The evolution and histopathology of adolescent tibia vara.

This clinical, radiographic, and histologic study clarifies the evolution of the distinct clinical and radiographic disorder known as adolescent tibia vara (Blount's disease). Although previous reports have suggested that the disorder occurs in a limb that has been normally aligned until adolescence, we have found that most children with adolescent tibia vara maintain a mild degree of infantile physiologic genu varum. Then, concurrent with the adolescent growth spurt, certain children with predisposing factors, such as obesity, extreme activity, or rapid growth, injure the posteromedial physis as a result of repetitive trauma due to normal use of a limb already in mild varus. The result is growth suppression, further varus, and a classic radiographic presentation. Histologic examination in two cases suggests injury to the growth plate as demonstrated by fissuring and clefts in the physis as well as fibrovascular and cartilaginous repair tissue at the physeal-metaphyseal junction. Transverse trabeculae, resembling growth arrest lines, were noted in the adjacent metaphysis; however, true bony bridging of the growth plate was not seen. Recommended treatment is corrective osteotomy below the growth plate.