1. Department of Orthopaedic Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee
2. Department of Neurological Surgery, Vanderbilt University School of Medicine, Nashville, Tennessee
3. Department of Physical Medicine & Rehabilitation, Vanderbilt University Medical Center, Nashville, Tennessee
4. Department of Neurological Surgery, Mayo Clinic, 200 First Street SW, Rochester, Minnesota
5. Carolina Neurosurgery & Spine Associates, Carolinas Healthcare System, Charlotte, North Carolina
6. Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee
7. Department of Neurosurgery, University of Tennessee Health Sciences Center, Semmes-Murphey Neurologic & Spine Institute, Memphis, Tennessee
8. Department of Neurological Surgery, University of California, San Francisco, California
9. Department of Neurosurgery, University of Utah, Salt Lake City, Utah
10. Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia
11. Department of Neurosurgery, Penn State University, Hershey, Pennsylvania
12. Department of Neurological Surgery, Carolina Neurosurgery and Spine Associates and Neurological Institute, Carolinas Healthcare System, Charlotte, North Carolina
13. Department of Orthopedics Surgery and Neurosurgery, Vanderbilt Spine Center, Vanderbilt University Medical Center, Nashville, Tennessee
14. Springfield Neurologic and Spine institute, Springfield, Missouri
15. Department of Neurosurgery, Brain and Spine Center, Holland, Michigan
16. Department of Neurosurgery, Bay Care Clinic Neurological, Green Bay, Wisconsin
17. Department of Neurosurgery, University of Illinois College of Medicine at Peoria, Peoria, Illinois
18. Department of Neurosurgery, University hospital, Augusta, Georgia
19. Department of Neurosurgery, Weill Cornell Medical Center, New York, New York
20. Tallahassee Neurological Clinic, Tallahassee, Florida