1. Department of Spine Surgery, Nagaoka Red Cross Hospital, Niigata, Japan;
2. Department of Orthopedic Surgery, Niigata University Medical and Dental Hospital, Niigata, Japan;
3. Department of Rheumatology, Nagaoka Red Cross Hospital, Niigata, Japan;
4. Division of International Health, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan;
5. Department of Orthopedic Surgery, Toyosaka Hospital, Niigata, Japan