1. Department of Orthopedic Surgery, Herlev Hospital, University of Copenhagen, Denmark;
2. Department of Orthopedics, Karolinska Institutet Danderyds Sjukhus AB, Stockholm, Sweden;
3. Department of Orthopedic Surgery, Aalborg University Hospital, Aalborg, Denmark;
4. Norwegian Arthroplasty Register, Department of Orthopedic Surgery, Haukeland University Hospital, Norway