Orthopaedic Surgery - Metatarsus Adductus

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Basics

Metatarsus adductus is a congenital foot deformity in which the forefoot is deviated medially relative to the hindfoot.

The heel remains in a:

Neutral or mildly valgus position, and unlike clubfoot, there is no fixed equinus deformity.

It is one of the most common congenital foot deformities encountered in children and is usually apparent during the newborn period.

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Synonyms

Metatarsus adductus has also been called:

Metatarsus varus

Metatarsus internus

Hooked forefoot

C-shaped foot

Older terminology may occasionally overlap with terms such as pes varus or Z-foot, although these terms can also describe different deformity patterns.

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Classification

Classification is based primarily on:

Flexibility and severity of forefoot adduction.

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Flexible Deformity

The forefoot can be passively corrected to:

Neutral or beyond neutral.

This is the most favorable pattern and commonly resolves spontaneously.

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Partially Flexible Deformity

The deformity can be improved with manipulation but cannot be fully corrected to neutral.

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Rigid Deformity

The forefoot cannot be passively corrected to neutral.

Rigid deformities are less likely to resolve spontaneously and are more likely to require treatment.

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Heel Bisector Method

Severity is commonly estimated clinically using the heel bisector line.

The examiner visually draws a line along the longitudinal center of the heel and observes where it crosses the forefoot.

Normally, the line passes approximately between the second and third toes.

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Mild Deformity

The heel bisector passes through the:

Third toe.

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Moderate Deformity

The heel bisector passes between the:

Third and fourth toes.

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Severe Deformity

The heel bisector passes between the:

Fourth and fifth toes or farther laterally.

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Prevention

There is no established method for preventing metatarsus adductus.

The condition is believed to arise during fetal development rather than from postnatal activity.

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Epidemiology

Metatarsus adductus occurs in approximately:

1–10 per 1,000 infants.

Males and females are affected with approximately equal frequency.

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Risk Factors

Recognized associations include:

Family history of metatarsus adductus

Developmental dysplasia of the hip

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Genetics

The condition occurs more frequently among children with an affected:

First-degree relative.

However, it does not generally follow a simple Mendelian inheritance pattern.

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Etiology

The exact cause is unknown.

There is no consistent association with:

Birth order

Gestational age

Maternal age

The most widely accepted explanation is that metatarsus adductus may result partly from intrauterine positioning or mechanical constraint.

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Associated Conditions

The most important associated condition is developmental dysplasia of the hip (DDH).

Historical studies have reported DDH in approximately 1–5% of children with metatarsus adductus.

Because of this association, the hips should be carefully examined.

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Diagnosis

Diagnosis is primarily clinical.

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Signs and Symptoms

The characteristic deformity is:

Medial deviation of the forefoot, sometimes accompanied by varying degrees of forefoot supination.

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Foot Shape

The foot commonly has:

A concave medial border

and

A convex lateral border.

There may be visible prominence at the base of the fifth metatarsal.

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Hindfoot Position

The hindfoot remains:

Neutral or mildly valgus.

The heel is not characteristically in varus.

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Ankle Position

The ankle should not have a fixed equinus contracture.

The foot can generally be dorsiflexed into a neutral or plantigrade position.

This feature helps distinguish metatarsus adductus from clubfoot.

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Medial Crease

A deep medial plantar crease may indicate:

A more pronounced or less flexible deformity.

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Natural History

The majority of flexible metatarsus adductus deformities improve spontaneously during infancy and early childhood.

Historical studies have reported that without treatment:

Approximately 86% became normal

Around 10% remained mildly adducted

Only a small minority remained significantly adducted

Most persistent mild deformities remain asymptomatic.

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Symptoms

Most infants are asymptomatic.

Later concerns, when present, are usually related to:

Cosmetic appearance

Shoe fit

Persistent rigid deformity

Functional disability is uncommon in mild residual deformity.

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Physical Examination

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Flexibility

The most important examination feature is the ability to passively correct the forefoot.

The examiner gently abducts the forefoot while stabilizing the hindfoot.

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Flexible Foot

A flexible deformity can be corrected to:

Neutral or beyond neutral.

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Rigid Foot

A rigid deformity remains adducted despite gentle manipulation.

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Ankle Range of Motion

Assess ankle dorsiflexion and plantarflexion.

Normal dorsiflexion helps confirm the absence of fixed equinus.

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Hindfoot Examination

The hindfoot should remain:

Normally aligned or mildly valgus.

Fixed hindfoot varus suggests another diagnosis.

