Clinical basis for a mechanical etiology in adolescent Blount's disease.

The exact etiology and treatment of adolescent Blount's disease remains uncertain. In this study, the clinical and radiographic characteristics of eight consecutive patients (ten knees) with late onset tibia vara are reviewed to identify common features suggestive of aberrant mechanical forces causing their deformity. Consistent clinical features include progressive varus during the adolescent growth spurt and gross obesity. All patients were black, most were males with unilateral disease, and the only female patient had bilateral involvement. All were symptomatic cases, but in no case was trauma the cause of their disease. In addition, measurements of the physeal widths of the proximal tibia and distal femur on preoperative x-rays demonstrate consistent characteristics compatible with aberrant forces predicted by Heuter-Volkman and Delpech's laws. The clinical findings along with our surgical results confirm that these patients are best treated by corrective osteotomy to neutral mechanical axis and that over-correction is unwarranted.