1. Department of Traumatology, University Hospital of Rotterdam, Erasmus Medical Center, Dr Molewaterplein 40, 3015 GD Rotterdam, The Netherlands.
2. Department of Public Health, Center for Clinical Decision Sciences, Erasmus Medical Center, PO Box 1738, 3000 DR Rotterdam, The Netherlands.
3. Department of Orthopeadics, University Hospital of Utrecht, PO Box 85500, 3508 GA Utrecht, The Netherlands.
4. Department of Surgery, Onze Lieve Vrouwe Hospital, PO Box 95500, 1090 HM Amsterdam, The Netherlands.
5. Department of Surgery, Ikazia Hospital, Montessoriweg 1, 3083 AN Rotterdam, The Netherlands.
6. Department of Surgery, St Franciscus Hospital, Kleiweg 500, 3045 PM Rotterdam, The Netherlands.