Osteochondroses - David Houlihan-Burne 4/3/2002

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

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