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