The Liquid Lift: Looking Natural Without Lumps

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.

Evaluation of Physicochemical Properties Following Syringe-to-Syringe Mixing of Hyaluronic Acid Dermal Fillers

BACKGROUND

Historically, soft-tissue hyaluronic acid (HA) fillers have been mixed with agents to reduce pain or alter physicochemical properties.

OBJECTIVE

Evaluate the impact of dilution and mixing on HA filler physicochemical properties.

MATERIALS AND METHODS

Crosslinked HA filler (VYC-20L, 20 mg/mL) was diluted to 15 mg/mL using saline through 5 or 10 passes between 2 syringes connected using a luer connector. Extrusion force, rheological properties, and microscopic appearance were assessed. Undiluted VYC-15L (15 mg/mL) served as the control.

RESULTS

Average extrusion force was higher for diluted VYC-20L versus the control, with an increase in slope for gel diluted using 5 passes (0.65) and 10 passes (0.52) versus the control (<0.1). For diluted samples mixed with 5 or 10 passes, the rheological profile was different between the 2 halves of the syringe, with the second half more elastic than the first half, compared with the consistent profile of undiluted samples. Microscopically, diluted VYC-20L samples seemed more liquid near the luer and more particulate near the piston compared with the control, which was smooth throughout.

CONCLUSION

In addition to potentially introducing contamination, diluting or mixing soft-tissue HA fillers yields a heterogeneous product with physicochemical characteristics that vary substantially throughout the syringe.

A Dark Side of the Cannula Injections: How Arterial Wall Perforations and Emboli Occur

BACKGROUND

Though most injectors prefer to use a cannula rather than a needle, there have been reported cases of blindness following cannula injections. This study investigated possible situations in which a cannula can injure an artery to gain more insight about the vascular complication and its prevention.

METHODS

To understand how an arterial injury occurs, five situations favoring vascular injury were simulated and tested. Experiments were performed in 100 arterial segments of 10 soft embalmed cadavers with red latex injections to the arteries. The frontal branch of the superficial temporal artery with a diameter between 1.2 and 1.5 mm was chosen for the experiment with a 25G cannula. Five situations were created to simulate any possibility that the cannula can penetrate through the arterial wall. Two factors were varied for simulation of specific danger situations. Factors that vary were as follows: (1) the angles between the cannula and the artery when the cannula touched the artery, and (2) the segments of the artery with different features.

RESULTS

The cannula could penetrate the arterial wall in some specific situations with a different chance in each situation. The perpendicular angle between the artery and the cannula was one of the essential situations for vascular injury. Situations that had a similar effect of the perpendicular arterial surface related to the cannula axis also favored vascular injuries.

CONCLUSION

During a blinded insertion of cannula injections to reach the target area, the injector cannot discriminate the sensation at the cannula tip between the resistance of a fibrous septum in the way of the insertion and the resistance of encountering an artery. To prevent arterial emboli, the cannula trajectory should not be close to the main artery in the region. This allows a physician to safely perform an intermittent forceful insertion without an arterial injury during an attempt to perform a gentle cannula insertion.

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 .