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 5 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 through 22 and 27 G microcannulas and assessed for occlusion patterns, fragment morphology, and particle size. Flow dynamics were recorded through 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; interquartile range, 0.024-0.254 mm2) generating high rates of occlusion predominantly in channels ≤300 µm (P < .0001). A 22 G injection produced larger particles and higher occlusion rates than 27 G (31% vs 17%, P = .025), most notably with large-particle, high-elasticity products. Fragment morphology varied with rheology: solid gels fractured into ovoid embolic particles, whereas soft, high-tan δ gels formed filamentous, nonocclusive strands. Across all products, particle size was lower in the microvascular simulation compared with previous 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.