PEER-REVIEW | INJECTABLES | liposuction (non-disposable) metallic8 cannulas which


required sterilisation before re-use. However, particular care must be taken to carefully monitor the process to insure there is no risk of disease transmission. Hence, now that disposable microcannulas are affordable and available, the author’s preferred choice is to always use disposable microcannulas rather than to sterilise.


of a metallic cannula with that of a standard needle for


soft tissue augmentation of the nasolabial folds. Hexel concluded cannula were safe and useful to inject hyaluronic acid fillers into nasolabial folds with less pain, oedema, haematoma, and redness than needles. In 2012, Lazzeri et al11


, surveyed a total of 32 cases in


29 articles on permanent blindness from cosmetic filler injections. There were 15 cases after adipose injections and 17 non-adipose cases using corticosteroids, paraffin, silicone oil, collagen, polymethylmethacrylate, hyaluronic acid, and calcium hydroxyapatite. Lazzeri’s prevention recommendation:


use


microcannulas. While it is incontrovertible that


blunt-tip microcannulas are thought to be less likely to penetrate blood vessels12


tipped hypodermic needles, substantiating research is lacking13


. Of


course, even a blunt tip does not insure that one cannot penetrate any tissue — if one is forceful and aggressive enough — but safer tools are instrumental in producing better results. Nevertheless, a consensus is growing for the use of microcannula over the hypodermic needle14, 15 Early pioneers used readily available larger gauge


. and other tissue than sharp-


Figure 1 (A) The blunt tip microcannula, (B) TSK by Air-Tite microcannula with port at end of tapered blunt end tip


Selection of pilot The microcannula, being blunt tipped, is specifically designed to not penetrate tissue readily so a ‘pilot’ or introducer needle is necessary to create the opening through the skin. Of course, the larger the opening the easier it is to insert the microcannula, but correspondingly, the greater trauma results in more pain, bruising, and swelling. On the other hand, the smaller the opening, the more difficult it is to insert the microcannula which can result in significant pain upon repeated attempts and failures at entry. Consequently, the ideal selection is dependent upon the dexterity of the individual injector to choose the smallest pilot needle which rarely requires re-entry. The author’s choice is a 23 gauge ½” pilot needle for the 27 gauge standard diameters of both Juvederm® and Restylane.


While it is incontrovertible


that blunt-tip microcannulas are thought to be less likely to penetrate blood vessels and


other tissue than sharp-tipped hypodermic needles,


substantiating research is lacking.


Insertion of pilot The author prefers to insert the pilot needle at a 30º to 45º angle quickly into the superficial subcutaneous tissue in the direction the author wishes the microcannula to travel. Insertion too superficially will not penetrate the skin adequately and create difficulty in traversing the entry for the microcannula. Again, it is more painful to repeatedly attempt to place the microcannula through too shallow or tiny a pilot hole, rather than to just inject once with a hypodermic needle. Insertion too deeply will cause unnecessary trauma to tissue and may precipitate the very bruising the injector wishes to avoid. Leave the needle in place a few seconds to allow for haemostasis and enough time for the needle to create a transitory channel through tissue to ease entry.


Figure 2 Pilot needle placement for Juvederm® lip enhancement


Selection of disposable microcannula The differences between microcannulas are substantial in that some disposable microcannulas are so flexible, you cannot place cosmetic filler precisely where desired, and others are so rigid, you increase the likelihood of penetrating blood vessels as well as increasing the resulting pain. More importantly, the tip of the microcannula is vital to your ability to perform a smooth entry, in that a tapered tip is easier to place than one which is rounded and blunt. The other point to make is that the tip is best tapered for easier entry, but not too pointed that it facilitates entry into blood vessels or is at risk for breakage if weakened structurally. In the author’s practice, a tip break has never occurred from any reputable brand after thousands of uses over the years. The other critical issue in the differentiation of


26 ❚


microcannulas is the placement of the extrusion port or opening at the end of the microcannula. Ideally, the


January/February 2015 | prime-journal.com


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