1. Department of Orthopedic Surgery, Sapporo Medical University School of Medicine, Sapporo, Hokkaido 060-8543, Japan
2. Department of Orthopedic Surgery, Akita University School of Medicine, Akita, Akita 010-8543, Japan
3. Department of Public Health, Sapporo Medical University School of Medicine, Sapporo, Hokkaido 060-8543, Japan
4. Department of Medical Oncology and Hematology, Sapporo Medical University School of Medicine, Sapporo, Hokkaido 060-8543, Japan
5. Department of Pediatrics, Sapporo Medical University School of Medicine, Sapporo, Hokkaido 060-8543, Japan
6. Department of Diagnostic Pathology, Sapporo Medical University School of Medicine, Sapporo, Hokkaido 060-8543, Japan