1. Department of Anaesthesiology; Glostrup Hospital; University of Copenhagen; Glostrup Denmark
2. Department of Orthopedics; Glostrup Hospital; University of Copenhagen; Hvidovre Denmark
3. Department of Anaesthesia; Centre of Head and Orthopedics; Copenhagen University Hospital; Rigshospitalet; Copenhagen Denmark
4. Section of Acute Pain Management; Copenhagen University Hospital; Rigshospitalet; Copenhagen Denmark