A Three-Morphotype Classification of Lip Aging Derived from Digital Image Analysis

Background: Lip aging is a heterogeneous and visually complex process, yet a standardized morphological classification applicable to clinical practice is still lacking. Current approaches mainly focus on volumetric loss or perioral rhytids, while the geometric features of the lips, including borders, projection, and eversion, remain poorly codified. Methods: Fifty anonymized lip images acquired under standardized conditions using digital facial imaging were independently evaluated by five physicians experienced in esthetic medicine. Images were classified according to three predefined morphotypes representing distinct patterns of lip aging. Inter-rater reliability was assessed using Fleiss’s kappa statistic. Results: Three recurrent morphotypes were consistently identified: devolumized lips, central lips, and chapped lips. Overall, 87% of images were assigned to one of the three morphotypes by at least four of five evaluators, while 13% were classified as undefined due to mixed features. Inter-rater agreement was substantial (κ = 0.89; 95% CI 0.79–0.99), confirming high reproducibility of the proposed classification. Conclusions: This study proposes a simple and reproducible image-based morphotypic classification of lip aging that captures recurrent visual patterns within this cohort. The framework may facilitate standardized clinical communication, support personalized rejuvenation strategies, and provide a foundation for future quantitative imaging studies and AI-based phenotype recognition in esthetic and reconstructive practice.