1. Department of Orthopaedic Surgery, Faculty of Medicine, University of Tsukuba: 1-1-1 Tennodai, Tsukuba city, Ibaraki 305-8575, Japan
2. Department of Orthopaedic Surgery, Ibaraki Prefectural University of Health Sciences Hospital, Japan
3. Department of Cardiovascular Surgery, University of Tsukuba Hospital, Japan
4. Department of Integrative Physiology, Graduate School of Medicine, Kyorin University, Japan
5. Department of Orthopaedic Surgery, Kikkoman General Hospital, Japan