Validation of a Fiducial Frame System for Image-guided Otologic Surgery Utilizing Baha® Bone Screws

Image-guided otologic surgeries performed on healthy patients require non-invasive fiducial systems that achieve submillimetric target registration error (TRE). We have described such a system that attaches repeatably to a subject via a dental bite block [1]. We now describe a new method for the clinical validation of such a system that can be conducted in the laboratory with no intraoperative data collection. The method relies on the participation of patients with bone-anchored hearing-aids (BAHA®), which require the implantation of a titanium screw behind the ear. By attaching a fiducial marker to this screw, we can measure TRE at the screw with high accuracy. From those measurements we can estimate TRE at other positions. Results of measurements on a cadaveric skull agree with a previous study that required the implantation of intracranial posts [9] and show that the system achieves submillimetric accuracy in the inner ear.