1. Department of Orthopaedic Surgery, Yagi Orthopaedic Hospital, Sapporo, Hokkaido, Japan
2. Centre for Sports Medicine, Hokkaido University Hospital, Sapporo, Hokkaido, Japan
3. Department of Orthopaedic Surgery, Faculty of Medicine and Graduate School of Medicine, Hokkaido University, Sapporo, Hokkaido, Japan