Cross-linked hyaluronic acid filler hydrolysis with hyaluronidase: different settings to reproduce different clinical scenarios

Skin necrosis is the most severe complication arising from hyaluronic acid injection. To avoid skin necrosis, hyaluronidase should be injected along the course of the involved artery, to allow blood flow restoration. We evaluated the ability of hyaluronidase to degrade a hyaluronic acid (HA) filler in two simulated clinical situations—a compression case and an embolization case—to identify differences in the hyaluronidase injection. In the compression case, a bolus of HA filler was directly soaked in hyaluronidase solution; in the embolization case, a vein harvested from a living patient was filled with the same HA filler and then soaked in hyaluronidase. We then evaluated the quantity of HA remaining after 2 hours. While we found hydrolysis of hyaluronic acid in both cases, in the compression case, we detected almost complete hydrolysis, whereas in the embolization case we observed a reduction of the 60%. Our results support the hypothesis that vessel compression can be resolved with only one injection of hyaluronidase, while in the case of vascular embolization, repeated perivascular injections should be performed owing to the reduction of hyaluronidase activity.