1. Division of Orthopaedic Surgery, Oslo University Hospital, Oslo;
2. Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo;
3. Department of Clinical Medicine, University of Bergen, Bergen;
4. Department of Orthopaedic Surgery, St Olav’s University Hospital, Trondheim;
5. Department of Orthopaedic Surgery, Østfold Hospital Trust, Grålum, Norway.