1. Department of Orthopaedic Surgery, Hokkaido Orthopedic Memorial Hospital, Sapporo, Hokkaido, Japan
2. Department of Orthopaedic Surgery, Kobayashi Hospital, Kitami, Hokkaido, Japan
3. Department of Orthopaedic Surgery, Shinsyu University, School of Medicine, Nagano, Japan
4. Department of Orthopaedic Surgery, Hokkaido Chuo Rosai Hospital, Bibai, Japan