Infantile Blount's Disease (tibia vara)

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

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

Imaging

Treatment

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