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Superficial Dermal Injection of Hyaluronic Acid Soft Tissue Fillers: Comparative Ultrasound Study

BACKGROUND Superficial dermal injection of hyaluronic acids (HAs) has not been well studied. OBJECTIVES To study HAs injected into the superficial dermis using ultrasound examination and measurements, to evaluate induration and pain, and to examine histology. MATERIALS AND METHODS Three commercial HAs were injected into the superficial dermis (0.2 mL). The HAs used were a biphasic gel, a monophasic monodensified gel, and a monophasic polydensified gel. Ultrasound measurements and images were obtained, pain assessed, and biopsies performed at 7 days. RESULTS Participants experienced pain from the HAs that did not contain lidocaine. After 8 days, the biphasic HA papules appeared erythematous, with two‐thirds reporting the biphasic HA papules as tender. Ultrasound demonstrated superficial placement of HA gels in the upper dermis. The gels each exhibited unique characteristic patterns on ultrasound. Skin biopsies of the superficial dermal placement confirmed earlier patterns. Superficial placement of the biphasic product is associated with tenderness and an eosinophilic inflammatory infiltrate. CONCLUSION Superficial placement of HAs is possible, as demonstrated by ultrasonography. Gels that do not have lidocaine within them are more painful. Injection of biphasic HA gels superficially in the dermis is associated with clinical erythema and tenderness and histology showing an eosinophilic infiltrate.