1. Division of Orthopaedic Surgery, Chiba Children’s Hospital, 579-1 Heta-chou, Chiba City 266-0007, Chiba, Japan.
2. Department of Orthopaedic Surgery, Chiba University, School of Medicine, 1-8-1, Inohana, Chuo-ku, Chiba City 260-0856, Chiba, Japan.