Orthopaedic Surgery - Monteggia Fracture

Basics

A Monteggia fracture-dislocation is a combined injury involving an ulnar fracture or plastic deformation together with dislocation of the radial head.

Because the radius and ulna are linked by the:

Interosseous membrane, annular ligament, and proximal radioulnar soft tissues, deformity of the ulna can disrupt the normal relationship between the radial head and capitellum.

A Monteggia injury is sometimes missed because attention is focused on the obvious ulnar fracture while the radial head dislocation is overlooked.

Successful treatment requires restoration of:

Ulnar length and alignment

and

Concentric reduction of the radial head.

Bado Classification

The Bado system is the most commonly used classification.

It is based primarily on the direction of radial head dislocation and the associated ulnar deformity.

Type I

The radial head is dislocated anteriorly.

The ulna typically demonstrates anterior angulation.

This is the classic and most common pattern in children.

Type II

The radial head is dislocated posteriorly or posterolaterally.

The ulna usually has posterior angulation.

This pattern is particularly important in adults and may be associated with additional elbow injuries.

Type III

The radial head is displaced laterally or anterolaterally.

The ulna usually has a metaphyseal fracture with lateral angulation.

This is a relatively common pediatric pattern.

Type IV

Both the radius and ulna are fractured, with associated anterior dislocation of the radial head.

Epidemiology

Monteggia fracture-dislocations are relatively uncommon.

They can occur at any age but are especially important in children.

Pediatric Incidence

Peak incidence is approximately:

4–10 years of age.

Males and females are affected at roughly similar rates.

Common Patterns

In children, Bado Type I injuries predominate.

In adults, Types I and II are particularly important, with Type II injuries often associated with more complex elbow trauma.

Risk Factors

Any patient with a fracture or significant bowing of the:

Proximal or middle ulna

should be considered at risk for an associated radial head dislocation.

The elbow must therefore always be examined and imaged.

Etiology

Monteggia injuries occur because the radius and ulna function as a mechanically linked unit.

Trauma that fractures or deforms the ulna can disrupt the proximal radioulnar relationship and dislocate the radial head.

Type I Mechanism

Commonly proposed mechanisms include:

Hyperpronation

or

Hyperextension with rotational force.

Type II Mechanism

Type II injuries may result from:

Axial loading of a partially flexed elbow, often combined with posteriorly directed force.

Diagnosis

Signs and Symptoms

Acute injuries commonly produce:

Pain

Forearm swelling

Elbow swelling

Deformity

Tenderness over the ulna and elbow

Delayed Presentation

When the injury has been missed, patients may later develop:

A visible or palpable prominence around the elbow

Restricted elbow flexion or extension

Painful clicking

Loss of pronation or supination

The prominence may represent a persistently dislocated radial head.

Physical Examination

The entire forearm and elbow should be examined.

Inspection

Assess for:

Swelling

Angular deformity

Forearm bowing

Prominence of the radial head

Open injury

Palpation

Palpate:

The ulna along its entire length

Radial head region

Elbow joint

Wrist

Range of Motion

When tolerated, evaluate:

Elbow flexion and extension

Forearm pronation and supination

A dislocated radial head may mechanically restrict motion.

Neurovascular Examination

A complete distal neurovascular examination is mandatory.

Particular attention should be paid to the radial nerve and posterior interosseous nerve, because these may be injured or stretched during radial head dislocation.

Assess:

Wrist extension

Finger and thumb extension

Sensation

Capillary refill

Distal pulses

Imaging

Plain radiographs are usually sufficient to establish the diagnosis.

Required Views

Obtain:

True AP and lateral radiographs of the forearm

with visualization of both:

The elbow and the wrist.

If the elbow and wrist cannot both be adequately included on the same study, obtain separate radiographs.

Radiocapitellar Line

The most important radiographic check is the radiocapitellar line.

A line drawn along the longitudinal axis of the radial neck and shaft should intersect the capitellum on all properly positioned views.

Failure of the line to pass through the capitellum suggests radial head dislocation.

Ulnar Alignment

The ulna should also be assessed carefully for:

Fracture

Plastic deformation

Subtle bowing

Shortening

In children, even relatively mild ulnar bowing can be associated with radial head dislocation.

Post-Reduction Imaging

Radiographs must be obtained after reduction to confirm:

Restoration of ulnar alignment

and

Concentric radial head reduction.

MRI

MRI is not routinely required for an acute Monteggia injury.

It may be useful in selected chronic or unusual cases when soft-tissue anatomy or associated injury is uncertain.

Pathological Findings

At the time of injury, the annular ligament may be torn, stripped, or interposed within the radiocapitellar joint.

This interposition can prevent closed reduction.

Chronic Radial Head Dislocation

If the radial head remains unreduced for a prolonged period, secondary changes may develop, including:

Radial head deformity

Capitellar remodeling

Cartilage degeneration

Loss of normal joint congruity

These changes make late reconstruction more difficult.

Differential Diagnosis

Isolated Ulnar Fracture

An ulnar fracture may occur without radial head dislocation.

The radiocapitellar line should always be checked to confirm that the radial head remains aligned with the capitellum.

Isolated Radial Head Dislocation

Isolated traumatic radial head dislocation is uncommon.

When identified, other associated injury should be excluded.

Congenital Radial Head Dislocation

Congenital radial head dislocation may mimic a neglected Monteggia injury.

Features favoring a congenital disorder include:

Abnormal radial head shape

Loss of its normal concavity

Capitellar dysplasia

Bilateral involvement in some cases

Absence of a traumatic history

Treatment

General Principles

Treatment is directed toward:

Restoring normal ulnar length and alignment

and

Maintaining a stable radial head reduction.

