The Cavovarus Foot

 

Definition

  • The cavovarus foot is a foot with a high arch that maintains its position on weight bearing.
  • Pathology can be found in the hindfoot, midfoot, forefoot or a combination.

Figure 1: A cavovarus foot

 

Biomechanical consequences

  • The weightbearing area of the sole of the foot is reduced
  • The subtalar joint axis is more vertical
  • The talar head is externally rotated over the anterior process of the calcaneum
  • The subtalar and Chopart joints are more rigid
  • The foot is generally “stiffer” than normal
  • The ability of the foot to absorb impact is reduced

 

Aetiology

  • All forms of cavovarus foot essentially result from muscle imbalance
  • Can be divided into 2 main groups: 

Neuromuscular

  • 50% of all detectable lesions are a variant of Charcot Marie Tooth disease
  • in unilateral, progressive cavus foot, consider spinal cord tumour

Non-neuromuscular

  • idiopathic
    • the 'subtle cavus foot'
    • most are due to a plantar flexed 1st ray (?peroneus longus overactivity?)
  • traumatic (compartment syndrome, burns, fracture malunion)
  • undertreated talipes equinovarus

 

Table1: Classification of cavus foot aetiology

 

Charcot Marie Tooth Disease

  • In 1886:
    • Jean Martin Charcot and Pierre Marie (France) were physicians who described the condition
    • Howard Henry Tooth (UK) described the peripheral nerve pathology
  • 50% of all detectable lesions causing a cavovarus foot
  • Essentially a myelin sheath disorder; various types and inheritance, often with varying levels of penetration:
  1. Most common (50%): autosomal dominant / sporadic
  2. Next most common: autosomal dominant
  3. X linked: 10-20% of cases
  4. Rarest: autosomal recessive

 

Deformity vs muscle imbalance

Table 2: Deforming forces in a cavus foot

 

History

  • Pain and symptoms
  • Family history
  • Progression
  • Unilateral vs bilateral
  • Shoes
  • Treatment so far

 

Examination

Remember to do a full neurological exam; there is almost always a neurological condition as a cause (50% will be CMT).

Look at the lumbar spine:

  • scars
  • hair at the base of the spine
  • scoliosis

In the unstable ankle, always look carefully for a (subtle) cavo varus deformity

 

The Coleman Block Test

Figure 2a: Markedly varus right heel, adducted forefoot

Figure 2b: The outer border of the affected foot is placed on a 2cm board allowing the first ray to drop down; In this case, the heel corrects to neutral / slight valgus with apparent correction of the forefoot adductus.

 

Figure 3: Side view showing the first ray dropping down to the floor, effectively removing a deforming force

 

A positive Coleman block test (Fig 2) confirms that:

a) the subtalar joint is flexible and

b) at least part of the deformity is driven by a flexed first ray ("forefoot-driven"); this will need to be addressed to correct the deformity

 

Management

“The goal - as in any foot surgery - is a plantigrade, comfortable foot”

 

Conservative treatment

  • Orthoses (mostly accomoodative due to relative stiffness):
    • accommodative insoles (offloads bony prominences - MT heads, base of 5th MT), heel raise for equinus
    • corrective (e.g. heel wedge/tilt)
  • AFOs
  • Physiotherapy / calf stretching

 

Surgical Treatment

Decisions:

  1. Where is the deformity?
    • Hindfoot / midfoot / forefoot or a combination?
  2. Is the deformity rigid or flexible?
  3. Can I balance the soft tissues or do I have to perform bony procedures?
  4. Severity of the deformity

Soft tissue options:

  • Gastrocnemius / Achilles lengthening
  • Tibials posterior tendon transfer (last muscle to fail in CMT)
  • Peroneus longus to brevis tendon transfer (converts PL from a flexor of the first ray to a pure evertor of the foot)
  • EHL transfer / tenodesis (Jones procedure combined with a fusion of the IPJ for claw hallux; also elevates the 1st ray)
  • Flexor-extensor tendon transfer (FETT) procedure
  • Plantar fascia release (Steindler release)

Bony options:

  1. Lateral heel shift / Dwyer osteotomy
    • In polio, can do proximal translation of calcaneum (Samilson)
  2. Extension osteotomy of the 1st ray
  3. Midfoot osteotomy
  4. Triple fusion

Surgery is based on careful preoperative assessment of the whole condition. It is best regarded as a palette of procedures applied to the individual patient's deformity.

One size does not fit all!

 

FIgure 4: Radiograph of a cavovarus foot treated with calcaneal osteotomy, extension osteotomy of the first ray and tibialis posterior tendon transfer. Note - despite excellent correction, the patient required subsequent exostectomy of calcaneal plantar prominence.

 

 

References

Seaman TJ, Ball TA. Pes Cavus. 2023 Aug 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan PMID: 32310476

Abbasian A, Pomeroy G. The idiopathic cavus foot-not so subtle after all. Foot Ankle Clin. 2013 Dec;18(4):629-42

Aminian A, Sangeorzan BJ. The anatomy of cavus foot deformity: Foot Ankle Clin. 2008 13: 191-198 2008

Ward CM, Dolan LA, Bennett DL, et al.: Long term results of reconstruction for treatment of flexible cavovarus feet in Charcot-Marie Tooth disease. J Bone Joint Surg Am. 2008 90:2631-2642 2008

Maskill MP, Maskill JD, Pomeroy GC. Surgical management and treatment algorithm for the subtle cavo varus foot. Foot Ankle Int. 2010;31(12): 1057-63

Manoli A 2nd, Graham B. The subtle cavus foot, "the underpronator". Foot Ankle Int. 2005 Mar;26(3):256-63. doi: 10.1177/107110070502600313. PMID: 15766431

Samilson RL. Crescentic osteotomy os cslcis for calcaneovarus feet. Bateman JE Foot science. 1976 WB Saunders Philadelphia 18

Brewerton DA, Sandifer PH, Sweetnam DR. “Idiopathic” pes cavus: an investigation into its aeitiology. Br Med J.  2: 659-661 1963