Abstract

Objectives: The study aims to assess changes in lip print patterns (LPP) following lip augmentation (LA) with hyaluronic acid (HA) and examine their correlation with lip capacity and ultrasound (US) characteristics of the lips. Additionally, the study aims to provide practical guidelines for clinicians to determine lip capacity limits during HA injections, thereby reducing the risk of overcorrection and unnatural appearance. Introduction: In recent years, there has been a significant increase in the number of patients with overfilled lips and unnatural lip appearance following hyaluronic acid (HA) injection procedures. However, reliable tools for assessing lip capacity limits to prevent such outcomes are still unavailable. Materials / method: The study was conducted on 50 female patients aged 18 to 50. Digital photographs were taken before and after lip augmentation with HA, and lip print patterns were classified according to Suzuki and Tsuchihashi’s classification (only healed lips were assessed). In 15 cases, lips were evaluated using 48MHz and 20MHz ultrasound devices to examine differences in lip US anatomy based on lip capacity. Results: Lips with lip print pattern (LPP) types I,I',II showed a lower capacity for enlargement, with a higher risk of persistent swelling beyond the lip contour following HA injection. In contrast, lips with LPP types III,IV,V demonstrated greater capacity, a thicker submucosal layer, and a more clearly defined hook-shaped marginal part of the orbicularis oris muscle compared to lips with LPP types I,I',II. HA injections led to the transformation of LPP types III,IV,V into types I,I',II. In overcorrected lips, flattening, elongation, and the disappearance of LPP types I,I',II were observed. Conclusion: Features of low-capacity lips at higher risk of unnatural appearance after HA injections include lip print patterns (LPP) types I,I',II; a minimally defined marginal orbicularis oris muscle (OOrM) and a thin submucosal layer between the dry mucosa and OOrM, visible on US. Lips with LPP types III,IV,V are characterized by greater capacity, a clearly defined hook-shaped OOrM, and a thicker submucosal layer. Repeated HA injections transform LPP types III,IV,V into I,I',II, indicating that the lip capacity limit has been reached, and further injections should be avoided to prevent overcorrection.