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