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Equinovarus Foot

SUMMARY

  • Equinovarus Foot is an acquired foot deformity commonly seen in pediatric patients with cerebral palsy, spina bifida, and Duchenne Muscular Dystrophy that present with a equinovarus foot deformity. 

  • Diagnosis is made clinically with presence of an inverted heel with a supinated forefoot, often associated with pain and callous formation along the lateral border of the foot.

  • Treatment ranges from bracing to tendon transfers to osteotomies depending on the underlying etiology, severity of deformity, and rigidity of contracture.

EPIDEMIOLOGY

  • Incidence

    • common foot deformity seen with

      • cerebral palsy (usually spastic hemiplegia)

      • Duchenne muscular dystrophy

      • residual clubfoot deformity

      • spina bifida

      • tibial deficiency (hemimelia)

        • though this condition is very rare

ETIOLOGY

    • Pathophysiology

      • pathomechanics

        • imabalance of invertors and evertors (invertors overpower the evertors)

        • relative overpull of

          • tibialis posterior and/or

          • tibialis anterior

          • gastoc-soleus complex

        • example: in cerebral palsy

          • the causative muscles for the varus are the

            • anterior tibialis (AT) in 1/3 of patients

            • posterior tibialis (PT) in 1/3 and

            • both the AT and PT in the remaining 1/3

      • foot deformity muscle imbalance overview 

PRESENTATION

  • Symptoms

    • pain

      • painful weight bearing over the lateral border of the foot

    • instability

      • during stance phase

      • results in shortened single limb stance

    • poor shoe and/or brace fitting and shoe wear problems

  • Physical Exam

    • inspection 

      • inverted heel (tibialis posterior typically implicated)

      • supinated forefoot (tibialis anterior)

      • callous and pain along lateral border

      • intoeing gait (foot progression angle is more internal than knee progression angle)

    • provocative tests

      • active dorsiflexion of foot

        • if foot supinates with dorsiflexion, the anterior tibialis is implicated

      • confusion test

        • indications

          • used in those with poor selective motor control, as in CP, and cannot dorsiflex foot when asked)

        • method

          • patient performs active hip flexion (with or without resistance) while seated

          • results in ankle dorsiflexion due to mass action pattern of leg

          • if the foot supinates with dorsiflexion, the tibialis anterior is likely a contributing to the varus deformity

    • Coleman block test

      • indications

        • to test rigidity of the varus deformity

        • do not do this in children with limited balance such as CP

      • method

        • patient stands on a block with the first ray off the block

        • if the varus corrects, the deformity is flexible

    • manual manipulation of the hindfoot

      • can be used to asses rigidity of the varus deformity

        • passive eversion of the hindfoot past neutral demonstrates that the varus deformity is flexible

IMAGING

  • Radiographs

    • recommended views

      • AP + lateral of foot

    • findings

      • forefoot adduction is seen on the AP radiograph 

      • the talus and calcaneus are more parallel than in typical feet

      • one can often "look down" the sinus tarsi through a visual hole there

      • the calcaneus looks foreshortened on the lateral view

      • the metatarsals are often "stacked" on the lateral view (instead of being in line with one another)

      • stress fractures along the fourth and/or fifth metatarsal bases can develop secondary to repetitive load along the lateral border of the foot.

STUDIES

  • Dynamic EMG

    • may be useful in distinguishing whether tibialis anterior and/or tibialis posterior is/are causing the varus in CP

TREATMENT

  • Nonoperative

    • ankle foot orthosis (AFO)

      • helps provide stability for the foot and a more stable base of support during gait

      • should have a "wrap around" hindfoot component of the brace to help control the varus and minimize pressure points

    • serial casting

      • indication

        • rigid deformity

    • botulinum toxin injection into tibialis posterior and/or gastrocnemius

      • indication

        • flexible or dynamic deformities

        • desire to delay surgery

  • Operative

    • gastrocnemius recession or tendoachilles lengtheing (TAL) for equinus

      • indications

        • fixed equinus unresponsive to non-operative measures

        • gastrocnemius recession should be performed if the anke can be brought to neutral or above neutral with the knee flexed and hindfoot inverted, but not when the knee is extended

        • TAL should be performed if the ankle can not be dorsiflexed to neutral with the knee flexed or extended

    • split-posterior tibialis tendon transfer [SPOTT] or posterior tibial tendon lengthening (PTTL)

      • indications

        • soft tissue balancing is required if varus is flexible or rigid

        • varus foot recalcitrant to non-operative measures and posterior tibialis contributing to varus (dynamic EMG, when available is helpful)

        • tibialis posterior spastic in both stance and swing phase (continous activity)

        • common patient: spastic hemiplegia in ages 5 to 7 years old

      • technique

        • SPOTT

          • reroute half of tendon laterally and insert into peroneus brevis

        • PTTL

          • fractional lengthening of the tendon in the distal third of the lower leg

        • either PTTL or SPOTT may be combined with SPLATT

      • outcomes

        • results for both surgeries are good, without clear indications for transfer versus lengthening

    • split-anterior tibialis tendon transfer [SPLATT]

      • indications

        • overactive anterior tibialis on EMG

        • when anterior tibialis contributes to varus foot, whether flexible or rigid varus deformity

      • technique

        • split anterior tibialis transfer to cuboid, peroneus tertius, or peroneus brevis

        • may be combined with SPOTT or PTTL

    • calcaneal osteotomy

      • indications

        • required for a rigid hindfoot varus deformity

      • technique

        • lateral closing wedge osteotomy (Dwyer) to incur valgus to the heel, OR

        • lateral calcaneal sliding osteotomy to correct the varus

        • typically combined with soft tissue balancing (as above)

COMPLICATION

  • Overcorrection (resultant valgus deformity)

    • increased risk in

      • children who undergo surgery at younger age

      • children with diplegia (as oppose to hemiplegia)

  • Wound complications

    • most common with calcaneal osteotomy lateral incision

    • risk decreased by using absorbable suture

  • Hardware Pressure sores/ulcers

    • from buttons on bottom of foot (from SPLATT to cuboid)

    • has led some surgeons to always transfer SPLATT to peroneus tertius or brevis

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