Classic history and presentation: Infantile Blount disease is characterized by varus deformity of the proximal tibia. Approximately 50% of the cases are bilateral but not symmetric.
Prevalence:
- Age – Most common in children aged 2-5 years.
- Sex / gender – More common in boys than girls.
Pathophysiology: The exact etiology of infantile Blount disease is unknown. Histological evidence suggests replacement of physeal cartilage by fibrous tissue or physeal arrest between the epiphysis and metaphysis.
Grade / classification system:
Langenskiold Classification of Blount disease
Stage I (2-3 years of age)
Medio-distal beaking of the upper proximal tibial metaphysis.
Stage II (2.5-4 years of age)
Wedging of the medial part of the upper tibial epiphyseal secondary ossification center plus a saucer-shaped defect of the upper surface of the metaphyseal beak due to its dissolution, fragmentation, and collapse.
Stage III (4-6 years of age)
Stepping of the inferior-medial border of the secondary ossification center but without extending distally to the physeal plate level, plus deepening of the metaphyseal saucer into a step in the medial metaphysis.
Stage IV (5-10 years of age)
The epiphyseal secondary ossification center passes more distally and crosses distal to the physeal level to fill the metaphyseal step.
Stage V (9-11 years of age)
Separation of the most medial part of the ossification center from the bulk of the secondary ossification center to reside in the depth of the metaphyseal step below the physis. This is radiologically expressed as either a horizontal cleft (double epiphysis) or complete absence of the medial secondary ossification center as it will be overshadowed by the upper medial tibial metaphysis.
Stage VI (0-13 years of age)
Medial epiphyseal plate closure with a bony bridge.
Related topic: adolescent Blount disease
