Purpose: We evaluated the accuracy of surface registration with and without additional landmark registration during cranial electromagnetic navigation. Results were referenced to point by point registration with bone anchored fiducials. Methods:Using a commercially available electromagnetic navigation system, 4 rhinologic surgeons applied surface registration alone (SurfReg) and surface registration with additional anatomic landmarks (CombReg) in a macerated human skull. Point by point registration using bone anchored fiducials (RefReg) served as reference. Target registration error (TRE) served as a measure for accuracy. For TRE calculation, 16 landmarks on the viscerocranium, the frontal skull base and the middle cranial fossa were touched with a probe and the distance of the probe and the target was measured on a screenshot of the corresponding CT image in three planes. A mixed regression model with registration mode as fixed factor and examiner and target as random factors was used.Results: Mean (95% CI) TRE for SurfReg was 1.12 (0.86 to 1.39) mm and 1.21 (0.94 to 1.47) mm for CombReg (p=0.13). TRE of the RefReg was significantly lower (0.91 mm; 0.64 to 1.18; p<0.001). TRE varied significantly depending on target screw position. TRE did not vary significantly among different examiners. Conclusion:Surface registration is considered sufficiently accurate for clinical application during FESS and frontal skull base surgery. Additional landmarks did not improve accuracy when compared with surface registration alone. Additional time for landmark registration can therefore be spared.

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