1. The Danish Hip Arthroplasty Register
2. Department of Orthopaedic Surgery, Vejle Hospital, Vejle, Denmark
3. Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark
4. Department of Orthopaedic Surgery and Traumatology, Odense University Hospital, Odense, Denmark
5. Orthopaedic Research Unit, Department of Clinical Research, University of Southern Denmark, Odense, Denmark