Crista Fenestra Heights Measured by HRCT Predicts the Necessity for Extended Round Window Approach for Slim Modiolar Electrode.

Objective: To evaluate the morphology of the crista fenestra (CF) using three-dimensional reconstruction based on high-resolution computed tomography (HRCT) and to examine the influence of CF height on the insertion approach used for CI632/532 implants.

Study design: Retrospective study.

Setting: Tertiary referral center.

Patients: Forty-five ears of 37 patients who received CI632/532 implants were included.

Interventions: HRCT images were reconstructed into three-dimensional images, and CF structures were identified. The patients were divided into two group based on the insertion approach: round window approach (RW; n = 27) and extended round window approach (eRW; n = 18). To evaluate CF interference, 10 cases in the eRW group in which the sheath or electrode did not pass through the RW before widening the RW niche (nRW group) were specifically included in the analysis.

Main outcome measure: The identified CF cross-sections were confirmed by HRCT axial sectioning, and CF heights were measured.

Results: The mean CF height was significantly greater in the nRW group than in the RW group (0.97 vs. 0.78 mm).

Conclusion: CF was identified using three-dimensional computer graphics (3DCG) and the CF height on the HRCT axial sections. Thus, measuring the CF height using 3DCG reconstruction can facilitate the preoperative selection of the electrode insertion approach.