When administering a hyaluronic acid injection, the choice of product and the area to be treated are essential. But another, less obvious factor also plays an important role: the instrument used to perform the injection.

The doctor may use either a needle or a blunt-tipped cannula. These two instruments are not mutually exclusive: they have different characteristics and are often complementary.

The choice depends, in particular, on the anatomical area, the injection site, the product used, the desired result, and the practitioner’s experience.

From the Needle to the Cannula: A Brief History

Historically, the needle has been the standard instrument used for medical injections. Thin, rigid, and featuring a sharp bevel, it allows for direct penetration of the skin and the precise delivery of a substance.

With the development of dermal fillers—particularly hyaluronic acid—techniques have gradually evolved.

Microcanules with a blunt tip have thus become increasingly common in aesthetic medicine. Unlike a needle, their tip is generally not designed to pierce the skin directly. A small entry point, or “pre-puncture,” is first created using a needle, and then the cannula is inserted through it.

Depending on the model, the cannula—which may be flexible or semi-rigid—can then be advanced through the tissue, allowing a relatively large area to be treated from a limited number of entry points.

Both needles and cannulas are defined by their gauge (G)—an Anglo-Saxon unit that is inversely proportional and associated with an international color code—as well as by their length in millimeters (mm).

Today, both needles and cannulas are part of the injecting physician’s toolkit.

When is a needle used?

A needle is particularly useful when high precision in placement is required.

In particular, it allows for highly localized injections, the delivery of small amounts of product, or precise targeting of specific anatomical planes.

Depending on the indication and the technique chosen by the physician, it can, for example, be used in the periosteal layer for a precise bolus injection at lift points, in the intramuscular layer for botulinum toxin, in the subcutaneous layer for dermal fillers, or in the intradermal layer using the “blanching” technique to fill superficial fine lines.

Its advantages

The needle offers excellent precision and direct control over the injection site. It also allows for the use of various techniques: bolus, microdeposits, linear injections, or multiple punctures.

Its rigidity allows the practitioner to precisely control the direction and depth of the injection.

Its disadvantages

Because the tip of the needle is sharp, it passes through tissue and may puncture small blood vessels.

When multiple injection sites are needed, there may therefore be more skin marks, minor bleeding, or bruises.

When is a cannula used?

A cannula is distinguished primarily by its rounded, non-sharp tip. The medication is usually delivered through an opening located near its tip.

It is particularly well-suited for techniques that require distributing the product over a larger area or performing retrograde injections from a single entry point, using the technique known as “fanning.”

Depending on the anatomy and the indication, it can be used, for example, for certain supraperiosteal injections in the cheeks to achieve a lifting effect, interfascial injections in the temples to provide volume, or subcutaneous injections along the jawline to redefine it.

Its advantages

One of its main advantages is the ability to treat multiple areas using a small number of entry points.

Its foam tip also tends to push aside certain structures rather than passing directly through them. In some situations, this can reduce tissue trauma and the incidence of bruising.

The cannula is therefore particularly useful when you want to distribute a product evenly over a relatively large area.

Its disadvantages

A cannula is not always preferable to a needle.

Its flexibility can make certain very precise maneuvers more difficult. It may also require more manipulation within the tissues and is not equally suitable for all depths, all anatomical areas, or all products.

Is a cannula safer than a needle?

It is important to distinguish between the risk of a simple bruise and the much rarer but potentially serious vascular complications associated with dermal filler injections.

The foam tip on some cannulas may reduce the likelihood of directly entering a blood vessel under certain conditions, but no instrument can completely eliminate the risk of intravascular injection or vascular complications.

Safety therefore depends above all on a precise understanding of anatomy, the choice of injection site and equipment, technique, careful execution—injecting small amounts slowly—and the practitioner’s ability to quickly recognize and manage any complications. These principles form the basis of the SAMBA wheel guidelines.

So, needle or cannula?

There is no one-size-fits-all answer.

A needle often allows for greater precision; a cannula often makes it easier to distribute the product over a larger area with fewer entry points.

In many treatments, the doctor may, in fact, use both during the same session. The choice should therefore not be based on a systematic preference for one instrument over the other, but rather on the patient’s anatomy, the indication, the product being injected, and the technique best suited to each area.