The Lip Complexity Classification (LCC): A Proposed Framework Integrating Anatomical Assessment with Therapeutic Decision-Making in Lip Augmentation.

Background: Lip augmentation with hyaluronic acid (HA) fillers remains one of the most technically demanding procedures in aesthetic medicine due to the complex interaction between anatomical variability, tissue quality, dynamic muscular activity, aging-related changes, and previous aesthetic interventions. Although several assessment tools exist for evaluating lip volume, there is currently no standardized system designed to stratify lip treatment complexity and guide therapeutic decision-making. This study proposes the Lip Complexity Classification (LCC), a novel framework intended to correlate anatomical complexity with treatment objectives and injection strategies. Methods: A conceptual classification system was developed based on anatomical principles and clinical experience. The LCC integrates five key assessment domains: relative lip volume, shape and symmetry, signs of perioral aging, tissue quality, and history of previous treatments. Patients are stratified into three complexity grades (Grade I-III) according to the highest-complexity criterion identified during clinical assessment. For each grade, specific therapeutic objectives, proposed treatment strategies, and technique-oriented approaches were defined. Results: The proposed classification distinguishes three progressively complex clinical scenarios. Grade I (low complexity) is characterized by preserved anatomy and is primarily managed through compartment-based volumization strategies. Grade II (moderate complexity) includes early structural deterioration, mild asymmetry, or functional imbalance, requiring combined restoration of lip architecture and selective treatment of adjacent perioral structures. Grade III (high complexity) encompasses advanced anatomical deterioration, significant tissue compromise, and sequelae of previous aesthetic treatments, frequently requiring multilayer lip and perioral rehabilitation. The framework establishes a direct relationship between complexity grade, therapeutic objectives, anatomical targets, product selection, injection depth, and technical approach. Conclusion: The Lip Complexity Classification (LCC) provides a structured, multidimensional framework for assessing lip treatment complexity beyond lip volume alone. As a conceptual framework requiring further validation, the LCC may support treatment planning, procedural standardization, and medical education, while providing a basis for future integration with AI-assisted assessment, non-invasive imaging, and multimodal treatment strategies. Its reliability, validity, clinical utility, safety, and potential impact on treatment outcomes and procedural standardization remain to be established. Prospective studies are required to establish its reproducibility and clinical utility before routine implementation in clinical decision-making.