1. 1Departments of Neurosurgery, Johns Hopkins University, Baltimore, Maryland;
2. 2Departments of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota; and
3. 3Combined Neurosurgical & Orthopaedic Spine Program, University of British Columbia, Vancouver, Canada
4. 4University of Toronto, Ontario, Canada;
5. 5Northwestern University, Chicago, Illinois; and
6. 6The University of Texas M.D. Anderson Cancer Center, Houston, Texas; and