1. Department of Orthopedic Surgery, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
2. Keio Spine Research Group (KSRG), Tokyo, Japan
3. Koga Hospital Spine Center, Koga, Japan
4. Spine and Spinal Cord Center, International University of Health and Welfare (IUHW) Mita Hospital, Minato-ku, Tokyo, Japan
5. Department of Orthopedic Surgery, School of Medicine, International University of Health and Welfare (IUHW), Narita, Chiba, Japan
6. Department of Orthopedic Surgery, Isehara Kyodo Hospital, Isehara, Kanagawa, Japan
7. Department of Orthopedic Surgery, Fujita Health University, Toyoake, Mie, Japan
8. Department of Orthopedic Surgery, Ogikubo Hospital, Suginami, Tokyo, Japan
9. Department of Preventive Medicine and Public Health, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
10. National Hospital Organization Murayama Medical Center, Musashimurayama City, Tokyo, Japan