1. Department of Neurosurgery, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
2. Department of Spine Surgery, Loretto Hospital, Freiburg, Germany
3. Vanderbilt University Medical Center, Nashville, Tennessee, USA
4. Casal Dots SLU and Asepeyo Hospital, Madrid, Spain
5. Center for Advanced Spine Care of Southern Arizona, Tucson, Arizona, USA