OBJECTIVE Minimally-invasive image-guided approach to cochlear implantation (CI) involves drilling a narrow, linear tunnel to the cochlea. Reported herein is the first clinical implementation of this approach. STUDY DESIGN Prospective, cohort study. METHODS On preoperative CT, a safe linear trajectory through the facial recess targeting the scala tympani was planned. Intraoperatively, fiducial markers were bone-implanted, a second CT was acquired, and the trajectory was transferred from preoperative to intraoperative CT. A customized microstereotactic frame was rapidly designed and constructed to constrain a surgical drill along the desired trajectory. Following sterilization, the frame was employed to drill the tunnel to the middle ear. After lifting a tympanomeatal flap and performing a cochleostomy, the electrode array was threaded through the drilled tunnel and into the cochlea. RESULTS Eight of nine patients were successfully implanted using the proposed approach with six insertions completely within scala tympani. Traditional mastoidectomy was performed on one patient following difficulty threading the electrode array via the narrow tunnel. Other difficulties encountered included use of the back-up implant when an electrode was dislodged during threading via the tunnel, tip fold-over, and facial nerve paresis (House-Brackmann II/VII at 12 months) secondary to heat during drilling. Average time of intervention was 182±36 minutes. CONCLUSION Minimally-invasive, image-guided CI is clinically achievable. Further clinical study is necessary to address technological difficulties during drilling and insertion and to assess potential benefits including decreased time of intervention, standardization of surgical intervention, and decreased tissue dissection potentially leading to shorter recovery and earlier implant activation.

Purpose To introduce a novel microstereotactic frame, called the Microtable, consisting of a tabletop that mounts on bone-implanted spherical markers. The microtable is customized for individual patient anatomy to guide a surgical instrument to a specified target. Methods Fiducial markers are bone-implanted, and CT scanning is performed. A microtable is custom-designed for the location of the markers and the desired surgical trajectory and is constructed using a computer-numerical-control machine. Validation studies were performed on phantoms with geometry similar to that for cochlear implant surgery. Two designs were tested with two different types of fiducial markers. Results Mean targeting error of the microtables for the two designs were 0.37±0.18 and 0.60±0.21 mm (n = 5). Construction of each microtable required approximately 6 min. Conclusions The new frame achieves both high accuracy and rapid fabrication. We are currently using the Microtable for clinical testing of the concept of percutaneous cochlear implant surgery.

Percutaneous cochlear implant access using customized drill guides based on preoperative CT scans and image-guided surgery technology can be safely accomplished.

Objective-Percutaneous cochlear implant (PCI) surgery consists of drilling a single trough from the lateral skull to the cochlea avoiding vital anatomy. To accomplish PCI, we utilize a patientcustomized, micro-stereotactic frame, which we call a "microtable" because it consists of a small Correspondence to: Robert F. Labadie. Note: The authors have applied for multiple patents on this technology, some of which may lead to commercialization with the potential for financial benefit to them. NIH Public Access Author ManuscriptOtol Neurotol. Author manuscript; available in PMC 2011 January 1. Published in final edited form as:Otol Neurotol. 2010 January ; 31(1): 94-99. doi:10.1097/MAO.0b013e3181c2f81a. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript tabletop sitting on legs. The orientation of the legs controls the alignment of the tabletop such that it is perpendicular to a specified trajectory.Study design-Prospective. Setting-Tertiary referral center.Patients-Thirteen patients (eighteen ears) undergoing traditional CI surgery.Intervention(s)-With IRB approval, each patient had three fiducial markers implanted in bone surrounding the ear. Temporal bone CT scans were obtained and the markers were localized, as was vital anatomy. A linear trajectory from the lateral skull through the facial recess to the cochlea was planned. A microtable was fabricated to follow the specified trajectory.Main outcome measure(s)-After mastoidectomy and posterior tympanotomy, accuracy of trajectories was validated by mounting microtables on bone-implanted markers and then passing sham drill bits across the facial recess to the cochlea. Distance from the drill to vital anatomy was measured.Results-Microtables were constructed on a CNC milling machine in under 5 minutes each. Successful access across the facial recess to the cochlea was achieved in all 18 cases. The mean ± standard deviation from mid-portion of the drill to the facial nerve was 1.20 ± 0.36 mm and from the chorda tympani was 1.25 ± 0.33 mm.Conclusions-These results demonstrate the feasibility of PCI access using customized, microstereotactic frames.

Objective Percutaneous cochlear implantation (PCI) surgery uses patient-specific customized microstereotactic frames to achieve a single drill-pass from the lateral skull to the cochlea avoiding vital anatomy. We demonstrate the use of a specific microstereotactic frame, called a “Microtable”, to perform PCI surgery on cadaveric temporal-bone specimens. Study Design Feasibility study using cadaveric temporal-bones. Subjects and Methods PCI drilling was performed on six cadaveric temporal-bone specimens. The main steps involved were (1) placing three bone-implanted markers surrounding the ear, (2) obtaining a CT scan, (3) planning a safe surgical path to the cochlea avoiding vital anatomy, (4) constructing a microstereotactic frame to constrain the drill to the planned path, and (5) affixing the frame to the markers and using it to drill to the cochlea. The specimens were CT scanned after drilling to show the achieved path. Deviation of the drilled path from the desired path was computed, and the closest distance of the mid- axis of the drilled path from critical structures was measured. Results In all six specimens, we drilled successfully to the cochlea preserving the facial nerve and ossicles. In 4/6 specimens, the chorda tympani was preserved, and in 2/6 specimens, it was sacrificed. The mean ± standard deviation error at the target was found to be 0.31±0.10 mm. The closest distances of the mid-axis of the drilled path to structures were 1.28±0.17 mm to facial nerve, 1.31±0.36 mm to chorda tympani, and 1.59±0.43 mm to ossicles. Conclusion In a cadaveric model, PCI drilling is safe and effective.