Forearm Fractures - Pediatric

Forearm fractures are the most common paediatric fractures, accounting for up to 45% of all childhood fractures. The distal third is the most frequently affected site, but the mid-shaft both-bone fracture is the one that matters most, because a malreduced shaft costs the child forearm rotation.

Who. The peak age is 4-14 years, boys more often than girls, hurt on playground equipment and in sport. Both-bone fractures are more common than single-bone fractures, and the incidence is increasing as play becomes more active.

Mechanism. Falls from height on playground equipment, sports injuries and cycling accidents. Direct trauma is less common. An unusual pattern should raise the question of non-accidental injury.

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A functional unit. The radius and ulna work as one, connected by the proximal and distal radioulnar joints and stabilised by the interosseous membrane. Forearm rotation is pronation and supination; in neutral rotation the thumb points up and the radial bow lies lateral.

The radial bow. The natural bow of the radius gives clearance for the muscle bellies and is essential for full pronation-supination. Lose the bow and rotation is restricted.

Why Monteggia and Galeazzi injuries occur. Because the two bones are bound together, an injury to one can affect the other or the proximal or distal radioulnar joint. That is the whole reason an ulna fracture can present with a dislocated radial head, and a radius fracture with a disrupted DRUJ.

Deforming forces. The muscle attachments decide the position in which a fracture is reduced and held:

• Proximal fractures (above pronator teres): the proximal fragment is supinated by biceps and supinator while the distal fragment is pronated by pronator teres, so reduce in supination
• Mid-shaft fractures (below pronator teres): both fragments carry pronation and supination forces, so reduce in neutral
• Distal fractures: reduce in pronation, the most common reduction position

The four patterns. Paediatric forearm fractures are classified by how the cortex fails, and the patterns reflect the soft bone and thick periosteum of the child:

• Plastic (bowing) deformation: the bone bows with no visible fracture line or cortical break. Stable if the bow is under 20°
• Buckle (torus): compression of one cortex with no displacement and no break-through. Stable
• Greenstick: one cortex breaks completely while the other stays intact. Stability is variable
• Complete: both cortices are disrupted. Unstable

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Monteggia: the Bado classification. A Monteggia lesion is an ulna fracture with a dislocated radial head; the Bado types are set out below.

Type I is an extension injury and by far the most common in children.

Galeazzi. A fracture of the radius, typically in the distal third, with subluxation or dislocation of the DRUJ. It is less common in children than in adults and often more stable, because the periosteum is intact.

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History. The mechanism and the time since injury, hand dominance and sports involvement, previous fractures, and any numbness or tingling in the hand.

Examination. Look for deformity and swelling and for any open wound, even a needle-prick. Document the neurovascular status of the median, ulnar and radial nerves and look for the signs of compartment syndrome. Palpate the elbow and the wrist for tenderness; rotational alignment is hard to judge in the acute setting.

Rotation. Rotation cannot be assessed on a radiograph. Compare pronation and supination with the opposite side clinically; after reduction the hand should lie flat with the forearm supinated. Any rotational malunion is permanent.

Differential diagnosis. A child with a painful, swollen forearm after a fall is not always a simple shaft fracture. Distinguishing these patterns changes management entirely, and the most dangerous error is treating an isolated bone fracture and missing the associated joint injury.

The views. The joint above and below a forearm fracture must be imaged, so a forearm series is never complete without the elbow and the wrist.

The radiocapitellar line. A line drawn through the centre of the radial shaft should pass through the centre of the capitellum on every view: AP, lateral and obliques. It can only be judged on a true lateral of the elbow, so insist on one. If the line misses the capitellum, the radial head is dislocated.

Measuring angulation. On the AP view measure the coronal-plane angulation, apex medial or lateral; this plane is less forgiving of residual deformity. On the lateral view measure the sagittal-plane angulation, apex anterior or posterior; this plane, the plane of elbow and wrist motion, remodels better. If you are concerned that the radial bow has been lost, compare it with the opposite side.

