Orthopaedic Surgery - Cavus Foot

Basics

Cavus foot is characterized by an abnormally elevated medial longitudinal arch, often accompanied by deformity of the hindfoot, forefoot, or both.

The deformity may be flexible in its early stages but can gradually become rigid as secondary soft-tissue contractures and bony changes develop.

Epidemiology

Cavus feet are relatively common and may occur in otherwise healthy individuals or as a manifestation of an underlying neurologic or musculoskeletal disorder.

Approximately 10% of the healthy population may demonstrate some degree of cavus foot.

A substantial proportion of clinically significant cases, historically estimated at approximately 80%, are associated with an underlying neurologic disorder.

Risk Factors

Important risk factors include neuromuscular disease, previous trauma, connective tissue disorders, and congenital deformities.

Any condition that creates chronic imbalance between the muscles acting across the foot and ankle can contribute to development of a cavus deformity.

Genetics

Several disorders responsible for cavus foot are hereditary.

The most common inherited cause is Charcot-Marie-Tooth disease, also known as hereditary motor and sensory neuropathy.

The classic form of Charcot-Marie-Tooth disease is often inherited in an autosomal dominant pattern.

Pathophysiology

Neuromuscular disease is the most common underlying cause of clinically significant cavus deformity.

Abnormal muscle strength and imbalance can produce progressive muscle atrophy, fibrosis, deformity, and joint contracture.

The deformity often begins as a flexible abnormality during childhood or adolescence and gradually becomes more rigid with growth and progression of the underlying disease.

Muscle Imbalance

Different patterns of muscle imbalance can produce different forms of cavus foot.

Excessive pull from the peroneus longus or posterior tibialis may contribute to abnormal plantarflexion or inversion forces.

Weakness of the intrinsic foot muscles can allow the long flexor tendons to dominate, resulting in clawing of the toes and progressive forefoot deformity.

Connective Tissue Disorders

Connective tissue abnormalities may also contribute to cavus foot.

Conditions such as Marfan syndrome can alter the structural support and mechanical balance of the foot.

Associated Conditions

The underlying cause should be investigated because cavus foot may be the first indication of a neurologic disorder.

The differential diagnosis differs depending on whether the deformity is bilateral or unilateral.

Bilateral Cavus Foot

Bilateral cavus deformity is commonly associated with generalized or hereditary neurologic disease.

Important causes include Charcot-Marie-Tooth disease, Friedreich ataxia, syringomyelia, myelomeningocele, muscular dystrophy, spinal cord tumor, and polyneuritis.

Unilateral Cavus Foot

A unilateral cavus deformity should raise concern for a focal neurologic or traumatic cause.

Potential etiologies include previous poliomyelitis, prior compartment syndrome of the leg or foot, traumatic peripheral nerve injury, spinal nerve root injury, severe burns, and spinal cord tumors.

A new unilateral deformity warrants particularly careful neurologic investigation.

Diagnosis

Signs and Symptoms

The characteristic finding is a high medial longitudinal arch.

Patients may also develop calluses beneath the forefoot or heel because of abnormal pressure distribution.

Some individuals remain asymptomatic, while others have pain, difficulty fitting shoes, instability, or progressive deformity.

Hindfoot Varus

The heel may be positioned in varus, causing the patient to bear excessive weight along the lateral border of the foot.

Marked hindfoot varus can predispose to recurrent lateral ankle sprains and chronic ankle instability.

Plantarflexed First Ray

A relatively plantarflexed first metatarsal or first ray is common.

This can drive the hindfoot into varus during weight-bearing and is important when distinguishing a flexible from a fixed hindfoot deformity.

Metatarsalgia

Patients may develop metatarsalgia, particularly beneath the metatarsal heads.

The elevated arch and altered forefoot loading produce excessive plantar pressure and can lead to painful callus formation.

Shoe-Wear Difficulty

Rigid or severe cavus deformity may make conventional footwear uncomfortable.

Prominent metatarsal heads, claw toes, a high instep, or lateral foot overload can create pressure points and skin irritation.

Ankle Instability

Severe cavovarus alignment increases the tendency for the ankle to invert.

Patients may therefore experience recurrent ankle sprains or chronic lateral ankle instability.

History

A complete birth, developmental, neurologic, and medical history is essential when evaluating cavus foot.

The clinician should determine when the deformity was first noticed, whether it is progressing, and whether symptoms such as weakness, numbness, gait disturbance, or balance difficulty are present.

Family History

A family history of cavus foot, neuropathy, gait abnormalities, or muscle weakness should be explored.

A positive family history may suggest an inherited disorder such as Charcot-Marie-Tooth disease.

