High-Frequency Ultrasound for Long-term Safety Assessment of Poly-L-Lactic Acid Facial Filler.

[BACKGROUND] Injectable poly- l -lactic acid (PLLA) is a new type of biodegradable dermal filler that has been utilized for soft tissue filling. However, there is no convenient and reliable method to assess the long-term safety of PLLA filler.

[OBJECTIVE] To assess the long-term safety of PLLA injection into nasolabial folds by high-frequency ultrasound and to select the ultrasonic probes with the most appropriate frequency.

[MATERIALS AND METHODS] After a 30-month PLLA injection into the deep dermis of the nasolabial fold, subjects were examined by high-frequency ultrasound with the 20 MHz and 50 MHz probes.

[RESULTS] Twenty subjects with nasolabial fold contour deficiency were enrolled in this study. After a 30-month PLLA injection in nasolabial folds, PLLA degraded entirely in 16 subjects (16/20, 80%), and abnormal echo in the skin was observed in 4 subjects (4/20, 20%) caused by undegraded PLLA microparticles, PLLA microparticles deposition, fibrous nodules, and granuloma. The 20-MHz probe is more appropriate than the 50-MHz probe for evaluating the adverse effects of PLLA injection.

[CONCLUSION] High-frequency ultrasound is a rapid, reliable, and noninvasive method to monitor the degradation condition of PLLA and the formation of papules and nodules associated with PLLA injection.