Paediatric Distal Radius, Buckle and Physeal Wrist Fractures

Paediatric distal radius injuries are among the most common fractures in childhood, usually after a fall on an outstretched hand. They range from a stable compression injury to a displaced fracture involving both cortices or the distal radial physis, and the clinical skill is matching the amount of treatment to the true stability of the injury.

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Naming the injury. A buckle fracture is a compression bulge in the cortex, stable because there is no complete cortical disruption, and it should not be treated like a displaced fracture. Conversely, a complete metaphyseal fracture or displaced physeal injury should not be softened into the word "buckle" just because the child is young: it is a complete fracture wearing a nicer name.

The goals. Identify the pattern, protect the skin and nerves, and avoid unnecessary follow-up for stable buckle fractures. Reduce unacceptable deformity gently, use a well-moulded non-tight cast when one is needed, and give families clear cast and swelling return advice.

Mechanism. Most paediatric distal radius fractures follow an axial load through an extended wrist. The pattern depends on bone elasticity, cortical failure, the integrity of the periosteal hinge, and whether the force exits through the metaphysis or the physis.

Remodelling. Remodelling potential is excellent near the distal radial physis, and how much a deformity will correct depends on the age of the child, the plane of the deformity and its proximity to the physis.

• Younger children have more growth remaining; remodelling is less reliable in adolescents and in injuries close to skeletal maturity
• Sagittal-plane deformity remodels more predictably than coronal deformity, and rotation does not remodel reliably
• The closer the fracture lies to the distal radial physis, the greater the correction available
• Remodelling is also less reliable in unstable complete fractures

Shortening or bayonet apposition may be acceptable in selected young children, but it should not be used as a blanket rule for adolescents near skeletal maturity.

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The physes. The distal radial physis contributes major forearm growth, which is why physeal injuries require surveillance. Distal ulna physeal injury deserves its own attention: growth disturbance can create ulnar variance and distal radioulnar joint problems, and it should not be forgotten when the radius fracture dominates the X-ray.

Classification by fracture type drives treatment: a stable buckle fracture is a different injury from a displaced metaphyseal or physeal one.

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Stability. Each pattern is then graded by how far it can be trusted to stay where it is:

• Stable: a true buckle, minimal pain, no deformity, intact cortex
• Potentially unstable: greenstick, complete fracture, associated ulna fracture
• Unstable: displaced complete fracture, bayonet apposition in an older child, displaced physeal injury
• High-risk: open injury, neurovascular symptoms or compartment concern

Transitional fractures. A transitional fracture may look like a Salter-Harris III on the AP view but show a Salter-Harris II component on the lateral, so both projections are needed to define the fracture.

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History

The history should separate a stable low-energy wrist injury from a displaced fracture, associated injury or safeguarding concern.

Examination

Inspection separates a comfortable stable injury from a deformed unstable fracture, and what separates a buckle from a displaced physeal fracture is cortical stability, deformity, tenderness pattern and radiographic alignment. Skin, deformity, median nerve and perfusion are checked before any cast goes on, because they detect urgent problems. Do not force wrist movement when the diagnosis is clinically obvious.

Tenderness and sensation. Localise the pain to the distal radius or ulna and feel over the physis itself: local physeal tenderness can be the clue to a physeal injury, and it changes follow-up. Test ulnar and radial sensation as well as the median nerve.

The lateral view is essential, because a subtle dorsal buckle can be missed on the AP alone.

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Reading the film. Look at both cortices, and confirm there is no physeal extension, before calling a buckle fracture. Then assess dorsal or volar tilt, translation, shortening and any associated ulna fracture, and do not miss a distal ulna physeal injury. In adolescents, consider a carpal injury if the pain is not explained by the distal radius findings.

Repeat imaging. Whether and when to repeat the films depends on stability, age, reduction and the local fracture protocol.

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The first decision is whether the injury is truly stable. A true buckle fracture can be managed simply because it is a stable compression injury; a displaced complete or physeal fracture needs an alignment assessment, a reduction decision, a good cast and follow-up.

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The treatment steps up with instability:

• Splint for stable buckle injuries
• Cast for pain control or for stable fractures needing support
• Reduce displaced fractures or unacceptable alignment
• Operate for irreducible, open, neurovascular-compromising or unstable patterns

The stable buckle fracture

Explanation and movement. Explain to the family that this is a stable compression injury, and encourage finger, elbow and shoulder movement. When the diagnosis is secure and the family has clear return advice, a true torus fracture should not need repeated X-rays, prolonged casting or fracture-clinic congestion.

Return to sport. This depends on pain-free wrist motion, resolution of tenderness and the injury pattern, and a buckle fracture returns earlier than a displaced physeal or complete metaphyseal fracture. Avoid contact sport until the child is pain-free and the advised timeframe is complete.

Displaced metaphyseal and physeal fractures

Give analgesia and appropriate sedation, reduce unacceptable angulation or displacement gently, and apply a well-moulded cast that is not tight. Arrange fracture-clinic follow-up with repeat imaging when there is a risk of displacement.

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The cast mould. After reduction of a displaced fracture, the quality of the cast mould is the surgeon-controlled factor that most predicts redisplacement. A good cast is three-point moulded and elliptical (flattened) rather than round in cross-section.

