Histological and Clinical Appraisal of Distribution and Long Acting New Hyaluronic Acid into the Subcutaneous Fat of the Forehead to Improve Horizontal Lines.

BACKGROUND: A new hyaluronic acid (HA) was appraised to improve forehead horizontal lines (FHL). Histological analysis correlated the gel distribution with clinical findings and also with wrinkle depth, 48 h and 12 months after HA application.
METHODS: The new filler composed by 24 mg/ml of HA cross-linked with BDDE 2.0 ppm was injected into the subcutaneous fat, just beneath the dermis, through a retrograde backflow injection technique applied in sequence. Biopsies were taken with a 3.0-mm-diameter skin punch before HA application, 48 h and 12 months after HA application for histological evaluation.
RESULTS: Subcutaneous application created a compact cylindrical filament as pattern of gel distribution, which acted as strut raising the FHL to the level of the surrounding tissues. Diameter average of the filament 48 h after HA application was 1.18 mm and at month twelve 0.34 mm. The residual amount of the gel at month twelve ensured the long acting of the HA into the subcutaneous fat. FHL depth of 251.83 µm before HA application and 190.20 µm after 12 months indicated that the residual amount of gel at month twelve still projected FHL.
CONCLUSION: High cohesivity of HA and low density of forehead subcutaneous fat caused the gel to take the form of a compact cylindrical filament. The small amount of gel still presenting into the subcutaneous fat 12 months after application validated the long acting of the HA. Evidence-based analysis showed that this new filler might be considered a safe alternative for improvement in the FHL. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .