Definition
Cavus is an abnormally high medial longitudinal arch. The clinically important deformity is often cavovarus, with a plantarflexed first ray and hindfoot varus.
Causes
Always consider a neurological cause, particularly when deformity is bilateral or progressive.
Examples:
- Charcot-Marie-Tooth disease
- spinal dysraphism or cord pathology
- previous poliomyelitis
- cerebral palsy
- post-traumatic imbalance
- idiopathic cavus
Assessment
History:
- progression
- recurrent ankle sprains
- lateral foot pain
- callosities
- weakness or sensory symptoms
- family history
Examination:
- hindfoot varus
- plantarflexed first ray
- claw toes
- callosity under first/fifth metatarsal heads
- peroneal and tibialis anterior strength
- intrinsic muscle wasting
- ankle stability
- Achilles tightness
Ask about:
- recurrent ankle sprain
- lateral foot pain
- callosity
- shoe wear
- weakness
- sensory symptoms
- family history
- progression
Examine motor balance, particularly peroneus longus/brevis, tibialis anterior/posterior and intrinsic muscles.
The Coleman block test is central. Correction of hindfoot varus when the first ray is allowed to drop suggests a flexible hindfoot driven by a plantarflexed first ray.
Coleman block test
Place the heel and lateral border of the foot on a block, allowing the first ray to hang free.
- hindfoot corrects: varus is driven mainly by the plantarflexed first ray and remains flexible
- hindfoot remains in varus: hindfoot deformity is fixed or independently driven
This distinction guides surgery.
Imaging
Obtain weight-bearing foot and ankle radiographs. Assess:
- arch height and Meary alignment
- calcaneal pitch
- first-ray plantarflexion
- hindfoot alignment
- degenerative change
Treatment goals
Create a foot that is:
- plantigrade
- stable
- pain free or less painful
- shoeable
Operative principles
Surgery is tailored to the deformity and muscle imbalance rather than using one standard operation.
Options may include:
- plantar fascia release in selected flexible deformity
- first-ray dorsiflexion osteotomy
- calcaneal osteotomy
- tendon transfer to rebalance muscle forces
- Achilles or gastrocnemius lengthening when indicated
- midfoot osteotomy
- arthrodesis for rigid painful deformity or advanced arthritis
Neurological progression must be considered before choosing reconstruction.
Define the deformity
Cavus is an abnormally high medial longitudinal arch, but clinically the important question is the deformity pattern and its driver.
Components can include:
- plantarflexed first ray
- hindfoot varus
- forefoot adduction
- claw toes
- tight plantar fascia
- Achilles or gastrocnemius tightness
- lateral overload
Many adult cavovarus feet are associated with neurological disease, so a new or progressive deformity warrants a neurological history and examination.
Radiographs
Weight-bearing films help define:
- arch height
- hindfoot alignment
- first-ray plantarflexion
- forefoot adduction
- degenerative change
- previous fracture or coalition
Mechanical consequences
A cavovarus foot concentrates load laterally. Consequences can include:
- recurrent lateral ligament injury
- peroneal tendon pathology
- fifth-metatarsal stress injury
- painful callosity
- ankle varus arthritis
If the underlying alignment is not corrected, isolated treatment of a lateral ligament or peroneal tendon problem may fail.
Non-operative treatment
For mild flexible deformity:
- footwear modification
- appropriate orthoses
- stretching
- strengthening
- management of neurological disease
Orthotic design should accommodate or correct the actual driver. A rigid cavus deformity may need pressure relief rather than aggressive correction.
Surgery
Surgery is tailored to flexibility and deformity location.
Options may include:
- plantar fascia release
- first-ray dorsiflexion osteotomy
- calcaneal osteotomy
- tendon transfer to rebalance forces
- correction of toe deformity
- midfoot osteotomy
- fusion when deformity is rigid or arthritic
The rule is to correct bony alignment and muscle imbalance together where required.
FRCS synthesis
A good answer follows:
- identify neurological cause
- determine whether hindfoot is flexible
- identify the deformity driver
- correct alignment
- rebalance muscle forces
- protect pressure-sensitive areas
Do not propose an isolated lateral ligament reconstruction in an uncorrected cavovarus foot.