1. Department of Orthopaedics, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
2. Department of Health sciences, Community and Occupational Medicine, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
3. Department of Orthopaedics, Leiden University Medical Centre, University of Leiden, Leiden, the Netherlands
4. University Hospital for Orthopedics and Trauma Surgery Pius-Hospital, Medical Campus University of Oldenburg, Oldenburg, Germany
5. Department of Orthopaedic Surgery and Traumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Copenhagen, Denmark
6. Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
7. Department of Clinical Epidemiology, Leiden University Medical Centre, University of Leiden, Leiden, the Netherlands