Dr Marcus Mehta explores the use of cannulas for dermal filler placement and provides his tips for success for those newer to aesthetic medicine
The use of blunt-ended cannulas has increased in the last five years, with more evidence emerging showing that they allow for a safer dermal filler treatment of key areas of the face. Studies have indicated that blunt-ended cannulas are able to reduce trauma to tissues, decrease the risk of vascular injury and also lessen bruising, meaning lower downtime for patients.
In my practice, I now use cannulas for more than 80% of my patient cases, and as the industry advances, I have seen more and more practitioners switch to cannula use for most areas of the face.
One of the fears practitioners have when switching from needle to cannula is the technicality involved, which requires extra training and practice to become competent at. Aesthetic medicine education has traditionally focused around needle use rather than cannula because it is easier to teach and learn when starting out. In this article, I will explore the pros and cons of cannula use, explain how I use cannulas in my practice and provide some of my top tips to get the most out of them.
There are many benefits to using cannulas for your dermal filler treatments, which include: lowered risk, less downtime and accurate and different product placement.
When injecting filler, one of the most severe risks is causing obstruction to a blood vessel. Vascular occlusion can occur as a result of compression or direct occlusion when filler blocks a blood vessel due to inadvertent puncture of the vessel wall.1,2 Injections with a cannula have been shown in the literature to be less likely to cause vascular occlusion due to them being blunt.3
Although cannulas have a lowered risk of causing a vascular occlusion, it is important to note that it is not impossible. When we are speaking about gauge of needles or cannulas, the larger the number the smaller the diameter of the instrument. Cannulas that are 27 gauge and smaller have the same arterial penetration force as a needle, so offer no safer advantage.4 One clinical study examined 294 penetration procedures of the facial and superficial temporal arteries performed in four fresh frozen cephalic specimens using both needles (20, 22, 25, and 27 gauge) and cannulas (22, 25, and 27 gauge). The study showed that all measured sizes of cannulas except 27 gauge required greater forces for intra-arterial penetration compared with correspondingly sized needles. The authors stated that this confirmed the safety of 22 and 25 gauge cannulas for the use of facial soft-tissue fillers; however, they found that 27 gauge cannulas required similar forces as 27 gauge needles, indicating that an artery could be penetrated with a similar force independent of whether the injector used a 27 gauge needle or a 27 gauge cannula.4
Using a cannula for filler allows for longer threads of product to be injected, meaning the practitioner is able to treat larger areas and ensure a smoother result, especially when injecting in the subcutaneous fat. In my experience, this allows for a cosmetic result that is better for the patient as it reduces the risk of aggregation of the filler which can cause lumps.
When using a cannula, you get tactile feedback when moving through facial layers, especially when pushing through the superficial musculoaponeurotic system (SMAS). This allows you to accurately know that you are sub-SMAS and in deep fat when injecting. This is not possible with a needle when the only real feedback you get is when you touch the periosteum, denoting you are supra-periosteal with the needle tip.
A 2017 study where 10 fresh-frozen cephalic foreheads (nine male, one female) were injected with radiopaque material using both needles and cannulas demonstrated the accuracy of cannula use.5 In this study, the needle injection relied on a perpendicular transcutaneous approach, whereas cannulas were moved in the supra-periosteal plane until reaching the same location as the needle – here, radio opaque material was injected. In this study, the authors noted that in 60% of injections using a needle, the implanted material changed its plane; this was not observed when using the cannula (0%; P=0.003). They went on to say that if precision in filler injection is defined as the filler material remaining in the plane of intended implantation, then using cannulas resulted in a more precise injection of material as compared to needles. Applications with needles resulted in the distribution of material into more superficial layers, which was not noted for cannulas.5
Another 2017 study involved the injection of cadaver heads with dye material and soft-tissue fillers at multiple aesthetic facial sites on the supraperiosteum.6 The authors concluded that although direct extrapolation from cadavers to the in vivo situation cannot be made, the use of a cannula resulted in more precision in product placement. This was because with the sharp needle, the material was injected on the periosteum, and then migrated in a retrograde direction along the trajectory of the needle path, ending up in multiple anatomic layers.6
Although there are many benefits to using cannulas, there are also considerations to be mindful of. As mentioned above, much like aspiration with a needle, using a cannula is not a fail-safe option for preventing vascular occlusion. It is still possible to penetrate a vessel and cause damage with a cannula.4 In my practice I use 22 gauge and 25 gauge cannulas, but never a 27 gauge or anything smaller to reduce the risk of vessel penetration.
