Monteggia Fractures in Children

The adult injury, where open reduction and plate fixation of the ulna is the rule rather than the exception, is developed in Monteggia fractures; the mirror-image lesion in Galeazzi fractures.

The lesion. A Monteggia fracture-dislocation is a fracture of the ulnar shaft with dislocation of the radial head at the radiocapitellar joint. Giovanni Monteggia described it in 1814; Bado classified it in 1967.

Who. A rare injury, less than 2% of paediatric forearm fractures, with a peak age of 4-10 years. It is often associated with high-energy trauma but can occur from a simple fall, and Bado Type I (anterior) is by far the most common pattern in children.

Why it is missed. In a child the ulnar injury is not always a clean break: it often presents as plastic deformation, a bow in the ulna with no fracture line. A radial head cannot dislocate without ulnar pathology or an annular ligament rupture, which is rare in isolation, so if you see a dislocated head with no obvious ulnar fracture lines, look for bowing. Up to 50% are missed at the first presentation, and the missed paediatric Monteggia is the most common malpractice case in paediatric orthopaedics, one of the most frequently missed and most litigated childhood injuries.

View larger

Mechanism. A fall on the outstretched hand with forced pronation transmits force through the interosseous membrane to fracture the proximal ulna and dislocate the radial head; a direct blow to the forearm is the other mechanism.

The forearm ring. The forearm and elbow work as a ring made of the radius, the ulna, the proximal radioulnar joint and the distal radioulnar joint, and the two bones are bound together by the interosseous membrane. Break the ring in one place and it often gives way in another: an ulna that shortens or angulates forces the radius it is tethered to out of its joint, which is why reducing the ulna is what reduces the radial head.

The stabilisers. The soft-tissue structures that hold the proximal radius in place:

• Annular ligament - the primary stabiliser of the proximal radioulnar joint, encircling four-fifths of the radial head. In a Monteggia lesion it usually ruptures or becomes interposed, blocking reduction
• Interosseous membrane - its central band is a stout structure that transfers load from radius to ulna and prevents excessive proximal migration of the radius
• Quadrate ligament - connects the neck of the radius to the supinator crest of the ulna
• Lateral collateral ligament complex - provides varus stability to the elbow, and is often injured in the varus Type III pattern

The radiocapitellar joint. The radial head ossifies at 3-5 years and the capitellum at 1 year, so in the youngest children the line that tests the joint is drawn through the radial neck rather than the head. What that line should show, and on which view to trust it, is covered under Investigations.

Bado also described Monteggia equivalent lesions: injury patterns that behave like a Monteggia, with radial head instability or dislocation, but do not show the classic complete ulnar fracture plus dislocation. They matter because they fall into exactly the same missed-diagnosis trap, and they are managed on the same restore-the-ulna logic.

History. Establish the mechanism and where it hurts, and ask about the elbow and the forearm separately. "Wrist" pain may be referred, or it may be the other lesion: check for a Galeazzi as well.

Look. The forearm is angulated and swollen around the elbow and the fracture site. The radial head may be palpable as a prominence in the antecubital fossa in a Type I injury or behind the elbow in a Type II.

Feel. Tenderness runs along the ulnar shaft. Palpate the radial head and place it relative to the lateral epicondyle.

The nerves. The posterior interosseous nerve is the motor branch of the radial nerve, and it is a pure motor nerve, unlike the superficial radial branch, so a PIN palsy has no sensory loss. Examine it before any manipulation and document it:

• Thumbs up - extensor pollicis longus, the hitchhiker sign
• Finger extension at the metacarpophalangeal joints, and index extension for extensor indicis
• Wrist extension weak and deviates radially
• Sensation is intact

The ulnar nerve is injured less often; assess the interossei.

Red flags. Before planning the reduction, check for:

• Open fracture (usually Gustilo I)
• Compartment syndrome (pain out of proportion)
• Skin tenting (impending open fracture)
• Polytrauma (for example, Monteggia plus femoral fracture)

Documenting it. An emergency department note that covers what matters reads something like this:

"6yo female, fall on outstretched hand. Isolated injury. O/E: Deformity L forearm. Closed neurovascularly intact. PIN function normal (thumbs up). X-ray: Midshaft ulna fracture with anterior radial head dislocation (Bado I). Plan: Ketamine procedural sedation for closed reduction. Discussed risks (PIN palsy, loss of reduction, cast issues) with parents. Consented."

