Blount disease (tibia vara): Another skeletal disorder associated with childhood obesity

Abstract

BLOUNT DISEASE (tibia vara) ~ is a skeletal disorder characterized by bowed legs and tibial torsion. Radiographically, the affected extremities show enlargement or a beaktike projection of the medial aspect of the proximal metaphysis of the tibia (Fig. 1); the abnormality involves the medial portion of the proximal secondary center as well. Growth appears deficient medially, resulting in medial angulation of the diaphysis of the tibia. Because this line of weight bearing is through the medial aspect of the bone, its medial cortex becomes thickened. :5 Microscopic examination of affected areas demonstrates distorted bone trabeculae containing focal areas of cartilage that coincide with the radiolucent areas. ~-3 The causes of Blount disease are unknown. Females appear to be more frequently affected than males, ~,4 although agreement is not uniform? Age of onset distinguishes patients with the infantile type, with onset between one and 3 years of age, and the juvenile type with onset after 8 years of age~ 1,3, 4 The occasional appearance of more than one case in the same family suggests a hereditary component, 3,6 and an increased prevalence among West Indian children indicates the possibility of a racial predisposition? Affected children have no evidence of rickets and only rarely a history of trauma. ~' 2 Pathologic examination has shown no evidence of aseptic necrosis or inflammation. ~-~ Obesity has frequently been mentioned in association with the infantile type of the disease, ~-4.6 but the interrelationship of obesity and Blount disease has never been examined in detail. Two cases of the infantile type of Blount disease