RESUMEN
INTRODUCTION: Myomodulation is a technique aimed at enhancing the dynamics of muscle contraction and relaxation through methods like hyaluronic acid (HA) injection. Achieving optimal outcomes depends on the precise placement of the injected product within the targeted anatomical plane. This is particularly important in the forehead, an area with elevated vascular risk. The selected treatment techniques must ensure both efficacy and safety. This study aims to assess the anatomical precision of HA injections in the forehead using different techniques and devices. METHODS: Four fresh frozen specimens were injected with HA by five experienced board-certified plastic surgeons using three different techniques/devices: (1) a 50 mm, 22G microcannula; (2) a 13 mm, 27G needle with the bevel down at a 45-degree angle; and (3) the same needle positioned at a 90-degree angle. Ultrasound analysis was used to evaluate the precision of each approach. RESULTS: Both the cannula technique and the needle technique with the bevel down at a 45-degree angle consistently delivered the filler to the supraperiosteal layer in 100% of cases without spreading. However, the 90-degree needle technique, despite correct placement on the periosteum, resulted in filler dispersion across multiple layers. CONCLUSION: The accuracy of filler placement in the forehead is influenced by the choice of device and its angulation. It is recommended to use a cannula with the entry point at the frontalis crest or a needle angled at 45 degrees to the skin. The use of a needle at a 90-degree angle should be avoided to ensure precise placement and avoid filler migration. NO LEVEL ASSIGNED: 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 .
RESUMEN
Improvements in Botulinum toxin type-A (BoNT-A) aesthetic treatments have been jeopardized by the simplistic statement: "BoNT-A treats wrinkles". BoNT-A monotherapy relating to wrinkles is, at least, questionable. The BoNT-A mechanism of action is presynaptic cholinergic nerve terminals blockage, causing paralysis and subsequent muscle atrophy. Understanding the real BoNT-A mechanism of action clarifies misconceptions that impact the way scientific productions on the subject are designed, the way aesthetics treatments are proposed, and how limited the results are when the focus is only on wrinkle softening. We designed a systematic review on BoNT-A and muscle atrophy that could enlighten new approaches for aesthetics purposes. A systematic review, targeting articles investigating BoNT-A injection and its correlation to muscle atrophy in animals or humans, filtered 30 publications released before 15 May 2020 in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Histologic analysis and histochemistry showed muscle atrophy with fibrosis, necrosis, and an increase in the number of perimysial fat cells in animal and human models; this was also confirmed by imaging studies. A significant muscle balance reduction of 18% to 60% after single or seriated BoNT-A injections were observed in 9 out of 10 animal studies. Genetic alterations related to muscle atrophy were analyzed by five studies and showed how much impact a single BoNT-A injection can cause on a molecular basis. Seriated or single BoNT-A muscle injections can cause real muscle atrophy on a short or long-term basis, in animal models and in humans. Theoretically, muscular architecture reprogramming is a possible new approach in aesthetics.