The other consideration is the patient fear surrounding cannulas, which can be difficult for practitioners to navigate. In my experience, patients are often more fearful of cannulas due to the fact that they appear to be longer/larger than needles. I find new patients who have seen cannula treatment on social media, for example, are quite scared as it can look more painful on video despite often being more comfortable than needles. I always try to educate my patients, and explain what a cannula is and the benefits before beginning treatment, and I try to avoid showing them the instrument itself.
As mentioned above, introductory dermal filler courses usually focus on using needles, so before you get started with cannulas you would require additional training (and a lot of practice) which takes time and is a cost to you and your business. However, this is integral to ensure you are skilled and knowledgeable in using this instrument. The other downsides which relate more to your business are that using cannulas might take slightly more treatment time than using a needle, and it’s an additional expense as dermal fillers often do not automatically come with a cannula.
The length of cannulas can range from short 13mm cannulas up to much longer 90mm cannulas. The area of the face you are treating will determine the cannula length best suited. For example, in the jawline I often use a 50mm cannula to help reach the chin tip, and along the jawline itself and in the lips and mid-face a 25mm or 30mm. When I started injecting with a cannula around four years ago, I found longer cannulas harder to use. My advice would be to get familiar with a shorter length before progressing on to longer cannula sizes such as a 50mm. When it comes to cannula brands, there are many brands available including TSK, Silkann and SoftFil. I personally use the SoftFil cannulas as I find the EasyGuide tool, which is a pre-hole needle guide, means I know where the insertion point is and I can get to the required depth easily. Other ways to help not lose the entry hole is to gently squeeze the skin so a small dot of blood forms on the skin, or better still, have an assistant pass you the cannula whilst you are still looking at where the insertion point has been made.
It’s important to take your time and practise using a cannula in different areas of the face. Sometimes, when you first insert a cannula you will find it difficult to progress from the insertion point. My advice would be to not panic, but spend time slowly attempting to progress the cannula gently; sometimes spinning the cannula can help move past this initial point.
One of the key things I learnt when using a cannula was being able to feel the layers as you go through them. When treating the mid-face for example – deep medial cheek fat or pre-zygomatic space – you want to be below the SMAS to access the deep fat. To get there you must pass through the SMAS with the cannula, and you will consciously feel a pop when you do. Practising this sensation allows you to be sure you’re in the correct plane – going on a cadaver training course is a great way to do this.
You should start to consider different areas where you could use a cannula, for example, the lips. For many new and even experienced practitioners who have been in the industry for a while, they are used to treating the lips with a needle, and the transition to using a cannula here is challenging as it takes some time to feel confident. My patient demographic is between 40 and 70 and I use a cannula to treat almost every lip I see in clinic. I find it volumises much more evenly, reduces pain and gives a result with much less downtime than a needle.
Cannulas form an important part of modern aesthetic practice, and learning to use them competently is a key skill in developing as a practitioner. The main benefit is reduced risk to key structures beneath the skin and allowing for different product placement; however, it is important to be mindful that vascular injury can still occur with a cannula.
As with all things in aesthetic medicine, combining treatment techniques as well as modalities is one of the best ways to achieve good results for your patients. I often use a needle alongside cannulas, for example, when treating the lips I use a cannula in the lip body and a needle in the vermillion border, or when treating the mid-face I use supraperiosteal boluses with a needle combined with cannula in the deep medial cheek fat. Having a good understanding of treatment techniques which often combine needle and cannula use allows for us to offer treatments that are the most effective and ‘above all’ safe for our patients.
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