Metatarsus Adductus

Metatarsus adductus is a common congenital foot deformity characterized by medial deviation of the forefoot at the tarsometatarsal joints, while the hindfoot remains in a neutral position. It occurs in approximately 1 in 1000 live births.

Key Characteristics:

• Medial deviation of metatarsals relative to hindfoot
• Normal hindfoot alignment
• C-shaped lateral border of foot
• Normal arch height
• Normal ankle position

Epidemiology

• Affects 1-2 per 1000 live births
• More common in firstborn children
• Bilateral in 50% of cases
• Associated with intrauterine positioning
• Higher incidence in twins

Etiology

• Intrinsic Factors:
  • Genetic predisposition
  • Family history
  • Muscle imbalance
• Extrinsic Factors:
  • Intrauterine positioning
  • Oligohydramnios
  • Multiple gestation
  • Large fetus

Clinical Presentation

• Physical Examination:
  • Bean-shaped foot appearance
  • Convex lateral border
  • Prominent base of 5th metatarsal
  • Normal hindfoot alignment
  • Preserved ankle motion
• Associated Findings:
  • Hip dysplasia (5-10% association)
  • Developmental torticollis
  • Plagiocephaly

Classification (Bleck's Classification)

• Mild:
  • Forefoot adduction <20°
  • Flexible deformity
  • Heel-bisector line passes through 3rd toe
• Moderate:
  • Forefoot adduction 20-30°
  • Partially flexible
  • Heel-bisector line passes through 4th toe
• Severe:
  • Forefoot adduction >30°
  • Rigid deformity
  • Heel-bisector line passes through 5th toe or lateral to foot

Diagnostic Approach

• Physical Examination Tests:
  • Heel bisector line assessment
  • Forefoot flexibility test
  • Great toe extension test
  • Bean-shaped foot appearance
• Imaging Studies:
  • Radiographs rarely needed in infants
  • Weight-bearing AP and lateral views in older children
  • Measure talus-first metatarsal angle
  • Assess tarsometatarsal alignment

Differential Diagnosis

• Talipes Equinovarus (Clubfoot)
• Skewfoot
• Congenital vertical talus
• Calcaneovalgus foot

Clinical Assessment Tools

• Heel Bisector Method:
  • Draw line through center of heel
  • Extend through 2nd web space
  • Assess relationship to toes
• Flexibility Assessment:
  • Manual correction of forefoot
  • Passive abduction range
  • Assessment of midfoot mobility

Treatment Approach

• Observation:
  • Mild flexible cases
  • Regular monitoring of progression
  • Spontaneous resolution in 80-90% of cases
• Conservative Treatment:
  • Stretching exercises
    • Passive forefoot abduction
    • Parent education
    • Regular monitoring
  • Serial casting
    • Weekly cast changes
    • 3-8 casts typically needed
    • Best results before 8 months of age
  • Orthotic devices
    • Reverse-last shoes
    • Night splints
    • Custom orthotics for older children

Surgical Management

Rarely needed (<5% of cases), but may be considered for:

• Severe rigid deformity
• Failed conservative treatment
• Age >4 years with significant deformity
• Procedures may include:
  • Capsulotomy of medial tarsometatarsal joints
  • Abduction osteotomy of cuneiforms
  • Lateral column shortening

Prognosis and Follow-up

• Excellent with early treatment
• 90% resolution with conservative management
• Regular monitoring until walking age
• Long-term follow-up for severe cases
• Monitor for developmental hip dysplasia