1. Oulu University Hospital, Department of Orthopedic and Trauma Surgery, Oulu, Finland
2. Department of Surgery, Central Hospital of Länsi-Pohja, Kemi, Finland
3. Department of Surgery, Kainuu Central Hospital, Kajaani, Finland
4. Department of Surgery, Lapland Central Hospital, Rovaniemi, Finland
5. Department of Surgery, North-Carelian Central Hospital, Joensuu, Finland
6. Department of Surgery, Central-Ostrobothnian Central Hospital, Kokkola, Finland