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Safer filler injections:
what research from 2021–2026 tells us

A summary of the latest evidence on blood vessels, needles versus cannulas, aspiration testing, ultrasound and managing complications, for anyone who wants to understand the facts before deciding.

By Dechowat Promda, M.D. · Updated 3 October 2026 · 7 min read

Principles of safer filler injection in the midface: needle versus cannula, aspiration testing and Doppler ultrasound
What research from 2021–2026 says about filler safety

At a glance

  • The most serious complication of filler is gel blocking an artery. It is rare, but most cases occur in the midface.
  • Data from more than 1.7 million syringes show that cannulas carry a lower risk of vascular occlusion than needles, but not zero.
  • Aspiration testing before injection helps only a little. A negative result does not mean the injection is safe.
  • Doppler ultrasound lets the doctor see blood vessels before injecting, but evidence that it actually reduces complications still awaits comparative studies.
  • What matters most is a doctor who knows the anatomy of each layer, and a clinic ready to respond immediately if something happens.

The main risk lies in the blood vessels, especially in the midface

An analysis of 120 patients with filler-related vascular occlusion, published in Aesthetic Surgery Journal Open Forum in 2025, found that 90% occurred in the midface, and 68% followed the course of the facial artery, which runs through the nasolabial fold, beside the nose and along the lips1.

In this group, 59% progressed to tissue ischemia, and the midface had a significantly higher rate of tissue necrosis than the lateral face (63% versus 33%)1. These figures come from people who had already developed complications, so they do not describe the risk of a routine injection. What they show is which areas call for extra caution.

Facial arteries do not stay at one depth along their whole course. Many run deep and then come up close to the skin in certain places, so the doctor needs to know which layer to inject at each point. See the 5-layer illustration on our home page.

Needle or cannula

A retrospective study in JAMA Dermatology gathered data from 370 dermatologists, covering about 1.7 million filler syringes over 10 years. It found vascular occlusion once per 6,410 syringes with needles and once per 40,882 syringes with cannulas, a risk roughly 77% lower2.

InstrumentVascular occlusion rateSuited to
Needle1 per 6,410 syringesAreas that need high precision, such as placement on the periosteum or fine details
Cannula (blunt tip)1 per 40,882 syringesWider areas in the fat layer, with fewer entry points

Both still carry risk, and a small cannula can still enter a blood vessel. So the research does not say one should always be used. It says the instrument should be chosen according to the area and the layer where the gel will be placed.

How much does aspiration testing help?

Aspiration testing means pulling the syringe plunger back slightly before injecting, to see whether blood flows back in. A multicenter study in Aesthetic Surgery Journal in 2025 performed 5,106 aspirations in 1,007 patients at 14 clinics in 9 countries. Only 0.69% were positive, and results varied widely between clinics, from 0% to 6.72%3.

The CMAC group's guideline puts the reliability of aspiration at around 33–63% and states that “a negative result does not mean the injection will be safe”4. Aspiration is therefore just one tool, not a shield. Real safety comes from choosing the right layer, injecting slowly, using low pressure and placing small amounts at each point.

Doppler ultrasound before injection

A 2026 review in Aesthetic Plastic Surgery recommends a high-resolution ultrasound scan before injecting in 4 high-risk areas: the forehead and between the brows, the nose, the groove beside the nostrils, and around the mouth. The scan shows where the vessels are and where they change depth5.

Newer devices attach the probe to the doctor's finger, so the image can be viewed while injecting. A 2026 study in Journal of Cosmetic Dermatology used this method to inject the nasolabial folds of 33 patients and found no vascular occlusion. However, the researchers clearly state that the study “does not prove it is safer” and that comparative studies are still needed6.

What the evidence says: ultrasound is a useful tool, especially in high-risk areas and for people who have had previous surgery or injections. But there is not yet a randomized controlled trial confirming that it reduces complications.

If a complication occurs, speed matters

The CMAC group's guideline recommends stopping the injection immediately if occlusion is suspected, assessing blood flow in the skin, and giving high-dose hyaluronidase (the filler-dissolving enzyme) repeatedly at intervals, with reassessment every hour, because gel has been found to remain in the vessels after an hour has passed4.

Speed is critical, especially when vision is affected. Animal data suggest the retina can tolerate loss of blood supply for about 97 minutes before permanent damage4. A clinic must therefore have the medication, equipment and procedures ready before the injection begins, not go looking for them after something has happened.

Questions to ask your doctor before an injection

  • Who will be injecting, and how often do they inject this area?
  • Which layer will the gel be placed in, will you use a needle or a cannula, and why?
  • Is the product registered with the Thai FDA? Can I see the box and the lot number?
  • Does the clinic have the filler-dissolving enzyme and a complication plan ready?
  • If I notice anything unusual after going home, whom can I contact at any time?

Read next: Filling the right layer: the 5 layers of facial anatomy and layered injection

References

  1. Khoshnaw N, Schelke L, Murray G, Velthuis P. Localization and Staging of Vascular Adverse Events After Facial Fillers: A Detailed Assessment. Aesthetic Surgery Journal Open Forum. 2025. doi:10.1093/asjof/ojaf064
  2. Alam M, Kakar R, Dover JS, et al. Rates of Vascular Occlusion Associated With Using Needles vs Cannulas for Filler Injection. JAMA Dermatology. 2021. jamanetwork.com
  3. Nikolis A, et al. Rates of Positive Aspiration Prior to Facial Hyaluronic Acid Filler Injections: Outcomes of a Multicenter, Cross-sectional Study. Aesthetic Surgery Journal. 2025;45(12):1285. academic.oup.com
  4. Murray G, Convery C, Walker L, Davies E. Guideline for the Management of Hyaluronic Acid Filler-induced Vascular Occlusion. Journal of Clinical and Aesthetic Dermatology. 2021;14(5):E61–E69. jcadonline.com
  5. Gonzalez C, Garzon H, Bravo C, Kroumpouzos G. Ultrasound Imaging of High-Risk Facial Areas for Injectables: A Practical Guide for Common Scenarios. Aesthetic Plastic Surgery. 2026;50(14):5881–5891. link.springer.com
  6. Lee W, Ascher B, Yi KH, Kim JS, Melin A, Kim SH. Study on Safe Filler Injection Techniques Using Cutting-Edge Ultrasound Technology. Journal of Cosmetic Dermatology. 2026. doi:10.1111/jocd.71046

This article is for general information and is not personal medical advice. Always consult a doctor before deciding on any treatment.