Long-Term Follow-Up of Longevity and Diffusion Pattern of Hyaluronic Acid in Nasolabial Fold Correction through High-Frequency Ultrasound

BACKGROUND: Injectable hyaluronic acid fillers have been widely applied in the clinical treatment of facial wrinkles. However, further information and clinical evidence concerning dermal changes and hyaluronic acid filler longevity after injection and diffusion pattern are limited. METHODS: The authors evaluated the longevity and diffusion pattern of two hyaluronic acid fillers generated by different cross-linking technologies used in the treatment of nasolabial folds using high-frequency ultrasound. Forty-one subjects were treated with Restylane 2 and the remaining 41 were treated with Dermalax DEEP. Wrinkle severity rating scale score and high-frequency ultrasound evaluation of nasolabial folds were performed before and after the injection of hyaluronic acid filler. The ultrasound images were acquired and analyzed to determine dermal thickness and the shape and distribution of hyaluronic acid filler. RESULTS: At 2 and 24 weeks from baseline, increased dermal thickness induced by hyaluronic acid filler treatment was not significantly different between groups. At 48 weeks after injection, increased dermal thicknesses of the Restylane 2 group (0.14 ± 0.12 mm) were much lower than those of the Dermalax DEEP group (0.20 ± 0.13 mm). Ultrasound examination revealed that hyaluronic acid materials form well-demarcated and hypoechogenic areas. Restylane 2 tended to form a more diffuse pattern, with multiple smaller bubbles, whereas Dermalax DEEP developed into a more localized configuration, with larger clumps. CONCLUSIONS: This study is the first long-term assessment of nasolabial fold correction that reveals the performance of different hyaluronic acid materials in vivo and validates high-frequency ultrasound as a simple and rapid modality. Hyaluronic acid fillers generated by different cross-linking technologies display differential diffusion patterns in skin tissues. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, II.