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Introduction
  • 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
  • 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 or to either peroneus brevis 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)
Complications
  • 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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