Tear Trough Filler Techniques Utilizing Hyaluronic Acid: A Systematic Review.

BACKGROUND: Hyaluronic acid soft-tissue augmentation fillers are commonly injected into multiple areas of the face, including the tear trough. Despite well-documented risks, there is no standardized, evidence-based approach to inject filler in this area, be it using a hypodermic needle or a microcannula. The authors, therefore, sought to establish a preference between the two methods to facilitate progression toward standardization and prevention of adverse events. METHODS: This is a systematic review of articles discussing hyaluronic acid tear trough injection techniques performed in vivo and related outcomes. Searches were conducted across The Cochrane Library, PubMed, Scopus, Web of Science, and Embase to yield relevant articles published before February of 2020. All selected articles incorporated discrete patient cases and were analyzed by a variety of variables assessing evidence strength, outcomes, technique, and patient safety. RESULTS: After appraisal, 42 articles met eligibility criteria: 20 using needles, 12 using cannulas, and 10 focusing on adverse events. Level III was the most commonly awarded evidence grade, corresponding to retrospective, nonexperimental descriptive studies. There were no statistically significant differences in reported aesthetic results, patient satisfaction, or incidence of adverse events across the needle-based and cannula-based articles. Some technique trends, such as targeted anatomical plane and needle position, emerged in subsequent articles. CONCLUSION: Given that there were no statistically significant differences in patient safety or outcomes, an evidence-based preference for needle or cannula injection into the tear trough cannot be made at this time. Current inconsistencies make tear trough injection procedures difficult to replicate, making standardization based on avoidance of adverse events not feasible.