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Cannulas vs. Needles

Cannulas vs. Needles


Maxine McCarthy (all rights reserved 2017)

In this paper I would like to explore the contrasting experiences of using blunt tip cannulas and needles to inject fillers. This is prior to documenting further exploration in this area to make a more comprehensive study available later this year.

I particularly want to describe some of the perceived advantages, analyse their performance criteria and argue that for much of the filler work we do Cannulas should be used and students should be trained to level 7 in order to use them.
I will refer anecdotally to the advantages of injecting filler with blunt tipped cannulas of various kinds in comparison with using needles, as there are no substantial experimental studies to establish how Perlane, Juvederm, Restylane, Radiesse or my favourite, Intraline perform differently in use to enhance cheek shape, for example, using cannulas and needles without distinguishing the skill of the aesthetic practitioner from the clinical equipment used.

If we were going to make this rigorous we would need to describe anatomically the dividing lines between the eyes, nasolabial folds, cheeks, fat pads and other features; and the appearance that one practitioner’s perceived advantage delivering more filler more quickly is another practitioner’s perceived disadvantage. The skill set of the clinical practitioner as ‘skilled artist’ appears all important and this is what we will argue in conclusion.

I can report that at Cosmetic Couture we have been using blunt tipped cannulas in all these areas and more with almost all the fillers and have found the experience of using Cannulas to compare favorably to the experience of using needles.

Cannulas seem safer in that logic dictates that a blunt tip can do less harm than a razor sharp needle tip.  Logic also suggests that it will take time and experience and careful training to level 7 to overcome the initial skill deficit in managing the complex art of manipulating a blunt tip cannula making them more accurate.

canualla vs needle

What little bruising there is results from inexperienced application which does not occur when the access point is accurately breached.

The lack of bruising is indicative of the absence of trauma, indicated by the absence of pain. Because there is little or no pain there is no need to inject anaesthetic except at the entry point.

But likewise, the absence of pain should be no green light for less skillful practitioners to go barging in with large volumes of filler spraying it all over the deep structures of the face. The artistry comes with experience, we have seen it take 2 years experience approximately with a proven number of treatments during that time.


At Cosmetic Couture we have used the blunt tipped cannulas in this range for most of the HA fillers listed above and can describe them as ‘safer’ in the right hands, and ‘more accurate’ used in the right pattern and with skillful manipulation through one or two ports which can be suggested by the picture below:


From the picture above you can see that the entry points to cheeks can be accessed without bruising or obvious swelling and little reported discomfort so far. Of course clients have always embraced new techniques with me and we look forward to doing more training and CPD in 2017, passing new knowledge and skills onto the many aestheticians that train at Cosmetic Couture.

entry points

For some it is the simplicity of the entry port that makes them say they will never face the needle again, and for those who fear needles or the pain then being able to access half the face from a couple of ports is obviously a brilliant advantage, assuming they do not experience discomfort. Areas that are not accessible by either needle or cannula need to be treated separately.

With the reduced number of entry points comes a reduction in time taken on the procedure as handling the diplomacy of repeated injection points is eliminated.  There needs to be more research on why the pain is reduced so much, but it would appear that there are few pain receptors susceptible to the blunt tipped cannula at this level, and the discomfort is a much milder secondary pressure or sensitivity issue. The subjectivity of this pain is also interesting when thinking about acupuncture, and the concept of dramatic placeoba effect.

Where there are specific filler demands, such as for Sculptra in close proximity to bone and thin dermis it is too difficult to use cannulas and we revert to needles in this case, where a number of other innovative pain reduction technologies can be employed.

Considering the tower technique?

Volumising is mainly less uncomfortable using cannulas, but of course with the bigger gauge cannulas, an even larger gauge needle must be used to generate a puncture site sufficiently big enough for the cannula, and the pain and bruising caused here can be significant.  This becomes a personal choice for the client, as too does the question of sensitivity to the cannula. Just as some clients have a fear of needles, so some clients have a fear of the uncomfortable sliding sensation that the cannula creates as it worms its way under and through the skin  and sometimes even sounds quite loud in creeping its way along, and this becomes a phobia. This effect is multiplied by the length of travel that the cannula has to go because the entry point is so far from the insertion point. Thus the perceived benefits can be varied, and the SKILL of the practitioner is actually more critical in achieving accuracy of delivery over greater distance of cannula tip to syringe.  Comparing the rigid pointed needle accuracy with the flexible blunted accuracy of the cannula is difficult, but I have been using cannulas for a long time and have become quite expert in their subtle manipulation beneath the dermis, suggesting to me that product placement is slightly less precise in some ways and more precise in others. Avoid using the cannula for the superficial fine lines and focus on using them for larger more significant features. A combination of both may be required.

Common sense tells us that though the cannula is less specifically damaging than the needle upon entering, it might be thought of as more invasive in the potential threat of spreading infection across a wide range of tissue geography possibly even providing a means, a channel as it were of infective spread which needs to be avoided.

