Background and objective: The use of conventional drilling procedures in cochlear implant surgery of ossified cochleae poses special risks to the facial nerve and the carotid artery. This study evaluated the alternate use of flexible fiberoptic endoscopy and mid-infrared laser surgery for recanalization of partially and artificially obliterated cochleae in freshly dissected human cadavers.
Study design/materials and methods: A pulsed Holmium:YAG-laser (lambda = 2120 nm) was used in the free-running mode (1180 mJ, 250 microseconds pulse, 5 Hz). A 660 microns optic quartz fiber was positioned in the center of the round window niche and slowly--endoscopically guided--advanced in contact shooting over 1.5 cm, creating by vaporization and photoablation a passage through the artificial bony occlusion in the basal segment of the cochlea.
Results: In all experiments, laser application (110-130 pulses) resulted in complete recanalization of the bony occlusions without damaging surrounding structures. The microendoscopy proved capable of guiding the laser fiber through the curved segment of the basal turn allowing identification of normal bone, bone cement, and laser-treated bone cement.
Conclusion: If partial ossification of the basal turn is present, this technique could give access to place analog as well as digital implants deep within the cochlea.