1. Department of Orthopedic Surgery Sapporo Medical University School of Medicine Sapporo Hokkaido Japan
2. Department of Orthopedic Surgery Akita University School of Medicine Akita Akita Japan
3. Department of Public Health Sapporo Medical University School of Medicine Sapporo Hokkaido Japan
4. Department of Medical Oncology and Hematology Sapporo Medical University School of Medicine Sapporo Hokkaido Japan
5. Department of Thoracic Surgery Sapporo Medical University School of Medicine Sapporo Hokkaido Japan