What can be accepted. Remodelling decides, and remodelling depends on age, plane and level. Younger children remodel more, and rotation never remodels:

• Under 10 years: up to 15-20° in the sagittal plane and 10-15° in the coronal plane
• Over 10 years: a maximum of 10° in either plane
• Rotation: zero tolerance; it must be anatomically reduced
• Level: a mid-shaft fracture is less forgiving than a metaphyseal one, and a fracture near the physis is more forgiving

Algorithm

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Buckle (torus) fractures. A stable cortical compression injury without displacement, and inherently stable. A splint or removable cast for 3-4 weeks, taken off by the parents, is safe, and follow-up radiographs are usually unnecessary; after FORCE, a soft bandage or removable splint with immediate discharge and no routine follow-up, the child stopping its use when it stops hurting. Do not overtreat them with an above-elbow cast; early mobilisation is safe.

Greenstick fractures. Under 10° of angulation, a below-elbow cast for 4-6 weeks with serial radiographs, because a greenstick can re-angulate. Over 15-20°, complete the fracture under sedation or general anaesthesia by breaking the intact cortex: left intact, that cortex acts as a spring, and completing it allows full reduction without spring-back and stops the cast loosening and the fracture re-angulating as the swelling subsides. Then an above-elbow cast with a proper three-point mould and close follow-up for the first 2 weeks, when loss of reduction is common. An incomplete reduction leads to cast loosening and re-angulation.

Complete both-bone fractures. Closed reduction under finger-trap or manual traction, correcting length, then rotation, then angulation, followed by an above-elbow cast with a well-moulded interosseous space and the forearm rotated as the deforming forces dictate (see Anatomy and Biomechanics). Post-reduction radiographs confirm the position: length re-established, angulation within the limits above, rotation anatomic. Consider ESIN if the fracture cannot be held.

The cast. A proper three-point mould is what holds the reduction, and the interosseous mould is the key part of it. Pad the bony prominences and make the cast well fitted but with room for swelling. Weekly radiographs for the first 2-3 weeks detect loss of reduction.

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Elastic stable intramedullary nailing. ESIN is preferred over plating in paediatric fractures, and its place is the fracture that a cast cannot hold. The indications:

• Unacceptable reduction after a closed attempt
• Re-displacement in the cast
• Open fracture
• Polytrauma
• An older child or adolescent with an unstable pattern
• Segmental fractures

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The management section stresses a well-moulded three-point cast, and the evidence (Bowman) shows that loss of reduction is common and happens early. The quality of the mould can be measured rather than judged by eye, and these indices are increasingly examined as the radiographic answer to "how do you know the cast is good?".

Oval, not round. A well-moulded forearm cast is oval in cross-section, flattened over the volar and dorsal surfaces by the three-point mould, and that oval is what the cast index measures. A round, over-padded cast is the commonest technical reason for loss of reduction, which usually occurs within the first three weeks (Bowman). If the cast index looks poor on the check radiograph, re-mould or re-cast rather than wait for the fracture to slip.

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Radius entry. The radial nail is passed retrograde, from a dorsal entry just proximal to Lister's tubercle or a lateral entry above the distal radial physis. Avoid a palmar entry because of the flexor tendons.

Ulna entry. The ulnar nail is passed antegrade, from the olecranon or the proximal metadiaphysis. Avoid the distal ulnar physis, which is small and subcutaneous.

Technical points. Pre-bend the nails to recreate the radial bow and keep clear of the physis. Nails of 2-2.5 mm are typical, and both bones should ideally be nailed. Seat the nails well to avoid irritation and protrusion, and remove them at 6-12 months.

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Open reduction. It is needed when:

• Closed reduction has failed
• The fracture is open
• There is an associated vascular injury
• A Monteggia is irreducible
• A Monteggia presents late

Approach. Henry's anterior approach for the radius and a direct subcutaneous approach for the ulna. Preserve the periosteum and avoid extensive stripping.

