Cavus Foot

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Cavus Foot: Definition & Anatomy - High Arches, Hidden Issues

  • Definition: Complex foot deformity with an abnormally high medial longitudinal arch; can be flexible or rigid.
  • **Key Anatomical Features (Triplanar Deformity):
    • Hindfoot: Varus (most common), ↑ calcaneal pitch angle.
    • Midfoot: Adduction, plantarflexion of first ray (creates cavus).
    • Forefoot: Adduction, pronation (compensatory), claw toes (MTPJ extension, IPJ flexion).
  • Terminology: Pes cavus, talipes cavus, high-arched foot. Normal vs. Cavus Foot Anatomy

⭐ The Coleman block test is essential to differentiate between forefoot-driven and hindfoot-driven cavus, guiding treatment decisions by assessing hindfoot flexibility when the first metatarsal is allowed to drop off the edge of a block.

Cavus Foot: Etiology & Pathomechanics - Why the Arch?

  • Etiology (Often Neuromuscular):
    • Neurological (Most Common):
      • Charcot-Marie-Tooth (CMT) (📌 Cavus Mostly Together)
      • Friedreich's Ataxia, Spinal Dysraphism, Polio
    • Other: Trauma (e.g., compartment syndrome, malunion), Congenital, Idiopathic
  • Pathomechanics (Muscle Imbalance):
    • Forefoot Driven: Peroneus Longus (PL) overpowers Tibialis Anterior (TA) → 1st ray plantarflexion.
    • Hindfoot Driven: Tibialis Posterior (TP) overpowers Peroneus Brevis (PB) → Hindfoot varus.
    • Intrinsic Imbalance: → Claw toes.
    • Result: ↑ Arch, rigid foot, ↓ shock absorption. Cavus vs Normal Foot Comparison

    ⭐ The Coleman block test helps differentiate flexible hindfoot varus (corrects with block) from rigid hindfoot varus in cavus foot, guiding surgical planning by assessing forefoot-driven deformity contribution to hindfoot varus.

Cavus Foot: Clinical Assessment - Spotting the Signs

  • History: Onset (congenital/acquired), progression, pain (location, character), instability, family history (e.g., Charcot-Marie-Tooth disease), footwear issues.
  • Observation:
    • High arch (medial longitudinal).
    • Hindfoot: Varus ("peek-a-boo" sign), increased calcaneal pitch.
    • Forefoot: Adduction, pronation, plantarflexed 1st ray.
    • Toes: Clawing. Callosities (lateral border, metatarsal heads).
  • Gait: Lateral weight-bearing, ankle instability.
  • Key Tests:
    • Coleman Block Test: Assesses hindfoot flexibility.
    • Thorough neurological examination (essential for etiology).

⭐ The Coleman block test is crucial: it differentiates a flexible hindfoot (corrects with block under lateral forefoot) from a rigid deformity, guiding surgical strategy.

Cavus Foot: Imaging & Classification - X-Ray Vision

  • X-Rays (Weight-Bearing):
    • Lateral View:
      • ↑ Meary's Angle: > (Talus-1st MT) - apex dorsal.
      • ↑ Hibb's Angle: >45° (Calcaneus-1st MT).
      • ↑ Calcaneal Pitch: >30°.
    • AP View:
      • ↓ Kite's Angle (Talocalcaneal): <20° (hindfoot varus).
  • Coleman Block Test: Differentiates flexible forefoot-driven hindfoot varus. Lateral X-ray of cavus foot with Meary's angle
  • Classification: Based on radiographic angles (severity) & deformity apex.

    ⭐ Meary's angle (talus-1st metatarsal) is key for identifying apex and severity of cavus deformity on lateral X-ray.

Cavus Foot: Management Principles - Fixing the Foot

  • Conservative: Stretching exercises, custom orthotics (e.g., UCBL, lateral wedge for forefoot/hindfoot), appropriate footwear modifications.
  • Surgical Goals: Relieve pain, improve stability, correct deformity.
    • Flexible Deformity: Plantar fascia release, tendon transfers (e.g., Peroneus Longus to Brevis, Hibbs).
    • Rigid Deformity: Bony procedures.
      • Osteotomies: Calcaneal (Dwyer), metatarsal (dorsiflexion).
      • Arthrodesis: For severe, arthritic joints (e.g., triple arthrodesis).
    • Apex of deformity guides surgical choice.

Lateral X-ray of surgically corrected cavus foot

⭐ The Coleman block test helps differentiate forefoot-driven cavus (plantarflexed first ray) from hindfoot-driven cavus, guiding surgical strategy.

High‑Yield Points - ⚡ Biggest Takeaways

  • Cavus foot: high-arched foot, often from neuromuscular disorders (e.g., Charcot-Marie-Tooth).
  • Symptoms: painful callosities (metatarsal heads), claw toes, ankle instability, hindfoot varus.
  • Coleman block test: crucial for assessing hindfoot flexibility and differentiating forefoot vs. hindfoot driven deformity.
  • Radiographs: ↑ calcaneal pitch, ↑ Meary's angle, abnormal Hibb's angle.
  • Treatment: orthotics initially; surgery (osteotomies, tendon transfers) for severe cases.
  • Investigate for neurological causes (e.g., spinal dysraphism), especially if unilateral.

Practice Questions: Cavus Foot

Test your understanding with these related questions

Which type of intra-articular fracture of the calcaneum is characterized by an increased Gissane's angle?

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Flashcards: Cavus Foot

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Hallux valgus leads to overriding of the _____ finger and prominence of the 1st MTP head

TAP TO REVEAL ANSWER

Hallux valgus leads to overriding of the _____ finger and prominence of the 1st MTP head

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