Cannula or needle injection: what is the difference?

1. What is a cannula?

It is a thin, flexible tube with a rounded, closed tip, with an opening on the side near its end. A small needle prick creates an entry point in the skin; the cannula is inserted through it, then slid beneath the skin in a fan pattern to deposit the product over the whole area to be treated. Injection cannulas generally range from 14 to 27 G: the higher the number, the finer the cannula.

1. 1Fine, pointed needle: several injection points; injection possible into the epidermis, dermis or fatty tissue
2. 2Straight blunt-tipped cannula: a single entry point, the area treated in a fan pattern; injection possible only into the fatty tissue

2. Cannula or needle: the difference

	Fine needle	Blunt-tipped cannula
Tip	Pointed, cuts the tissues	Rounded, pushes the tissues apart
Injection points	Several per area	Only one per area
Depth	Epidermis, dermis or fatty tissue	Below the dermis: fatty tissue, against the bone
Bruising, swelling	More frequent	Less frequent
Risk of injecting into a blood vessel	Higher	Reduced, but not zero
Precision at the surface	High (fine lines, lip border)	Low

3. The advantages of the cannula

• comfort: a single entry point, and less pain in most areas;
• less bruising, swelling and redness, and therefore shorter social downtime;
• greater safety in high-risk areas, such as around the eyes: its rounded tip pushes blood vessels aside instead of piercing them, which reduces the risk of injecting into a vessel;
• even distribution of the product over a large area.

Choosing a qualified, experienced and reputable surgeon reduces these risks, and in some cases eliminates them.

4. The limitations of the cannula

• it cannot inject within the thickness of the dermis: it is not suitable for fine lines or for defining the lip border;
• it can be more uncomfortable than the needle in certain areas, such as the lips or marionette lines, and some patients prefer the feel of the needle;
• being flexible, it passes poorly through certain deep membranes, such as the one covering the temporal muscle; a more rigid cannula or the needle is then used.

5. Areas where the cannula is often preferred

• the jawline and jaw: with two entry points, the whole length of the jaw can be treated, to redefine the jawline or accentuate the angle;
• tear troughs: a single entry point on the cheekbone, and the gel is placed deep, against the bone, which limits bruising and the risk of injecting into a vessel;
• the temples;
• the cheekbones: a large area treated from a single entry point;
• the cheeks: the product is spread in thin layers, as for a skin booster;
• the backs of the hands.

The needle is still often preferred for the lip border and lip volume, marionette lines, fine lines, the nose and anchor points against the bone.

6. How does a cannula injection session go?

At the practice, in about 15 minutes: disinfection, anaesthetic cream and cold or local anaesthesia, a small prick for the entry point, then injection with the cannula and massage. You can resume your activities immediately. A small bruise at the entry point is possible.

7. What about fat injections?

Fat is also reinjected with a cannula, in thin layers: this is the principle of microlipostructure (micro fat grafting), which uses miniaturised cannulas.

See also: hyaluronic acid injections.

Frequently asked questions