1. Division of Orthopedic Surgery, Oslo University Hospital Ulleval, Oslo, Norway;
2. Norwegian Arthroplasty Registry, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen, Norway;
3. Department of Clinical Medicine, University of Bergen, Bergen, Norway;
4. University of Oslo, Oslo, Norway;
5. Department of Orthopaedic Surgery, Traumatology and Odense University Hospital, and Department of Clinical Research, University of Southern Denmark, Odense, Denmark;
6. Danish Hip Arthroplasty Register, Denmark;
7. Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark;
8. The Swedish Hip Arthroplasty Register, Sweden;
9. Department of Orthopaedics, Institute of Surgical Sciences, Sahlgrenska University Hospital, University of Gothenburg, Sweden;
10. Coxa Hospital for Joint Replacement, and Faculty of Medicine and Life Sciences, University of Tampere, Tampere, Finland;
11. The Finnish Arthroplasty Register, Finland;
12. Department of Orthopaedics and Traumatology, Turku University Hospital, Turku.