Blount’s disease

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Progressive varus deformity in a previously normal tibia’ first described by Erlacher, in 1922, and knowledge was further developed by Blount, 1937. Walter Putnam Blount was an American paediatric orthopaedist (1900–1992).

  • Blount identified one form affecting infants, which is both more common and more aggressive, and another affecting older children (age > 8 years).
  • Infantile Blount’s typically affects children aged 2 to 4 years
  • Approximately 80% cases are bilateral, which can make it difficult to differentiate from physiologic genu varum in children up to 3 years of age.
  • Spontaneous deceleration of growth at posteromedial proximal tibial physis results in knee varus, flexion, medially rotated knee deformity
  • Genu varum increased (especially age > 2 years)
  • Medial tibial ‘beaking’ is evident on x-ray
  • Limb length difference
  • Classify according to Langenskiold
  • Differentiate from trauma, infection, vitamin D deficiency and skeletal dysplasia.
  • Plain radiographs demonstrate the metaphyseal-diaphyseal angles which, if greater than 16 deg, strongly suggests Blount’s disease.
  • Aetiology remains unknown, with associations of walking at an early age, obesity, vitamin D deficiency, and Hispanic or Black racial origin
  • All stages, once > age 4 years – surgical correction

 

Langenskiold Classification

  • II to IV – increasing medial metaphyseal beaking and slope
  • V and VI – epiphyseal-metaphyseal bony bar across physis
  • All stages, age > 4 years, usually involves surgical correction

Points to note:

  • Blount’s disease is the most common acquired pathological cause of genu varum, with treatment mostly depending on the severity.
  • Physiological bowing is the most common cause of genu varum in children and is benign, resolving with normal growth (genu varum after age 3 years unusual).
  • Differential diagnoses are many, and there are many genetic and metabolic conditions which should also be considered, eg achondroplasia, osteogenesis imperfecta, rickets, hemimelia, renal osteodystrophy

 

References

Blount W. Tibia vara. J Bone Joint Surg Am 1937; 19: 1e29.

Birch JG. Blount disease. J Am Acad Orthop Surg 2013; 21: 408e18.

Killen M-C, DeKiewiet G. Genu varum in children, Orthop Trauma 34:6: 369-378, 2020

 

Recent case history (all data, images provided with consent)

A 66 year old woman presented with L lateral forefoot pain, also R hip aching, and LBP.

History revealed childhood Blount’s disease, the use of a leg calliper, and two corrective surgical procedures. The first procedure for knee/tibial varus reduction, and the subsequent procedure a L leg shortening – in effort to reduce the L>R leg length following the procedure. The patients recalls discussion between doctors and her parents about ‘allowing for growth’, and later. ‘unfortunately shortened too much’.

Figures 1 – 4

Examination:

Imaging:

X-ray shows cross-wires from osteotomy in childhood (Figure 5)

Figure 5

Physical:

+ve Galleazzi sign [ https://angelaevanspodiatrists.com.au/galeazzis-test-a-useful-assessment-method-for-paediatric-limb-length-inequality/ ]

+ve stance leg length discrepancy (using ‘book test’, L approx. 15mm short) (Figure 6)

Stance, gait – L lateral forefoot loading in midstance, to ‘raise’ L side

Treatment: L full-length raise in-shoe, no symptoms, better balance (Figure 7).

Mild initial musculoskeletal aches with graduated use of L raise, and pain-free after 6 weeks.

Figures 6 – 7

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Angela Evans

 

Dr Angela Evans AM            
PhD, FFPM RCPS(Glasg)
www.angelaevanspodiatrists.com.au