Pes Cavus

1. Causes / Sequelae

a. Trauma

b. Neuromuscular Causes (NM)

  • CNS: Cerebral Palsy (CP)
  • Spinal Cord: Spina Bifida
  • Peripheral Nerve (PNS): Lower Motor Neuron lesions (e.g., CMT)
  • Muscular: Muscular Dystrophy

Most Common Cause - Bilateral: Charcot-Marie-Tooth (CMT) disease
- Unilateral: Spinal cord tumor

2. Charcot-Marie-Tooth (CMT) Disease

  • Inheritance: Autosomal Dominant (AD) — most common
  • Defect: PMP22 gene on Chromosome 17
  • Recessive forms: Rare, more aggressive

Pathophysiology

  • Imbalance between flexors and extensors due to weakness
  • TA (Tibialis Anterior) and Peroneus longus imbalance
  • 1st ray plantar flexion → longus overactivity
  • Heel varus due to tripod effect

Types

  • Clawing: due to excessive extensor recruitment
  • Equinus: due to gastrosoleus overpull

CMT Variants

Type Inheritance Pathology Features
Type 1 AD Demyelination Common
Type 2 AD Axonal loss Moderate
Type 3 AR Degenerative (severe, in infants) Rare

3. Clinical Features

  • Identify heel varus and cavus
  • Dynamic clawing observed during walking
  • Coleman Block Test — differentiates flexible vs. rigid deformity
  • Power testing & reflexes — identify neurological involvement
  • Silfverskiöld test — to assess gastrocnemius vs. soleus tightness
  • Examine spine and hand — for associated deformities

4. Radiological Features

Lateral X-ray Findings - Large, anterior apex Meary’s angle - Increased calcaneal pitch

5. Management

A. Non-Surgical

Footwear Modifications

Deformity Footwear Correction
Gastrosoleus tightness Heel lift
Hindfoot varus Medial heel cup + lateral posting
High arch Arch support (reduce forefoot pressure)
Claw toes Metatarsal bar (redistribute contact pressure)

B. Surgical

Principles

Aim: Stable, plantigrade, painless, flexible foot
Achieved by: 1. Bringing heel under leg
2. Correcting deformities to fit shoe
3. Balancing muscle forces

6. Surgical Procedures

  1. 1st Ray:
    • Plantar flexion correction → Dorsiflexion osteotomy
  2. Cavus:
    • Plantar fascia release
  3. Varus:
    • Lateral closing wedge calcaneal osteotomy
  4. Equinus:
    • Tendo-Achilles lengthening
  5. Claw Toes:
    • Flexible deformity: Flexor-to-extensor transfer (EDL, EHL)
    • Fixed deformity:
      • PIP joint fusion (Weil procedure)
      • PIP joint excision
      • MTP joint release

Big Toe (Hallux):
- MTP fusion + EHL to EPL transfer

Summary Table

Deformity Correction
1st Ray Dorsiflexion osteotomy
Cavus Plantar fascia release
Varus Lateral wedge calcaneal osteotomy
Equinus Tendo-Achilles lengthening
Claw Toes Flexor to extensor transfer / PIP fusion
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