Experiences in intraoperative computer-aided navigation in ENT sinus surgery with the Aesculap navigation system.

Five patients with chronic sinus pathology and an indication for sinus surgery were selected. For intraoperative navigation, we used Surgical Planning and Orientation Computer Systems (SPOCS) Aesculap navigation software (ISG Technologies, Mississauga, Ontario, Canada) and surgical instruments fitted with light-emitting diodes. Navigation procedures are described in detail in the article. The system's precision was measured by pointing at anatomical landmarks. The accuracy was measured as the distance in millimeters between the bony structures of the computed tomographic (CT) scan on screen and the cross-hair of the pointer tip displayed on the screen. Another parameter of the system's accuracy was calculated by the system itself as the root mean square error in millimeters between the markers' position as registered and their position in the CT data set. Axial 3/3/1-mm spiral CT provided sufficient resolution, and data transfer via optical disk was practicable. Positioning of the navigation equipment required some experience, and the registration of the patient's head position also needed attention, as the markers have to be pointed at precisely. During the operation, the position of the head-tracking system on the patient's head must remain unchanged to ensure a correct navigation display. The main advantage of the computed navigation system was the constant orientation provided during the sinus surgical procedure. Borders and critical anatomical structures could be identified in the corresponding CT data set, thus enabling the surgeon to decide on subsequent procedures. Use of the navigation system was found to increase the operation time by about 1 h, resulting in additional time under anesthesia. We found the SPOCS Aesculap computed navigation system to be an established technical aid, ready for use in ENT sinus surgery. In the cases reported here, a precision between 1 and 3 mm was obtained.