1Robert Jones & Agnes Hunt Orthopaedic Hospital NHS FT, Oswestry, United Kingdom
2University Hospital of North Tees, Stockton on Tees, United Kingdom
3Royal Liverpool and Broadgreen University Hospitals Trust, Liverpool, United Kingdom
4Parkside Hospital, London, United Kingdom
5South Tees Hospitals NHS Trust, Middlesborough, United Kingdom
6Harrogate Hospital, Harrogate, United Kingdom