Evaluation Of The Safety Of Poly-l-lactic Acid In Facial Rejuvenation Through High-frequency Ultrasound

BackgroundPoly-L-lactic acid(PLLA)is a new type of dermal filler,which degrades into carbon dioxide and water in vivo and activates fibroblast cells to stimulate collagen formation.Recently,many studies have found that PLLA has a long-term good efficacy and safety,even if it has been completely degraded,the proliferation of collagen fibers can also play a filling role.PLLA can be used in dermatology and cosmetic dermatology to cure facial volume loss and reduce facial wrinkles,having an extensive application potential.At present,there is still no research on the long-term follow-up of PLLA rejuvenation in China.What's more,most of the studies use evaluation methods such as clinical scoring scales to assess the efficacy of facial filling,which is easily influenced by subjective factors.High-frequency ultrasound,which refers to the frequency of more than 10MHz,can show the structure of skin clearly,measure skin thickness and dermal density,be used for the diagnosis of skin diseases,and evaluation of curative effect.High-frequency ultrasound as an objective imaging assessment method,its role in the evaluation of facial rejuvenation efficacy and safety remains to be further explored.ObjectivesThe aims of this study are to perform long-term follow-up in patients after PLLA facial filling to measure the efficacy and safety,and to explore the role of high-frequency ultrasound in evaluation of efficacy and complications of PLLA in facial rejuvenation.MethodsThis study is a long-term follow-up of patients who received an injection of PLLA dermal filler to treat nasolabial folds at the dermatology department of PUMCH from December 2017 to February 2018.20 cases were included in the study,and basic information such as age and sex were collected.The bilateral skins of nasolabial folds were evaluated by 20MHz and 50MHz high-frequency ultrasound at 120 weeks(±8 weeks)after the last injection.We used the MD-300S ? skin ultrasound system produced by Tianjin Maida Medical Science and Technology Co.Ltd.Statistical analysis and drawing are completed by Microsoft Excel and SPSS 20.0 software.Results1.The full structure of the skin can be shown by 20MHz ultrasound.50MHz ultrasound can only show the epidermis and dermis,but the resolution is higher and more details can be clearly shown.The thickness of the right nasolabial fold dermis was(1.47± 0.39)mm when the thickness of the left nasolabial fold dermis was(1.38 ± 0.30)mm(p<0.05).There was a significant difference.2.In 19 cases,the boundary between epidermis,dermis,and subcutaneous tissue of bilateral nasolabial folds was clear,and the density of dermis was uniform and no abnormal sign was found.A case showed abnormal signs in the echo of nasolabial folds,which could be identified by its position,echo density,border,and surrounding tissue.Conclusions1.PLLA dermal filler has good safety in long-term follow-up through high-frequency ultrasound in vivo.It degrades completely and is not easy to cause tissue changes such as nodules.2.High-frequency ultrasound can assess objective images and data to evaluate the changes of skins after dermal filling,which can be used for baseline measurement,the monitor of efficacy,and the evaluation of complications of facial rejuvenation.