Stability of Two Cross-Linked Hyaluronic Acid Gels for the Treatment of Temporal Fossa Volume Loss: A Preliminary Study Using MRI and Visual Observations

Introduction: Hyaluronic Acid (HA) gels are a commonly used option for correcting facial volume loss. Over the past 2 years, we have been testing the clinical results of two HA gels, without lidocaine, made by the same manufacturer using the patented “Inter- Penetrating NetworkLike” (IPN-Like) cross-linking technology. The aim of this work was to evaluate if there is a difference in the tissue stability and associated clinical outcomes between these two gels. Material and methods: A 67 and 75 years old Caucasian women, from our private aesthetic center, agreed to be injected with the different HA volumiser gel, one in each of their temporal fossae. The Stylage® XL and XXL HA gels (LABORATOIRES VIVACY, Archamps, France) were used for this study. The gels have different concentrations and levels of cross-linking, but have the same indications for correcting facial volume loss resulting from the ageing process. Clinical outcomes included assessing the degree of pain experienced by participants during and after injection using a Visual Analog Scale (VAS). Aesthetic improvement was evaluated using the Merz Analogic Scale® (MAS)® and Global Aesthetic Improvement Scale (GAIS) scales completed by patients and independent experts at different pre-set time-points using photographs taken from the front, profile and three-quarter left and right angles. Moreover, Serial magnetic Resonance Imaging (MRI) scans were used to assess the tissue behavior of the gels immediately after injection and then 6 monthly for 2 years. Results: Both gels led to an improvement in the patients’ clinical outcomes. This improvement persisted over time. The MRI scans showed that, at Day 0, the injected gel was spherical in shape and became elongated by 6 months. This appearance did not change throughout the follow-up period. The scans showed little resorption at 24 months. Conclusion: Despite the relatively advanced age of the two patients and the small quantities of gel injected, the IPN-Like cross-linked hyaluronic acid volumiser gels had a satisfactory sustainable clinical effect as assessed by patients and experts. There was a slight advantage in favor of the gel with the lower HA concentration but higher level of cross-linking (Stylage® XXL). Given the observed persistent effect of the gels in our preliminary observation, it is now important to conduct a larger study with longer follow- up.