Three-dimensional morphometry of the normal nasal septum on computed tomography: sex- and age-specific reference values from 1,373 adults

Abstract Purpose. Normative data for the three-dimensional anatomy of the nasal septum are sparse. We applied automated segmentation to a large series of adults with radiologically normal sinonasal anatomy to establish sex- and age-specific reference values for septal size, thickness, and midline deviation. Methods. Retrospective cross-sectional study of 1,373 adults (394 men, 979 women; age 18 to 90 years) with sinus computed tomography reported as normal. The septum was segmented by a validated three-dimensional convolutional network (held-out Dice 0.983), and 12 parameters were computed from each segmentation: volume, surface area, maximal and mean sagittal cross-sectional area, three linear extents, three thickness measures, and maximal midline deviation and deviation angle. Reference percentiles were computed by sex and by sex within four age bands; age trends were estimated by linear and quantile regression. Results. Median septal volume was 16,710 mm³ in men (5th to 95th percentile 13,594 to 20,455) and 12,500 mm³ in women (9,963 to 15,329); median mean thickness was 4.89 and 4.29 mm. All size and thickness parameters were larger in men. In men, volume, depth, height, and maximal thickness increased by 1.2 to 1.4% per decade of age; in women they were constant (sex-by-age interaction P ≤ 0.021). Midline deviation did not vary with age, and its 95th percentile was about 3 mm in both sexes. Conclusion. These sex- and age-specific percentiles provide a quantitative reference for interpreting septal anatomy on computed tomography, planning septal surgery, and selecting reference geometries for airflow modeling.