Remodelling and congruency of the hip joint in children with Perthes' disease treated with varus-derotation subtrochanteric osteotomy.

Background. Dislocation of the femoral head to the front and to the side during the course of Perthes' disease is the main threat to the development of the hip. Containment of the femoral head into the acetabulum is the main goal of conservative and operative treatment. The spherical shape of the acetabulum is used as the modelling factor for the femoral head during the regeneration period, which enables the femoral head to rebuild its spherical shape. The aim of the study is to present the changes occurring within the hip joint during the course of Perthes' disease, before and after operative treatment with varus-derotation subtrochanteric osteotomy, based on objective radiological measurements. Material and methods. 53 patients, aged from 5 to 10 years, were treated operatively. The necrosis period was assessed on radiographic examination according to Reiberg and Catterall. All patients were treated with varus-derotation subtrochanteric osteotomy, decreasing the neck-shaft angle to an average value of 111 degrees . During the follow-up period of 6 years, a control examination was performed every 12 months. Measurements were compared with norms published in the literature. Various parameters were assessed in this study to assess the proximal end of the femur bone (neck-shaft angle, epiphyseal head index of Heyman and Herndon) and the position of the femoral head inside the acetabulum (centre-edge angle, distance angle, acetabular head index of Heyman-Herndon). Results. During the 6-year follow-up period, the value of the neck-shaft angle remained within the range of norms for the age and group, and for operated limbs the value was lower than the norm. The other assessed parameters showed substantial improvement, which led to the preservation of the correct shape of both the femoral head and acetabulum and improved the congruency of the joint. Conclusion. The value of parameters assessed post-operatively show a substantial improvement compared with preoperative measurements. Good results are obtained as a result of varus-derotation subtrochanteric osteotomy in patients with Perthes' disease type III and IV according to Catterall, and lead to improvement in the congruency of the joint.