1. 1Liverpool Reviews and Implementation Group, University of Liverpool, Liverpool, U.K
2. 2Department of Pain Medicine, The James Cook University Hospital, Middlesbrough, U.K
3. 3Department of Neurology and Neurosurgery, Medisch Spectrum Twente, Enschede, the Netherlands
4. 4Centre for Pain Medicine, Erasmus MC, University Medical Centre, Rotterdam, the Netherlands
5. 5MRC/CSO Social and Public Health Sciences Unit and Robertson Centre for Biostatistics, Institute of Health and Wellbeing, University of Glasgow, Glasgow, U.K
6. 6College of Medicine and Health, University of Exeter, Exeter, U.K