We reviewed 14 patients (16 hips) treated by open reduction and upper femoral derotation osteotomy for congenital dislocation of the hip. Nine patients with 11 treated hips had growth deformities of the proximal femur; in all of them the top screw of the fixation plate lay within the cartilaginous precursor of the greater trochanter. In the five control hips the top screw was more distal. In the nine patients (mean follow-up 10.8 years) there was an increase of 14 degrees in the neck-shaft angle (p = 0.01) and of 18 degrees in the angle between the capital femoral physis and the shaft (p = 0.01) compared to the control group. This indicates that growth disturbance of the greater trochanteric apophysis as a result of plate fixation leads to long-term deformity.