In many acute pediatric injuries, reduction of the ulna automatically restores the radial head.

Pediatric Treatment

Closed reduction is successful in many children.

The reduction maneuver and cast position depend on the Bado pattern.

Type I

The ulna is reduced and the forearm is generally immobilized in:

Supination or neutral rotation with the elbow flexed substantially, often beyond 90°.

Historically, flexion greater than approximately 110° has been used in selected stable Type I injuries.

Type II

Reduction requires correction of the posterior ulnar angulation.

Immobilization position is individualized according to stability, often with less elbow flexion than Type I.

Type III

Reduction requires correction of:

Lateral or varus/valgus ulnar deformity, depending on the exact injury pattern.

The elbow and forearm are immobilized in the position that best maintains radiocapitellar stability.

Radial Head Reduction

After restoring the ulna, the radial head should be reassessed.

If it remains dislocated, gentle directed pressure may assist reduction.

Persistent failure to reduce raises concern for:

Annular ligament interposition, inadequate ulnar alignment, or another mechanical block.

Casting

A well-molded above-elbow cast is typically used in children after successful reduction.

If swelling is substantial, the cast may be:

Bivalved or otherwise adjusted to accommodate swelling.

Unstable Pediatric Injury

Open reduction and fixation are considered when:

Closed reduction cannot be achieved

Alignment cannot be maintained

The radial head remains unstable

The ulnar fracture is markedly displaced or comminuted

Adult Treatment

In adults, Monteggia fracture-dislocations are usually treated operatively.

The standard principle is:

Anatomic restoration and rigid fixation of the ulna, most commonly with plate-and-screw fixation.

Accurate reconstruction of the ulna often results in spontaneous reduction of the radial head.

Radial Head Surgery

If the radial head does not reduce after anatomic ulnar fixation, open reduction should be performed.

Possible causes include:

Annular ligament interposition

Entrapped capsule

Malreduction of the ulna

Pediatric Ulnar Fixation

When surgical fixation is required in a child, options include:

Intramedullary fixation

or

Plate fixation.

Intramedullary stabilization is useful for many simple fracture patterns.

A plate may be preferable when the fracture is:

Oblique, comminuted, unstable, or difficult to control with an intramedullary device.

Adult Ulnar Fixation

Adults generally require rigid plate fixation to restore:

Length, rotation, and angular alignment.

Even relatively small residual deformities of the ulna can prevent stable radial head reduction.

Late Diagnosis

Delayed recognition makes treatment more difficult.

Delay of Approximately 1–3 Weeks

Within the first several weeks, closed reduction may become difficult because of:

Fibrosis, soft-tissue interposition, and early healing of the ulna.

Open reduction may therefore be required.

Chronic Monteggia Injury

After a longer delay, reconstruction may require:

Ulnar osteotomy

Restoration of ulnar length and angulation

Open radial head reduction

Annular ligament reconstruction in selected cases

Annular Ligament Reconstruction

A classic procedure is the Bell–Tawse technique, in which a strip of triceps fascia is used to reconstruct the annular ligament around the radial neck and anchor it to the ulna.

The exact need for annular ligament reconstruction depends on chronicity and radial head stability after correction of the ulna.

Physical Therapy

Children

Formal physical therapy is usually unnecessary after uncomplicated treatment.

Children typically regain motion spontaneously with:

Normal use and home exercises.

Adults

Adults have a greater risk of elbow stiffness and often benefit from:

Supervised range-of-motion therapy

after sufficient fracture stability has been achieved.

Follow-Up

Pediatric Immobilization

Children are often immobilized for approximately 4–6 weeks, depending on:

Age, fracture healing, and stability of the radial head.

Adult Rehabilitation

Because elbow stiffness is common in adults, controlled motion is usually started earlier when fixation permits.

Early Follow-Up

Patients should generally be reviewed approximately 1 week after reduction.

The purpose is to confirm:

Maintained ulnar alignment

Persistent radial head reduction

Acceptable cast condition

Intact neurovascular status

Referral

Monteggia fracture-dislocations should be referred promptly to an orthopaedic surgeon because missed or inadequately reduced injuries can result in significant long-term dysfunction.

Prognosis

The prognosis is generally good when the injury is:

Recognized early, anatomically reduced, and followed carefully.

Stable pediatric injuries often have excellent outcomes after closed treatment.

Poor Prognostic Factors

Less favorable outcomes are associated with:

Missed or delayed diagnosis

Persistent radial head dislocation

Associated radial head fracture

Associated coronoid fracture

Complex adult injury patterns

Chronic instability

Chronic Injury Prognosis

Results of delayed reconstruction are less predictable because prolonged dislocation may cause:

Radial head deformity

Capitellar remodeling

Cartilage damage

Loss of forearm rotation

Complications

Potential complications include:

Redislocation of the radial head

Elbow stiffness

Loss of forearm rotation

Proximal radioulnar synostosis

Elbow instability

Malunion or nonunion of the ulna

Post-traumatic arthritis

Nerve Injury

Radial nerve or posterior interosseous nerve dysfunction may occur at the time of injury.

Many neuropraxic injuries recover spontaneously, but persistent deficits require further assessment.

Redislocation

Loss of ulnar alignment may cause the radial head to redislocate.

This is why early follow-up radiographs are essential.

Patient Monitoring

The patient should be reviewed early after reduction and then periodically until:

The fracture has healed

The radial head remains concentrically reduced

Elbow motion is satisfactory

Forearm rotation has returned

Key Principle

Every fracture of the proximal or middle ulna should prompt deliberate evaluation of the radiocapitellar relationship.

The defining treatment principle of a Monteggia injury is:

Restore the ulna first and confirm that the radial head is anatomically and stably reduced.