1. University of British Columbia, Vancouver, British Columbia, Canada
2. University of Virginia, Charlottesville, VA, USA
3. Mayo Clinic, Rochester, MN, USA
4. Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
5. Toronto Western Hospital, Toronto, Ontario, Canada
6. The UCLA Spine Center, Santa Monica, CA, USA
7. USC Spine Center, Los Angeles, CA, USA
8. Jefferson Medical College, The Rothman Institute, Philadelphia, PA, USA
9. University of California San Francisco, CA, USA
10. Indiana University, Indianapolis, IN, USA
11. Rush University Medical Center, Chicago, IL, USA
12. Kansas University Medical Center, Kansas City, KS, USA
13. Cleveland Clinic, Cleveland, OH, USA
14. University of Southern California, Los Angeles, CA, USA
15. University of Toronto, Toronto, Ontario, Canada
16. Oregon Health & Science University, Portland, OR, USA
17. Cleveland Clinic Foundation, Cleveland, OH, USA
18. University Hospitals Case Medical Center, Cleveland, OH, USA
19. University of Wisconsin Hospital and Clinics, Madison, WI, USA
20. Columbia University, New York, NY, USA
21. New York-Presbyterian/The Allen Hospital, New York, NY, USA