Residual shortening after osteotomy for Perthes' disease. A comparative study.

The residual shortening of the affected limbs in 55 patients treated by subtrochanteric varus derotation osteotomy was compared with that in 71 patients treated with weight-relieving calipers. When last examined, 43 of the former group and 47 of the latter had reached complete or near-complete skeletal maturity. The average follow-up was 9.1 years in the osteotomised patients and 5.25 years in the conservatively treated group. The average residual shortening (0.9 cm) was identical in both groups. In most patients the initial shortening caused by the osteotomy gradually corrected as, over a period of several years, the postosteotomy angle gradually became less varus. Any residual shortening depended principally on the severity of inhibition of endochondral ossification at the proximal femoral growth plate. Less residual shortening was seen in children who were under seven years of age at the onset of symptoms (under eight at operation) in whom the open-wedge technique of osteotomy was employed and who had good anatomical results.