Pes cavus

Synonym: claw foot

What is pes cavus?

Pes cavus is a deformity of the foot which has a very high arch and is relatively stiff. This deformity does not flatten on weight bearing.

A high arch with a medially angulated heel is called pes cavovarus. When this is complicated by foot drop and equinus of the ankle, this is called pes equinocavovarus.

In cases where the primary deformity is excessive ankle and hindfoot dorsiflexion, it is called pes calcaneovarus.

Pes cavus aetiology¹

This condition is caused by an imbalance between the agonist and antagonist muscles in the foot. There is often family history and it is usually bilateral.

• Progressive neurological disorders:
  

  • Hereditary sensorimotor neuropathies (HSMNs) or Charcot-Marie-Tooth (CMT) disease.

  • Hereditary sensory and autonomic neuropathies.

  • Friedreich's ataxia.

  • Spinal tumour or brain tumour.

  • Spinal trauma.

  • Syringomyelia.

  • Muscular dystrophy.

• Static neurological disorders:

  • Cerebral palsy.

  • Stroke.

  • Polio.

  • Spinal nerve root injury.

  • Peroneal nerve injury.

• Other causes:

  • Foot trauma.

  • Tarsal coalition.

  • Iatrogenic.

  • Scarring after compartment syndrome.

Pes cavus symptoms (presentation)

Patients often complain of pain, instability, difficulty walking or running and also problems with footwear.

There is often a range of other foot deformities also present - eg, claw toes, increased calcaneal angle.

Symptoms

These vary with degree of deformity:

• Pain in the side of the foot and the metatarsals.

• Calluses on the plantar aspect of the foot.

• Instability of the ankle.

Neuropathies may be accompanied by neuropathic pain. With progression, deformity and rigidity become more severe. This can lead to overload of the lateral side of the foot and even to stress fractures of the fifth metatarsal.

Peroneal tendinopathy, Achilles tendon disorders, plantar fasciitis and ankle impingement are more common.

NB: a spinal tumour should be suspected in any patient with new unilateral presentation, without previous trauma.

Signs

• Foot shape is best observed when the patient is standing.

• Inspect shoes for signs of abnormal wear.

• Observe gait for varus or foot drop.

• Passive movements should be assessed to look for any joint contractures.

• Perform neurological examination for a possible underlying cause.

Investigations²

Take a full family history. It is very important to establish whether there is an underlying neurological diagnosis and whether this is progressive or static. Neurological symptoms, such as sensory changes, weakness and clumsiness may be present. Back pain or headaches may signify a central cause.

• X-ray of foot (weight-bearing).

• MRI scan of the spine if a tumour is suspected.

• Electromyography and nerve conduction tests may be indicated for some patients.

Pes cavus treatment and management³

The aim of treatment is to preserve a painless and mobile foot. The management of pes cavus depends on the aetiology, rapidity of progression and also the severity of the symptoms.⁴ The risk of progression during childhood can be reduced by appropriate conservative treatment.

General measures

• Non-surgical treatment should be instituted early by orthotists and podiatrists.

• Physiotherapy to loosen tight muscles and improve strength of weak ones.

• Padding and orthotic shoes.

• Splints or appliances can be used for some patients.⁵

• A caliper may be given to patients with very severe deformity and refractory ankle instability.

Surgical measures

• Surgery is usually only justified when deformity is so pronounced or progressive that symptoms are intrusive and unresponsive to conservative treatments.⁶

• The aims of surgery are to:
  

  • Correct deformity.

  • Relieve pain and preserve joint motion if possible.

  • Re-balance muscle forces to aid gait and prevent progression of deformity.

• Depending on the nature of the deformity, procedures can be release of plantar fascia, tendon transfer, osteotomy (calcaneal or first metatarsal) and arthrodesis.⁴

• Many patients need several operations.