Non-surgical youth restoration is becoming more and more popular among men and women who wish to revert the signs of ageing without operative procedures and with minimal downtime. Facial aging occurs due to loss of volume of the facial fat compartments and bony skeleton degeneration. The application of dermal fillers and neurotoxins can significantly restore facial appearance. Despite being relatively simple and straightforward when done by a fully qualified practitioner, the procedure is still associated with significant complications such as Tyndall effect, necrosis, blindness or even stroke (DeLorenzi, 2013; King, 2016; Ansari et al, 2018).

Safety versus sharpness

Injecting the dermal filler can be done using different size needles or blunt cannulas, depending on the area treated, the desired effect and the experience of the person performing the procedure.

Generally, cannula is considered safer as it lacks the sharpness of the needle. There are many reported incidents of skin necrosis or vascular occlusion when using needles, as they can penetrate the vessel easily (Jewell, 2018). However, it still has its area of application, especially when precision in volume augmentation is needed. In these situations, the sharp needle has created an advantage over the cannula. It can be appreciated that the needle acts like a microscalpel, and the risk of vascular penetration, vascular occlusion, bleeding and haematoma, nerve or muscle injury, periosteal microtrauma, etc, is much higher. Taking this into consideration, the needle can still be used effectively for filler delivery, injecting the product as a slow, continuous bolus in the supra-periosteal layer and doing regular aspirations to check for vascular injury.

The risk of cannulas

Though most injectors use cannulas as they are proven to be safer, experience shows that cannulas that are size 27G or smaller have the same sharpness as a needle, hence the increased risk of intra-arterial delivery of filler. There are studies describing vascular trauma caused even by 25G cannulas when the axis of injection is perpendicular to the arterial wall; there is also a significant correlation between the cannula size and the force needed to penetrate a vessel with smaller cannulas, 27G, needing less force to penetrate the vessel (Tansatit, 2017; Ugradar and Hoenig, 2019).

An ideal method

In view of the aforementioned, this raises the question of which is the ideal method for filler delivery and whether one is superior to the other. In the authors’ view, both methods have their benefits depending on the specific area of application. Using non-traumatic cannula for dermal filler placement is considered safer and less painful; it creates a layer of product confined to the deep anatomical layers, which is the effect sought after when we want to achieve lifting effect, deep volumetric augmentation and panfacial rejuvenation. The blunt tip of the cannula allows the practitioner to manoeuvre it through different anatomical layers -subdermal, subcutaneous, submuscular and supraperiosteal - by lifting the cannula during insertion. The position of the cannula can be checked by lifting the cannula after insertion: the subcutaneous layer will allow lifting of the cannula and observing its definition. The subcutaneous layer allows lifting of the cannula, but definition is not seen. When in the submuscular layer, the cannula cannot lift as the movements are very much retained. When in the supraperiosteal layer, the cannula slides easily due to its intimate contact with the bone. The sharp needle technique can achieve delivery of boluses of filler in the desired planes when done via injections perpendicular to the bone; however, it can distribute the product in multiple layers, and we can even observe retrograde migration of the filler (van Loghem et al, 2018).

Benefits and disadvantages of cannula

There are several benefits and disadvantages to using cannula, including:
• Safer
• Less pain
• Less bruising
• Can monitor the plane where the filler is being delivered
• Equal distribution of filler in the same plane
• Cannulas size 25G or less can still cause vascular trauma and embolization
• Lack precision for fine touch-ups in the less experienced hand

Benefits and disadvantages of needle

There are several benefits and disadvantages to using a needle, including:
• 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
• More painful
• Delivers the filler in multiple tissue layers (periosteum, muscle, fascia, dermis).

Conclusion

Facial restoration by dermal fillers can be done using both blunt tip cannula technique or conventional needles, especially when done by experienced medical personnel. However, in the authors’ opinion, using a cannula is the better method as it is safer, less painful, causes less bruising and there is significantly less potential to penetrate blood vessels and cause vascular occlusion. We are mindful that these thinner cannulas that are size 25G and less can behave as needles and cause vascular embolization and tissue necrosis.

References
1. Ansari ZA, Choi CJ, Rong AJ, Erickson BP, Tse DT. Ocular and cerebral infarction from periocular filler injection. Orbit. 2018;38(4):322-324. https://doi.org/10.1080/0 1676830.2018.1537287
2. DeLorenzi C. Complications of injectable fillers, part I. Aesthet Surg J. 2013; 33(4):561-575
3. Jewell M. Commentary on: cannula vs sharp needle for placement of soft tissue fillers: an observational cadaver study. Aesthet Surg J. 2018; 38(1) 89-91. https://doi.org/10.1093/asj/sjx223
4. King M. Management of Tyndall effect. J Clin Aesthet Dermatol. 2016; 9(11):E6-E8
5. Tansatit T, Apinuntrum P, Phetudom T. The dark side of the cannula injections: how arterial wall perforations and emboli occur. Aesthetic Plastic Surg. 2017; 41(1):221-227. https://doi.org/10.1007/s00266-016-0725-7
6. Ugradar S, Hoenig J. Measurement of the force required by blunt-tipped microcannulas to perforate the facial artery. Ophthalmic Plast Reconstr Surg. 2019; 35(5):444–446. https://doi.org/10.1097/IOP.0000000000001302
7. van Loghem JAJ, Humzah D, Kerscher M. Cannula versus sharp needle for placement of soft tissue fillers: an observational cadaver study. Aesthet Surg J. 2018; 38(1): 73-88. https://doi.org/10.1093/asj/sjw220