Until recently, all locations for bone conduction (BC) stimulator described in the literature were situated outside of the real otic capsule. In recent studies 2 new sites for the BC titanium implant were proposed to directly stimulate the cochlea from the closest possible distance, which was the bone forming the ampulla of the lateral semicircular canal (SC) and the bone between the superior and lateral SC. They proved to be the most efficient in terms of transmission of vibratory energy into the inner ear and could be introduced in the field of BC hearing rehabilitation. To the best of our knowledge the anatomy of the space between SC has not been studied so far. However, screwing the BC implant into the proposed new locations directly at the otic capsule and drilling the bone near the SC cast doubt on the safety of this procedure. In this study we aimed to present a detailed analysis of the anatomy of the otic capsule, especially as regards the space between the SC that seems to be safer.
Sixteen fresh frozen cadaveric temporal bones scanned with micro-computed tomography and analyzed using the multiplanar reconstruction option. The anatomy of the space between the SC was analyzed in detail for the purpose of direct BC stimulation of the inner ear.
At least 3 mm of bony tissue is available above the bony space between the crura of the superior SC above the lateral SC, where the new location for the titanium BC implant is proposed. As regards the limitations of the length of screw the BC implant to be screwed, the smallest distance is at least 4 mm of bone thickness.
The bone between the crura of the superior SC is the best placement to screw the BC implant directly to the otic capsule. The implant direction should be parallel to the plane of the lateral SC. This location, the direction, and the limitation of the screw length of the BC implant to a maximum of 7 mm present the lowest potential risk of damage to the inner ear.

© 2020 S. Karger AG, Basel.

References

PubMed