Tethered Cord Consideration

A sudden increase in cavus deformity in a child with myelomeningocele or lipomeningocele may indicate tethering of the spinal cord.

Progressive deformity in this setting warrants neurologic and spinal evaluation.

Physical Examination

The examination should assess the entire lower extremity rather than the foot alone.

Motor strength of all muscles crossing the ankle should be measured bilaterally.

The pattern of weakness may provide clues regarding the underlying neurologic disorder.

Toe Deformities

Associated claw-toe deformities should be identified.

These often result from intrinsic muscle weakness and relative overpull of the long toe flexors and extensors.

Plantar Fascia

The plantar fascia should be assessed for tightness or contracture.

A shortened plantar fascia can help maintain the elevated arch and may contribute to rigidity of the deformity.

Neurologic Examination

Reflexes and sensation to light touch should be evaluated carefully.

Reduced reflexes, sensory loss, or distal weakness may indicate peripheral neuropathy.

Upper-Extremity Examination

The upper extremities should also be examined, particularly for intrinsic hand muscle wasting.

This can provide additional evidence of a generalized hereditary neuropathy such as Charcot-Marie-Tooth disease.

Spine Examination

The spine should be inspected for scoliosis, dimples, skin markings, hairy patches, or other abnormalities that may indicate occult spinal dysraphism or another spinal disorder.

Coleman Block Test

The Coleman block test helps determine whether hindfoot varus is flexible or rigid.

The patient stands with the heel and lateral border of the foot supported on a block while the first metatarsal and great toe hang freely off the edge.

Principle of the Coleman Block Test

Allowing the first ray to drop freely removes the effect of a plantarflexed first metatarsal on hindfoot alignment.

If the hindfoot varus corrects toward neutral, the deformity is considered flexible and forefoot-driven.

Rigid Hindfoot Varus

If the hindfoot remains in varus despite unloading the first ray, the deformity is considered rigid.

A rigid deformity is more likely to require a bony corrective procedure rather than soft-tissue treatment alone.

Electrodiagnostic Studies

Electromyography and nerve conduction studies may assist in diagnosing Charcot-Marie-Tooth disease, hereditary motor and sensory neuropathies, and lumbar radiculopathy.

These tests can characterize the distribution and severity of nerve dysfunction.

Imaging

Weight-Bearing Radiographs

Standing radiographs of the foot should be obtained to evaluate alignment and the severity of deformity.

Two useful measurements are the calcaneal pitch angle and the Meary angle.

Calcaneal Pitch

The calcaneal pitch is the angle between the inferior surface of the calcaneus and the floor.

An increased calcaneal pitch supports the presence of a high-arched cavus foot.

Meary Angle

The Meary angle is formed by the longitudinal axes of the talus and first metatarsal.

Abnormal angulation reflects disruption of normal longitudinal alignment and helps characterize the location and severity of the cavus deformity.

Spinal Imaging

When the cause of cavus foot is uncertain, radiographs or MRI of the spine may be indicated.

These studies can identify occult spinal cord abnormalities, tumors, tethering, or other neurologic causes.

Differential Diagnosis

Muscle wasting can sometimes make the longitudinal arch appear unusually high even when a true structural cavus deformity is not present.

The clinician should distinguish apparent high arch from fixed bony or soft-tissue deformity.

Treatment

General Measures

No treatment is required when the patient is asymptomatic, functionally normal, and has healthy skin without pressure lesions.

Management is directed toward symptoms, progression, instability, and the underlying cause.

Insoles and Metatarsal Support

A padded insole with an arch support or metatarsal bar may reduce plantar pressure and relieve metatarsalgia.

The orthosis should redistribute pressure rather than excessively increase an already high arch.

Lateral Heel Wedge

A lateral heel wedge may help correct a flexible hindfoot varus deformity by encouraging the heel toward a more neutral position.

It is most effective when the hindfoot remains passively correctable.

Bracing

A brace may be useful when significant muscle weakness produces instability.

Bracing can also help patients who have both cavus deformity and chronic ankle instability.

Stretching

Regular stretching may help maintain flexibility and slow the development of fixed contractures.

Particular attention may be given to the plantar fascia and other tight muscle-tendon units.

Orthoses

Custom-made foot orthoses can reduce pain in patients with cavus feet from a variety of causes.

They are particularly useful for redistributing abnormal plantar pressures and improving shoe tolerance.

Cavovarus Deformity

Cavovarus feet are often less well tolerated than isolated mild cavus feet.

Progressive deformity may lead to shoe-wear difficulty, recurrent ankle instability, painful calluses, metatarsalgia, and eventually arthritis.

Physical Therapy

Physical therapy may include stretching of the plantar fascia and other contracted muscles or tendons.

