Stereotactic computer-assisted navigational sinus surgery: accuracy of an electromagnetic tracking system with the...

The InstaTrak system by Visualization Technologies, Inc. (Woburn, MA) has recently introduced attachments that can be utilized to localize the tip of the XPS Straightshot debrider (Xomed Industries, Jacksonville, FL) during image-guided surgery. The accuracy of these newer attachments has not been objectively tested in a clinical setting. Our primary objective was to compare the actual instrument (XPS debrider tip) location with its computer screen location in the coronal, sagittal, and axial views. This was considered to be the "accuracy" of the instrument being tested. We secondarily compared its accuracy with the accuracy of the 0 degree and 45 degrees curved localizing aspirators in a prospective study. The manufacturer also recommends that the same headset used during scanning be utilized during surgery. A second objective therefore was to determine if a headset other than the one used during CT scanning could be used intraoperatively with an acceptable level of accuracy. Accuracy of the instruments between the patients' own headset (used during CT scanning) and a generic or research headset (not used during scanning) was compared intraoperatively. The third and final objective was to determine if the same headset could be used repeatedly with an acceptable level of accuracy. Generic "research" headsets were therefore utilized for a total of five surgeries per headset and visual accuracy between the multiply utilized research headsets and the patients' own headsets was recorded and compared. Anatomic localization accuracy was 1.06 mm for the XPS debrider, 0.89 mm for the 0 degree aspirator, and 1.05 mm for the 45 aspirator when the patients own headset was utilized. When the research (generic) headset was utilized the respective values were 0.69 mm for the debrider, 0.77 mm for the 0 degree aspirator, and 0.99 mm for the 45 degrees aspirator. With multiple utilization of a single headset, there was no significant loss in accuracy. In conclusion, the accuracy of the newly marketed attachment for the debrider was found to be comparable to the standard aspirators. Accuracy remained acceptable when a headset other than the one used during CT scanning was used intraoperatively. No loss in accuracy was noted when a headset was utilized more than once.