CT-Derived Anatomical Factors Associated with Operative Time and Hearing in Endoscopic Stapes Surgery: A...

Background/Objectives: The objective of this study is to evaluate anatomical factors associated with operative time and audiological outcomes in endoscopic stapes surgery, with particular focus on quantitative temporal bone CT measurements. Methods: A retrospective review was conducted of 40 patients (51 ears) who underwent exclusive endoscopic stapes surgery between 1 April 2014 and 31 March 2023 by a single surgeon. Preoperative and postoperative audiometric data, operative time, and high-resolution temporal bone CT measurements-including scutum angle and external auditory canal (EAC) cross-sectional area-were analyzed. Correlation analysis was performed to assess associations with operative time and air-bone gap (ABG) closure. Receiver operating characteristic (ROC) analysis was conducted as an exploratory assessment to identify anatomical thresholds associated with prolonged operative time. Additional analyses were performed to evaluate the potential influence of surgical period on operative time. Results: Significant improvements were observed in postoperative air conduction, bone conduction, and ABG (all p < 0.0001). Mean ABG closure was 21.4 dB, and 74.5% of ears achieved postoperative ABG ≤ 10 dB. Operative time demonstrated a strong positive correlation with scutum angle (r = 0.8968, p < 0.0001) and a moderate negative correlation with EAC area (r = -0.5759, p < 0.0001). No significant correlation was identified between CT measurements and audiological outcomes. Exploratory ROC analysis suggested that an EAC area < 0.1922 cm² and scutum angle > 71.4° were associated with longer-than-median operative times. No significant difference in operative time was observed among the three predefined surgical periods, and linear regression analysis demonstrated no significant association between surgical period and operative time. Conclusions: Endoscopic stapes surgery provides favorable audiological outcomes. While preoperative CT-based anatomical parameters were not associated with hearing results, narrower EAC dimensions and larger scutum angles were associated with increased operative time under the endoscopic approach. These findings may facilitate preoperative surgical planning by identifying patients who are likely to present greater technical difficulty during endoscopic stapes surgery. However, the proposed CT thresholds should be regarded as exploratory findings and require prospective external validation before routine clinical implementation.