We all know what a needle is — a small tube with a point at one end and an opening at both ends for delivery of a medication or a filler. We are not talking about sewing needles here. A cannula is also a tube designed to either inject a substance or remove a substance like fat with liposuction.
This discussion is to compare medical needles with micro-cannulas (very small cannulas). Both can be purchased at the same diameter and even length. A cannula has a blunt tip compared to a needle. How does the medication come out of the end since the tip is somewhat round?
A cannula has a hole or holes near the end, but at the side of the cannula near the tip, instead of at the very end like needle.
What are the advantages of one verses the other?
A needle sharply penetrates skin and any soft tissue such as fat, muscle, arteries, veins, and nerves. When it penetrates arteries or veins, it causes bleeding and bruising, which can take days or weeks to subside.
A cannula cannot penetrate skin, so the hole must first be made with a needle and the cannula can be inserted into the hole made by the needle. A cannula is dull, so it must be pushed much harder than a needle to penetrate to the desired area. However, since arteries, veins, and nerve are more elastic then veins, the cannula pushes them aside without penetration – in most cases.
My experience with the micro-cannulas is with injecting fillers, such as Restylane, Juvederm , Artefill, and Sculptra into depressed areas in he face.
Which one causes less discomfort is according to each individual patient. Some say the needle and others say the cannula, but the bruising is definitely much less with a cannula. This has been very important when injecting around the eyes. No one wants black eyes when visiting the plastic surgeon, and injecting into the hollow under the lower lid is a very common procedure in my office.
Another common location for using cannulas is when injecting the lips. The injections are smoother and leave no bruising or “fat lip.”
When someone is on anti-coagulants, the cannulas should be used when possible. The cannula that I have the most experience with is the DermaSculpt Micro-cannula.
So, there you have it. I like micro-cannulas for certain indications and will continue using them
in the future.
E. Ronald Finger, MD, FACS
