A temporal bone study of insertion trauma and intracochlear position of cochlear implant electrodes. II: Comparison of Spiral Clarion™ and HiFocus II™ electrodes

The newer electrode was consistently positioned closer to the modiolus than the previous device whereas the angular depth of insertion measured for the two electrodes was similar. The incidence of trauma was minimal when either electrode was inserted to a depth of less than 400°. However, severe trauma was observed in every case in which the HiFocus II™ with positioner was inserted beyond 400° and in some cases in which the Spiral Clarion™ was inserted beyond 400°. To evaluate the possible role of electrode size in the trauma observed we modeled both devices relative to the dimensions of the scala tympani. We found that the fully inserted HiFocus II™ electrode with positioner was larger than the scala tympani in approximately 70% of temporal bones measured. The results suggest that both the Clarion™ spiral and HiFocus II™ with positioner can be inserted with minimal trauma, but in many cases not to the maximum depth allowed by the design.