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Updated: Dec 29 2023

Adolescent Blount's Disease

Images photo - courtesy Miller_moved.png blounts.jpg epiphyseal widening.jpg diaphyseal angle_moved.jpg angle_moved.png epiphysiodesis- courtesy Miller_moved.png
  • 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
          • risk of hardware failure
            • tibial metaphyseal screw most common site of failure
            • risk factors
              • earlier onset of disease
              • increased severity of deformity
              • cannulated screws
              • higher BMI
      • 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
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