1. Department of Orthopaedic Surgery, Akershus University Hospital, Lørenskog, Norway;
2. Norwegian Hip Fracture Register, Department of Orthopaedic Surgery, Haukeland University Hospital, Bergen;
3. Department of Clinical Sciences, University of Bergen, Bergen, Norway;
4. Department of Orthopaedic Surgery, Oslo University Hospital, Oslo, Norway;
5. Department of Orthopaedics, Skåne University Hospital, Lund University, Malmö, Sweden;
6. Institute of Clinical Medicine, University of Oslo, Norway