1. Rush University Medical Center, Chicago, IL, USA
2. AOSpine International, Davos, Switzerland
3. University of Toronto, Toronto, Ontario, Canada
4. University of British Columbia, Vancouver, British Columbia, Canada
5. Radboud University Medical Centre, Nijmegen, Netherlands
6. University Medical Center Utrecht, Utrecht, Netherlands
7. Emory University, Atlanta, GA, USA
8. Pontificia Universidade Catolica do Paraná, Curitiba, Brazil