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Updated: Jun 5 2024

Anterolateral Bowing & Congenital Pseudoarthrosis of Tibia

Images photo - courtesy Miller_moved.jpg bowing xray - courtesy Miller_moved.png pseudo xray - courtesy Miller_moved.png fibula graft - courtesy Miller_moved.png
  • summary
    • Anterolateral Bowing and Congenital Pseudoarthrosis of the Tibia are congenital conditions, most commonly associated with Neurofibromatosis Type 1, that present with a bowing deformity of the tibial.
    • Diagnosis is confirmed with radiographs of the tibia. 
    • Treatment is nonoperative with bracing for patients who are weightbearing without pseudoarthrosis or fracture. Surgical correction is indicated in the presence of pseudoarthrosis or fracture 
  • Epidemiology
    • Incidence
      • Extremely rare
      • 1:140,000-190,000
    • Risk Factors
      • Up to 55% associated with Neurofibromatosis Type 1
      • 15% associated with Fibrous Dysplasia
  • Etiology
    • Pathophysiology
      • pseudoarthrosis in not congenital, but in fact develops post-natally due to fracture non-union
    • Three types of tibial bowing exist in children
      • anterolateral bowing (this topic)
      • posteromedial bowing (physiologic)
      • anteromedial bowing (fibular hemimelia) 
    • Anterolateral bowing is a continuum of disease that can be divided into
      • anterolateral bowing of tibia 
      • congenital pseudarthrosis of tibia 
    • Associated conditions
      • neurofibromatosis type I
        • is found in 50-55% of patients with anterolateral bowing
        • only 6-10% of patients with neurofibromatosis will have anterolateral tibial bowing
  • Classification
    • Numerous classification systems have been proposed (Boyd, Andersen, Crawford) however none guide management or are predictive of outcome
    • Two classification criteria have been proposed to guide treatment:
      • The presence or absence of fracture
      • The age at which fracture occurs
        • "Early onset" < 4 years old
        • "Late onset" > 4 years old
  • Presentation
    • Symptoms
      • majority present with bowing in the first year of life
    • Physical exam
      • deformity
      • careful skin examination for cafe-au-lait spots and other signs of neurofibromatosis
  • Treatment
    • The lesion does not self-resolve, and once fracture occurs there is low likelihood of spontaneous resolution
    • Nonoperative
      • bracing in clamshell orthosis or patellar tendon bearing (PTB) orthosis
        • indications
          • children of ambulatory age (weight bearing)
          • bowing without pseudarthrosis or fracture
            • spontaneous remodeling is not expected
        • goal is to prevent further bowing and fractures
        • osteotomy for bowing alone is contraindicated
        • technique
          • maintained until skeletal maturity
    • Operative
      • surgical fixation
        • indications
          • bowing with pseudarthrosis or fracture
      • amputation
        • indications
          • typically indicated after multiple failed surgical attempts at union
          • severe limb length discrepancy
          • dysfunctional angular deformity
          • Method- Syme or Boyd amputation
  • Techniques
    • Surgical fixation
      • goals
        • resection of pseudarthrosis to grossly normal bone
        • correction of alignment
        • bone grafting and stabilization of the remaining segments
        • intramedullary splinting of the bone is desired
      • techniques
        • intramedullary nailing with bone grafting
          • Resect the pseudarthrosis
          • Tibial shortening
          • Fixation with intramedullary rod
          • Bone graft
        • free vascularized fibular graft (Farmer's Procedure)
          • contralateral fibula is used, ipsilateral is involved in pseudarthrosis
        • Ilizarov or circular frame fixation with lengthening or bone transport
    • Amputation
      • Ankle disarticulation (Boyd or Syme amputation) preferred over resection at pseudoarthrosis site
      • Persistent motion at pseudoarthrosis site managed by prosthetic socket
  • Complications
    • Recurrent fracture
      • seen in 50% or more of patients even after initial union
    • Valgus deformity

    • Limb length discrepancy at skeletal maturity (average 5cm)

    • No treatment is considered to produce results in a predictable and acceptable fashion
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