[1] Univ Oxford, Nuffield Dept Orthopaed Rheumatol & Musculoskeleta, Oxford OX3 9DU, England
[2] Oxford Univ Hosp NHS Fdn Trust, Emergency Med Res Oxford EMROx, Oxford, England
[3] Univ Edinburgh, Ctr Clin Brain Sci, Edinburgh, Scotland
[4] Edinburgh Royal Infirm, Dept Clin Neurosci, Edinburgh, Scotland
[5] Salford Royal NHS Fdn Trust, Complex Spinal Dept, Salford, England
[6] Royal Devon & Exeter NHS Fdn Trust, Exeter Spinal Surg Unit, Exeter, England