Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

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Radial Head Dislocation

Basics
Description
  • Isolated traumatic dislocation of the radial head is a rare injury seen mainly in children, although several reports have described this injury in adults.
  • Congenital and developmental radial head dislocations are seen more commonly, although they rarely are seen in the absence of other congenital abnormalities of the elbow or forearm.
  • The radial head may be dislocated anteriorly, anterolaterally, posteriorly, or posterolaterally.
  • Classification:
    • Direction of radial head displacement: Anterior, posterior, or lateral
    • Pathogenesis: Traumatic, congenital, or pathologic
Epidemiology
Radial head dislocations are uncommon injuries, usually occurring with an associated ulna fracture.
Risk Factors
  • OI
  • Fibrous dysplasia
  • Osteochondromas
  • Achondroplasia
  • Congenital forearm synostosis
Genetics
No genetic inheritance pattern for radial head dislocation is known, but because the main restraints to radial head dislocation in the normal elbow are ligamentous, children with ligamentous laxity (e.g., achondroplasia) may have a predisposition to such conditions without associated fractures.
Pathophysiology
  • In the normal elbow, the critical restraint to radial head dislocation is the annular ligament.
    • This ligament usually is torn or severely stretched in the case of a dislocation.
  • In the congenitally dislocated radial head, a hypoplastic capitellum and an ovoid radial head are essentially pathognomonic.
  • Proximal ulnar bowing also is evident on radiographs, although this finding is not unique to the congenital dislocation.
Etiology
The mechanism of injury is believed to be a fall onto the outstretched hand with the elbow extended and the forearm pronated, resulting in a varus stress on the elbow.
Associated Conditions
  • In the setting of trauma, this injury may be associated with a proximal ulna fracture, a radial neck fracture, or an elbow dislocation.
  • Isolated radial head dislocations, particularly posterior dislocations, may be associated with radial nerve or posterior interosseous nerve stretch injuries.
Diagnosis
Signs and Symptoms
  • Pain, swelling, and decreased supination or pronation of the forearm are the main symptoms of the traumatic dislocation.
  • The congenitally dislocated radial head:
    • Normally is painless in childhood, although it usually is discovered in the young child after elbow trauma
    • Also may come to attention secondary to a painless lateral prominence in the setting of a posterolateral dislocation
Physical Exam
  • Perform a complete neurovascular examination at presentation and before undertaking any manipulations.
  • Examine the function of the radial nerve because it may have undergone traction injury.
  • Perform an examination of the contralateral elbow to rule out bilateral radial head dislocations, which may suggest a congenital dislocation and pre-existing disease in the affected elbow.
  • On physical examination, hold the elbow immobile and flexed with the forearm in pronation.
    • The child often refuses to use the injured arm.
    • The radial head usually can be palpated, particularly with posterior and posterolateral dislocations, in which there is little overlying soft tissue.
    • Nearly full flexion and extension usually are noted, although some limitation often exists at 1 extreme, depending on the direction of the dislocation (mildly limited flexion if anteriorly dislocated and extension if posteriorly dislocated).
    • Supination and pronation are markedly limited and cause pain.
Tests
Imaging
  • Radiography:
    • AP and lateral radiographs of the elbow usually are sufficient for making the diagnosis and for assessing reduction.
    • A separate film of the forearm usually is helpful to look for ulnar bowing or shortening, which may contribute to the dislocation.
    • Abnormalities of the capitellum and radial head may suggest a congenital dislocation.
    • Radiographs of the contralateral elbow should be obtained to rule out bilateral involvement, which also would indicate a congenital dislocation.
    • Congenital dislocations may be associated with a dysplastic capitellum, a bowed ulna, a relatively long radius, or an ovoid radial head, but a long-standing traumatic dislocation may have similar radiographic findings unilaterally.
