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Injection savvy: Using anatomy to your advantage

Article-Injection savvy: Using anatomy to your advantage

Dr. Arthur Swift

Intravascular injections happen. But if you know your facial anatomy and attend to needle depth, it is possible to minimize these. That’s according to Arthur Swift, M.D., who presented an attentive audience with the intricate technical details of safe, effective facial injections at last year’s Cosmetic Bootcamp in Aspen. 

"If you understand the science behind the filler, know your injection anatomy and understand beauty and aging, you're going to use much less product than you have in the past," says Arthur Swift, M.D., a Montréal-based plastic surgeon. "This approach also maximizes results and minimizes intravascular issues. The face is teeming with blood vessels, so the idea of not piercing any one of them is ludicrous.  What is crucial is to make sure you are either above or behind the vessel and not inside it when you inject."

Related: Injection depth and botulium toxin for treatment of eyebrow asymmetry

In This Article:

Vital Anatomy

Anatomy of the Upper Face

The Temoral Region


Vital Anatomy

The shift from filling individual lines to performing deeper injections that contour and volumize requires injectors to exercise extreme caution, says Dr. Swift. "Whenever you're injecting under the skin, 'you're no longer in Kansas, Dorothy,' as I say. Now you're blindly encountering vital structures."

When an intravascular injection occurs, "As you put pressure on the plunger, you exceed systolic heart pressure — the product will disregard the direction of blood flow and seek the pathway of least resistance, which may be in a retrograde/proximal direction. Once you release the pressure on the syringe, the product will then flow with the blood antegrade. It is no longer where you've injected it, and it will flow forward clogging the distal arterioles." However, "If you skewer the vessel and inject behind it, you won’t deposit any product intravascularly —  it is intravascular embolization that causes the disastrous problems like visual loss."

When injecting near vital structures, "It is critical that you understand the depth of your needle tip. The anatomy in the face is too complex and varied to precisely know whether the artery is running slightly to the right or the left of where it is delineated in anatomy textbooks. But vessel depth in specific zones is fairly predictable, and if you appreciate the depth of your needle, you will minimize your risk of intravascular accidents."

In other words, said Dr. Swift, "I have coined the term injection anatomy to denote the study of regional anatomy as it relates to surface landmarks and the underlying depth of vital structures." He offers the example of an injection to the tear trough or nasal dorsum that cannulates the angular artery.

"If you catch the artery a little lower, say, towards the base of the nose, the product will most likely flow retrograde down the larger facial artery towards the mandible. When you release the pressure, the product flows antegrade with the blood and may actually embolize the inferior labial or superior labial artery. As a result, the threatened skin necrosis (livedo reticularis) is seen at the level of the lips, proximal to your injection point." If acted upon quickly, "This situation may be salvageable."

However, he says, "Injecting slightly higher into the angular artery or dorsal nasal artery may result in product flow in the other direction (towards the eye) if there is less resistance. Product then will flow backwards in the ophthalmic artery, and when you release the pressure, the central retinal artery may be embolized with resultant visual loss." Despite treatments including carbonic anhydrase inhibitors, hyperbaric oxygen and massive retrobulbar doses of hyaluronidase, says Dr. Swift, "We have not yet been able to reverse the blindness or ophthalmoplegia that may occur."

Anatomy of the Upper Face


Anatomy of the Upper Face

In the upper third of the face, he says, the supraorbital and supratrochlear arteries provide the main blood supply to the forehead. "It’s nice that we have surface landmarks or reference points, because we're not going to x-ray everybody to determine bony anatomy." With the patient looking forward, he suggests making a mark on the supraorbital rim that aligns with the medial iris. Beneath this mark, "You'll feel the supraorbital notch (when present). It's the most consistent finding in forehead anatomy, as studies have shown it to be within 1 mm of this point.  This is where the supraorbital artery will exit the skull as an extension of the ophthalmic artery inside the orbit."

