1. Liverpool Reviews and Implementation Group; Department of Health Services Research; University of Liverpool; Liverpool U.K
2. Health Economics Unit; Institute of Applied Health Research; University of Birmingham; Birmingham U.K
3. Faculty of Health; Birmingham City University; Birmingham U.K
4. Department of Pain Management; Russells Hall Hospital; Dudley U.K
5. Department of Pain and Anaesthesia; The James Cook University Hospital; Middlesbrough U.K
6. Populations; Evidence and Technologies Group; Division of Health Sciences; University of Warwick; Coventry U.K