1 Department of Surgical Sciences - Orthopaedics, Uppsala University, Uppsala, Sweden. nils.hailer@uu.se.
2 Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway; Department of Clinical Medicine, University of Bergen, Norway.
3 Turku University Hospital and University of Turku, Finland.
4 Copenhagen University Hospital, Bispebjerg, Department of Orthopaedic Surgery and Traumatology & University of Copenhagen Department of Clinical Medicine, Faculty of Health and Medical Sciences, Denmark.