1. Department of Anaesthesiology; Centre of Head and Orthopaedics; Copenhagen University Hospital; Rigshospitalet Copenhagen Denmark
2. Department of Anaesthesiology; Zealand University Hospital; Køge Denmark
3. Department of Anaesthesiology and Danish Pain Research Centre; Aarhus University Hospital; Aarhus C Denmark
4. Department of Anaesthesiology; Helsinki University Central Hospital; Jorvi Hospital; Helsinki Finland
5. The Pain Clinic; Department of Anaesthesiology, Intensive Care and Pain Medicine; University of Helsinki and Helsinki University Hospital; Helsinki Finland
6. Department of Anaesthesiology and Intensive Care Copenhagen University Hospital; Bispebjerg and Frederiksberg Hospitals; Copenhagen Denmark
7. Copenhagen Trial Unit; Centre for Clinical Intervention Research; Copenhagen University Hospital; Copenhagen Denmark