1. Kaiser Permanente, San Diego, CA, USA;
2. Institute of Clinical Sciences, Department of Orthopaedics, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden;
3. Swedish Hip Arthroplasty Register, Gothenburg, Sweden;
4. Turku University Hospital, Turku, Finland;
5. South Australia Health & Medical Research Institute, Adelaide, SA, Australia;
6. University of South Australia, Adelaide, SA, Australia;
7. Harvard Medical School, Boston, MA, USA;
8. Southern California Permanente Medical Group, Irvine, CA, USA