Orthopaedic Surgery - Radial Head Dislocation

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Basics

Radial head dislocation is displacement of the radial head from its normal articulation with the:

Capitellum

and

Proximal ulna.

An isolated traumatic radial head dislocation is:

Rare, particularly in adults.

It is seen more often in:

Children

and most traumatic cases occur in association with an:

Ulnar fracture or deformity.

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Monteggia Injury

The most important associated injury is a:

Monteggia fracture-dislocation

in which radial head dislocation occurs together with fracture or deformity of the:

Proximal ulna.

Because subtle ulnar bowing may be present even without an obvious fracture line, the entire forearm should be evaluated.

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Direction of Dislocation

The radial head may dislocate:

Anteriorly

Anterolaterally

Posteriorly

Posterolaterally

or, less commonly,

Laterally.

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Classification

Radial head dislocation can be classified according to:

Direction of displacement

and

Pathogenesis.

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By Direction

Anterior

Posterior

Lateral

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By Cause

Traumatic

Congenital or developmental

Pathologic

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Congenital Radial Head Dislocation

Congenital and developmental radial head dislocations are more common than isolated traumatic dislocations.

They frequently occur in association with other abnormalities of the:

Elbow

Forearm

or

Skeleton.

They are usually chronic and may be discovered incidentally.

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Epidemiology

Radial head dislocation is:

Uncommon.

Most traumatic cases occur together with:

Proximal ulnar injury.

Isolated traumatic radial head dislocation is particularly rare.

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Risk Factors and Associated Disorders

Conditions associated with developmental or pathologic radial head dislocation include:

Osteogenesis imperfecta

Fibrous dysplasia

Multiple osteochondromas

Achondroplasia

Congenital radioulnar synostosis

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Genetics

There is no single inherited pattern for radial head dislocation itself.

However, several genetic skeletal disorders may predispose to abnormal radial head development or instability.

Potential mechanisms include abnormalities involving:

Ligament structure

Endochondral ossification

Forearm growth

and

Elbow development.

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Annular Ligament

The principal soft-tissue stabilizer of the radial head is the:

Annular ligament.

This ligament encircles the radial head and holds it against the:

Radial notch of the ulna.

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Pathophysiology

In an acute traumatic dislocation, the annular ligament is usually:

Torn

or

Severely stretched.

Loss of annular ligament restraint permits the radial head to move away from its normal articulation with the capitellum.

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Congenital Anatomy

Congenital radial head dislocation is associated with characteristic developmental abnormalities.

These may include:

Hypoplastic capitellum

Ovoid or dome-shaped radial head

Proximal ulnar bowing

Relative radial overgrowth

These findings help distinguish congenital disease from an acute traumatic dislocation.

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Etiology

A typical traumatic mechanism is:

Fall onto an outstretched hand

with the:

Elbow extended

and

Forearm pronated.

This may generate:

Varus stress

and rotational forces across the elbow.

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Monteggia Mechanism

In Monteggia injuries, additional:

Rotational

and

Axial compression forces

produce a fracture or plastic deformation of the ulna together with radial head displacement.

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Associated Injuries

Traumatic radial head dislocation may occur with:

Proximal ulna fracture

Ulnar plastic deformation

Radial neck fracture

Elbow dislocation

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Nerve Injury

Posterior and posterolateral radial head dislocations may stretch the:

Radial nerve

or

Posterior interosseous nerve.

Neurologic examination is therefore essential.

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Diagnosis

Diagnosis is based on:

Mechanism

Physical examination

and

Radiographs.

One of the most important tasks is distinguishing:

Acute traumatic dislocation

from

Congenital or long-standing dislocation.

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Signs and Symptoms

Acute traumatic dislocation typically produces:

Elbow pain

Swelling

Reduced forearm rotation

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Pronation and Supination

Loss of:

Pronation

and

Supination

is often more pronounced than loss of flexion and extension.

Forearm rotation may be:

Painful and markedly restricted.

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Congenital Dislocation

Congenital radial head dislocation is often:

Painless during childhood.

It may be discovered after an unrelated injury or because of:

Visible lateral prominence

Restricted forearm rotation

or elbow asymmetry.

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History

Important questions include:

Was there recent trauma?

Was the child ever known to have elbow deformity previously?

Are both elbows affected?

Is there a known skeletal disorder?

How long has motion been limited?

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Physical Examination

A complete examination should be performed before any reduction maneuver.

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Neurovascular Examination

Assess:

Radial pulse

Capillary refill

Median nerve function

Ulnar nerve function

Radial nerve function

Posterior interosseous nerve function

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Radial Nerve Examination

Particular attention should be paid to:

Wrist extension

Finger extension

Thumb extension

because radial or PIN traction injury may occur.

