1. Stoke Mandeville Spinal Foundation, National Spinal Injuries Centre, Stoke Mandeville Hospital, Aylesbury, United Kingdom.
2. Harris Manchester College, University of Oxford, Oxford, United Kingdom.
3. Clinical Epidemiology Unit, School of Population Health, University of Queensland, Herston Road, Brisbane, Australia.
4. Spine Unit, Department of Orthopaedics, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.