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Hip Examination

Because of the association with DDH, the clinician should assess:

Hip abduction

Leg-length symmetry

Ortolani and Barlow maneuvers in appropriate infants

Other signs of hip instability or dysplasia

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Imaging

Radiographs are not necessary in most infants with typical flexible metatarsus adductus.

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Indications for Radiographs

AP and lateral foot radiographs may be considered when:

The deformity is rigid

The diagnosis is uncertain

Another congenital foot abnormality is suspected

The deformity persists in an older child

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Pathological Findings

The principal abnormality is medial deviation of the forefoot.

The remaining structures of the foot are generally normal.

The hindfoot and ankle are typically unaffected.

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Differential Diagnosis

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Clubfoot

Clubfoot is the most important differential diagnosis.

Unlike metatarsus adductus, clubfoot usually demonstrates:

Hindfoot varus

Ankle equinus

Forefoot adduction

Midfoot cavus

The entire foot is turned inward, and the deformity is typically more rigid.

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Skewfoot

Skewfoot may resemble metatarsus adductus but generally combines:

Forefoot adduction with hindfoot valgus and midfoot abduction.

It is a more complex deformity.

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Treatment

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General Principles

Most children require only:

Observation and parental reassurance.

Spontaneous improvement is common, particularly when the foot is flexible.

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Parental Education

Parents should be informed that:

Most flexible deformities improve naturally during growth and do not impair walking.

Early aggressive treatment is usually unnecessary.

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Observation

Observation alone is appropriate for most infants with:

Mild or moderate flexible metatarsus adductus.

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Stretching

Gentle stretching may be recommended for flexible deformities.

Parents can perform stretching during:

Diaper changes or routine daily care.

The forefoot is gently brought toward neutral while the hindfoot is stabilized.

Forceful manipulation should be avoided.

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Serial Casting

Serial manipulation and casting may be considered for:

Severe, rigid, or persistent deformity that does not improve spontaneously.

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Timing

Older treatment protocols often began casting around 6–12 months of age if substantial deformity persisted.

Current management is individualized according to:

Rigidity, severity, progression, and age.

Because many deformities improve naturally, routine casting of flexible feet during the first several months of life is generally unnecessary.

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Cast Treatment

Casting is performed serially to gradually correct the forefoot.

Treatment may continue for:

Several weeks to several months, depending on severity and response.

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Shoes and Orthoses

After correction, some children may be placed in:

Straight-last or reverse-last shoes, orthoses, or other supportive footwear.

Their necessity varies, and many flexible cases do not require special shoes.

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Activity

Children may participate in:

Normal weight-bearing and age-appropriate activities as tolerated.

No routine activity restrictions are required.

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Physical Therapy

Formal physical therapy is usually unnecessary.

Parents can often perform the recommended stretching program themselves.

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Surgery

Surgery is rarely required.

It is reserved for older children with:

Persistent, rigid, symptomatic deformity despite appropriate nonoperative treatment.

Historically, operative correction has generally been considered only after approximately 4 years of age.

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Surgical Procedures

Options may include:

Lateral column shortening osteotomy

and

Medial cuneiform opening-wedge osteotomy.

More complex reconstruction may be required in severe residual deformity.

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Follow-Up

Follow-up frequency depends on:

Severity, flexibility, age, and whether treatment is being performed.

Children with mild flexible deformity may require only occasional reassessment.

Moderate, severe, or treated deformities require closer follow-up.

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Prognosis

The long-term prognosis is excellent.

More than 95% of children with mild or moderate deformity have favorable outcomes in long-term studies.

Most patients develop:

Normal or near-normal foot function without pain or activity limitation.

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Flexibility and Prognosis

Flexibility is useful in guiding management, although its value as an exact predictor of long-term outcome remains imperfect.

Rigid deformities are generally more likely to persist.

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Complications

The principal complication is:

Persistent residual forefoot adduction.

Significant functional problems are uncommon.

Complications related to treatment, particularly excessive casting or surgery, are also uncommon when management is appropriate.

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Patient Monitoring

Children with persistent deformity should be reassessed periodically.

Monitoring should include:

Heel bisector position

Forefoot flexibility

Hindfoot alignment

Ankle range of motion

Footwear tolerance

Hip examination

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Key Principle

Metatarsus adductus is usually a benign, self-correcting congenital forefoot deformity.

The most important management decision is to distinguish:

A flexible deformity that can be safely observed

from

A persistent rigid deformity that may benefit from serial casting or, rarely, surgery.