Microvascular Insights Into Hyaluronic Acid Filler Dispersal Within an Artificial Model of Arterial Embolism.

Background: Hyaluronic acid (HA) filler-induced vascular occlusion is a serious complication in aesthetic medicine, yet the microvascular behavior of HA gels under physiologically relevant flow conditions remains poorly characterized.

Objectives: To evaluate the embolic fragmentation, dispersal, and occlusive behavior of five commercially available HA fillers within a physiologically calibrated microvascular perfusion model.

Methods: Five HA fillers were tested using a modified PULSAR system incorporating a branched microtubular adapter (200-1000 µm channels) with physiologic arterial flow parameters. Products were injected via 22G and 27G microcannulas and assessed for occlusion patterns, fragment morphology, and particle size. Flow dynamics were recorded via videography and fragment characteristics were analyzed using imaging software. Statistical comparisons were conducted across products and cannula gauges.

Results: HA gels fragmented extensively into microparticles (mean area = 0.140 mm²; IQR: 0.024-0.254 mm²) generating high rates of occlusion predominantly in channels ≤ 300 µm (p < 0.0001). 22G injection produced larger particles and higher occlusion rates than 27G (31% vs. 17%, p = 0.025), most notably with large particle, high-elasticity products. Fragment morphology varied with rheology: solid gels fractured into ovoid embolic particles, while soft, high-tan δ gels formed filamentous, non-occlusive strands. Across all products, particle size was lower in the microvascular simulation compared to prior macrovascular experiments, indicating vessel-caliber-dependent fragmentation.

Conclusions: HA fillers behave as deformable embolic particles that disperse distally under physiologic microtubular conditions. These findings support a concurrent microembolic mechanism underlying filler-induced ischemia. Product rheology, cannula gauge, and vascular anatomy are important determinants of embolic particle behavior.