1. Department of Orthopedic Surgery, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan
2. Department of Public Health, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan
3. Department of Orthopedic Surgery, Hokkaido Saiseikai Otaru Hospital, Otaru, Hokkaido, Japan
4. Department of Musculoskeletal Oncology, National Cancer Center Hospital, Tokyo, Japan