[Intraoperative precision of mechanical, electromagnetic, infrared and laser-guided navigation systems in computer-assisted surgery].

Intraoperative precision in computer-assisted surgery depends on the characteristics of a navigation system, the precision of correlation between object and data set, the position, number and fixation of landmarks, and the parameters of the data set. The characteristics of a navigation system, in particular the immanent precision, can be detected by the use of the geometric model and navigation analyzer developed at the University of Regensburg with the support of Carl Zeiss, Germany. The precision of five navigation systems of different types and technology was measured: Viewing Wand (ISG, mechanical system), the SMN microscope (Carl Zeiss, infrared system with laser autofocus), the MKM system (Carl Zeiss, robot platform with laser autofocus) and the STP pointer (Leibinger, infrared system). The immanent precision of these systems ranges from 0.1 to 2.0 mm. An electromagnetic system (3-Space Digitizer, Polhemus) was compared; this produces serious spherical deviations of 10.0 to 20.0 mm in the presence of metal, surgical and rotating instruments, and circuits. The application of these different systems for craniomaxillofacial surgery is discussed.