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Infantile Blount's Disease (tibia vara)

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Topic updated on 05/26/16 1:29pm
Introduction
  • Blount's disease is progressive pathologic genu varum centered at the tibia
  • Best divided into two distinct disease entities
    • Infantile Blount's (this topic)
      • pathologic genu varum in children 0 to 4-5 years of age 
      • more common
      • typically affects both lower extremities
    • Adolescent Blount's 
      • pathologic genu varum in children > 10 years of age
      • less common
      • less severe
      • more likely to be unilateral
  • Etiology
    • 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
  • Risk factors
    • overweight children that are early walkers (less than one year)
  • Prognosis
    • best outcomes are associated with early diagnosis and unloading of the medial joint with either bracing or an osteotomy 
  • Differential diagnosis
    • the following conditions can also lead to pathologic genu varum
      • osteogenesis imperfecta
      • osteochondromas
      • trauma
      • various dysplasia
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
Presentation
  • Physical exam
    • genu varum deformity
      • usually bilateral in infants
      • may exhibit positive 'cover-up test'
    • often associated with internal tibial torsion
Imaging
  • Radiographs q
    • 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
      • 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
        • <10 ° has a 95% chance of natural resolution of the bowing
      • tibiofemoral angle 
        • angle between the longitudinal axis of the femur and tibia
Treatment
  • Nonoperative
    • brace treatment with KAFO q
      • indications
        • Stage I and II in children < 3 years  q
      • 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 q
      • indications
        • Stage I and II in children > 3 years q
        • Stage III, IV, V, VI in children < 3 
        • failure of brace treatment q
        • metaphyseal-diaphyseal angles > 20 degrees
      • technique
        • 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
Surgical 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

 

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Qbank (12 Questions)

TAG
(SBQ04.3) A valgus producing proximal tibial osteotomy with 10 degrees of overcorrection is the most appropriate treatment for which of the following patients with tibia vara? Topic Review Topic

1. A 4-year-old obese child with Blount's disease, Langenskiöld stage IV
2. An 18-month-old child with a proximal tibia metaphyseal-diaphyseal angle of 11 degrees
3. A 2-year-old obese child with Blount's disease, Langenskiöld stage II disease
4. A 5-year-old child with untreated renal osteodystrophy and a proximal tibia metaphyseal-diaphyseal angle of 16 degrees
5. A 8-year-old child with distal femoral varus and a lateral distal femoral angle of 95 degrees

PREFERRED RESPONSE ▶
TAG
(OBQ08.124) A 32-month-old male with severe infantile Blounts disease has been treated with full time bracing for the past year. At most recent follow-up, the varus deformity of his bilateral legs has worsened despite compliance with bracing. What treatment is now recommended? Topic Review Topic

1. Observation, discontinuation of bracing
2. Observation, continuation of full-time bracing
3. Bilateral proximal tibial osteotomies
4. Bilateral distal femur osteotomies
5. Bilateral proximal tibial medial hemiepiphysiodesis

PREFERRED RESPONSE ▶
TAG
(OBQ08.183) Lateral tibial physeal stapling is a treatment option for adolescent Blount’s disease. How is the staple an example of the Hueter-Volkmann principle? Topic Review Topic

1. Increased compression along the growth plate slows longitudinal growth
2. Decreased compression along the growth plate slows longitudinal growth
3. Increased tension along the growth plate slows longitudinal growth
4. Decreased tension along the growth plate slows longitudinal growth
5. Increased compression along the plate increases longitudinal growth

PREFERRED RESPONSE ▶
TAG
(OBQ05.23) A 30-month-old boy has worsening bilateral bowleg deformities, and radiographs depicting Langenskiold stage II are shown in Figure A. The most appropriate initial management should consist of which of the following? Topic Review Topic
FIGURES: A          

1. Observation
2. Bracing with knee-ankle-foot orthoses
3. Bracing with ankle-foot orthoses
4. Proximal tibia/fibula valgus osteotomy with bar resection
5. Proximal tibia/fibula valgus osteotomy with hemiepiphysiodesis

PREFERRED RESPONSE ▶
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