1. Combined Neurosurgical and Orthopedic Spine Program, Department of Orthopedic Surgery, University of British Columbia, Vancouver, BC, Canada
2. Department of Neurology and Neurosurgery, McGill University, Montreal, QC, Canada
3. Department of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, QC, Canada
4. Department of Anaesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, BC, Canada
5. Department of Anaesthesiology and Perioperative Care, St Paul’s Hospital, Vancouver, BC, Canada