The dermal filler can be injected using different size needles or blunt cannulas. The choice of which is used depends on the area being treated, the desired effect and the experience of the person performing the procedure.
In general, a cannula is considered safer as it lacks the sharpness of the needle. There have been many reported incidents of complications (skin necrosis or vascular occlusion) when using needles as they can penetrate blood vessels easily. Despite this, as mentioned above, needles are better for precision volume augmentation.
Overall the risks can be drastically reduced by the performing clinician. The clinician can do steps such as administering the filler slowly as a continuous bolus in the supra-periosteal layer, and doing regular aspirations to check for vascular injury.
Benefits and disadvantages of cannula:
can monitor the plane where the filler is being delivered,
equal distribution of the filler in the same plane,
cannulas size 25G or less can still cause vascular trauma and embolisation,
lack of precision for fine touch-ups in the less experience hand.
Benefits and disadvantages of needle:
Good for contouring and fine adjustments
Easy to penetrate and manoeuvre within all tissue layers
Can cause vascular trauma
Higher risk to deliver embolus into a vessel
Delivers the filler in multiple tissue layers
Most injectors use cannulas for their proven safety advantages over needles. However, cannulas that are size 27G or smaller have the same sharpness as a needle, and therefore a similar risk of vascular damage and occlusion. Several studies have been done showing vascular trauma even with 25G cannulas and other studies have looked into the correlation between the cannula size and the force needed to penetrate a vessel. The later showed that small cannulas, 27G, needed less force to penetrate the vessels.
Cannulas have the advantage of allowing the practitioner to manoeuvre it through different anatomical layers. The depth can easily be checked by lifting the cannula and also the feedback to the clinician about how easily the cannula moves. Needles are good at achieving delivery of boluses in the desired planes when injected perpendicular to the bone, however, it can also distribute the product in multiple layers.
The use of either needle or cannula is still down to the individual’s preference. There are advantages to both methods and it often comes down to the training and skill of the injector and also the specific area that is being treated.
The Aesthetic Doctor is trained in both needles and cannulas and will discuss the indications for their uses at your consultation, depending on the area to be treated