Speed and ease of use balance against this, and the option some specialists include is the use of tower technique with needles to build up pyramids of filler to minimize the injection points required. The claim for precise buttressing using these constructions does indeed compete for the exact elevation of superficial depressions and the precise elimination of unsightly contours.

Injectors following this plan have often used epinephrine in the injection to reduce bruising by vaso constricting the impacted blood supply. As a non medic this should not be used as it is POM – increasing the risk of side effects.

The very slow injection of the needle can allow tissue to part rather than be torn or cut in order to allow the procession of the needle tip.  When accompanied with a little lidocaine the needle insertion can appear as pain free as any cannula.

Where the superficial injection wins out is doing vermillion borders and the most delicate of fine lines around the lips it is normally because of the incredible precision required in location, volume, choice of weight, migration and proliferation of filler.

By contrast the wider diameter cannula can produce an incredible inflation effect for a whole area and seem the more logical choice.

Weighing up the advantages and disadvantages is by no means straight forward. Blunt tipped micro cannulas help the jawline because the smoother continuous length required is more easily delivered, so too for cheeks, large sections of lips and big brows. The relative depth of the cannula injection means that an underlying sculptural effect can be created, lifting from deep below the surface and creating a contour on the visible upper layer that does not betray the work done below.

For the description of needle injection positives we can create a kind of parallel world where everything is simple. But this is an improbably straight forward world compromised by hidden complexity: atomic weight, viscosity, cross linking, monophase short medium and long term water absorption and rate of expansion. So it is not actually that straightforward. And  to top it all, some simple physics, that with cross linked molecules of HA so large, the surface area  to weight ratio follows predictably bizarre logic, 1 cubic millimeter, has a surface area of 4, 2 cubic millimeters has a surface area of 6 not 8, 8 cubic millimeters has a surface area of 24 square mm  not 32 . so calculating the absorption rate and volume goes all over the place just when the calculations via maths or experience need to be more accurate than ever.

So, the enduring analysis is that when you scale the complexity of the manipulation of Cannula vs the simplicity of Needle you have to consider the precise outcome you require, and if you are prepared to expose yourself as a practitioner to the difficulty and raise yourself to the task then the cannula is 9 out of 10 as opposed to the needle 7 out of 10. But without the training and anatomical understanding required the cannula is not precise enough to simply be picked up by anyone trained below level 7 and score this highly.

Describing the complexity of the anatomy itself helps to explain this; with Cannula the art is to get the tip to precisely the right level and then deliver all the material at exactly the right place, neither above nor below, and make the calculation before hand as to exactly how long the withdraw and inject product phase will be to accommodate precisely the right amount to elevate, contour, mould, shape, fix, or prepare the clients face.

This complex process can become even more complicated with the addition of anti bruising strategies such as mixing lidocaine with the filler. With the increased confidence knowing that the process is pain free comes the possibility of slowing the whole placement down, squeezing even more slowly as the cannula moves through the three dimensional space appropriately, allowing the material product in itself to be solely responsible for minute pressures which can be seen and felt by the injector, providing more accurate feedback on the placement. This is when it really does feel like an art form, human sculpture in both senses of the word.

Calculating the speed of delivery actually helps us focus on the unconscious algorithm that our practitioners brain uses to sculpt, factoring in the filler product’s atomic weight, molecular size, cross linking scale, viscosity, the needle gauge and length, the tissue density and anatomical placement level, the water absorption factor and the swell consequences; all of these over time – seconds, hours, days weeks months, then to cap it all, the fade away effect.

The way that the blunt cannula tip processes the various types of tissues has been well discussed, and I plan another more academic article to further the discussion, but here I want to describe my experience of the tip pushing aside all the various features of the anatomy and physiology of the integumentary system rather than cutting them.

By way of indicating my experience I will start by detailing the way the blunt tipped cannula deals with blood vessels. Feeling the resistance that tissue puts up to the movement forward of the cannula is a way of measuring the relative friction of general and safe transport. From that average resistance you can then spot the additional burden of blood vessels ahead of the tip. By comparison with the pop of the needle piercing one or the tug of snagging one, the ‘push aside’ gives the momentary feeling of redirection, a bit like squeezing through a crowded room on the way to the bar, and then the very slight surge forward as the blood vessel obstacle is passed.

There is always to be taken into account the very slight increase in friction the further the length of the cannula goes into the tissue, and then as each additional blood vessel is passed a little extra lateral pressure is added to the cannula too, thus giving further resistance. This compares very favorably to piercing and damaging the vessel, as indicated in the stark graphic I wanted to include here but will have to wait until my next report when I will also comment upon the HEE reports assessment of high risk areas for needle such as the temple, where there is a danger of blinding. But needles are rarely used so wildly as to do this damage, and I for one have never made such a mistake, in years of needling. So the blunt tipped cannula needs to be judged on its own merits more pushing aside or snagging other features of the integumentary system such as sebaceous glands, sweat glands, hair follicles, hairs, and aspects of the anatomy and physiology of face; bone, muscle.