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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 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
  • 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 
    • early walkers (< 1 year)
    • Hispanic and black
  • 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
  • Differential diagnosis
    • 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)
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 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 
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 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
      • 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
        • <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
      • overcome the varus/flexion/internal rotation deformity
      • indications
        • Stage I and II in children > 3 years q
        • Stage III, IV, V, VI 
        • age ≥ 4y (all stages) 
        • failure of brace treatment q
          • 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
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
Complications
  • Compartment syndrome (with high tibial/fibular osteotomy)
    • prophylactic release of anterior compartment
 

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(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? Review Topic

QID: 60
FIGURES:
1

Observation

22%

(267/1223)

2

Bracing with knee-ankle-foot orthoses

63%

(769/1223)

3

Bracing with ankle-foot orthoses

3%

(32/1223)

4

Proximal tibia/fibula valgus osteotomy with bar resection

5%

(63/1223)

5

Proximal tibia/fibula valgus osteotomy with hemiepiphysiodesis

7%

(81/1223)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

(SBQ04PE.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? Review Topic

QID: 2188
1

A 4-year-old obese child with Blount's disease, Langenskiöld stage IV

67%

(284/423)

2

An 18-month-old child with a proximal tibia metaphyseal-diaphyseal angle of 11 degrees

1%

(5/423)

3

A 2-year-old obese child with Blount's disease, Langenskiöld stage II disease

6%

(26/423)

4

A 5-year-old child with untreated renal osteodystrophy and a proximal tibia metaphyseal-diaphyseal angle of 16 degrees

11%

(46/423)

5

A 8-year-old child with distal femoral varus and a lateral distal femoral angle of 95 degrees

13%

(57/423)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1
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(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? Review Topic

QID: 510
1

Observation, discontinuation of bracing

4%

(92/2064)

2

Observation, continuation of full-time bracing

15%

(302/2064)

3

Bilateral proximal tibial osteotomies

68%

(1398/2064)

4

Bilateral distal femur osteotomies

3%

(64/2064)

5

Bilateral proximal tibial medial hemiepiphysiodesis

10%

(204/2064)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(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? Review Topic

QID: 569
1

Increased compression along the growth plate slows longitudinal growth

86%

(1315/1536)

2

Decreased compression along the growth plate slows longitudinal growth

2%

(34/1536)

3

Increased tension along the growth plate slows longitudinal growth

8%

(119/1536)

4

Decreased tension along the growth plate slows longitudinal growth

3%

(44/1536)

5

Increased compression along the plate increases longitudinal growth

1%

(18/1536)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1
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