Fig. 4.

Screen shots of the navigation system (Vector Vision, Brainlab) displaying the CT-2D-fluoro matching. a segmented L4 vertebra of the preoperative acquired CT data superimposed on intraoperative acquired fluoroscopic images; b segmented S1 vertebra from the preoperative CT data superimposed on intraoperative acquired fluoroscopic images; c, d results of the matching procedures and virtual visualization of instrument movement (left drill guide, right pedicle awl) based on CT-fluoro-matched images