Elbow Resources

Elbow dislocation (R)(M) Elbow dislocation (R)(M)


Anatomy and biomechanics
Nearly 50% of the stability of the elbow is provided by the ulnohumeral articulation.
The anterior band of the MCL is very important. This is usually completely disrupted in elbow dislocation, as is the lateral ligament complex.
The lateral ligamentous complex keeps the ulna from subluxating posteriorly and rotating away from the humerus in supination (posterolateral rotatory instability). Note that the capsule is attached 6mm from the tip of the coracoid process, and brachialis is attached 11mm distal to the coronoid tip.

Pathoanatomy
The MCL is usually disrupted; the lateral collateral ligament is usually disrupted; the anterior elbow capsule, brachialis, articular cartilage and flexor pronator origin can be disrupted. There is often a shear fracture of the tip of the coracoid. Fractures are seen in 40% of elbow dislocations.
Osteochondral injuries are seen in almost 100% of cases.

Epidemiology
Second most common dislocation after the shoulder.

Clinical
Usual mechanism of injury is a fall onto an outstretched hand. Commonly seen after MVA, sports injuries. Concomitant other injury to upper limb in 10%.
There is a 20% incidence of median or ulnar nerve neurapraxia.
Arterial injuries are rare.

Classification
Simple (no associated fracture) vs. complex (associated fracture).
Described by position of distal segment on XR; most are posterolateral (90%). (Most paediatric supracondylar fractures are posteromedial).
Also classified as dislocation or subluxation (perched dislocation, seen in less than 10%).

Treatment
Goal is a stable elbow that tolerates early motion.
Initial treatment is with closed reduction under sedation, then assessment of the stable ROM. After a week, or less, ROM is started within the stable range. The results are compromised if the elbow is kept motionless for more than 2 weeks . As there has been a trend towards early ROM the incidence of redislocation and instability has not increased. The secondary stability provided by the dynamic muscle action, in concert with primary stability from the ulno-humeral articulation, is enough to provide stability. However, O'Driscoll advocates immobilizing young patients for longer (3-4 weeks).
If the elbow is only stable in full pronation, indicative of gross PLRI, then a cast brace is applied with the forearm fully pronated, and full movements are encouraged. The cast brace is applied for 3-6 weeks.
Post reduction XR should be taken, and assessed for widening of the joint space (associated with osteochondral fragments) and posterior translation of the radial head and gaping of the ulno-humeral joint (indicative of posterolateral rotatory instability),
In complex dislocations, associated fractures (except for type I coronoid fractures) must be fixed or an unstable elbow will result. If the elbow is still unstable after ORIF of fractures, the MCL needs to be reconstructed. The MCL will usually have been avulsed from the humeral origin. Note that there is no advantage to routine repair of the collateral ligaments over early ROM.
If the elbow is still unstable, a hinged external fixator is required.
In older patients with severely comminuted complex elbow dislocations an elbow arthroplasty may be preferred.

Results
Simple elbow dislocations usually have an excellent outcome – return of functional ROM and at least 85% of normal strength.
The commonest complication is loss of extension – usually in the order of 10-15 degrees; this is related to the length of immobilization.
Recurrent dislocation is rare: 1-2%. PLRI is more common. The risk of redislocation is higher in young patients (under 15) and in patients with loose bodies in the joints.
The incidence of heterotopic ossification is around 5%, increasing if there are associated elbow injuries. It is typically located in the brachialis muscle.
Distal radioulnar joint instability may result if there is an associated radial head fracture; the head needs to be fixed or replaced, thus restoring the radial length, and if necessary the DRUJ needs to be stabilized with K wires between radius and ulna, proximal to the DRUJ.
The results of complex dislocation are poorer.
The long term results of dislocations are good. At an average of 24 years after simple dislocation, none of 52 patients had symptoms of instability, although 15% had signs of valgus instability on examination. 38% had radiographic evidence of mild OA (Joseffson 1984).
This can be compared with patients who had dislocation and radial head fracture, with excision of the radial head; by 14 years postop severe arthritis had developed in more than half of the patients (Joseffson 1989).

Chronic dislocations
The clinical results are variable. If there is little pain and function is reasonable the dislocation may be accepted. If pain and loss of function are significant, then open reduction is required.
The procedure involves anterior and posterior capsulectomy, MCL slide off the humerus, LUCL repair and application of a hinged distractor for approximately 4-6 weeks.

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