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Contralateral Elbow

Examine the opposite elbow.

Bilateral radial head dislocation strongly suggests:

Congenital or developmental disease.

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Position of the Arm

A child with an acute injury may hold the elbow:

Flexed

and the forearm:

Pronated

while refusing to use the arm.

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Palpation

The displaced radial head may be palpable.

This is especially true with:

Posterior

or

Posterolateral dislocation

because there is relatively little overlying soft tissue.

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Flexion and Extension

Elbow flexion and extension may remain nearly full.

However:

Anterior dislocation may limit flexion.

Posterior dislocation may limit extension.

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Forearm Rotation

Pronation and supination are usually:

Markedly restricted

and may reproduce significant pain.

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Imaging

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Plain Radiographs

Initial imaging usually includes:

AP

and

Lateral views of the elbow.

These are often sufficient to identify radial head malalignment.

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Radiocapitellar Line

A line drawn along the longitudinal axis of the:

Radius

should intersect the:

Capitellum

on every properly positioned radiographic view.

Failure of this:

Radiocapitellar line

to pass through the capitellum suggests radial head dislocation.

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Forearm Radiographs

Radiographs of the entire forearm are important to evaluate for:

Ulnar fracture

Ulnar bowing

Plastic deformation

Ulnar shortening

These abnormalities may explain persistent radial head displacement.

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Congenital Radiographic Findings

Features suggesting congenital dislocation include:

Dysplastic or hypoplastic capitellum

Ovoid radial head

Proximal ulnar bowing

Relative radial overgrowth

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Bilateral Imaging

If congenital dislocation is suspected, radiographs of the opposite elbow may help identify:

Bilateral involvement.

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Chronic Traumatic Dislocation

Long-standing unreduced traumatic dislocation may eventually resemble congenital disease because of adaptive remodeling.

Potential findings include:

Radial head deformity

Capitellar dysplasia

Ulnar bowing

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Heterotopic Ossification

Heterotopic bone around the radial head may suggest:

Old trauma

or a long-standing unreduced dislocation.

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Differential Diagnosis

Important alternatives include:

Radial head subluxation

Congenital radial head dislocation

Monteggia fracture-dislocation

Occult ulnar fracture or plastic deformation

Radial neck fracture

Generalized skeletal dysplasia

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Treatment

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General Principles

Treatment depends on whether the dislocation is:

Acute traumatic

Chronic traumatic

or

Congenital.

The distinction is essential because congenital dislocations are usually:

Not treated with acute reduction.

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Congenital Dislocation

An asymptomatic congenital radial head dislocation generally requires:

Observation.

Surgery is reserved for selected patients with:

Pain

Progressive functional limitation

or other significant symptoms.

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Acute Traumatic Dislocation

An acute isolated traumatic dislocation should generally undergo:

Prompt closed reduction.

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Closed Reduction

A commonly described technique involves:

Gentle longitudinal traction

with the elbow extended, followed by:

Correction of the deforming stress

Forearm supination

and

Direct pressure over the radial head.

The exact maneuver depends on the:

Direction of dislocation.

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Confirmation of Reduction

After reduction:

Forearm rotation should improve

and the radiocapitellar relationship should be confirmed radiographically.

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Immobilization

Following stable reduction, the elbow is usually immobilized in approximately:

90° of flexion.

A:

Posterior splint

is often adequate.

In younger children who may remove the splint, a:

Bivalved cast

may be necessary.

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Stability After Reduction

The elbow and radial head should be assessed through a safe arc of:

Flexion

Extension

Pronation

Supination

to determine stability.

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Delayed Presentation

As time passes, closed reduction becomes progressively more difficult because of:

Scar formation

Soft-tissue contracture

and

Adaptive deformity.

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Injuries Older Than Approximately 1 Week

If a traumatic dislocation is more than about:

7 days old

and closed reduction is unsuccessful, operative reduction may be necessary.

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Chronic Dislocation

After several weeks, successful closed reduction becomes unlikely.

Open reduction is generally required when meaningful reconstruction remains feasible.

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Long-Standing Dislocation

After several years, adaptive deformity of the:

Radial head

and

Capitellum

may prevent stable anatomic reduction.

Management must then be individualized according to:

Pain

Motion

Age

and

Degenerative change.

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Monteggia Injury in Children

In children, restoration of:

Ulnar length and alignment

is the key to reducing the radial head.

Treatment may involve:

Closed reduction

or, when necessary,

Operative fixation of the ulna.

