Unilateral late-onset tibia vara associated with bilateral proximal femoral growth disturbance in monozygotic twins: case report.

Clinical and histopathological similarities and rare association of Blount's disease with various proximal femoral physeal affections (i.e. adolescent coxa vara and slipped capital femoral epiphysis) are well known. Association of tibia vara with another epiphyseal disease of the proximal femur has not been reported previously. In this paper, a monozygotic set of twins with concordant bilateral epiphyseal growth disturbance of the proximal femur and unilateral late-onset tibia vara is presented. Radiological characteristics of the affected knees revealed a wedging in the proximal tibial epiphysis, depression of the medial joint surface and varus deformity of the tibia. Proximal femurs of both cases showed aspheric congruity, coxa magna, shortness of the femoral neck, and subchondral cystic changes. The presented cases support the genetic etiology of tibia vara, and association of the two conditions is unique.