1. Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan
2. Keiyu Orthopaedic Hospital, Tatebayashi, Japan
3. Department of Intelligent Machines and System Engineering, Hirosaki University Graduate School of Science and Technology, Hirosaki, Japan
4. Division of Human Mechanical Systems and Design, Hokkaido University Graduate School of Engineering, Sapporo, Japan