Congenital Foot Deformity

Congenital Foot Deformity
B. J. Manaster, MD, PhD, FACR
DIFFERENTIAL DIAGNOSIS
Common
  • Metatarsus Adductus
  • Pes Planovalgus (Flexible Flatfoot)
  • Club Foot (Talipes Equinovarus)
  • Tarsal Coalition
Less Common
  • Congenital Vertical Talus (Rocker Bottom Foot)
  • Pes Cavus (Mimic)
  • Polio (Mimic)
  • Cerebral Palsy (Mimic)
Rare but Important
  • Metaphyseal Bar
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
  • Hint: Do not attempt to diagnosis foot deformities without weight-bearing films
  • Hint: Most congenital foot deformities can be diagnosed by evaluation of 3 relationships
    • Hindfoot equinus or calcaneus
      • On lateral radiograph, normal angle between lines bisecting calcaneus and tibia ranges between 60° and 90°
      • Hindfoot equinus: Tibiocalcaneal angle > 90° (excessive plantarflexion of calcaneus)
      • Hindfoot calcaneus: Tibiocalcaneal angle < 60° (excessive dorsiflexion of calcaneus); also termed “cavus”
    • Hindfoot varus or valgus
      • On lateral radiograph, normal angle between lines bisecting talus and calcaneus ranges between 25° and 55° (termed Kite angle or lateral talocalcaneal angle)
      • On AP radiograph, normal angle between lines bisecting talus and calcaneus ranges between 15° and 40°
      • Varus hindfoot: ↓ talocalcaneal angle (bones approach parallel), < 25° on lateral and < 15° on AP
      • Valgus hindfoot: ↑ talocalcaneal angle (bones diverge): > 55° on lateral and > 40° on AP
    • Forefoot varus or valgus
      • On lateral radiograph, metatarsals normally are moderately superimposed, with 5th in plantar-most position; angle of inclination of metatarsals gradually ↑ from 5° for 5th to 20° for 1st
      • On AP radiograph, metatarsals normally show moderate convergence of bases
      • Varus forefoot: Inversion and supination; on lateral, ↓ superimposition of metatarsals (ladder-like) with 5th MT in plantar-most position; on AP, ↑ overlap of MT bases
      • Valgus forefoot: Eversion and pronation; on lateral, ↓ superimposition of metatarsals with 1st MT in plantar-most position; on AP, ↓ convergence of MT bases
  • Hint: Most congenital foot deformities match type of hindfoot and forefoot deformities
    • Varus hindfoot with varus forefoot
    • Valgus hindfoot with valgus forefoot
  • Hint: If hindfoot and forefoot deformities are unmatched (i.e., varus hindfoot and valgus forefoot or valgus hindfoot and varus forefoot), usually due to spastic foot
Helpful Clues for Common Diagnoses
  • Metatarsus Adductus
    • Most common structural foot abnormality of infants
    • Adduction of metatarsals; normal hindfoot
    • Rarely imaged, since it is flexible deformity and self-correcting
  • Pes Planovalgus (Flexible Flatfoot)
    • Common (4% of population)
    • Note: It is flexible; non-weight-bearing radiographs are normal
    • Abnormalities on weight-bearing radiographs
      • Hindfoot valgus, forefoot valgus, no equinus
  • Club Foot (Talipes Equinovarus)
    • Incidence 1:1,000 births
    • M > F = 2-3:1
    • Constant structural abnormalities
      • Hindfoot equinus, hindfoot varus, forefoot varus
  • Tarsal Coalition
    • Painful flatfoot: Persistent or intermittent spasm of peroneal muscles
    • Usually secondary to congenital lack of segmentation of bones of hindfoot
    • Symptoms begin in late 1st or 2nd decade
    • Secondary signs
      • Talar beak: Due to excessive motion at talonavicular joint because of rigid subtalar joint
      • “Ball and socket” tibiotalar joint: Conversion of this hinge joint to rounded articulation; generally due to unusually extensive subtalar coalition
    • Calcaneonavicular coalition
      • Anterior process of calcaneus extends and broadens at union with navicular
      • Directly visualized on oblique radiograph
    • Talonavicular coalition
      • Generally mid subtalar joint (sustentaculum tali) and not directly visualized
      • Diagnosed by CT or MR where this portion of subtalar joint is directly visualized on radiographs
      • Rarely will involve posterior &/or anterior subtalar facets
    • 25% bilaterality
Helpful Clues for Less Common Diagnoses
  • Congenital Vertical Talus (Rocker Bottom Foot)
    • Rigid flatfoot
    • Isolated, or part of several syndromes (frequently associated with meningomyelocele)
    • Constant structural abnormalities
      • Hindfoot equinus
      • Hindfoot valgus
      • Plantarflexed talus, dislocated from navicular
      • Forefoot valgus
  • Pes Cavus (Mimic)
    • Multiple etiologies; none are strictly congenital, hence “mimic” designation
      • Upper motor neuron lesions (Friedrich ataxia)
      • Lower motor neuron lesions (poliomyelitis)
      • Vascular ischemia, Charcot-Marie-Tooth, Chinese bound foot
  • Polio (Mimic) and Cerebral Palsy (Mimic)
    • Spastic abnormalities, often with mismatch of hindfoot and forefoot abnormalities (varus-valgus)
    • Soft tissues show muscle atrophy
Helpful Clues for Rare Diagnoses
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Aug 10, 2016 | Posted by in PEDIATRICS | Comments Off on Congenital Foot Deformity

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