The views. Dedicated elbow and wrist views, not forearm views alone, and the elbow view must be a true lateral, because that is the only projection on which the radiocapitellar line can be trusted.

The radiocapitellar line. A line drawn along the radial neck shaft should pass through the centre of the capitellum. On the lateral view, a line that passes anterior to the capitellum means an anterior dislocation (Type I), posterior means a posterior dislocation (Type II), and centred is normal.

The line in a young child. The rule that the line must bisect the capitellum on every view is sound in a skeletally mature elbow and unreliable in a small child. In a series of 200 radiographically normal children's elbows aged 0 to 18, measured across six age bands (DOI), the line passed through the middle third of the capitellum in 93% on the lateral projection but only 74.5% on the AP. The age gradient is the striking part: on the AP it rose from 8.3% at 0 to 3 years to 94.1% at 16 to 18 (P = 0.001), and on the lateral from 50% to 100% (P = 0.023). The authors conclude that these measurements must be interpreted with great caution in younger age groups, because that is exactly where the largest proportion of normal elbows fail to follow the established principle.

Both errors are live here, and they pull in opposite directions. Over-diagnosis is calling a dislocation in a toddler because the line misses the capitellum on the AP, when roughly nine in ten normal toddlers look that way on that view. Under-diagnosis is the graver risk, because a missed lesion becomes a chronically dislocated radial head. So do not abandon the line; use it properly. Draw it on a true lateral, where it is reliable even in young children; treat an AP appearance alone as insufficient grounds to diagnose or exclude a dislocation under about four years; and compare the contralateral elbow. The strongest safeguard is not the line at all but the rule that any apparently isolated ulnar shaft fracture, or any ulnar plastic deformation, demands dedicated elbow views and a high index of suspicion.

The ulnar bow. Look for plastic deformation, comparing with the other side if unsure. The normal ulna has a slight posterior bow and is never bowed anteriorly.

View larger

View larger

View larger

View larger

The differential is anything that produces radial head malalignment or a proximal forearm injury on a paediatric radiograph, and the discriminator is almost always the radiocapitellar line plus the state of the ulna. Mistaking a congenital dislocation for an acute one leads to an unnecessary attempted reduction; a traumatic Monteggia always has an ulnar abnormality, whether a fracture or plastic deformation.

The goal. Anatomic reduction of the ulna, in length and in angulation, after which the radial head reduces indirectly. Reduce the ulna to reduce the radius; if ulnar length is not restored, the head will not reduce or will not stay reduced.

Where and how. Go to theatre: muscle relaxation is the key, and sedation in the emergency department often fails because of spasm. Get length first, and pull hard, because a short ulna will not let the head back in. Mould the interosseous space by squeezing the radius and ulna apart. Confirm the result on a true lateral and do not accept obliques, since the radiocapitellar line is only valid on a true lateral.

View larger

AcuteChronic (Missed)

Bado I (anterior). Traction in extension restores length, then the elbow is flexed to 100-110° with the forearm fully supinated, and the ulnar angulation is moulded out with a valgus or varus mould as needed. The long arm cast holds the same position, flexion at 100-110° and supination. Supination tightens the interosseous membrane and relaxes the biceps, the main deforming force on the proximal radius; flexion relaxes the biceps as well and pushes the radial head back. Neutral rotation is not enough.

The manoeuvre itself, step by step:

1. Traction - an assistant holds the humerus while the surgeon pulls traction on the forearm in extension
2. Supination - fully supinate the forearm
3. Correction - apply pressure over the posterior ulna to correct the anterior angulation
4. Reduction - maintaining traction and pressure, flex the elbow past 90°; there is usually a "clunk" as the radial head reduces
5. Check - verify the reduction on fluoroscopy, then cast in 100-110° of flexion and supination

Monitor the distal vascular status in hyperflexion.

Bado III (lateral). Traction in extension, then a valgus stress to correct the ulnar varus; cast in extension or slight flexion with a valgus mould. The varus is hard to hold in a cast, so the ulna often needs an intramedullary nail.

Bado II (posterior). Extension of the elbow reduces the posterior head, with pronation; the cast is in extension, which is uncommon and awkward, or the fracture is fixed, though it rarely needs ORIF.

Bado IV. Both bones are fractured, and open reduction and internal fixation is usually required for stability.

