Percutaneous access to the petrous apex in vitro using customized micro-stereotactic frames based on image-guided surgical technology.

Conclusion. Our study demonstrates (in cadavers) the ability to obtain a minimally invasive approach to access the petrous apex using patient-customized micro-stereotactic frames based on pre-intervention radiographic studies. Objective. To conduct in vitro studies to demonstrate the feasibility of percutaneous petrous apex access using customized, bone-mounted, micro-stereotactic frames. Methods. Cadaveric temporal bone specimens (n=10) were affixed with three bone-implanted fiducial markers. CT scans were obtained and used in planning, in reference to the fiducial markers, a straight transmastoid infralabyrinthine trajectory from the mastoid surface to the petrous apex without violating the basal turn of the cochlea or the carotid artery. A drill press was mounted on the customized frame and used to guide a 2 mm drill bit on the desired trajectory. The course of the drill bit and its relationship to surrounding vital anatomy (cochlea, carotid artery, facial nerve, and internal jugular vein) were determined by repeat CT scanning. Results. In 10 of 10 specimens, the drill bit trajectory was accurate with clearance (mean+/-standard deviation in mm) from the cochlea, facial nerve, carotid artery, and jugular vein of 3.43+/-1.57, 3.14+/-1.15, 4.57+/-1.52, and 6.05+/-2.98, respectively.