Computer assisted localization in endoscopic sinus surgery - The Insta Trak system.

Background: image-guided surgery is: increasingly acknowledged as useful te chnology also for endoscopic sinus surgery. For many years our department h as been involved in the development and testing of devices for image-guided endoscopic sinus surgery. Since January 1997 we have been testing the "Ins ta Trak" System, which is based on electromagnetic tracking and was especia lly designed for use in endoscopic sinus surgery. Methods: We tested practi cability and accuracy of the system in a wide range of cases from standard sphenoethmoidectomies to tricky frontal sinus surgery, from endoscopic tumo ur surgery to endoscopic repair of CSF fistulas. System accuracy was assess ed by means of visual landmarks which could be clearly identified endoscopi cally as well as via computer screen. Additionally we measured the time for setting up the system, total operating time and rating of the subjective s urgeon's assessment of the system's usefulness in each particular case. Res ults: We present the results according accuracy and practicability in 45 pa tients, who were operated on under computer-aided guidance. Our overall exp erience with the "Insta Trak" system was very positive. It was no longer th e indeed promising, but still rather circumstantial and not always reliable technique we were used to. Operating the system was relatively easy and di d 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. Inc orrect use of the device, however, may significantly increase the possible weight of system errors. Conclusions: The system accuracy was high and "Ins ta Trak" proved to be practicable and efficient in daily clinical routine. Especially in complicated cases like revision surgery "Insta Trak" proved t o be extremely helpful. Whether a system like "Insta Trak" will be definite ly able to lower complication rater in FESS is still an open question. Cert ainly in the near future no such navigational device will become a substitu te for the surgeon's understanding of anatomy. In our opinion and experienc e "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 indee d helpful tool.