Abstract
Objectives: Intraoperative navigational devices are used during minimally invasive skull base procedures to identify important landmarks and minimize surgical risks. The goal of this study was to evaluate the accuracy of the registration process and to identify potential sources of error.
Methods: Preoperative imaging with CT or MRI was performed using the Stryker Image Guidance System with skin fiducials in a standard array. The head was immobilized intraoperatively with Mayfield head pins. Registration accuracy and the location of excluded fiducials were recorded in 18 endoscopic anterior cranial base procedures.
Results: The median error of the initial registration was 2.4 mm (range, 1.7–5.6 mm). The median error of the final registration was 1.5 mm (range, 0.6–1.9 mm) following exclusion of a median of 2 fiducials (range, 1–4). In 89% of cases, the operative field was located in the highest zone (green) of accuracy. Excluded fiducials were most often located in postauricular and lateral locations. Reasons for exclusion included high error of individual fiducials, lost or displaced fiducials, or failure to include fiducials within the scanned area. There were no operative complications secondary to inaccurate identification of anatomical landmarks.
Conclusions: The Stryker Image Guidance System is highly accurate using skin fiducials for registration during endoscopic anterior cranial base surgery. The accuracy of registration is enhanced by the exclusion of individual fiducials with high registration errors. Deformation of soft tissues during the preoperative scan decreases the accuracy of post-auricular and lateral fiducials. The time between scanning and surgery should be minimized to prevent displacement of fiducials.