Comprehensive Measurements and Analyses of Ear Canal Geometry From Late Infancy Through Late Adulthood: Age-Related Variations and Implications for Basic Science and Audiological Measurements.

This study provides a comprehensive analysis of ear canal geometry from 0.7 to 91 years, based on high-resolution computed tomography scans of 221 ears. Quantified features include cross-sectional areas along the canal's length, total canal length, curvature, and key anatomical landmarks such as the first and second bends and the cartilage-to-bone transition. Significant developmental changes occur during the first 10 years of life, with adult-like characteristics emerging between ages 10 and 15 years, likely coinciding with puberty. Substantial interindividual variability is observed across all ages, particularly in the canal area. The canal becomes fully cartilaginous at and lateral to the second bend by 0.7 years, with further growth occurring only in the bony segment thereafter. These anatomical findings have important implications for audiologic threshold assessments, wideband acoustic immitance measures, age-appropriate hearing aid fitting schedules, and surgical planning, particularly in pediatric populations where anatomical variation is greatest.