1. Department of Orthopaedic Surgery, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
2. Center for innovating Medicine Engineering (CIME), University of Tsukuba, Ibaraki, Japan
3. Department of Rehabilitation Medicine, University of Tsukuba Hospital, Ibaraki, Japan
4. Department of Neurosurgery, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan
5. Department of Orthopaedic Surgery, Kikkoman General Hospital, Chiba, Japan
6. Faculty of Systems and Information Engineering, University of Tsukuba, Ibaraki, Japan