Cochlear Duct Length Variability in the South Indian Population using High-resolution Computed Tomography Temporal Bone

Abstract Background: Cochlear duct length (CDL) is a crucial anatomical parameter influencing cochlear implantation (CI) electrode selection and surgical outcomes. Due to ethnic and individual variability, population-specific CDL data are essential for optimal implant planning. This study aimed to estimate CDL variability in the South Indian population using high-resolution computed tomography (HRCT) and validated predictive models. Methodology: A retrospective cross-sectional study was conducted on 186 HRCT temporal bone scans of patients without otologic trauma. The basal turn diameter (“A” value) was measured from the round window to the lateral wall through the modiolar axis, and CDL was calculated using the formula CDL = 4.16A – 3.96. Data were analyzed using SPSS v21. Statistical tests included the Mann–Whitney U test, Wilcoxon signed-rank test, and Spearman’s correlation, with P < 0.05 considered significant. Results: The mean age of participants was 38.3 ± 18.75 years. The average CDL was 32.34 ± 2.39 mm (range 24.48–39.37 mm), indicating wide interindividual variation. Males had significantly longer CDLs (32.69 ± 2.41 mm) than females (31.86 ± 2.29 mm, P = 0.002). The right cochlea (32.50 ± 2.51 mm) was marginally but significantly longer than the left (32.18 ± 2.27 mm, P = 0.044). No significant correlation was found between CDL and age ( P = 0.493). The 15-mm variation between the shortest and longest cochleae emphasizes substantial anatomical diversity within the population. Conclusion: This study demonstrates significant individual, gender, and side-related variations in CDL in the South Indian population. These findings underscore the need for individualized, population-specific CDL assessment to optimize electrode selection and improve CI outcomes.