Understanding Facial Danger Zones: A Probabilistic Approach

Guide to Safe Injecting

One of the worst things you can be taught as an injector is that anatomy is so variable that you can’t predict where anything is. This is a terrible belief. If anatomy was that variable, humans wouldn’t even look like other humans to each other.

The truth is we are all pretty similar inside with some occasional variations. We need to think probabilistically – where is the likely position of the artery or the foramen, for example? Not where has it been on some rare cadaver, because that doesn’t really help you. We need to focus on useful information that over a career decreases risk.

The Power of Understanding Depth and Position

Understanding how depth and position changes risk allows you to use this knowledge in conjunction with other safety methods like checking for pulses, ultrasound, surface anatomy, aspirating, and choosing cannula or needle in the right positions. All other safety measures still apply, but let’s start by understanding the probable risk with injecting in different parts of the face.

Here’s a helpful approach: ask yourself, “What would be the most dangerous way I could possibly inject?” Because you can always do the exact opposite of that and avoid that danger.

The Most Dangerous Areas of the Face

Let’s start with the most dangerous parts of the face, because we’re concerned not just about the vessel in the area, but where the vessel comes from and therefore the other structures that are involved.

The Supratrochlear Artery Zone

The most dangerous area would be anything to do with the brain or the eye. The supratrochlear artery comes from the back of the eye. It’s also connected to the ophthalmic artery and therefore to your brain. Blocking this artery is catastrophic, and deep injections on the bone here are most likely to cause problems.

The Supraorbital Artery

The next artery along is the supraorbital artery, which also emerges from the same place, so it has the same risks, but it’s a smaller artery. Deep injections on the bone here would be the most risky place to inject.

The Infraorbital Artery

The infraorbital artery runs through the maxilla, becoming the maxillary artery. The maxillary artery supplies the midface. A blockage to the maxillary artery would cause a nasopharynx or soft palate necrotic injury, as well as the superficial injury to the cheek that we all expect. Never inject deeply with a needle near this foramen.

The Mental Foramen

The next foramen to be aware of is the mental foramen where the mental artery emerges. An occlusion to the mental artery can cause an occlusion to the chin and the lip, but deeper still, if it was to get into the alveolar artery, you may affect the teeth. While complications like this are rare, a deep injection here is still likely to affect the mental artery.

The Facial Artery

The biggest artery of the face is the facial artery, and the most likely place to find it is deep near the mandibular notch. So the worst injection you could do would be a high volume deep injection right on the mandibular notch. When injecting around the jawline, it’s often safer to use a cannula when passing this area and to be more superficial in the fat.

The Hidden Danger: Parallel Artery Injections

Now that you understand the deep danger points, there’s another type of danger that’s down to injection technique – the parallel arteries. There are many parts of the face where we tend to want to be parallel to an artery that lies underneath.

The Nose: Highest Risk for Parallel Injection

The best example with the highest risk is using a cannula to inject the nose. The dorsal nasal arteries tend to run just lateral to the dorsum of the nose, but they’re parallel with the angle of entry used by many injectors.

When you are parallel with an artery, it’s far easier to cannulate that structure, slide inside the vessel, and then when you inject, virtually all the product will flow up towards the eye and the brain. This is why it’s a particularly dangerous injection.

To avoid this, you can:

• Use needle injections
• Use periosteal injections
• Use a cannula in a safer way with lots of movement
• Validate that you’re not inside a vessel
• Aspirate
• Use ultrasound
• Compress the vessel while you inject

All of these safety steps chip away slightly at the risk.

The Nasolabial Fold

Another rare but possible side effect is caused by a parallel injection near the facial artery, even with a cannula. Needles or cannulas that run up parallel to the facial artery, usually when treating the nasolabial fold, have a higher risk of getting inside the artery.

This is one reason why the deep periosteal injection used by so many injectors became so popular – because at least it’s deep underneath the artery and you’re not injecting in a way that’s likely to cannulate. In theory, the worst-case scenario in most cases would be that you’d impale the artery rather than cannulate it, meaning filler still passes out underneath the artery and not inside it.

The Lips: Most Common Occlusion Site

The lips are probably the most common place to get a vascular occlusion. The reason for this is that underneath the orbicularis oris is exactly where the artery tends to reside. The superficial labial artery just underneath the orbicularis oris is parallel with the insertion point of a needle.

