1. Department of Anaesthesiology Zealand University Hospital Køge Denmark
2. Department of Health Sciences, Faculty of Medicine Lund University Lund Sweden
3. Department of Anaesthesiology, Centre of Head and Orthopaedics Copenhagen University Hospital, Rigshospitalet Copenhagen Denmark
4. Department of Anaesthesiology Bispebjerg and Frederiksberg University Hospital Copenhagen Denmark
5. Department of Anaesthesiology Næstved Hospital Næstved Denmark
6. Department of Orthopedics Bispebjerg and Frederiksberg University Hospital Copenhagen Denmark
7. Department of Orthopedics Zealand University Hospital Køge Denmark
8. Department of Orthopedics Nykøbing Falster Hospital Nykøbing Falster Denmark
9. Department of Orthopedics Nordsjællands Hospital Hillerød Denmark