    • Heterotopic ossification in the soft tissues about the radial head may suggest an old, unreduced traumatic dislocation.
  • Some authors advocate elbow arthrograms if it is difficult in young children to distinguish between congenital and traumatic causes.
    • A congenital dislocation would show an ovoid radial head within the joint capsule.
    • A traumatic dislocation would be associated with a normally shaped radial head.
    • In the acute situation, extravasation of the arthrogram’s contrast agent occurs.
Differential Diagnosis
  • Subluxated elbow
  • Congenital dislocation
  • Monteggia fracture with an occult fracture
  • Radial neck fracture
  • Generalized disorder (OI, fibrous dysplasia, osteochondromas)
Treatment
General Measures
  • It is important to distinguish a traumatic from a congenital dislocation because the latter does not require treatment.
  • If the condition is judged to be an acute, traumatic dislocation, closed reduction usually can be performed in the acute setting.
    • With gentle traction and the elbow in full extension, varus stress is applied to the elbow joint.
    • The forearm is supinated while direct pressure is applied to the radial head to reduce it.
    • The reduction then is held in 120° of flexion for children (90° and in supination for adults).
    • A posterior splint usually suffices, although a bivalved cast may be necessary in the young child who may remove the splint.
  • If the injury is >7 days old, open reduction may be necessary if closed reduction is unsuccessful.
    • After 3 weeks, a successful closed reduction is impossible, and open technique is universally required.
    • For long-standing traumatic dislocations (>2-3 years), deformation of the radial head and capitellum may occur, which would preclude a stable reduction.
Special Therapy
Physical Therapy
  • Full, pain-free ROM of the elbow (flexion, extension, supination, and pronation) are the goals of treatment of this injury.
  • Elbow ROM exercises are begun as early as possible without compromising the stability of the joint.
  • The pediatric elbow is more forgiving than the adult’s with respect to regaining full ROM after prolonged immobilization.
Medication
First Line
  • Symptomatic treatment for pain is suggested.
  • Analgesia is a necessary part of rehabilitation after surgery or cast immobilization.
  • In a patient with a history of heterotopic ossification or neurologic injury (which may predispose to heterotopic ossification), prophylaxis with indomethacin may decrease the incidence of heterotopic ossification of the elbow.
Surgery
  • In the unstable reduction, a prolonged period of immobilization may be necessary to allow for fibrous tissue to confer stability.
    • Occasionally, the immobilization may be augmented by a Kirschner wire across the radiocapitellar joint.
  • When elbow contractures are of concern (in patients >30 years old, particularly the elderly) or in patients with long-standing dislocations, a radial head resection may be performed to begin early ROM of the elbow.
  • With open reduction of the radiocapitellar joint, most surgeons advocate repair or reconstruction of the annular ligament.
    • May be performed successfully up to 2 years or more after traumatic dislocation
    • Any ulnar bowing should be addressed at the same time.
Follow-up
Prognosis
  • The prognosis is excellent for a functional ROM of the elbow, forearm, and wrist, particularly in patients <30 years old.
  • Mild ROM restrictions may be present compared with the contralateral side but usually none that would be noted by the patient.
Complications
  • Recurrent dislocations
  • Decreased ROM secondary to contracture or heterotopic ossification
  • Radial or posterior interosseous nerve palsies and degenerative changes of the radiohumeral joint
Patient Monitoring
Patients are followed at 1-month intervals until they regain their ROM.
Miscellaneous
Codes
ICD9-CM
832.9 Dislocation of radial head
Patient Teaching
  • Patients are instructed on the need for home ROM exercises.
  • Patients also are told that they may lose 10° of elbow extension.
FAQ
Q: What are the signs of a radial head dislocation?
A: A bony prominence anteriorly (with block to full flexion) or posteriorly (with block to full extension).
Q: Is surgery indicated for a radial head dislocation?
A: Usually a closed reduction can be undertaken within the 1st few weeks after injury. If closed reduction fails, or the dislocation is detected late, then surgery is indicated.

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