Cavus Foot (Pediatric)

The deformity. Paediatric cavus foot is a three-dimensional deformity: a high medial longitudinal arch, often with hindfoot varus and forefoot adduction. It is less common than flatfoot in children, bilateral in 80% and often asymmetric, and it is progressive if left alone.

This page is about the child. If your patient is a skeletally mature adult, the deformity, the workup and the operations differ enough that cavovarus foot is the page you want. In the child the cavus is a symptom you are being shown, and often the first sign of an underlying neurological condition, so the job is to find what is causing it before you correct anything - which is why this page spends more effort on the spine and the nerves than on the osteotomies.

Why the child differs. Adult cavovarus is predominantly CMT-related; the paediatric differential is broader and includes idiopathic cases, spinal dysraphism and other neuromuscular conditions. Neurological causes are commoner in children than in adults, and idiopathic cases may be familial, with an autosomal dominant pattern in some families.

Where the deformity comes from. Cause dictates both the workup and the order of treatment:

• Neurological - 50-60%. CMT is the commonest inherited neuropathy and presents in childhood or adolescence; spinal dysraphism covers spina bifida, tethered cord and diastematomyelia; cerebral palsy gives a spastic cavus from muscle imbalance; residual polio is less common now but still seen; and the wider hereditary motor and sensory neuropathies cover various other types. Progressive, bilateral and accompanied by muscle wasting, and treatment begins with the underlying condition before staged correction.
• Idiopathic - 30-40%. No identifiable cause, and may be familial. Progression is variable and the deformity may stabilise, so conservative treatment comes first and surgery only if it progresses.
• Post-traumatic - 5-10%. Compartment syndrome or malunion. Unilateral, with a history of trauma, and the correction addresses the underlying deformity.
• Arthrogryposis - multiple joint contractures, the foot among them.
• Muscular dystrophy - Duchenne and other types.

Natural history. The muscle imbalance does not stop, so the deformity worsens over the years, and the consequences accumulate:

• Lateral ankle instability - recurrent sprains from a varus heel strike
• Peroneal tendinopathy
• Metatarsalgia - the plantar-flexed first ray and the claw toes concentrate pressure
• Stress fractures - lateral column overload, commonly the fifth metatarsal
• Arthritis - midfoot and ankle degeneration by adulthood if untreated

Why early matters. Recognising the deformity early lets the underlying cause be worked up and treated, and intervening early prevents the severe fixed deformity that ends in triple arthrodesis.

The tripod model. The classic driver, Coleman's tripod model, is a plantar-flexed first metatarsal. In CMT the peroneus longus is relatively spared and overpowers a weak tibialis anterior, so it is the strong longus, not a weak one, that pulls the first ray down. The first ray drops plantarwards, the medial arch rises, and the forefoot has to pronate to bring the heel to the ground, which produces a functional hindfoot varus.

What follows from it. The compensations become the deformity: forefoot pronation to accommodate the plantar-flexed first ray, hindfoot varus that is functional at first and becomes fixed, claw toes from flexor overpull with intrinsic weakness, and a tight plantar fascia that holds the arch elevated.

Do not recite the tripod as settled. Dynamic pedobarography in 118 CMT feet found first-ray contact preceded fifth-ray contact in only 39.7% of varus feet - no different from non-varus feet (34.0%, p=0.526). Around 60% landed already in varus before the first ray touched down, meaning the foot is often pre-positioned in varus by proximal muscle imbalance rather than levered there by the forefoot (Ferguson 2024).

The surgical consequence is real. Rebalance the deforming forces; do not assume a first-ray osteotomy alone addresses the cause.

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Calcaneocavus breaks the rule. In this pattern the calcaneus is dorsiflexed rather than the forefoot plantarflexed, usually following poliomyelitis or triceps weakness, and plantar release with forefoot osteotomy will not correct it.

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What the assessment is for. Two questions run in parallel: how much of the deformity is fixed, and what is causing it. Missing the underlying diagnosis delays appropriate treatment and may allow progression to a severe fixed deformity.

History. Ask when the high arch was first noticed and whether it is getting worse, then ask the questions that decide how hard you look for a cause:

• Family history - CMT, other neuropathies, or a similar foot deformity in a relative
• Neurological symptoms - weakness, numbness, balance problems
• Spinal symptoms - back pain, bladder or bowel problems, which point to a tethered cord
• Functional limitations - ankle sprains, metatarsalgia, difficulty with shoes
• Bilateral involvement - and whether the two feet are affected equally

Red flags. Each of these moves the diagnosis away from idiopathic cavus:

• Progressive weakness - suggests a neurological cause
• Family history of CMT - autosomal dominant inheritance
• Back pain or urinary symptoms - suggest dysraphism
• Unilateral, with a history of trauma - a post-traumatic cause
• Rapid progression - may indicate spinal pathology

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Examination. Work through the foot in the same order every time, and finish with the neurological assessment rather than leaving it out.

