1. Department of Orthopedics, University Medical Center Utrecht, the Netherlands
2. Department of Neurosurgery, State University of Campinas, Campinas, Cidade Universitária Zeferino Vaz—Barão Geraldo, Campinas—SP, Brazil
3. Department of Orthopedics, Sun Yat-sen University, Guangzhou, Haizhu District, Guangdong Province, China
4. Department of Orthopaedics, Cajuru Hospital, Catholic University of Paraná, Curitiba, Av. São José, Brazil
5. Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, PA, USA
6. Center for Spinal Surgery, Schön Klinik Nürnberg Fürth, Germany
7. Department of Orthopaedic Surgery, Inselspital, University Hospital Bern, Switzerland.