1 University of Calgary Spine Program and Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta, Canada Division of Orthopedic Surgery, Dalhousie University, Halifax, Nova Scotia, Canada Division of Orthopedic Surgery, University of Western Ontario, London, Ontario, Canada Division of Orthopedic Surgery, University of Alberta, Edmonton, Alberta, Canada Division of Orthopedic Surgery, Dalhousie University, St. John, New Brunswick, Canada Division of Orthopedic Surgery, Trillium Health Centre, Mississauga, Ontario, Canada Division of Orthopedic Surgery, University of Montreal, Montreal, Quebec, Canada Division of Orthopedic Surgery, University of British Columbia, Vancouver, British Columbia, Canada.