Osteochondroses - David Houlihan-Burne 4/3/2002

BLOUNT’S DISEASE

Genu Varum

Causes - Physiological, Osteogenesis imperfecta, osteochondromas, metabolic aberrations, trauma, dysplasis (especially focal fibrocartilaginous dysplasia), Blount’s

Physiological bowing (normal in <2yrs) v. Blount’s

Blount’s disease (aka Tibia vara , osteochondrosis deformans) –rare,   disorder of posterior medial tibial physes.

Varus, internal torsion and genu recurvatum

Erlacher 1922, Blount 1937 ( JBJS 19:1-29, 1937)

 

Infantile (< 3yr) v Adolescent   v Juvenile (6-9)   ( added by Thompson   in 1984)

 

Infantile is usually bilateral (60%) and associated with internal tibial torsion

Adolescent is unilateral and less severe (is pathologically compared with SUFE)

 

Aetiology

  • Multifactorial – Weight Bearing must occur (Does not occur in nonambulants)
  • Rpt trauma + pre-existing varus
  • ( 20 deg varus in 2 yr old of normal weight will retard medial tibial growth plate)
  • Ligamentous laxity - < 3 yo with lateral thrust gait and genu varum                                        
  • ? Genetic – 9 - 43 % have affected sib or parent
  • African-American
  • Increase in boys in adolescent gp                  
  • Early walkers              
  • Obesity (particularly for adolescent type)

 

Histology   Not AVN

  • Disorganisation of cartilage cells throughout physis (worse medially)
  • Islands of acellular fibrosis and of densely packed hypertrophic cartilage
  • Transphyseal blood vessels
  • Adolescent similar to SUFE

 

Staging (Langenskiold and Riska) I-VI – (Based on 17 cases in 1952)                                

 

Radiographs

  • Medial metaphyseal fragmentation – Pathognomonic
  • Abnormal Epiphyseal / metaphyseal angle
  • Drennen’s angle > 11 degrees (JBJS 64[A]:1159, 1982)
  • Metaphyseal beaking

                       

Treatment

Based on age and stage of disease

Racial group can affect outcome

 

Infantile Blount’s      

< 3 yrs old       Bracing (HKAFO). Overcorrect to valgus. If neutral TibFem axis not achieved after

1 yr then HTO.

> 4 yrs old       HTO (Rab oblique osteotomy) to correct varus and int. rotation (overcorrect)

( J Paed Orthop 8:717, 1988)

Also Chevron, intraepiphyseal, epiphyseal and metaphyseal

Plating for older children. Also x-fix, Iliozarov, combined HTO and med plateau elevation.

 

 

 

Adolescent

Alignment procedure – Plating, x-fix, ilizarov. Lateral epipysiodesis

Often distal femur needs addressing with valgus osteotomy

 

Treatment Summary

 

AGE

STAGE

TREATMENT

<18 mo

I-II

None

18-24 mo

I-II

A-Frame / Blount’s brace (night)

2-3 yr

I-II

Modified Locked KAFO

3-8 yr

III-V

Valgus rotational osteotomy

3-8 yr

VI

Resection of bony bridge

 

 

 

 

 

 

 

 

 

 

 

Recurrence rate

High in juvenile type, absent in adolescent type ( J Paed Orthop 4:185-194:1984)

Up to 75 % in children > 5 yrs old having HTO   crt 30 % if done at younger age

In infantile group the older you are the higher recurrence and the more operations required to correct deformity

 

Authors

Langenskiöld A, Riska EB

Title

Tibia vara (osteochondrosis deformans tibiae): a survey of seventy-one cases

Reference

J Bone Joint Surg 46-A:1405, 1964

Summary

Descriptive paper of 71 cases seen in Helsinki . Infantile v adolescent type. Infantile – (61 cases), uni- or bilateral, obese children. Deformity first recognised between 1 – 3 ½   yo but xray changes (stage I-II) are rarely seen before ie very difficult to distinguish between physiological bowing and Blounts initially. 44 cured with one op (done between 2-8 yo) If after 8yo cure not guaranteed. Spontaneous straightening very rare with progression through stages the rule. Progression through the stages does not correlate with clinical progression. Stage II – IV may be maturation of the skeleton with tibial epiphysis adapting its shape to the step like defect in the metaphyseal ossification zone. But as a rule Stage V is followed by Stage VI. Aetiology discussed – a developmental not congenital condition. Abnormal pressure from weight bearing on medial part of proximal epiphyseal cartilage is decisive. Adolescent – (10 cases)unilateral, less severe angulation, less severe Xray changes (flatter osseous epiphysis, no steplike epiphyseal deformity). Spontaneous regression may occur and treatment is different from infantile type. Only surgery before growth cessation if progression is proved

 

 

 



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