1. Department of Orthopaedic Surgery, Rothman Institute & Thomas Jefferson University Hospital, Philadelphia, Pennsylvania;
2. Department of Neurosurgery, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania;
3. Department of Orthopaedic Surgery, Northwestern Memorial Hospital, Chicago, Illinois;
4. Departments of Orthopaedic Surgery and
5. Department of Orthopaedic Surgery, Mayo Clinic, Rochester, Minnesota;
6. Department of Neurosurgery, University of Virginia, Charlottesville, Virginia;
7. Panorama Orthopedics & Spine Center, Denver, Colorado;
8. Department of Orthopaedic Surgery, University of British Columbia, Vancouver, British Columbia, Canada;
9. Department of Neurosurgery, University of Saskatchewan, Saskatoon, Saskatchewan, Canada;
10. Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts;
11. Department of Neurosurgery, Rush University Medical Center, Chicago, Illinois;
12. Department of Orthopaedic Surgery, Emory University, Atlanta, Georgia; and
13. Neurosurgery, University of Toronto, Ontario, Canada;
14. Department of Neurosurgery, University of Maryland, Baltimore, Maryland