1. Department of Orthopaedic Surgery, The University of Tokyo Hospital, Tokyo;
2. University of Tokyo Spine Group (UTSG), Tokyo;
3. Department of Spine and Orthopedic Surgery, Japanese Red Cross Medical Center, Tokyo;
4. Department of Orthopedic Surgery, Kanto Rosai Hospital, Kanagawa;
5. Department of Orthopedic Surgery, Yokohama Rosai Hospital, Kanagawa;
6. Department of Spinal Surgery, Japan Community Health-care Organization Tokyo Shinjuku Medical Center, Tokyo;
7. Department of Orthopedic Surgery, Japanese Red Cross Musashino Hospital, Tokyo;
8. Department of Orthopedic Surgery, Saitama Red Cross Hospital, Saitama; and
9. Spine Center, NTT Medical Center Tokyo, Tokyo, Japan