1. Spine Research Unit, Vall d’Hebron Research Institute, Barcelona;
2. Spine Surgery Unit, Vall d’Hebron University Hospital, Barcelona, Spain;
3. Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Switzerland;
4. Norton Leatherman Spine Center, Louisville, Kentucky;
5. Spine Surgery Unit, Bordeaux University Hospital, Bordeaux, France;
6. Department of Neurosurgery, University of Virginia Medical Center, Charlottesville, Virginia;
7. Spine Center Division, Schulthess Klinik, Zurich, Switzerland;
8. Denver International Spine Center, Presbyterian St. Luke’s/Rocky Mountain Hospital for Children, Denver, Colorado;
9. Spine Surgery Unit, La Paz University Hospital, Madrid, Spain;
10. Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, New York;
11. Department of Orthopaedic Surgery, University of Kansas Medical Center, Kansas City, Kansas;
12. Department of Orthopedic Surgery, University of California, Davis, Sacramento, California;
13. Duke University Medical Center, Durham, North Carolina;
14. Department of Orthopedics and Traumatology, Acibadem University, Istanbul, Turkey; and
15. Department of Neurosurgery, University of California, San Francisco, California