Investigation of Vascular Behaviour and Tissue Response Following Intra-Arterial Injection of Poly D,L-Lactic Acid...

(1) Background: Hybrid injectable biomaterials incorporating poly-D,L-lactic acid (PDLLA) and hyaluronic acid (HA) have emerged as an important class of biostimulators in aesthetic medicine, combining immediate soft-tissue augmentation with sustained collagen biostimulation. Although inadvertent intravascular injection is uncommon, it may lead to severe vascular complications. However, experimental data on the intravascular behaviour of PDLLA-HA hybrid biostimulators remain limited. This study evaluated vascular flow changes, countercurrent flow, and tissue response following intra-arterial injection of Juvelook^® and Juvelook Volume^® (VAIM Co., Ltd., Seoul, Republic of Korea) in a rabbit ear model. (2) Methods: A total of 112 rabbits (56 animals per product) were studied using an identical protocol. Each rabbit received bilateral intra-arterial injections of either 0.1 or 0.2 mL of PDLLA-HA hybrid biostimulator prepared at the manufacturer's recommended 6 mL reconstitution or at serial dilutions ranging from 12 to 42 mL. Immediate vascular flow, countercurrent flow, macroscopic skin changes, and histopathological findings were evaluated over a 7-day observation period. (3) Results: At an injection volume of 0.1 mL, both products dispersed throughout the arterial system without persistent vascular occlusion or tissue necrosis. At 0.2 mL, transient vascular occlusion occurred in the standard (6 mL) and 12 mL dilution groups, with spontaneous restoration of blood flow within 5 min. Countercurrent flow was observed only in the Juvelook Volume^® (VAIM Co., Ltd.) cohort under these conditions. No skin necrosis, intravascular thrombosis, or embolisation was observed. Histopathological examination demonstrated preserved vascular integrity, with only focal perivascular foreign-body reactions consistent with injectable biomaterials. (4) Conclusions: Neither biostimulator caused persistent vascular occlusion or clinically significant tissue injury under the experimental conditions investigated. Injection volume and dilution influenced transient vascular flow disturbance and countercurrent behaviour. These findings provide experimental evidence that improves current understanding of the short-term intravascular behaviour of PDLLA-HA hybrid biostimulators and may contribute to future assessments of vascular safety.