1. Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
2. Department of Surgery, Faculty of Medical Sciences, University of Kragujevac, 34000 Kragujevac, Serbia
3. Department of Traumatology, Clinic for Orthopedics and Traumatology, University Clinical Center Kragujevac, 34000 Kragujevac, Serbia
4. Department of Spinal Surgery, Clinic for Orthopedics and Traumatology, University Clinical Center Kragujevac, 34000 Kragujevac, Serbia
5. Department of Epidemiology, Faculty of Medical Sciences, University of Kragujevac, 34000 Kragujevac, Serbia