1. Department of Spine Surgery, Clinica del Campestre and Hospital Pablo Tobón Uribe
2. Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS)
3. Department of Spine Surgery, Hospital Clinic de Barcelona
4. Department of Orthopedics, Clinica del Campestre
5. Department of Epidemiology and Clinical Research, Clinica del Campestre