When to operate. Failure to maintain the ulnar reduction, an unstable fracture, or a Letts B or C ulna (complete or comminuted) is an indication for intramedullary nailing or open fixation. This is the relationship the evidence section documents: in the multicentre ulnar-pattern series, every treatment failure was a complete fracture managed without stabilisation, and incomplete fractures can usually be managed closed.

After the reduction. Confirm that the radiocapitellar line is restored in all views.

What chronic means. Presentation more than 4 weeks after injury, often months or years later, with the radial head still dislocated. The child has limited flexion (Type I) or extension (Type II), a prominence or "bump" at the elbow, valgus deformity and, rarely and late, PIN symptoms.

Algorithm

View larger

Observation has a place for the asymptomatic older child, over about 10-12 years, with a good range of motion; the head may form a false joint.

Ulnar osteotomy is the operation for the rest, and ulnar lengthening is the priority:

• Restore ulnar length, which is crucial
• Create space for the radial head
• Angulate the ulna, over-correcting, to lever the radial head back
• Add annular ligament reconstruction (Bell-Tawse, triceps fascia) if needed
• Add open reduction of the radiocapitellar joint to clear fibrosis if needed

Timing. Delay to surgery is the strongest predictor of failure and the most consistent predictor of redislocation. Most evidence favours operating within the first year; beyond this the radiocapitellar joint and the ulnar geometry remodel unfavourably, though exact cut-offs remain debated.

Radial head excision is a salvage for pain at skeletal maturity. It is not done in the growing child, because it causes proximal migration of the radius at the wrist.

View larger

Flexible intramedullary nailing of the ulna is indicated for the unstable Type I or III fracture and for failure of closed reduction.

Preparation. Set up before the tourniquet goes up:

• Position - supine, arm on a radiolucent hand table
• Image intensifier - from the head or across from the surgeon, with the monitor at the foot of the bed
• Draping - sterile tourniquet high on the arm; drape to include the shoulder so the limb can be rotated
• Instruments - small fragment set, flexible nails (TENs), wire driver, oscillating saw if an osteotomy is needed
• Consent - infection, nerve injury (PIN), loss of reduction, removal of metalwork

In the chronic (missed) Monteggia, once an ulnar osteotomy has restored length and angulation and the radial head has been openly reduced, the annular ligament is usually deficient and the joint must be stabilised. Knowing the options, and which the evidence actually favours, is a common viva follow-up.

View larger

View larger

View larger

PIN palsy. The most common complication, in 10-20% of cases, particularly with Type III (lateral) or Type I injuries, where the nerve is stretched. It is almost always a neurapraxia that resolves spontaneously, usually within 6-12 weeks, and more than 90% recover spontaneously, so do not rush to explore; arrange electromyography if there is no recovery after 3 months. This is why the pre-reduction examination must be documented.

View larger

Before the cast comes off. Check the radiograph first: the ulna should be healing and the radial head reduced. If the ulna has angulated, the radial head may have subluxated.

Treated acutely, the prognosis is excellent and most children regain a full range of motion; recurrence is rare if ulnar length is maintained. Missed and treated late, the prognosis is guarded: reconstruction by osteotomy improves pain and stability but often leaves some stiffness.

Global epidemiology:

• Monteggia fracture-dislocations account for less than 2% of paediatric forearm fractures, with a peak incidence at 4-10 years of age and a slight male predominance in most reported series.
• Common mechanisms worldwide are falls onto the outstretched hand, falls from playground equipment (monkey bars, trampolines) and direct blows to the forearm; in lower-resource settings, road traffic and fall-from-height injuries contribute a higher proportion of high-energy Bado IV patterns.
• Bado Type I (anterior) predominates in children (roughly 70%), with Type III (lateral) the second most common; Types II and IV are uncommon in the paediatric population.

Side-by-side practice and guidance:

Fixation of the complete ulna. A complete ulnar fracture needs stabilisation, but the choice between elastic intramedullary nailing, plating and external fixation is institution-dependent. Elastic nailing is increasingly favoured over external fixation for lower residual pain and better cosmesis.

The asymptomatic missed case. Whether to operate on an older child with a chronically dislocated but pain-free, well-functioning elbow is unsettled. Some advocate observation, given the surgical morbidity and the risk of stiffness; others reconstruct to prevent late pain, instability and tardy PIN palsy.