CAS of the paranosal sinuses - Technology and clinical experience with the Vector-Vision-compact-system in 102 patients

Introduction: Functional endonasal sinus surgery has gained significant importance in the treatment of chronic inflammatory sinus disease over the past 20 years. Still, the risk of jeopardizing adjacent structures, i.e. the anterior skull base, optic nerve or carotid artery, is increased, especially in revision cases. Several attempts have been made in the past to reduce the risk of iatrogenic injuries due to this kind of surgery and to increase the safety of the procedure, one of them being the introduction and clinical application of image guided and computer assisted surgery (CAS) respectively. A new method of patient registration for the CAS is the non-contact laser registration (z-touch(TM) laser). The main advantage of the laser registration device, is that it is no longer necessary to equip the patient with special markers or with a headset for the registration scan, therefore additional CT scans can be avoided. Material and Methods: In this study we summarize our experience with the Vector Vision compact navigation system. The study population contained 102 patient, treated over a period of 18 months (Sept. 2000-Dez. 2001). The indications for the CAS were mainly revision operations of recurrent nasal polyps, mucoceles or other chronic rhino-sinus diseases, especially of the frontal sinus. In 35 cases the headset registration was applied, in all other cases we used the z-touch(TM) laser registration. Results: The preoperative planning time was significantly lower for z-touch(TM) laser registration (empty set 5,2 min) compared to the headset registration (empty set 20,2 min), the set-up-time in the operation room was nearly the same, 7 min for z-touch(TM) laser registration and 6 min for headset registration. The most important criterion for CAS, of course, is accuracy during surgery; here we also observed an increased accuracy for the z-touch(TM) laser registration. Conclusions: Our data confirm earlier observations indicating that CAS enhances safety during endoscopic sinus surgery especially in revision cases. In addition it might be a helpful adjunct for the beginner and even advanced surgeon during routine sinus procedures. Nevertheless, CAS should not be misinterpreted as a substitute for thorough and meticulous studying of this delicate area including cadaver studies. Our results further demonstrate that the faster and simple registration method allows us to use the system more frequently, thereby increasing the number of navigated cases. The accuracy we can achieve varies between 0.9 and 2.4 mm, with a mean value of 1,3 in the x- and y-axis and 1,4 in the z-axis. In addition it is also possible to use imaging data sets obtained prior to the intent to operate. This not only reduces the cost for imaging studies, but also minimizes the manpower needed to place the fiducials, organize and perform additional acquisition of images.