summary Infantile Blount's disease is progressive pathologic genu varum centered at the tibia in children 2 to 5 years of age. Diagnosis is suspected clinically with presence of a genu varum/flexion/internal rotation deformity and confirmed radiographically with an increased metaphyseal-diaphyseal angle. Treatment ranges from bracing to surgery depending on patient age, severity of deformity, and presence of a physeal bar. Epidemiology Risk factors overweight children early walkers (< 1 year) Hispanic and African American Etiology Best divided into two distinct disease entities Infantile Blount's(this topic) pathologic genu varum in children 2 to 5 years of age male > female more common bilateral in 50% Adolescent Blount's pathologic genu varum in children > 10 years of age less common less severe more likely to be unilateral Pathophysiology likely multifactorial but related to mechanical overload in genetically susceptible individuals including excessive medial pressure produces an osteochondrosis of the medial proximal tibial physis and epiphysis osteochondrosis can progress to a physeal bar Anatomy Genu varum is a normal physiologic process in children physiologic genu varum genu varum (bowed legs) is normal in children less than 2 years genu varum migrates to a neutral at ~ 14 months continues on to a peak genu valgum (knocked knees) at ~ 3 years of age genu valgum then migrates back to normal physiologic valgus at ~ 7 years of age Classification Langenskiold Classification type I thru IV consist of increasing medial metaphyseal beaking and sloping type V and VI have an epiphyseal-metaphyseal bony bridge (congenital bar across physis) provides prognostic guidelines Infantile versus Adolescent Blount's Infantile Blounts Adolescent Blounts Age 2-5yrs >10yrs Bilaterally 50% bilateral Usually unilateral Risks Early walking, large stature, obesity Obesity Classification Langenskiold No radiographic classification Severity More severe physeal/ epiphyseal disturbance Less severe physeal/ epiphyseal disturbance Bone Involvement Proximal medial tibia physis, producing genu varus, flexion, internal rotation, AND may have compensatory distal femoral VALGUS Proximal tibia physis, AND may have distal femoral VARUS and distal tibia valgus Natural History Self-limited - stage II and IV can exhibit spontaneous resolution Progressive, never resolves spontaneously (thus bracing unlikely to work) Treatment options Bracing and surgery Surgery only Presentation Physical exam genu varum/flexion/internal rotation deformity usually bilateral in infants may exhibit positive 'cover-up test' often associated with internal tibial torsion leg length discrepancy usually NO tenderness, restriction of motion, effusion lateral thrust on walking Imaging Radiographs views ensure that patella are facing forwards for evaluation (commonly associated with internal tibial torsion) findings suggestive of Blounts disease varus focused at proximal tibia severe deformity asymmetric bowing medial and posterior sloping of proximal tibial epiphysis progressing deformity sharp angular deformity lateral thrust during gait metaphyseal beaking different than physiologic bowing which shows a symmetric flaring of the tibia and femur measurements metaphyseal-diaphyseal angle (Drennan) angle between line connecting metaphyseal beaks and a line perpendicular to the longitudinal axis of the tibia >16 ° is considered abnormal and has a 95% chance of progression Drennan angles between 11-16° necessitate close observation for the progression of tibia vara <10 ° has a 95% chance of natural resolution of the bowing tibiofemoral angle angle between the longitudinal axis of the femur and tibia Differential The following conditions can also lead to pathologic genu varum persistent physiological varus rickets osteogenesis imperfecta MED SED metaphyseal dysostosis (Schmidt, Jansen) focal fibrocartilaginous defect thrombocytopenia absent radius proximal tibia physeal injury (radiation, infection, trauma) Treatment Nonoperative brace treatment with KAFO indications Stage I and II in children < 3 years technique bracing must continue for approximately 2 years for resolution of bony changes outcomes improved outcomes if unilateral poor results associated with obesity and bilaterality if successful, improvement should occur within 1 year Operative proximal tibia/fibula valgus osteotomy overcome the varus/flexion/internal rotation deformity indications Stage I and II in children > 3 years Stage III, IV, V, VI age ≥ 4y (all stages) failure of brace treatment progressive deformity metaphyseal-diaphyseal angles > 20 degrees technique perform osteotomy below tibial tubercle staged procedures may be required for Stage IV, V, VI epiphysiolysis required in stage V and VI outcomes risk of recurrence is significantly lessened if performed before 4 years of age growth modulation technique tension band plate and screws physeal bar resection indication at least 4y of growth remaining technique perform together with osteotomy interpositional material is usually fat or PMMA hemiplateau elevation technique may be performed together with osteotomy Techniques Proximal tibia/fibula valgus osteotomy goals of correction overcorrect into 10-15° of valgus because medial physeal growth abnormalities persist distal segment is fixed in valgus, external rotation and lateral translation technique staples and plates function by increasing compression forces across the physis which slows longitudinal growth (Heuter-Volkmann principle) temporary lateral physeal growth arrest with staples or plates can be used increasing use for correction in younger patients include a bar resection (epiphysiolysis) when a physeal bar is present (Langenskiold V and VI) consider hemiepiphysiodesis if bar > 50% medial tibial plateau elevation is required at time of osteotomy if significant depression is present consider prophylactic anterior compartment fasciotomy Complications Compartment syndrome (with high tibial/fibular osteotomy) prophylactic release of anterior compartment Recurrence of tibial vara severe cases of Infantile Blount's disease may develop a physeal bar can result in progressive varus after a well executed proximal tibial valgus osteotomy may require a lateral tibial hemiepiphysiodesis or bar resection Prognosis Best outcomes with early diagnosis and unloading of the medial joint with either bracing or an osteotomy Young children with stage II and stage IV can have spontaneous correction