Fixation options include:

Intramedullary nail

or

Plate and screws

depending on the fracture pattern.

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Chronic Monteggia Injury

Chronic Monteggia lesions may require:

Open radial head reduction

Ulnar osteotomy

and sometimes

Annular ligament reconstruction.

Correction of ulnar deformity is critical because persistent bowing can prevent a stable radial head reduction.

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Monteggia Injury in Adults

Adult Monteggia fracture-dislocations generally require:

Open reduction and internal fixation of the ulna.

Restoration of anatomic ulnar alignment usually allows the radial head to reduce.

If it remains displaced, the radiocapitellar joint must be:

Directly evaluated and reduced.

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Physical Therapy

The rehabilitation goal is restoration of:

Pain-free elbow flexion

Extension

Pronation

Supination.

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Early Motion

Range-of-motion exercises should begin:

As early as stability permits

because prolonged immobilization increases the risk of:

Elbow stiffness.

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Pediatric Recovery

Children generally regain elbow motion more reliably after immobilization than:

Adults.

Adults are more prone to:

Persistent contracture.

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Medication

Pain control may include:

Acetaminophen

NSAIDs

or other appropriate analgesics.

Postoperative or post-reduction analgesia should facilitate:

Early rehabilitation.

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Heterotopic Ossification Prophylaxis

In selected high-risk adult patients with previous heterotopic ossification or major neurologic injury, prophylaxis may be considered.

Historically, agents such as:

Indomethacin

have been used, although prophylaxis should be individualized according to current surgical practice and patient risk.

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Surgery

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Unstable Reduction

If the radial head remains unstable after reduction, a longer period of:

Immobilization

may be required.

Rarely, temporary fixation across the:

Radiocapitellar joint

with a Kirschner wire has been described.

Because transarticular pinning carries risks, it is reserved for selected unstable injuries.

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Annular Ligament Repair

During open reduction, the annular ligament may be:

Repaired

or

Reconstructed

when it is necessary to maintain radial head stability.

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Ulnar Deformity

Any significant:

Ulnar bowing

Malalignment

or

Shortening

should be corrected at the same time.

Failure to restore ulnar anatomy can cause persistent or recurrent radial head displacement.

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Radial Head Resection

Radial head excision is not appropriate in:

Children

because of the risk of forearm instability and growth-related problems.

In selected skeletally mature adults with chronic painful irreducible dislocation and substantial degenerative change, excision may occasionally be considered as a salvage procedure.

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Follow-Up

Patients should be followed closely until they regain satisfactory:

Elbow motion

Forearm rotation

and

Neurologic function.

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Prognosis

The prognosis after prompt treatment of an acute traumatic dislocation is generally:

Excellent.

This is particularly true in patients younger than approximately:

30 years.

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Range of Motion

Mild residual loss of:

Pronation

Supination

Flexion

or

Extension

may occur but is often not functionally important.

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Chronic Injury Prognosis

Outcome is less predictable when treatment is delayed because chronic dislocation may result in:

Joint remodeling

Contracture

Radial head deformity

Capitellar degeneration

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Complications

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Recurrent Dislocation

Failure of the annular ligament to heal or persistent ulnar malalignment may result in:

Recurrent radial head instability.

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Stiffness

Prolonged immobilization or scar formation may cause:

Loss of elbow motion

and

Reduced forearm rotation.

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Heterotopic Ossification

Heterotopic bone formation may further restrict:

Elbow motion

particularly after high-energy trauma or surgery.

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Nerve Injury

Potential neurologic complications include:

Radial nerve palsy

and

Posterior interosseous nerve palsy.

Many traction-related palsies recover spontaneously, but serial examination is required.

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Degenerative Change

Long-standing incongruity may eventually produce:

Radiocapitellar osteoarthritis

and chronic pain.

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Patient Monitoring

Follow-up should assess:

Radiocapitellar alignment

Elbow stability

Pronation and supination

Flexion and extension

Radial and posterior interosseous nerve function

Patients should continue rehabilitation until:

Functional range of motion is restored and the radial head remains stable.

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Key Principle

Radial head dislocation is an uncommon injury that should always prompt evaluation of the entire ulna and forearm for a Monteggia injury or subtle ulnar bowing.

The diagnosis is confirmed when the:

Radiocapitellar line fails to intersect the capitellum.

Acute traumatic dislocations are generally treated with:

Prompt reduction and short-term immobilization followed by early motion, whereas congenital dislocations are usually observed and chronic traumatic cases may require:

Ulnar correction, open radial head reduction, and annular ligament reconstruction.