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Elbow dislocation

Description

Dislocation of the elbow (3 articulations --ulno-trochlear hinge joint, and radio-capitellar and proximal radio-ulnar pivot joints) occurs when the active and passive stabilizing mechanisms fail under stress. Sequential disruption of the stabilizing mechanisms from lateral to medial is the basis for Morrey’s instability scale (Types I- Posterolateral; II- Varus; IIIa – Valgus; IIIb- Gross).




Structure and function

Active stabilizers include muscles crossing the elbow joint that act by generating protective compressive joint reaction forces. Maximum compression is generated by elbow flexors Biceps and Brachialis, and the elbow extensors Triceps and Anconeus. Passive stabilizers include capsuloligamentous restraints (primary) and highly congruous bony articulations (secondary).
Varus (and posterolateral) stress is resisted actively by the lateral extensor-supinator muscle group, and passively by the Lateral Collateral Ligamentous complex (most importantly the Lateral Ulnar Collateral bundle; Others-Annular ligament stabilizes the proximal radio-ulnar joint, Radial Collateral ligament, Accessory Lateral Ulnar collateral, Quadrate ligament and oblique cord) and the Coronoid process.
Valgus stress is resisted actively by the medial flexor-pronator muscle group, and passively by the Medial Collateral Ligamentous complex (most importantly the Anterior bundle; Others- Posterior bundle, and Transverse ligament of Cooper) and the radial head.
Both varus and valgus stresses are resisted passively by the Anterior capsule and the Olecranon process during full elbow extension.




Epidemiology

The elbow is the most common upper extremity joint to be acutely dislocated in children, and second in incidence to the shoulder in adults. Chronic or recurrent instability after traumatic dislocation is uncommon. Young males are the most commonly affected group.
Elbow dislocations are classified as the more common simple (soft tissue injury only, low-high energy trauma) and less common complex (with bony injury as well, high energy trauma) types.  Further sub classification is based upon the direction of displacement (anterior, posterior, medial, lateral) of the radius and ulna w.r.t. the humerus.
The commonest simple dislocation is the posterior/postero-lateral type, which occurs secondary to a fall on an outstretched hand. Anterior, Medial and Divergent types are less common, and occur secondary to motor vehicle accidents. Complex dislocations are sub classified as anterior and posterior.




Clinical presentation

History – H/O trauma (fall on outstretched hand, motor vehicle accident, fall on/ blow to bent elbow)
Symptoms- pain around elbow, swelling, limitation of elbow motion, numbness/ tingling, weakness.
Signs- Inspection and palpation of the elbow joint revealing guarding of the limb, swelling, and instability may be sufficient for making a preliminary diagnosis, and may negate the requirement of the painful stress testing (lateral pivot shift, valgus, varus).
 It is vital to examine (a) the whole limb – for associated bony injuries, especially the wrist/hand (b) digital perfusion and distal pulses - for vascular (most commonly Brachial artery) injury, and (c) sensory-motor examination – for nerve (Median, Ulnar) injury.




Red flags

Limb vascular and sensory-motor status must be documented both immediately and post-reduction in all cases of acute elbow dislocation. Massive swelling indicates high risk of compartment syndrome, and arm elevation, serial neuro-vascular examinations, and, if required, fasciotomy, must be performed
Forcible manipulation without muscle relaxation and analgesia should be avoided to reduce future risk of Myositis Ossificans.




Differential diagnosis

Evaluation for (a) compartment syndrome and (b) fractures around the elbow joint is essential for management.  Elbow structures commonly fractured in complex elbow dislocation include the Radial head and the Coronoid process (together with elbow dislocation, referred to as the terrible triad) as well as the distal humerus. Other notable associations include Monteggia and Olecranon fractures.




Objective evidence

Acute dislocation: Pre-reduction x-rays provide  evidence including effusion (anterior fat pad sign), direction of dislocation (subtype), and periarticular fracture (simple vs. complex). Biplanar (AP in full elbow extension, Lateral in 90° elbow flexion) views are sufficient in adults, while oblique views may be needed in children, especially to document lateral condyle fracture. Fluoroscopy during reduction is helpful in ensuring a congruous reduction. Post-reduction x-rays should document an intact radio-capitellar line as evidence of adequate reduction, and may additionally reveal associated fractures. 3D CT is useful in presurgical planning of complex elbow dislocations to document intraarticular fragments and fractures. MRI may be used to look for Osteochondral fractures in children.
Chronic/ recurrent elbow dislocation and late complications: Stress x-ray views, ultrasound and MRI can identify underlying ligament damage. CT, bone scan and x-rays can document Myositis ossificans Arthroscopy/arthrography can be used to identify intraarticular loose bodies.




Risk factors and prevention

Throwing (baseball pitching, football passing, etc), non-throwing (tennis, golf, etc.) sports that stress the elbow joint are important risk factors, especially in the skeletally-immature population. Avoidance of overuse and proper technique can help avoid injury.
Contact sports leading to a fall on outstretched hand /elbow, and high-velocity trauma to the elbow sustained in motor vehicle accidents are other important risk factors for acute dislocation.
Recurrent dislocation occurs when ligament injuries may have been missed at initial presentation. Non-preservation of radial head in case of extensive Medial Collateral ligamentous complex damage can also predispose to recurrent instability.




Treatment options

Initial management involves emergent reduction of the elbow under muscle relaxation and analgesia, preferably in the OR using fluoroscopy to ensure congruent reduction. Reduction maneuvers involve application of gentle distal longitudinal forearm traction and arm counter-traction, with the patient prone and elbow flexed (arm / forearm hanging over the side), accompanied by appropriately directed pressure (e.g. Posterior dislocation – anteriorly directed pressure on the Olecranon). Post-reduction clinical documentation of adequate ROM and elbow stability and satisfactory neuro-vascular status, as well as x-ray documentation of joint congruence is essential to proceed to further non-operative management.
Non-operative management of simple dislocations (both stable and unstable types) involves splinting in 90 °of elbow flexion for 1-2 weeks, follow-up x-rays at 3-5 days and 10-14 d post-reduction, and range of motion exercises with interval splinting/sling, as tolerated over 3-6 weeks post reduction.
Operative management is required urgently for neurovascular compromise (exploration and repair), unstable complex dislocations (open reduction and internal fixation, and reconstruction of ligaments; arthroscopic repair when possible), and compounded fractures (external fixation).




Outcomes

Adequately treated simple elbow dislocation has a better prognosis compared with complex dislocation. Commonly used functional outcome instruments (DASH, MEPI and Oxford questionnaire) report an overall favorable long term prognosis, with higher rates of elbow stiffness, residual pain and instability reported in complex dislocation. Loss of extension is the commonest limitation in ROM, but is not a limitation for work and ADLs for most patients. Outcomes can be improved by early mobilization (3 weeks post injury.
Other long term complications that may require treatment include heterotopic ossification (prophylaxis - irradiation and Indomethacin; treatment -excision), lack of neurologic recovery within 3 months (exploration), Volkmann’s Ischaemic Contracture (reconstructive surgery and muscle transfer).




Holistic medicine

 




Miscellany

 




Key terms

elbow, varus and valgus stress, simple and complex type, postero-lateral dislocation, throwing sports, compartment syndrome, urgent gentle reduction, early mobilization, good prognosis




Skills

Clinical and radiographic skills to identify elbow dislocation and type, and perform urgent reduction and splinting / casting, followed by definitive treatment.
Identification and management of compartment syndrome and neuro-vascular status  pre- and post-reduction is vital.


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