Blount's Disease

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Original Editors - Rachael Lowe

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Description

Blount's disease, also known as tibia vara, is a developmental growth disorder of the tibia that causes the lower leg to angle outwards, causing bowing of the leg. It is characterised by progressive multiplanar deformities of the leg caused by disordered endochondral ossification of the proximal medial tibia.

The cause of Blount's disease is assumed to be multifactoral, mostly mechanically due to childhood obesity. This can be described by the effects of increased weight on the growth plates. The medial proximal tibia fails to develop normally, causing angulation of the bone.  Unlike bowlegs, which tend to straighten as the child develops, Blount's disease is progressively worsening. It can cause severe bowing and can affect one or both legs.

Clinically Relevant Anatomy

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Etiology / Epidemiology

The following are known epidemiological characteristics of Blount's disease:

• This condition is more common among children of African and Scandanavian ancestry.
• It is associated with obesity, short stature, and early walking.
• There does not appear to be an obvious genetic factor.

Classification

Blount's disease is mostly catagorised into early-onset if it develops in children under 4 years old, and late-onset, when it develops after the age of 4. The late-onset type can further be classified into juvenile (age 4 - 10) and adolescent (after the age of 10) Blount's disease.

t. Also, there are comparable histologic findings at the proximal tibial growth plate9-11

Clinical Presentation

• Unilateral or bilateral (mostly with early onset) presentation
• Multiplanar deformities of the lower leg includes:
  • Tibial varus
  • Procurvatum
  • Internal torsion
  • Limb shortening
  • Distal femoral varus (in late-onset)

• 
  

This entity can lead to a progressive deformity with gait deviations, limb-length discrepancy, and premature arthritis of the knee6-8.

Diagnostic Procedures

X-rays is used as the main tool for diagnosis.

The radiographic changes are divided into 6 progressive stages in early onset Blount's disease.

• X-rays
• . Langenskiold ¨ 2 described six radiographic stages of progressive changes at the proximal tibial epiphysis and metaphysis in children with early-onset Blount disease (Fig. 3). With advancing age and higher Langenskiold ¨ stageUnilats (V and VI), irreversible physeal changes with permanent inhibition of the medial portion of the tibial growth plate can occur. Although the Langenskiold classification is useful, there ¨ is substantial interobserver variability, especially with regard to the intermediate stages12. Loder and Johnston13 studied the applicability of the Langenskiold classification to a predomi- ¨ nantly nonwhite population (one in which 73% of the patients
  

Outcome Measures

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Medical management

Conservative management

Children who develop severe bowing before the age of 3 may be treated with bracing. However, bracing may fail, or bowing may not be detected until the child is older.

Surgical management

• Realignment tibial osteotomy: To be done before the age of 4 to decrease the risk of recurrent lower extremity deformity and to restore leg length where needed.
• Distraction osteogenesis: For late-onset disease:
  • Aim to achieve multiplanar correction
• The growth of just the outer half of the tibia can be surgically restricted to allow the child’s natural growth to reverse the bowing process. This much smaller surgery is most effective in children with less severe bowing and significant growth remaining.

Differential Diagnosis

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Resources

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Case Studies

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References

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