource Center Joint Disorders
Specialty Site Neurology & Neurosurgery
Specialty Site Orthopaedics
Specialty Site Pediatrics
Frequency
United States
The rate of elbow dislocation is 6-13 cases per 100,000 people, and this injury occurs more frequently in males than in females. Of all elbow dislocations, 10-50% are sports related. More than 90% of elbow dislocations are posterior dislocations.
Functional Anatomy
The elbow is primarily a flexion-extension hinge joint, which also allows for pronation and supination. Normal range of motion (ROM) at the elbow should be extension to 0° and flexion to 150°.1,2
The humerus and ulna form a very stable unit, which is generally resistant to disruption unless considerable force is applied. This inherent stability also reduces the likelihood of redislocation. The primary bony stabilizers are the coronoid and radial head.
The medial collateral ligament (MCL) and lateral collateral ligament (LCL) comprise the ligamentous stability of the elbow and act as a back-up system to the elbow's natural bony stability. The MCL consists of 3 bands, the anterior oblique, posterior oblique, and the transverse. The anterior band provides most of the resistance to valgus stress. The LCL has 2 bands, the ulnar collateral and radial collateral.
The 2 main compartments of the elbow are the anterior and posterior compartments. The anterior compartment contains the brachial artery and the ulnar and median nerves. This compartment is more commonly affected by dislocations and is the reason for clinical concern regarding brachial artery disruption and median or ulnar nerve entrapment.1,2,4,6
The ulnar nerve passes posteriorly to the medial epicondyle of the humerus, and then it travels deep in the forearm before becoming more superficial again at the wrist. The close proximity of the ulnar nerve to the medial epicondyle allows for the increased likelihood of entrapment when a dislocation occurs. The median nerve is also frequently affected and travels intimately with the brachial artery, which predisposes to simultaneous injury for both the artery and nerve. The posterior compartment contains the radial nerve and triceps brachii muscle.
Anatomically, the mechanism for elbow dislocations is believed to occur as a continuum of damaged/torn structures, beginning laterally with the ulnar portion of the LCL, followed by complete LCL disruption, then damage to the anterior and posterior compartments. The posterior MCL can then become damaged, leaving the anterior portion intact. Further force can allow the elbow to pivot about the anterior bundle of the MCL, potentially damaging it. The LCL, therefore, is considered to be the initial weak link in elbow dislocations.
In the pediatric population, the clinician should be aware of the 6 ossification centers of the elbow joint as well as the annular ligament. The capitellum, radial head, internal (medial) epicondyle, trochlea, olecranon, and external (lateral) epicondyle (CRITOE) is the order in which the ossification centers appear. These centers may often be mistaken for fractures on x-rays. NOTE: A general rule of thumb for the time of appearance of the ossification centers is "1-3-5-7-9-11," which are the ages in years, corresponding to the CRITOE pneumonic.
In cases in which there is radial head subluxation, the radial head slips under the annular ligament and becomes trapped.
Sport-Specific Biomechanics
Biomechanically, no single sport definitively increases the risk of elbow dislocations; however, sports that increase the likelihood of a person falling onto an outstretched hand (ie, FOOSH injury) (eg, gymnastics, rollerblading, cycling) may theoretically increase the risk of elbow dislocation.
Clinical
History
- In posterior elbow dislocations, the patient often describes falling on an outstretched hand (ie, the FOOSH injury) as the mechanism of injury. Some clinicians speculate that the elbow is more likely to dislocate when it is slightly abducted and flexed. When compressive forces are directed on to the outstretched hand, the radius and ulna, along with the valgus force at the elbow, suffer the common posterolateral dislocation. These forces also contribute to associated fractures. In addition, hyperextension at the elbow has been seen with elbow dislocations.
- Anterior dislocations are usually the result of a direct posterior blow to a flexed elbow. Associated fractures of the olecranon are commonly seen.
- Divergent dislocations are very rare injury and are associated with significant high-energy trauma to the elbow.
- In children, radial head subluxations often occur when the arm is pulled. The child commonly holds the arm pronated, mildly flexed, and abducted against the body and refuses or fights any manipulation of the affected arm.
- Essential elements of the dislocation history include the mechanism of the injury, the time between the injury and presentation, functioning, previous attempts at reduction/manipulation, swelling, location, and the type of pain.
Related Medscape topics:
Resource Center Fracture
Resource Center Joint Disorders
Resource Center Trauma
Physical
Neurovascular assessment and documentation of the clinical evaluation are essential in any elbow dislocation because associated brachial artery and ulnar nerve injuries are frequent. Median nerve injuries are also common.
- Evaluate the injury for swelling.
- Note any deformities that are present.
- Posterior elbow dislocations often have a very prominent olecranon and a forearm that appears foreshortened.
- Anterior elbow dislocations have the appearance of an elongated forearm, and the arm is held in extension.
- Touch sensation of the median and ulnar nerves can be quickly assessed by testing the distal palmar aspect of the first through fifth digits. (The ulnar nerve innervates the medial one half of the fourth digit and the fifth digit, as well as the dorsal side of the same digits.)
- Motor function of the median and ulnar nerve can be quickly assessed by evaluating the abduction and adduction strength of the digits (ulnar nerve) and the opposability of the thumb (median nerve).
Related Medscape topics:
Resource Center Vascular Surgery
Specialty Site Neurology & Neurosurgery
Specialty Site Orthopaedics
Causes
Unlike the shoulder, a previous elbow dislocation does not predispose a patient to future dislocations. Elbow dislocations are commonly caused by a fall on an outstretched hand or by a traumatic event. Radial head subluxations in children are usually caused by pulling or yanking on the child's arm when the child's elbow is extended.
More on Elbow Dislocation |
 Overview: Elbow Dislocation |
| Differential Diagnoses & Workup: Elbow Dislocation |
| Treatment & Medication: Elbow Dislocation |
| Follow-up: Elbow Dislocation |
| Multimedia: Elbow Dislocation |
| References |
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References
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Further Reading
Keywords
elbow dislocation, dislocation of elbow, dislocated elbow, radial head dislocation, ulnar dislocation, radial head subluxation, FOOSH injury, falling on an outstretched hand, nursemaid's elbow, elbow injury, elbow trauma
