1. Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg;
2. Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg/Mölndal;
3. Centre of Registers Västra Götaland;
4. Section of Orthopaedics, Department of Surgical Sciences, Uppsala University, Uppsala;
5. Department of Orthopaedics, Uppsala University Hospital, Uppsala, Sweden