Accuracy of image-guided surgical systems at the lateral skull base as clinically assessed using bone-anchored hearing aid posts as surgical targets.

OBJECTIVE: Image-guided surgical (IGS) technology has been clinically available for more than a decade. To date, no acceptable standard exists for reporting the accuracy of IGS systems, especially for lateral skull base applications. We present a validation method that uses the post from bone-anchored hearing aid (BAHA) patients as a target. We then compare the accuracy of 2 IGS systems-one using laser skin-surface scanning (LSSS) and another using a noninvasive fiducial frame (FF) attached to patient via dental bite-block (DBB) for registration. STUDY
DESIGN: Prospective.
SETTING: Tertiary referral center. PATIENTS: Six BAHA patients who had adequate dentition for creation of a DBB. INTERVENTION(S): For each patient, a dental impression was obtained, and a customized DBB was made to hold an FF. Temporal bone computed tomographic (CT) scans were obtained with the patient wearing the DBB, FF, and a customized marker on the BAHA post. In a mock operating room, CT scans were registered to operative anatomy using 2 methods: 1) LSSS and 2) FF. MAIN OUTCOME MEASURE(S): For each patient and each system, the position of the BAHA marker in the CT scan and in the mock operating room (using optical measurement technology) was compared, and the distances between them are reported to demonstrate accuracy.
RESULTS: Accuracy (mean +/- standard deviation) was 1.54 +/- 0.63 mm for DBB registration and 3.21 +/- 1.02 mm for LSSS registration.
CONCLUSION: An IGS system using FF registration is more accurate than one using LSSS (p = 0.03, 2-sided Student's t test). BAHA patients provide a unique patient population upon which IGS systems may be validated.