Concept of a frameless computer-assisted navigation surgery system at the skull base, the nose and the paranasal sinuses

Objective: Surgical treatments of the base of the skull and the paranasal sinuses are often difficult because of the complex anatomy and the delicate structures. Serious complications such as loss of an eye, deafness, facial nerve paralysis or other neurological complications have been reported. To improve the safety of such operations, computer-assisted navigation Our computer-assisted system is working on the base of intraoperative tracking of the head and the instruments, which are equipped with infrared diodes and registered by a system surgery stands the test. Material: We introduce the system which was developed in Berne. camera. The CT acquisition of the head is done without any head-holding device. The pictures get stored in a computer for preparation of the operation, the segmentation and the three-dimensional reconstruction to define the ideal operation trajectories and different anatomical landmarks. During the operation, reference diodes are fixed on a metallic stick on a maxi!la splint. The surgeon determines the preplaced landmarks by making use of a pointer equipped with diodes. The computer permits now matching the CT images with the head of the patient. At this moment, the positions of the head and the instruments are in real time. Surgery is frameless and permits mobility of the head during the operation. Patients: This navigation system has been used in Berne since the spring of 1997. During 5 months, 19 navigation operations were performed for various pathologies at the anterior and lateral base of the skull as well as for endonasal abnormalities. Results: No surgical complications occurred in these complex and difficult operations at the skull base. The clinically measured accuracy of the system was 0.5-2 mm (mean: <1 mm) at the anterior skull base and 1-2.5 mm (mean <1.5 mm) at the lateral skull base. Conclusion: The use of this navigation system helps the surgeon to identify important anatomical structures and permits a safe and efficient surgery without additional loss of time. Besides, such a system facilitates the surgical approach. New minimally invasive operations might become possible.