Location of the supratrochlear artery is more variable, appearing 8 mm to 12 mm medial to the location of the supraorbital artery, Dr. Swift says. To find the supratrochlear artery, he recommends having the patient frown. "The most medial frown line overlies the supratrochlear artery as verified by Doppler studies. Interestingly, there is also literature that notes in 3 or 4% of patients, the supratrochlear artery emerging with the supraorbital through the supraorbital notch or foramen." The most medial frown line may have to be recreated by pushing with one's thumb in patients who have had neuromodulator treatments for glabellar frown lines, he adds.

Like the supraorbital artery, says Dr. Swift, the supratrochlear emerges from its deep location at the supraorbital rim to supply the skin, soft tissue, muscle and pericranium of the forehead. Both these vessels head north, branching in virtually any direction, he says.

"We have no clue of their exact path in the forehead other than their depth in specific zones. Within the first 1.5 cm, those arteries will perforate through the galea, which is the deep fascia on the undersurface of the frontalis muscle. They run cephalad either on the galea or inside the muscle, making their way to the muscle surface, to ride underneath the anterior frontalis fascia overlying the muscle.  Therefore, it would seem extremely hazardous to inject under the skin with a needle" within 1.5 cm vertical to the supraorbital rim in the region of these arteries.

Conversely, he says that the area that extends vertically cephalad from this zone, and horizontally to either temporal fusion line, is relatively avascular, as there are no vessels lying on bone, except for a small periosteal branch of the supratrochelar artery. "If you're going to inject for contour in the mid to upper forehead, you must stay on bone. The worst that could happen is that you might inadvertently skewer an artery and inject behind it, but the galea will protect the vessel and splay the product across the bone, which is exactly what we want.  This is using anatomy to disperse the product to your advantage."

Additionally, Dr. Swift cautions that the deep branch of the supraorbital nerve doesn't follow its superficial counterparts because it must supply the scalp and back of the head. "So it runs consistently 1 to 1.5 cm medial to the temporal fusion line, which you can feel. You don’t want to hurt the patient, so if you know the nerve is lying on periosteum in this area, and there is volume loss, insert the needle more medially and push the product laterally over the nerve."

The Temporal Region


The Temporal Region

In the temporal region, "The temporal fossa houses the temporalis muscle. As a muscle of mastication, superiorly it is stuck to the underlying bone in order to have a good purchase as it pulls up on the condyle of the mandible. It's more of a rudimentary muscle of mastication that was more necessary when we were swinging from trees because we had to bite for defense. You cannot inject under this muscle high up in the fossa because it is so adherent to the underlying bone."  Therefore, he says, injecting on bone one cm below the palpable temporal fusion line would actually mean injecting intramuscularly.

Regarding the vessels in this area, says Dr. Swift, the transverse frontal branch of the superficial temporal artery runs in the sleeves of the superficial temporal fascia on the deep temporal fascia (which is a continuation of the galea of the forehead), along with a plexus of veins.

Therefore, "My injection technique for temples is very simple — I inject 1 cm up from the lateral orbital rim and 1 cm lateral to the temporal fusion line, high up in the thinner fibers of the temporalis muscle. The depth here is maybe 4 mm before you hit bone. Again, you must make sure you are on bone — the worst that will happen is that you skewer an artery or vein that you couldn’t palpate. On the temporal bone in this region there are really no vessels of concern, as the terminations of the deep temporal arteries (anterior and posterior) are very small and more posterior."

He also advises keeping a finger above the injection point while injecting so that the product doesn't diffuse posteriorly under the hair-bearing scalp. "It's rare that I have to use more than 0.5 cc of appropriate product here —   I choose a higher G prime product, as it will try to lift and hit the undersurface of the deep temporal fascia, spreading between it and the muscle, creating a type of tent pole and overlying canopy. You can actually see the product flowing down towards the zygoma."

Dr. Swift reports no relevant disclosures.

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