Huang ZY, et al. - In this study, the contact area and the coincidence rate were assessed between the proximal and distal fragments at different femoral osteotomy levels and lengths. The optimal location of subtrochanteric femoral shortening transverse osteotomy was ascertained in patients with unilateral Crowe type IV developmental dysplasia of the hip (DDH). Researchers evaluated consistency between the proximal and distal segments as a possible predictive indicator of the union at the osteotomy site. A retrospectively review was designed to include 57 patients with unilateral Crowe type IV DDH who had undergone x-ray imaging of both hip joints. The results of this study indicate that femoral shortening transverse osteotomy at the optimal subtrochanteric level can predictably elevate the contact area and coincidence rate, which may contribute to the union at the osteotomy site. It seems appropriate that osteotomy location should be shifted slightly distally recognizing the stability of the prostheses.