Pes Cavus

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Definition

  • Foot with high arch that fails to flatten with weight bearing
  • Deformity may be hindfoot, forefoot or both

Aetiology

  • The origin is often obscure but general cause related to Muscle Imbalance
  • Duchenne believed due to intrinsic imbalance
  • Others believe extrinsic imbalance
  • Probably combination of both
  • 66% found to be due to neurological disease (Brewerton 1963)
  • 33% seen to have Charcot-Marie-Tooth disease
  • Myelodysplasia & Poliomyelitis next in order

Epidemiology

Anatomy

Most of the following relates to idiopathic pes cavus

  • 1. Dropping of Forefoot
    • First ray drops initially
    • The forefoot is supinated
    • Initially flexible but later rigid
  • 2. Contracture of the Plantar Fascia
    • Increases height of the longitudinal arch
    • The fascia further shortens with forefoot pronation & heel varus
  • 3. Varus of Heel
    • As forefoot fixed in pronation then heel varus must occur to allow placement of metatarsals on ground
    • Initially only with weight bearing but eventually fixed
    • As the heel varus ↑ the TA worsens the varus due to medial displacement
  • 4. Clawing of Toes
    • Overactivity of the EDL
    • Initially reduced when foot dorsiflexed
    • Then fixed with MT head callosities & PIPJ callosities dorsally

Pathology

  • Two main theories related to muscle imbalance
    • 1. Weakness of Intrinsics
    • 2. Overactivity of Extrinsics
  • Acute contracture
  • Develops rapidly in paralytic disease (ie Polio)
  • Postural contracture
  • Immobility & oedema
  • Muscle Imbalance
  • Variable imbalance
    • » In poliomyelitis see weakness of posterior calf musculature with normal anterior leg
  • Thus deformity with unopposed tibialis anterior function
    • » Charcot-Marie-Tooth is opposite to polio with weak anterior compartment & normal posterior
  • Forefoot equinus develops due to weakness of tibialis anterior & normal peroneus longus as the peroneus longus depresses the first metatarsal & not opposed with tib ant
  • The peroneus brevis weak with normal tibialis posterior & hence varus of hind foot
  • The Long toe extensors attempt to elevate the foot & hyperextend the MTPJ & long flexors tighten & pull the distal joints into flexion
  • The hindfoot secondarily inverts to allow placement of the metatarsals evenly on floor

Classification

Idiopathic

  • Most common type
  • Develops after 3 years of age
  • Males = Females
  • Often associated with spina bifida occulta

Secondary

  • Neuromuscular disease
    • Head
      • Cerebral palsy
      • Friedreichs ataxia
      • Spinocerebellar swgeneration
    • Cord
      • Charcot-Marie-Tooth disease type 2
      • Spina bifida
      • Poliomyelitis
      • Syrinx
      • Diastematomyelia
      • Tethered cord
      • Cauda equina tumour
    • Nerve
      • CMT type 1
      • Neurolemmoma
      • Nerve injury
    • Myopathies
      • Trauma
      • Compartment Syndrome sequelae
      • Direct trauma to foot (malunion of midfoot fracture)
      • Plantar fibromatosis
      • Talipes equinovarus – often previously treated ß don’t forget CTEV!
      • Arthrogryposis

History

  • Increased stress in heel & metatarsal head regions
  • Thus
  • Inability to stand or walk for long periods
  • Fatigability
  • Thick callus formation on plantar aspect of foot & toes
  • Ankle instability
  • Ulcer formation over toes
  • Shoe wear problems

Examination

  • High arch
  • First MT drop & pronation
  • Tight plantar fascia
  • Cock up deformity of all toes at MTPJ
  • Flexion deformity of all toes at IPJ
  • Varus heels
  • Heel not in equinus
  • Deformities initially flexible & then rigid
  • Flexibility of hind foot deformity assessed with Coleman Block Test
  • Determine if Hindfoot deformity will correct after Forefoot corrected
  • Place the lateral border of forefoot on block & allow medial forefoot pronation to correct
  • Then assess the correction of hindfoot
  • Flexibility of the forefoot assessed by applying upward force on the MT heads & see if corrects
  • Assess
    • Joint motion
    • Muscle power – individually
    • Neurological exam to exclude dysraphism
    • Back for usual stigmata of dysraphism
    • Sensation
    • Hands
  • Stages
    • First Degree
      • Foot normal
      • Deformity mainly when foot relaxed
      • Easy correction of forefoot & hindfoot
    • Second Degree
      • Equinus & pronation of first ray irreducible
      • Early contractures of the Plantar fascia & Clawing of Big toe
    • Third Degree
      • Other MT claw & become increasingly irreducible
      • Heel varus not correctable
      • No bony deformity on XR
      • Some degree of passive reduction possible
    • Fourth Degree
      • Pronounced deformity with no passive correction
      • Structural changes at apex of the foot at Medial Cuneiform
      • Some midtarsal movement remains
    • Fifth Degree
      • Most extreme degree
      • All components firmly fixed
      • Midtarsal structural defects present
      • Toes dislocated at MTPJ
      • Severely disabled