Where the trouble is. ESIN is elegant in younger children, but its problems cluster in adolescents near skeletal maturity, where a straight elastic nail struggles to restore the radial bow and often forces an open reduction. That is why plating is increasingly chosen as the child approaches maturity; the numbers, and their limits, are in Areas of Uncertainty and Debate below.

Refracture. It occurs in 5-10% of forearm fractures. The risk factors are an early return to full activity, removal of the cast too early, initial cortical comminution and stress risers from the previous fracture. Protect for 6 months after healing by avoiding high-risk activities; some surgeons recommend a splint for sport during this period, others recommend no specific protection, and either way the family is counselled about the risk.

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Good outcomes. Expect an excellent result when the rotation is anatomically reduced, the angular malunion is within acceptable limits, any Monteggia or Galeazzi has been identified and treated, and the forearm has been protected from refracture.

Poor prognostic factors. The failures of those same steps:

• Rotational malunion
• Missed Monteggia, with chronic radial head dislocation
• Late diagnosis of compartment syndrome

Side-by-Side Guideline and Society Positions

High-Resource vs Limited-Resource Practice

Monteggia fracture-dislocation. The triad is an ulna fracture, a radial head dislocation and a disrupted annular ligament. The most common lesion in children is Bado type I, an extension injury with apex-anterior ulnar angulation and anterior dislocation of the radial head. Closed reduction of the ulna usually reduces the radial head with it; the arm is held in an above-elbow cast in flexion and supination, and the radiocapitellar line is checked again after reduction. If the radial head remains dislocated, open reduction may be needed, because the annular ligament may be entrapped.

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Galeazzi fracture-dislocation. Reduce the radius fracture; the DRUJ usually reduces spontaneously in children. Hold in an above-elbow cast in supination.

Plastic deformation. Bowing of the bone without a visible fracture line is unique to paediatric bone, and a significant bow restricts rotation. A bow under 10° is accepted; 10-20° is considered for reduction; over 20° requires reduction under general anaesthesia with sustained force. The technique is sustained pressure over the apex of the deformity for 2-3 minutes, under which the bone slowly straightens; it cannot be snapped and must be bent gradually.

Areas of Uncertainty and Debate

Exact acceptable angulation thresholds. There is no universally agreed figure. Published thresholds vary by age, fracture level and plane, and most are based on retrospective series rather than trials. The figures used here, 10 degrees over 10 years and 15-20 degrees under 10 years, are pragmatic conventions, not hard biological limits.

One bone or both at surgery. When operating on a both-bone fracture, some surgeons nail only the more unstable bone, arguing that the second reduces and stays once one is stabilised. Others routinely fix both to maximise stability. Evidence is limited and practice varies.

ESIN versus plating in adolescents. As children approach skeletal maturity, remodelling falls and ESIN may fail to restore the radial bow. Comparative data (Freese et al.) show plating restores anatomy more reliably: the radial bow was significantly smaller and more distal after nailing, and 76% of nailed patients needed an open reduction of at least one bone. The complication comparison points the same way but is not statistically significant in a series of 32 plated against 70 nailed, so it is a trend rather than a proven difference. Plating costs a larger scar; the frequently quoted 91% reoperation rate for nails is mostly planned implant removal, not failure.

Routine implant removal after ESIN. Whether nails should always be removed is debated. Removal avoids late irritation and theoretical refracture through a stress riser, but adds a second anaesthetic and procedure. Practice ranges from routine removal at 6-12 months to leaving asymptomatic nails in situ.

Follow-up radiographs in stable patterns. Following the FORCE trial, torus fractures increasingly receive no follow-up imaging at all. Extending a 'minimal follow-up' approach to other stable patterns, such as the minimally angulated greenstick, is an active area of de-implementation.