Dislocation and subluxation during femoral lengthening.

Femoral lengthening by callus distraction was performed on 26 femurs of 18 patients with various disorders between 1988 and 1992. Age at surgery ranged from 6 to 17 years (13 years on average). The amount of lengthening varied from 2 to 7.5 cm (mean 5 cm). Follow-up evaluation of femoral-head displacement was based on the change of center-edge (CE) angle. The hips were divided into two groups based on the preoperative CE angle; one group consisted of 14 hips with a CE angle > 20 degrees and the other group consisted of 12 hips with an angle of < or = 20 degrees. In the first group, none of the hips deteriorated; however, five of 12 hips in the second group did deteriorate. One hip developed complete dislocation and the other four showed a decrease in the CE angle. Four of five deteriorated hips had a history of congenital dislocation of the hip and the other had multiple epiphyseal dysplasia. In cases in which the CE angle is < or = 20 degrees preoperatively, bony procedures such as innominate osteotomy should precede femoral elongation.