The cast index. This is the internal sagittal (lateral) cast width divided by the internal coronal (AP) cast width, measured at the fracture level. A well-moulded elliptical cast has an index around 0.7; an index above 0.8, a round and poorly moulded cast, is strongly associated with loss of reduction. The three-point, gap, padding and Canterbury indices are related measures, and all quantify moulding or contact and predict redisplacement.

Acting on it. If the post-reduction cast index is above 0.8 or the mould is poor, anticipate redisplacement. Re-mould (for example, wedge) or review early, and have a low threshold for fixation in the older child.

The physis. Classify the Salter-Harris pattern and reduce gently if the position is unacceptable. The number of reduction attempts is itself a risk, because each forceful manipulation of a physeal fracture adds arrest risk. Beyond 10 days from injury, manipulation should be abandoned altogether, and a late displaced physeal fracture is usually better accepted and remodelled than re-reduced.

Surveillance. Growth disturbance may be delayed (Harris lines later), and more growth remaining means more surveillance. Follow physeal injuries for growth disturbance when the risk is meaningful; the complications section sets out in whom it is.

Fixation and special cases

Open fractures and neurovascular compromise are managed urgently. Consider fixation for unstable, irreducible or recurrently displaced patterns, and for unacceptable alignment in the older child.

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What "unacceptable" means

No validated threshold. The word "unacceptable" appears throughout any account of these fractures, and there is no validated threshold behind it. The most recent current-concepts review states plainly that even among experts there is little consensus on the optimal treatment of displaced metaphyseal fractures.

The 15° convention. The figure most often quoted, 15° of angulation, is described in the literature as the maximum acceptable limit but was never derived from an outcome study. The one series that specifically examined malunions above it found that all 40 fractures remodelled, from a mean of 23° down to 8° in the sagittal plane, so treat any single number you are given as convention.

Time, not speed. In that series remodelling speed was not related to age (mean 2.5° per month, faster with greater initial angulation). What younger children have is more time, not faster correction, and an adolescent near maturity has neither: growth remaining is the binding constraint.

Making the call. The decision is made from the child's age, the plane of the deformity and the physis, not from a protractor reading alone. Accepting a deformity in a young child with a sagittal-plane malunion is a defensible, evidence-consistent choice rather than a compromise.

Early

• Median nerve symptoms
• Cast tightness, swelling or pressure injury
• Loss of reduction
• Compartment syndrome, rare but serious
• Missed associated elbow or carpal injury

Acute median nerve dysfunction. A displaced distal radius fracture can injure the median nerve by stretch, contusion or compression. The first step is prompt fracture reduction, which relieves most stretch or compression neurapraxia, and then the nerve is re-examined. Two situations follow:

• A neurapraxia that is stable or improving after reduction is observed with serial examination
• A deficit that is progressive, or persists or worsens after an adequate reduction, is acute carpal tunnel syndrome: a surgical emergency requiring urgent carpal tunnel release (decompression)

Avoid over-flexed (Cotton-Loder) casting, which raises carpal tunnel pressure and can precipitate median neuropathy.

Late

• Malunion with residual deformity
• Distal radial or ulnar physeal arrest
• Wrist stiffness from over-immobilisation
• Refracture after early return to sport
• Cosmetic deformity or functional limitation if alignment is unacceptable

Who actually gets a growth arrest

"Follow physeal injuries for growth disturbance" is only useful if you know in whom. The risk is not spread evenly, and three variables separate a child who needs a single check from one who needs surveillance to maturity:

Two consequences for practice. First, the consent conversation for a displaced Salter-Harris III/IV injury in a child with substantial growth remaining is a different conversation from the one for an undisplaced Salter-Harris II, and quoting a single pooled figure flattens a tenfold difference. Second, these are the children in whom repeated forceful manipulation must be avoided, because each additional attempt at closed reduction adds insult to a germinal layer that is already injured.

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Paediatric distal radius fractures are a worldwide problem and the single most common skeletal injury requiring intervention in children. Practice varies more by health-system resource and local protocol than by true biological difference, so the global picture matters for any exam answer.

Global epidemiology

• Distal forearm fractures account for roughly a quarter to a third of all childhood fractures, with peak incidence around the pubertal growth spurt.
• Boys are affected more often than girls overall, mirroring activity exposure; in the FORCE cohort 61 percent were boys.
• Rising incidence has been linked to increased sport participation, higher body mass index and reduced bone mineral density in some populations.
• Distal ulnar physeal injuries show growth disturbance in around one in five cases, and intra-articular (Salter-Harris III/IV) distal radius fractures in around two in five.

Side-by-side guidance

Registry and trial evidence

• Paediatric fracture care is driven by trial evidence rather than implant registries (registries dominate adult arthroplasty, not childhood fractures).
• The FORCE equivalence RCT (965 children, 23 UK hospitals) is the landmark dataset supporting bandage-and-discharge for torus fractures.
• Cohort data from North American children's hospitals define the growth-arrest risk that justifies physeal surveillance.

High- versus limited-resource practice

• In well-resourced systems the debate is about doing less: removable splints, no routine repeat films and reduced clinic visits for buckle fractures.
• In limited-resource settings the priorities are accurate triage to avoid missing displaced or physeal fractures, safe casting where image-guided fixation is unavailable, and clear caregiver safety-netting because follow-up may be difficult.
• Across all settings the universal non-negotiables are neurovascular assessment, recognition of the physis and a well-moulded, non-tight cast when immobilisation is used.

Several questions in paediatric distal radius care remain genuinely unresolved, and examiners reward candidates who can state both sides rather than quote a single number.

Common pitfalls