Cavovarus Foot in Pediatrics & Adults - Pediatrics

summary
- Cavovarus Foot is a common condition that may be caused by a neurologic or traumatic disorder, seen in both the pediatric and adult population, that presents with a cavus arch and hindfoot varus.
- Diagnosis is made clinically with the presence of a foot deformity characterized by cavus, hindfoot varus, plantarflexion of the 1st ray, and forefoot adduction. A coleman block test is useful to assess for the flexibility of the hindfoot deformity to assist with surgical planning.
- Treatment ranges from orthotics to operative soft tissue release and operative osteotomies depending on patient age and flexibility of the foot deformity.

Epidemiology
- Demographics
  - seen in both pediatric and adult populations
- Anatomic location
  - when bilateral often hereditary or congenital

Etiology
- Deformity characterized by
  - cavus (elevated longitudinal arch)
  - plantarflexion of the 1st ray and forefoot pronation
  - hindfoot varus
  - forefoot adduction
- Pathophysiology
  - neurologic
    
    67% due to a neurologic condition
    
    diagnosis of neurologic condition is critical to render appropriate treatment
    
    unilateral - rule out tethered spinal cord or spinal cord tumor
    
    bilateral - most commonly due to Charcot-Marie-Tooth (CMT) disease
    
    muscle imbalances generate deformity
    
    weak tibialis anterior and peroneus brevis overpowered by strong peroneus longus and posterior tibialis
    
    results in plantarflexed 1st ray and forefoot pronation with compensatory hindfoot varus
    
    with the 1st metatarsal plantflexed and forefoot pronated, the medial forefoot strikes ground first
    
    the subtalar joint supinates to bring the lateral forefoot to the ground and maintain three-point contact, resulting in hindfoot varus
    
    while initially flexible, hindfoot varus can become rigid with time
  - idiopathic
    
    usually subtle and bilateral
  - traumatic
    
    talus fracture malunion
    
    compartment syndrome
    
    crush injury
- Associated conditions
  - conditions which present with cavovarus foot
    
    Charcot-Marie-Tooth disease
    
    Cerebral palsy
    
    Freidreich's ataxia
    
    Spinal cord lesions
    
    Polio
    
    Amnitoic band syndrome (ABS)
  - conditions caused by the presense of cavovarus foot
    
    see complications below

Presentation
- History
  - recurrent ankle sprains and lateral ankle pain
    
    peroneal tendon pathology
  - lateral foot pain
    
    excessive weight bearing by the lateral foot due to deformity
    
    can result in 5th metatarsal stress fractures
  - painful plantar calluses under 1st metatarsal head and 5th metatarsal head or base
  - plantar fasciitis
    
    elevated medial arch, forefoot pronation and tight gastronemius lead to contracture of the plantar fascia
- Physical exam
  - Coleman block test
    
    evaluates flexibility of hindfoot deformity
    
    technique
    
    place 1" block under the lateral foot
    
    eliminates contribution of the plantarflexed 1st ray and forefoot pronation to the hindfoot deformity
    
    findings
    
    flexible hindfoot will correct to neutral or valgus when block placed under lateral aspect of foot
    
    rigid hindfoot will not correct to neutral
    
    guides surgical treatment
    
    flexible hindfoot deformities resolve with forefoot corrective procedures
    
    rigid hindfoot deformities require corrective hindfoot osteotomy in addition to forefoot procedures
  - peek-a-boo heel
    
    anterior standing examination shows varus heel "peeking" around the ankle
  - prominent first metatarsal fat pads
  - Silfverskiold test
    
    check dorsiflexion with both knee flexion and knee extension
    
    if tight only with knee extension, then gastrocnemius is tight
    
    if tight also with knee flexion, then soleus is also tight
    
    gastronemius tightness often present with cavovarus foot
  - altered gait
    
    unstable base of support
    
    increased double limb stance and decreased single limb stance
  - wasting of 1st dorsal interosseous muscle of the hand
    
    suggestive of CMT
  - spine exam
    
    scoliosis is suggestive of CMT
    
    spinal dysraphism

Imaging
- Radiographs
  - recommended views
    
    standing anteroposterior (AP), lateral radiographs of the ankle
    
    standing AP, lateral and oblique radiographs of the foot
  - findings
    
    AP foot
    
    talocalcaneal angle < 20° (nl 20-45°)
    
