Cannulas, specifically, blunt microcannulas, can be used to administer fillers by advanced injectors. They a favorable over needles because they have a blunt round tip and are flexible, leading to the following advantages:
- Less discomfort – one entry point can serve a large area, thus avoiding multiple dermal penetrations which is more uncomfortable.
- Less bruising – the rounded/blunt tip tends to bend around blood vessels rather than nick or penetrate them.
- More accurate – a recent study shows that the filler is most likely to be deposited in the area of the exit port vs a needle which has been shown to have filler travel up the shaft (back flow)
- Safer – cannulas are less likely to give intraluminal vessel injections because of the blunt tip and therefor less possibilities of vascular compromise and blindness.
However, a recent publication by Drs Pavicic, Cotofana et al. has shown that #4 comes into question with certain cannulas. There study consisted of a total of 294 penetrations of the superficial temporal artery in cadavers using 22, 25, and 27 gauge cannulas and needles. The force applied to enter the vessel was measured for each. The cannulas had statistically higher forces needed to enter the vessel for the 22 and 25 gauge cannulas.
Interestingly, there was no difference in the forces when comparing 27g cannulas and needles.
The conclusion was that a 27g cannula was not safer than a 27g needle when used for filler injections. While 27g cannulas can be used, it is up to the injector to realize these are not safer than needles and to take the appropriate safety measures during treatments.
Source: Dr. Steve Weiner, Facial Plastic Surgeon Blog