1. Department of Neurological Surgery, University of Washington, Seattle, Washington;
2. Department of Orthopedics and Trauma Surgery, Faculty of Medicine and University Hospital Cologne, University of Cologne, Germany;
3. Department of Orthopedics and Trauma Surgery, Krankenhaus Porz am Rhein, University of Cologne, Germany;
4. Department of Neurosurgery, Warren Alpert Medical School, Brown University, Providence, Rhode Island;
5. Texas Back Institute, Plano, Texas;
6. Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan;
7. Department of Neurosurgery, Geisinger Neuroscience Institute, Danville, Pennsylvania; and
8. Department of Neurological Surgery, Washington University School of Medicine, St. Louis, Missouri