Anthropometric Analysis of the Clinically Measured Breast Footprint: An Exploratory Study of BMI and Thoracic Width Associations with Apparent Horizontal Expansion

<b>Background/Objectives</b>: Breast morphology is commonly described using volume, projection, and ptosis, whereas proportional relationships within the breast footprint are less frequently quantified. Routine clinical measurements describe the apparent or clinically measured breast footprint rather than the fixed anatomical footprint. This exploratory study examines how body mass index and thoracic width are associated with the clinically measured horizontal and vertical dimensions of the breast footprint and introduces the height-to-base-width (H/B) ratio as a simple descriptive index. <b>Methods</b>: Anthropometric measurements from 50 women undergoing aesthetic breast surgery were retrospectively analyzed. Breast base width and breast height were obtained using standardized upright clinical measurements. BMI was used as a surrogate of adiposity, while thoracic circumference measured at the inframammary fold (band size) served as a proxy for thoracic frame size. Associations were examined using Spearman correlation and multivariable regression. <b>Results</b>: BMI showed a strong positive association with clinically measured breast base width (ρ = 0.691, <i>p</i> < 0.001) but only a weak association with breast height (ρ = 0.327, <i>p</i> = 0.0777). Thoracic width was inversely associated with the H/B ratio (ρ = -0.549, <i>p</i> = 0.002). Multivariable analysis identified BMI as the principal determinant of measured base width, whereas vertical footprint dimensions showed limited responsiveness to BMI variation. <b>Conclusions</b>: Higher BMI was associated with horizontal expansion of the measured breast footprint, while vertical dimensions remained comparatively stable. These findings reflect soft-tissue redistribution and measurement-dependent footprint appearance rather than alteration of the underlying anatomical footprint. The H/B ratio emerges as a potential descriptive index for apparent footprint proportions, meriting further investigation and prospective validation.