Updated: 10/4/2018

Fibular Deficiency (anteromedial bowing)

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Introduction
  •  Three types of tibial bowing exist in children
    • anterolateral bowing (neurofibromatosis) 
    • posteromedial bowing (physiologic) 
    • anteromedial bowing (this topic)
  • Fibular deficiency
    • consists of shortening or entire absence of the fibula
    • previously known as fibular hemimelia
    • the most common congenital long bone deficiency
    • usually involves the entire limb
  • Genetics
    • no known inheritance pattern
    • linked to sonic hedge-hog gene
  • Associated conditions   
    • anteromedial tibial bowing  
      • most common cause is fibular hemimelia
    • ankle instability 
      • secondary to a ball and socket ankle 
    • talipes equinovalgus
    • tarsal coalition (50%)
    • absent lateral rays
    • femoral abnormalities (PFFD, coxa vara)
    • developmental dysplasia of the hip
    • cruciate ligament deficiency
    • genu valgum
      • secondary to lateral femoral condyle hypoplasia
    • significant leg length discrepancy  
      • shortening of femur and/or tibia 
Classification
  • Achterman & Kalamchi
    • based on amount of fibula present
  • Birch Classification
    • based on limb length and foot function
    • directs treatment
Achterman and Kalamchi Classification
Type Characteristics  Treatment  Example
Type IA
  • A portion of fibula remains present but proximal fibular epiphysis is distal to level of proximal tibial physis while distal fibula is proximal to the talus. 
 
  • Heel lift (if LLD >2cm)
  • Contralateral epiphysiodesis
  • Limb lengthening (at/near maturity)
 
Type IB
  • Partial absence of the fibula (30-50%) 
  • Distal portion is unable to support the ankle joint
  • Contralateral epiphysiodesis
  • Limb lengthening
  • Supramalleolar osteotomy (to correct ankle valgus)
  • Corrective foot procedures to achieve stable, plantigrade foot
  • Proximal tibial osteotomy (for genu valgus)


   
Type II
  • Complete absence of fibula 
  
  • Multiple Ilizarov surgeries to equalize limb lengths, achieve stable ankle, plantigrade foot
  • Foot ablation/amputation 
  
 
Presentation
  • Physical exam
    • classic findings  
      • short limb
      • skin dimpling over midanterior tibia
      • equinovalgus foot
    • other findings
      • often missing lateral toes
      • genu valgum
Imaging
  • Radiographs 
    • fibula is either absent or shortened
    • tibial spines are underdeveloped
    • intercondylar notch is shallow
    • ball and socket ankle joint
      • secondary to tarsal coalitions
Treatment
  • Goals
    • treatment determined by the stability and level of foot and ankle function, as well as the degree of limb shortening
      • not based on amount of fibula present
  • Nonoperative
    • observation
      • shoe lift
      • bracing
  • Operative
    • contralateral epiphysiodesis alone
      • indications
        • mild projected LLD (<5cm or <10%)
        • stable, plantigrade foot
    • limb lengthening procedure alone
      • indications
        • plantigrade, functional foot with a stable ankle
        • LLD < 10%
      • technique
        • involves resection of fibular anlage to avoid future foot problems
    • contralateral epiphysiodesis + limb lengthening procedure
      • indications
        • moderate LLD (10-30%)
    • Syme amputation (preferred to Boyd amputation)
      • Boyd is more bulbous and only about 1cm longer
      • indications
        • nonfunctional, deformed, unstable foot
        • LLD > 30%
        • unable to cope psychologically with multiple limb lengthening procedures
        • cosmesis
      • technique
        • amputation usually done at ~1 year of age to allow early prosthesis fitting, better psychosocial acceptance
      • results
        • 88% satisfaction with amputation vs 55% satisfaction with limb lengthening
 

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