1. Department of Orthopedic Surgery, Hokkaido University Graduate School of Medicine, Sapporo, Japan
2. Department of Advanced Medicine for Spine and Spinal Cord Disorders, Hokkaido University Graduate School of Medicine, Sapporo, Japan
3. Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
4. Faculty of Health Science, Hokkaido University, Sapporo, Japan