Read the sole. Callus and footprint tell you how the foot is actually loaded, before any radiograph is taken.

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Differential Diagnosis of the High-Arched / Cavus Foot in Children

Where each of these is worked up. The differential above is really a differential of causes, and each has its own page: Charcot-Marie-Tooth disease and the wider family of hereditary motor and sensory neuropathies (which is where the muscle-balance logic behind every tendon transfer is set out), tethered cord syndrome for the asymmetric foot with spinal stigmata, Friedreich's ataxia where cavus comes with ataxia and cardiomyopathy, spastic equinovarus foot for the cerebral palsy pattern, and clubfoot for the residual or overcorrected foot that looks cavus but has a treatment history behind it. The radiographic measurement the whole assessment turns on is Meary's angle.

Radiographs. Take them weight-bearing, and know what each view answers:

• AP foot - forefoot adduction, the metatarsal break pattern, degenerative change
• Lateral foot - the calcaneal pitch (normal 20 degrees), the Meary angle for the lateral arch, and first metatarsal plantar-flexion
• AP ankle - ankle joint arthritis, and talar tilt from chronic instability
• Hindfoot alignment view (Saltzman) - quantifies hindfoot varus; a plumb line falling medial to the heel means varus

The numbers to quote. Calcaneal pitch greater than 30 degrees is cavus, a Meary angle less than 150 degrees means an elevated lateral arch, and a talar-first metatarsal (Meary) line with its apex plantar is cavus. These measurements are what surgical planning and the monitoring of progression are built on.

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Neurological work-up. Order it when the history, the examination or an asymmetric deformity raises the question of a cause:

• Nerve conduction studies - reduced motor and sensory conduction velocities in CMT type 1, the demyelinating form
• Electromyography - a denervation pattern in the affected muscles
• Genetic testing - PMP22 duplication for CMT1A, which accounts for 70% of CMT cases
• MRI of the spine - for any suspicion of spinal dysraphism or tethered cord, and critical in the child

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MRI of the foot and ankle. This is a surgical planning study rather than a diagnostic one. It shows the peroneal tendons, where split tears and subluxation are common with a varus hindfoot, chronic ATFL and CFL injury from recurrent sprains, degenerative change in the ankle cartilage, and the quality of the plantar fascia and posterior tibial tendon that any soft-tissue balancing will rely on.

The decision. Most children with mild cavus never need surgery, and many cases stabilise or improve with growth, so conservative treatment is first-line for the mild and the flexible foot. Surgery belongs to the foot that progresses, hurts, or has gone fixed - and because a fixed deformity is harder to correct, it should not be delayed unnecessarily.

Algorithm

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Whose protocol this is. The timeline below follows the bony procedures. An isolated plantar fascia release is different: that foot weight-bears in its cast.

Long-term follow-up. Annual clinical and radiographic assessment, particularly where the underlying cause has not been addressed, with further procedures if the deformity recurs.

Results. Staged correction gives good to excellent results in 80-90%, better outcomes than single-stage correction, and most children return to normal activities.

Predictors of a poor outcome.

• Underlying neurological cause not addressed
• Fixed deformity at presentation
• Overcorrection to valgus
• Nonunion after calcaneal osteotomy
• Growth disturbance

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Global epidemiology. Charcot-Marie-Tooth disease is the most common inherited peripheral neuropathy, with population prevalence generally cited around 1 in 2,500, and CMT1A (PMP22 duplication) accounting for the majority of demyelinating cases. Because over half of children with CMT develop foot and ankle problems, of which cavovarus is by far the commonest pattern, cavovarus foot is a near-universal management consideration in paediatric neuromuscular clinics worldwide (Olney, Foot Ankle Clin 2000, PMID 11232232; Schwend & Drennan, J Am Acad Orthop Surg 2003, PMID 12828450). In a paediatric population, neurological causes (CMT, spinal dysraphism, cerebral palsy, residual polio in low-income settings) predominate over the idiopathic cavus that is relatively more common in adults.

Side-by-side guidance and consensus across regions. There is no single high-level (RCT-based) international guideline that dictates operative thresholds for paediatric cavovarus; practice is built on instructional reviews, expert consensus and observational cohorts. The convergent principles below are drawn from the verified evidence base.