Rotational deformity in congenital hypoplasia of the femur.

Congenital shortening of the femur is associated with significant limb-length discrepancy, distal femoral valgus with condylar hypoplasia, anteroposterior knee instability, and an external rotation deformity. This latter deformity has not been described or characterized in the literature. Eight patients with hypoplastic femora were evaluated clinically and radiographically including computed tomography (CT) anteversion studies. The average limb-length inequality at the time of examination was 7.8 cm. All affected extremities had significant retroversion averaging 17.4 degrees, representing a mean difference of 43.1 degrees from the contralateral normal anteversion of 25.7 degrees. Associated limb deformities included deficiency of the fibula in five patients and absent lateral foot rays in two patients. Five of the eight patients have undergone femoral lengthening with correction of angular, length, and rotational abnormalities through two-level osteotomy. The patient with femoral hypoplasia should have evaluation of length and angular abnormalities and rotational deformity as well.