Investigations

Xrays

  • Weight-bearing A-P & Lateral films
    • Lateral
      • Talus & calcaneum parallel
      • Sinus tarsi clearly visible
      • Increased Mearys Angle (Angle between long axis of first MT & Talus) – normally 0 but ↑ in pes cavus
    • AP
      • Talus & Calcaneum superimposed – due to heel varus
  • Spine
  • Increased interpedicular distance
  • Congenital abnormality
  • Spina bifida occulta
  • Diastematomyelia
  • Others
  • MRI of brain & cord
  • NCS
  • Biopsy of peripheral nerve & muscle

Differential Diagnosis

Treatment

  • Principles
    • Correct the forefoot equinus & pronation
    • Never idiopathic unless exhaustive search fails to find another cause
    • Immature foot treated with soft tissue surgery only
    • Goal to produce plantar grade stable foot

First Degree (flexible)

  • Conservative treated favoured
  • Stretching programme
  • Large broad shoe to accommodate toes
  • AFO
  • Regular follow-up to recognise change requiring operative intervention
  • Does not affect progression but alleviates symptoms

Second Degree (1st ray fixed with claw, plantar fascia contracted)

  • Generally need surgery
    • Steindler Release
      • Longitudinal incision along medial aspect of calcaneum
      • Fascia released from calcaneal attachment
    • Release of
      • Abductor hallucis
      • FDB
      • Abductor digiti minimi
    • Subperiosteal dissection
    • Long plantar ligament released
    • Foot forcibly corrected
    • Jones Procedure
      • Dorsolateral approach to Great Toe
      • EHL divided 2cm from insertion into DP
      • Toe straightened & distal tendon inserted into the PP
    • Then incision proximally over MT
    • The proximal EHL tendon passed through the MT distally (via drill hole)
    • Sutured to itself with tension
    • Arthrodesis of the IPJ performed
    • Osteotomy of First Metatarsal
    • Dorsal closing wedge osteotomy at base
    • Fixed with pin or screw
    • Tendon Transfers
    • Usually in Tibialis anterior loss (ie Charcot-Marie-Tooth)
    • Tib Post transfer
    • Peroneus longus to brevis

Third Degree (lesser toes also affected, fixed varus heel)

  • Also need to correct the lesser toe abnormalities
  • Transfer of long extensors to MT performed – Hibbs procedure
  • Extensor shift Procedure – Hibbs
  • Jones procedure
  • Extensor tendons of the lesser toes exposed
  • Tendons of 2nd & 3rd into 3rd MT
  • Tendons of 4th & 5th into 5th MT
  • (Can insert all tendons into intermediate cuneiform)
  • May add dorsal capsulotomies
  • Steindler release
  • Osteotomy of the Calcaneus – Dwyer will restore valgus appearance of heel
  • Dwyer Osteotomy
  • Outer surface calcaneum exposed
  • Peroneus Longus exposed
  • Wedge with 8-12mm base removed from calcaneum just below PL
  • Forced dorsiflexion closes osteotomy via tension in TA
  • Can also do calcaneal osteotomy to slide posterior calcaneus into more postero-superior position – Samilson Osteotomy

Fourth Degree (midfoot changes with no passive correction)

  • Same as above but need to add Midtarsal osteotomy
  • Japas V-shaped Osteotomy
  • Navicular area
  • Then extends to lateral & medial borders of foot through cuboid & medial cuneiform
  • Performed extraperiosteally
  • Attempt to retain midfoot movement
  • Cole anterior tarsal wedge Osteotomy
  • Wedge of bone distal to T-N & C-C joints
  • Avoid in skeletally immature as short foot results
  • More proximal than the Japas
  • “Operation of a thousand cuts”
  • Jones procedure
  • First MT osteotomy
  • Hibbs procedure
  • Tendon transfers – e.g. split tibialis anterior to peroneus tertius
  • Peroneus longus lengthening
  • Steindler release
  • Calcaneal osteotomy – Dwyer or lateral slide
  • Midtarsal osteotomy
  • TA lengthening (if very short with varus heel) » often left for 6 weeks to allow a lever force for the other procedures to take effect (Terry Maguire)

Fifth Degree (all components fixed, dislocation of MTPJ’s, severe disability)

  • Triple arthrodesis will correct deformity
  • Jones for the first & Metatarsal head excision & PIPJ fusion for lesser toes
  • Treatment of Cavus due to Muscle Imbalance
  • Tendon transfer in growing foot
  • Absent Tib Anterior (with normal PL) » transfer PL to lateral cuneiform
  • Polio
  • Weak calf muscles » transfer Tib Post & PL to TA

Complications

Prognosis

References