1Laboratory of Statistics, Osaka City University Faculty of Medicine, Osaka, Japan
2The Subcommittee on Low Back Pain and Cervical Myelopathy Evaluation of the Clinical Outcome Committee of the Japanese Orthopaedic Association, Japan
3Department of Orthopaedic Surgery, Keio University, Tokyo, Japan
4Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
5Department of Orthopaedic Surgery, School of Medicine, Fukushima Medical University, Fukushima, Japan
6Department of Orthopedic Surgery, Nippon Medical School, Tokyo, Japan
7Department of Orthopaedic Surgery, The University of Tokyo, Tokyo, Japan
8Department of Orthopaedic Surgery, Iwate Medical University School of Medicine, Morioka, Japan
9Department of Orthopaedic Surgery, Saitama Medical School, Irima-gun, Japan
10Department of Orthopedic Surgery, Yamaguchi University School of Medicine, Yamaguchi, Japan
11Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan
12Department of Orthopaedics, Kochi Medical School, Kochi, Japan
13Department of Orthopaedic Surgery, Hoshigaoka Koseinenkin Hospital, Osaka, Japan
14National Hospital Organization Osaka-Minami Medical Center, Kawachinagano, Japan
15Department of Internal Medicine, Houai Hospital, Osaka, Japan
16Department of Public Health, Osaka City University Faculty of Medicine, Osaka, Japan