Visualization of the different insertion angles (exemplary representation of a patient of conventional surgery group A). White arrow represents the optimal insertion vector (theoretical; through the middle cranial fossa). Green arrow represents the theoretical hybrid CBCT-laser-fluoroscopic-guided insertion vector. Red arrow represents the actual surgical insertion vector. (A) angle of deviation of the conventional surgery vector from the optimal insertion vector (angle alpha). (B) Angle of deviation of the hybrid CBCT-laser-fluoroscopic-guided insertion vector from the optimal insertion vector (angle beta). (C) Cutaneous distance between actual surgical vector and the theoretical hybrid CBCT-laser-fluoroscopic-guided vector