Elbow Dislocation

Elbow dislocation is the second most common major joint dislocation in adults after the shoulder, usually posterior or posterolateral after a fall on an outstretched hand.

Incidence peaks between 10 and 19 years, and nearly half of dislocations happen in sport. A simple dislocation has no fracture and usually does well with prompt reduction and early movement. A complex dislocation has an associated fracture, carries more risk of instability, stiffness and arthritis, and usually needs surgery.

The elbow has 3 articulations in 1 capsule: ulnohumeral (hinge), radiocapitellar and proximal radioulnar. Its bony congruence makes it inherently stable, so any dislocation means substantial soft-tissue injury.

Key stabilisers:

• •Medial collateral ligament: the anterior bundle is the main restraint to valgus stress
• •Lateral collateral complex: the lateral ulnar collateral ligament (LUCL) is the main restraint to posterolateral rotatory instability (PLRI)
• •Coronoid process: the anterior buttress against posterior dislocation; even small fractures can destabilise the joint

The Horii circle (O'Driscoll) describes soft-tissue failure from lateral to medial: stage 1, the LUCL (PLRI); stage 2, the anterior and posterior capsule (perched dislocation); stage 3, the medial side, from the posterior medial ligament (3A) to the whole medial ligament (3B) and beyond (3C).

Patterns:

• •Posterior or posterolateral: the large majority, from a fall on an outstretched hand with a valgus, supinating load
• •Posteromedial: a varus pattern, associated with an anteromedial coronoid facet fracture
• •Terrible triad: posterior dislocation with radial head and coronoid fractures; highly unstable

Nerves and vessels at risk: the median nerve and brachial artery anteriorly, and the ulnar nerve behind the medial epicondyle.