1. Faculty of Medicine, University of Ljubljana , Vrazov trg 2, 1000 Ljubljana , Slovenia
2. Department of Orthopaedic Surgery, Ljubljana University Medical Centre , Zaloška cesta 9, 1000 Ljubljana , Slovenia
3. Department of Spine Surgery, Valdoltra Orthopaedic Hospital , Jadranska cesta 31, 6280 Ankaran , Slovenia