    hindfoot varus
    
    talonavicular overcoverage
    
    talonavicular angle > 7° indicates forefoot adduction
    
    metatarsal overlap
    
    forefoot pronation
    
    lateral foot
    
    lateral talo-first metatarsal angle (Meary's angle) > 4° apex dorsal
    
    break in Meary's line caused by plantarflexion of the 1st ray
    
    calcaneal pitch or inclination angle > 30°
    
    sinus tarsi see-through sign and double talar dome sign
    
    due to external rotation of the ankle and hindfoot relative to the xray cassette, which is placed along the medial border of the adducted forefoot
    
    bell-shaped cuboid
    
    increased distance between base of 5th metatarsal and medial cuneiform
    
    oblique foot
    
    metatarsal stress fractures
    
    calcaneonavicular coalitions

Studies
- Electrodiagnostic Studies (EMG/NCS)
  - diagnostic algorithm for CMT generally dictates
    
    a neurologic physical exam
    
    electrodiagnostic studies
    
    genetic testing
- Genetic studies
  - used to confirm diagnosis after physical exam and electrodiagnostic studies

Treatment
- Nonoperative
  - accomodative shoe wear
    
    indications
    
    rarely sufficient except in mild deformity
  - full-length semi-rigid insole orthotic with a depression for the first ray and a lateral wedge
    
    indications
    
    mild cavus foot deformity in adult (not indicated in children)
  - supramalleolar orthosis (SMO)
    
    indications
    
    more severe cavovarus deformity recalcitrant to shoewear accomodations
  - ankle foot orthosis (AFO)
    
    indications
    
    may be needed if equinus also present, resulting in equinocavovarus foot deformity
    
    works best if equinus is a dynamic defomrity (not rigid)
  - lace-up ankle brace and/or high-top shoe or boots
    
    indications
    
    may consider in moderate deformities when patient does not tolerate the more rigid bracing with an SMO or AFO
- Operative
  - soft tissue reconstruction
    
    indications
    
    failure of nonoperative treatment
    
    performed with a combination of the following procedures
    
    plantar release
    
    indications
    
    cavus deformity
    
    technique
    
    plantar fascia release
    
    Steindler stripping (release short flexors off the calcaneus)
    
    peroneus longus to brevis transfer
    
    indications
    
    plantar flexed first ray
    
    technique
    
    decreases plantarflexion force on first ray without weakening eversion
    
    posterior tibial tendon transfer
    
    indications
    
    muscle imbalance
    
    posterior tibialis typically is markedly stronger than evertors and maintains strength for a long time in most cavovarus feet
    
    may consider transfer of posterior tibialis to dorsum of foot if severe dorsiflexion weakness of anterior tibialis
    
    lengthening of gastrocnemius or tendoachilles (TAL)
    
    indication
    
    true ankle equinus
    
    gastrocnemius recession produces less calf weakness and can be combined with plantar release simultaneously
    
    TAL should be staged several weeks after plantar release
    
    1st metatarsal dorsiflexion osteotomy
    
    indications
    
    flexible hindfoot varus deformities (normal Coleman block test)
    
    corrects the forefoot pronation driving the hindfoot deformity
    
    lateral ankle ligament reconstruction (e.g. Broström ligament reconstruction)
    
    indications
    
    chronic ankle instability due to lignamentous incompetence following long-standing cavovarus
    
    Jones transfer(s) of EHL to neck of 1st MT and lesser toe extensors to 2nd-5th MT necks
    
    indication
    
    toe clawing combined with cavus foot
    
    performed if the indication is met and time permits
    
    the modified Jones transfer for the hallux includes an IP joint fusion
  - lateralizing calcaneal valgus-producing osteotomy
    
    indications
    
    rigid hindfoot varus deformity (abnormal Coleman block test)
  - triple arthrodesis
    
    indication
    
    almost never indicated due to very poor long-term results

Complications
- Ankle instability
  - standard lateral ankle ligament reconstruction will fail if cavovarus deformity is not concomitantly addressed
  - untreated can lead to varus ankle arthritis
- Stress fractures
  - 5th metatarsal base (Jones fracture)
  - 4th metatarsal
  - navicular
  - medial malleolus
- Hallux sesamoiditis
  - overload from plantarflexed 1st metatarsal head
- Peroneal tendon pathology
  - tendonitis, tears, subluxation or dislocation
  - peroneus brevis most commonly involved
- Plantar fasciitis
  - contracture of the plantar fascia results from elevated medial arch, forefoot pronation and tight gastronemius

Prognosis
- Depends on
  - deformity severity
  - etiology
  - patient age