Orientation for cochlear implant surgery in cases with round window obstruction: a computer reconstruction study

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Abstract
In order to improve cochlear implant surgery in patients with obstructed round windows, surgical orientations of the round window and scala tympani relative to the stapes footplate were examined in ten normal temporal bones using a computer-aided, three-dimensional reconstruction and measurement technique. The round window was found to be exactly inferior to the midpoint of the inferior margin of the stapes footplate in most cases. An optimal point on the promontory wall for drilling to reach the bottom of the scala tympani of the basal turn was found to lie approximately 1.5 mm anterolateral or anterolateral inferior to a point 3 mm inferior to the midpoint of the inferior margin of the stapes footplate. A combination of the transmeatal and facial recess approaches made it possible to consistently reach the scala tympani, and demonstrated that this approach was also applicable to patients with obstructed round windows.