The goal is to preserve flexibility and slow progression toward a rigid deformity.

Strengthening and Proprioception

When ankle instability is present, strengthening, proprioceptive training, and closed-chain balance exercises may be helpful.

These exercises improve dynamic control of the ankle but do not correct a fixed structural cavovarus deformity.

Indications for Surgery

Surgery is usually considered for progressive deformity, persistent pain despite conservative treatment, chronic ankle instability, major shoe-wear difficulty, or rigid deformity associated with arthritis.

The procedure must be tailored to the specific components of the deformity.

Surgical Planning

Careful examination is required to determine which portions of the deformity are flexible and which are fixed.

Surgical treatment is usually stepwise and individualized, with correction of muscle imbalance, soft-tissue contracture, bony malalignment, and instability as needed.

Flexible Deformity

Flexible deformities can often be treated primarily with soft-tissue rebalancing procedures.

These may include tendon transfer, tendon lengthening, or plantar fascia release.

Rigid Deformity

Rigid deformities generally require osteotomy or arthrodesis because soft-tissue procedures alone cannot adequately correct fixed bony alignment.

The goal is to restore a plantigrade, stable, and pain-free foot.

Plantar Fasciotomy

A plantar fasciotomy may be used to release a contracted plantar fascia and help lower the excessively high arch.

It is often performed as one component of a larger reconstruction.

Midfoot and Metatarsal Osteotomies

Rigid cavus deformity may require midfoot or metatarsal osteotomies.

These procedures correct fixed bony angulation and redistribute plantar loading.

Calcaneal Osteotomy

When hindfoot varus is rigid, a lateral closing-wedge calcaneal osteotomy may be performed.

This repositions the heel into a more neutral alignment and reduces excessive loading along the lateral border of the foot.

Tendon Lengthening

Contracted muscle-tendon units may require surgical lengthening.

This decreases deforming forces and improves balance around the foot and ankle.

Tendon Transfers

Tendon transfers are commonly used when muscle imbalance is a major component of the deformity.

A functioning tendon is redirected to compensate for a weak muscle group and restore more balanced forces across the foot.

Chronic Ankle Instability

When chronic ligamentous instability accompanies cavovarus deformity, lateral ligament reconstruction may be required.

Correction of the cavovarus alignment is usually important as well, because ligament reconstruction alone may fail if the underlying varus deformity remains.

Tenodesis procedures may sometimes be added for additional stabilization.

Complex or Previously Operated Feet

Stiff or multiply operated cavus feet may require more extensive reconstruction.

Procedures such as navicular excision or cuboid closing-wedge osteotomy may be used in selected complex cases.

Triple Arthrodesis

Triple arthrodesis is generally reserved as a salvage procedure.

It may be indicated when previous reconstruction has failed or when the patient has a rigid deformity with painful arthritis involving multiple hindfoot joints.

Follow-Up

Patients with cavus foot should be followed periodically by an orthopaedic specialist, particularly when the deformity is progressive or associated with muscle weakness.

Monitoring should assess alignment, muscle strength, sensory status, skin integrity, ankle stability, and progression of contractures.

Timing of Reconstruction

Progressive deformity may be easier to correct before it becomes completely rigid.

Early recognition and reconstruction in selected patients may avoid the need for later fusion procedures.

Indications for Referral

All patients with symptomatic cavus feet should be considered for orthopaedic evaluation.

Referral is especially important when the deformity is unilateral, progressive, associated with neurologic signs, or causing recurrent instability or skin problems.

Prognosis

Cavus feet caused by an underlying neuropathy often progress gradually over time.

The rate and severity of progression depend on the underlying neurologic disease and the degree of muscle imbalance.

Neuropathic Ulceration

Patients with diabetes or Charcot-Marie-Tooth disease may lose protective sensation.

Abnormal pressure beneath prominent parts of the foot can then produce neuropathic ulceration.

Repeated ulceration may progress to infection and osteomyelitis.

Risk of Amputation

Severe neuropathic ulceration complicated by deep infection or osteomyelitis can eventually result in amputation.

For this reason, appropriate footwear, orthoses, routine skin inspection, and pressure reduction are especially important in patients with sensory loss.

Footwear in Athletes

For athletes with cavus feet, neutral cushioned running shoes may help reduce plantar pressures and lower the risk of repetitive pressure-related injury.

Footwear should be selected according to comfort, alignment, and the individual’s activity demands.

Patient Monitoring

Patients should be monitored for progressive arch elevation, increasing hindfoot varus, muscle weakness, sensory loss, recurrent ankle sprains, painful calluses, and skin ulceration.

Any rapid change in deformity or neurologic function should prompt investigation for an underlying or worsening neurologic disorder.