1. Spine Surgery Unit, Vall d’Hebron University Hospital, Barcelona, Spain
2. Spine Research Unit, Vall d’Hebron Research Institute, Barcelona, Spain
3. Spine Surgery Unit, Hospital La Paz, Madrid, Spain
4. CHU Bordeaux Pellegrin Hospital, Bordeaux, France
5. Department of Orthopaedics and Traumatology, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
6. Spine Center Division, Schulthess Klinik, Zurich, Switzerland