Percutaneous cochlear implant drilling via customized frames: an in vitro study.
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.


METHODS
Feasibility study using cadaveric temporal bones.


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 four of six specimens, the chorda tympani was preserved, and in two of six 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 the facial nerve, 1.31 +/- 0.36 mm to the chorda tympani, and 1.59 +/- 0.43 mm to the ossicles.


CONCLUSIONS
In a cadaveric model, PCI drilling is safe and effective.
Balachandran
Ramya
R
Department of Otolaryngology, Vanderbilt University, Nashville, TN, USA. ramya.balachandran@vanderbilt.edu
Mitchell
Jason E
JE
Blachon
Grégoire
G
Noble
Jack H
JH
Dawant
Benoit M
BM
Fitzpatrick
J Michael
JM
Labadie
Robert F
RF
D019929:Cochlear Implantation / Q000295:instrumentation / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D014057:Tomography, X-Ray Computed