ABSTRACT
BACKGROUND: MRI analyzed quantitatively the HA injected into the NLF subcutaneous fat to correlate the gel diffusion and degradation with the morphological changes of the NLF appearance for twelve months. Measurements of the gel diffusion and degradation were taken by MRI as parameters to assess the clinical efficacy and long-acting of the HA in NLF rejuvenation. METHOD: HA was applied into the superficial compartment of the subcutaneous fat of twenty NLFs. Each NLF received three injection points, from the nasal ala toward the oral commissure, 1.0-1.5 cm distant from each other, according to the NLF length. A bolus injection technique without retrograde backflow applied per injection point 0.15-0.20 ml of HA for moderate. NLF and 0.20-0.25 ml for severe NLF. Patients were evaluated through MRI and clinically twenty-four hours, one month and twelve months after the HA application. RESULTS: MRI, in T2-weighted, displayed the gel as a dense, spindle-shaped nodule as pattern of the gel diffusion, measuring its largest longitudinal and transverse axes. Twenty-four hours after HA application the longitudinal axis measured 1.79 cm, after one month 2.33 cm and at month twelve 0.91 cm. The transverse axis measured 0.92 cm at 24 hours, 1.13 cm after one month and 0.47 cm at month twelve. CONCLUSION: Despite reduction in size and denseness of the spindle-shaped nodule, the small amount of gel presenting into the subcutaneous fat after twelve months of the application evidenced the HA efficacy and long-acting in NLF rejuvenation. 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 .