Hyaluronic Acid Soft-tissue Fillers Research Articles

Biophysical Characteristics of Hyaluronic Acid Soft-Tissue Fillers and Their Relevance to Aesthetic Applications

Plastic and Reconstructive Surgery: November 2013 - Volume 132 - Issue 5 - p 1378 doi: 10.1097/01.prs.0000437345.32060.e9

Biophysical Characteristics of Hyaluronic Acid Soft-Tissue Fillers and Their Relevance to Aesthetic Applications

The purpose of this study was to present new rheologic data for hyaluronic acid filler products, correlate them with recent tissue integration studies, and provide a scientific rationale for selecting appropriate products for volume replacement within different tissue levels and anatomical zones. A brief overview of the methodology of filler rheology studies and data analysis is provided. Six U.S. Food and Drug Administration–approved, cross-linked, nonanimal-derived hyaluronic acid filler products and one hyaluronic acid product approved in Europe and elsewhere were studied: one cohesive polydensifiedmatrix hyaluronic acid (Belotero Balance, also known as Belotero Basic), two Hylacross hyaluronicacids (Juvéderm Ultra and Juvéderm Ultra Plus), one Vycross hyaluronic acid (Juvéderm Voluma), and three nonanimal stabilized hyaluronic acids (Perlane, Restylane and Restylane SubQ) [corrected].The elastic modulus, complex viscosity, and viscous modulus of each filler gel were quantified. Tan delta for each filler gel and also for calcium hydroxylapatite filler (Radiesse) was calculated at 0.7 Hz. Cohesive polydensified matrix hyaluronic acid (Belotero Balance) has the lowest elasticity and viscosity and the highest tan delta. This predicts its soft, flowing qualities and correlates with its homogeneous pattern of tissue integration after intradermal implantation. Nonanimal stabilized hyaluronic acid (Perlane and Restylane) has the highest elasticity and viscosity and low tan delta. This predicts its firm, less flowing qualities and correlates with a bolus-like pattern of tissue integration. Hylacross hyaluronic acid (Juvéderm) has intermediate elasticity, viscosity, and tan delta, correlating with its intermediate pattern of tissue integration. Rheologic evaluation reliably predicts tissue integration patterns and appropriate clinical applications of the studied fillers. Paradigms of layered filler placement can be designed to optimally address individual patient need.

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

Superficial dermal injection of hyaluronic acids (HAs) has not been well studied. To study HAs injected into the superficial dermis using ultrasound examination and measurements, to evaluate induration and pain, and to examine histology. 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. 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. 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.