[Computer assisted localization in endoscopic sinus surgery--state of the art? The Insta Trak system]

Image-guided surgery is increasingly acknowledged as useful technology also for endoscopic sinus surgery. For many years our department has been involved in the development and testing of devices for image-guided endoscopic sinus surgery. Since January 1997 we have been testing the "Insta Trak" System, which is based on electromagnetic tracking and was especially designed for use in endoscopic sinus surgery.

We tested practicability and accuracy of the system in a wide range of cases from standard sphenoethmoidectomies to tricky frontal sinus surgery, from endoscopic tumour surgery to endoscopic repair of CSF fistulas. System accuracy was assessed by means of visual landmarks which could be clearly identified endoscopically as well as via computer screen. Additionally we measured the time for setting up the system, total operating time and rating of the subjective surgeon's assessment of the system's usefulness in each particular case.

We present the results according accuracy and practicability in 45 patients, who were operated on under computer-aided guidance. Our overall experience with the "Insta Trak" system was very positive. It was no longer the indeed promising, but still rather circumstantial and not always reliable technique we were used to. Operating the system was relatively easy and did not require excessive computer skills. We measured an average accuracy of 0.69 mm with a maximum deviation of 2 mm in a single test measurement. Incorrect use of the device, however, may significantly increase the possible weight of system errors.

The system accuracy was high and "Insta Trak" proved to be practicable and efficient in daily clinical routine. Especially in complicated cases like revision surgery "Insta Trak" proved to be extremely helpful. Whether a system like "Insta Trak" will be definitely able to lower complication rates in FESS is still an open question. Certainly in the near future no such navigational device will become a substitute for the surgeon's understanding of anatomy. In our opinion and experience "Insta Trak" is a significant development in sinus surgery. However, one must be aware of the fact that it cannot be more than yet another and indeed helpful tool.