summary Adolescent Blount's Disease is a progressive, pathologic genu varum centered at the tibia in children > 10 years of age. Diagnosis is made clinically with presence of a genu varum deformity and confirmed radiographically with an increased metaphyseal-diaphyseal angle. Treatment is generally surgical epiphysiodesis or osteotomy depending on severity of deformity and amount of growth left. Epidemiology Risk factors obesity African-American descent Etiology Blount's disease is best divided into two distinct disease entities Infantile Blount's pathologic genu varum in children 2-5 years of age more common deformity rarely from femur typically affects both lower extremities Adolescent Blount's (this topic) pathologic genu varum in children > 10 years of age more likely to have femoral deformity less common less severe more likely to be unilateral Pathophysiology Blount's is thought to be caused by a dyschondrosis of medial physis of proximal tibia likely multifactorial but related to mechanical overload in genetically susceptible individuals Classification Infantile vs. Adolescent Blounts Infantile Blounts Adolescent Blounts Age 2-5yrs >10yrs Bilaterality 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 Location Physeal/epiphyseal Metaphyseal 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 hallmark is genu varum deformity obesity usually unilateral (compared to bilateral in infantile Blount's) limb-length discrepancy secondary to deformity mild to moderate laxity of medial collateral ligament Imaging Radiographs views standing long-cassette AP radiograph of both lower extremities ensure patellas are facing forward (commonly associated with internal tibial torsion) findings suggestive of adolescent Blount's disease narrowing of the tibial epiphysis widening of the medial tibial growth plate occasional widening of the lateral distal femoral physis metaphyseal beaking less commonly seen with adolescent Blount's measurements metaphyseal-diaphyseal angle (Drennan) angle between line connecting metaphyseal beaks and a line perpendicular to the longitudinal axis of the tibia >16 degrees is considered abnormal tibiofemoral angle angle between the longitudinal axis of the femur and tibia Treatment Nonoperative observation or bracing is unlikely to be successful - treatment is always surgical indications mild cases only outcomes poor outcomes - will progresse and cause medial joint pain and altered kinematics early onset arthritis is common in untreated cases Operative lateral tibia and fibular epiphysiodesis indications mild to moderate deformity with growth remaining outcomes up to 25% may require formal osteotomy due to residual deformity proximal tibia/fibula osteotomy indications more severe cases in the skeletally mature can be achieve with a valgus producing tibial osteotomy and plating can be achieved with gradual correction with external fixation outcomes multiplanar external fixation following osteotomy allows gradual angle and length correction and decreases risk on neurovascular structures distal femoral osteotomy or epiphysiodesis indications for distal femoral varus deformity of 8 degrees or greater Techniques Lateral tibia and fibular epiphysiodesis transient hemiepiphysiodesis technique tether physis with 8-plates or staple may remove implant once correction is achieved pros simple allows for gradual correction is children with adequate growth remaining implants may be removed cons requires significant growth remaining close observation is necessary following operation as growth plate may stop functioning or have a rebound period of accelerated growth permanent hemiepiphysiodesis technique obliteration of physis through small, lateral incision pros limited surgery overcorrection is uncommon does not limit ability to perform corrective osteotomy in future cons cannot correct rotational deformity up to 25% may require formal corrective osteotomy Proximal tibia/fibula osteotomy goals of correction overcorrection to valgus not indicated (as is the case in infantile Blount's) strive for neutral mechanical axis high tibial osteotomy with rigid internal fixation technique variety of techniques, including closing wedge, opening wedge, dome, serrated and inclined osteotomies variety of fixation devices including cast, pins and wires, screws, plates and screws post-op limited weight bearing with use of crutches for 6-8 weeks pros immediate correction cons potential for neurologic injury due to acute lengthening potential for compartment syndrome consider prophylactic fasciotomies osteotomy with external fixation and gradual correction technique perform osteotomy, and connect frame that allows for gradual correction Taylor Spatial Frame or Ilizarov ring external fixator post-op usually 12-18 weeks of treatment are needed pros gradual correction limits neurovascular compromise and risk for compartment syndrome allows for correction of deformity in all planes cons pin site infection duration of treatment bulk of construct