The biggest defense against this is to get your depth accurate. New injectors often don’t have the same resolution as experienced injectors. We’re thinking in terms of millimeters of depth here. If you understand depth, you should be able to place your needle relatively safely. But if you’re two to three millimeters deeper than you think you are, you might be right inside the vessel.

One simple way to validate this is always to do a depth check and aspirate before every injection. If you cannot see clearly the shape of your needle, then you might be too deep and you could be in a vessel.

The Columella: Deep Parallel Risk

A less common way to inject parallel to an artery is when trying to lift the tip of a nose. Many injectors are trained to inject from the tip of the nose all the way down to touch the maxilla and then inject up and lift the tip of the nose. It’s actually a really effective injection, but it is a bit dangerous.

A deep injection down the columella ends up being parallel with the columella artery. Although occlusions in this area from this particular injection are rare, it makes intuitive sense that high volumes in one injection are more likely to cause a blockage than if you separate them out into smaller injections, smaller volumes, and also going deeper. This artery runs at an intermediate depth – it’s above a layer of fat, which is above the cartilage and underneath the dermis.

The Forehead: Superficial Parallel Risk

The supratrochlear artery in the forehead tends to run superficially just underneath the crease that you can treat with dermal filler. Many patients who frown for long enough get a frown line so deep that you need a little bit of filler to unfold it.

If you are superficial and you do small volumes at a time, this can be safe enough, but we must consider that you are parallel with an artery that runs underneath. Ways to make yourself safer:

• Block the foramen while you’re injecting, so at least it’s only the superficial blood supply at risk
• Make sure you do a depth check and aspirate before each injection
• Be very superficial without being above the dermis (which would leave a line of filler)
• Use the right product – a very soft product in low volumes

Pressure Necrosis: A Different Type of Danger

The next danger to be aware of has nothing to do with large named blood vessels. It’s everything to do with capillaries getting squashed by high-pressure injections. This causes a form of necrosis that’s much more like a pressure sore than a vascular occlusion – it’s capillaries being occluded rather than larger vessels.

This seems to happen mostly in the midface: the glabella, the tip of the nose, and the chin. All these areas seem to have relatively thick dermis or very little potential space to allow filler to project the structure.

Preventing Pressure Necrosis

The easiest way to avoid causing this problem is to check how much space there is before you inject.

• The Tip of the Nose: If you squeeze the tip of the nose before you inject, you’ll get an idea about how much potential space there is in the structure. Very firm noses don’t create much space between the cartilage and the surface of the skin. There just isn’t room to expand the tissue without causing higher pressure.
• The Chin: You’ll find most patients’ chin tissue feels quite soft and it’s easy to imagine it expanding away from the bone and leaving a better-shaped chin. Whereas in some patients, you’ll try to squeeze and it simply will not move – it’s really tightly adhered. If you ignore this and inject a large amount of volume, you’ll find that the pressure in the chin can be so high that you get superficial blanching. One weird side effect from this is the loss of hair – in some men, you can lose part of your beard if you over-project a chin. The worst-case scenario is the skin itself doesn’t get blood supply and you get a superficial ulcerating type wound that can take several weeks to recover and may leave a permanent scar in rare situations.
• The Glabella: This is probably the area that’s most sensitive. Always check your filler – many fillers will say contraindicated in the glabella. This comes mainly from the pressure necrosis risk rather than occlusion of the supratrochlear artery. The tissue here is very thick, and if you inject directly into it with a firm filler, it causes blanching that may never stop. You have a white line that eventually turns to a black line as the tissue dies. The cure for this is to use very soft fillers in low volumes, which is typically all you need when treating a crease.

Turning Knowledge Into Confidence

If you made it to the end of this article and you’re thinking too much about complications and the worst that can happen, stop for a second. This information is all about helping you make decisions to reduce risk, therefore making you safer and more confident. You now have information that will help guide decisions that reduce risk.

Everything discussed here comes from years of experience. Many experienced practitioners will never have a single patient with a necrotic wound and will only rarely have vascular occlusions. If you take this information on board and use it, you should also become a more confident injector.

All you need to do is use the information rather than just focusing on the worst fear. Understanding these danger zones and how to navigate them safely is what separates nervous beginners from confident, safe practitioners.

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