Learning the inherent facial filler ‘danger zones’ can increase safety and effectiveness of facial filler procedures.

With no downtime and immediate results, facial filler injections are becoming an ever-more popular alternative to surgical rejuvenation of the face. According to ASAPS statistics in the US, around 750,000 hyaluronic acid filler procedures were performed in 2019.

However, serious complications have been reported, occurring especially with inadvertent injection blood vessel damage or injection of filler material into the blood vessels. Given the current trends, it becomes important that safe, predictable techniques are practiced in order to achieve optimal results.

In the paper ‘Maximizing Safety During Soft-tissue Filler Injections’ published in Plastic and Reconstructive Surgery January 2017 by US plastic surgeon Dr Rod J. Rohrich et al, the importance of anatomically based techniques are discussed to help minimise risks and complications in specific areas of the face, while maximising the safety of injection.

The paper found specific principles for safe filler injection, including staying clear of key danger zones, and using hyaluronic acid fillers when possible. In addition to this, the use of continuous motion and gentle injection techniques are said to increase the safety profile of injection.

General principles

Despite familiarity with injections, even the most experienced practitioners can have adverse events and poor aesthetic outcomes.

Injecting slowly with low pressure and in small increments allows more controlled injections eg, using small syringes (0.5 to 1cc). In high-risk areas, the authors suggest injecting anterograde and retrograde in constant motion using a serial puncture technique. Blunt or small-bore needles help stay in the desired plane.

Epinephrine can be used in combination with filler injections to stimulate vasoconstriction, effectively reducing the size of vessels and bruising. The authors note it is also important to use extreme caution when injecting in a previously traumatised area. The tissue planes may be scarred and the anatomy altered. Consider using dermal fillers with a low ‘G’ in high-risk areas when trying to diminish fine wrinkles.

These more effectively fill wrinkles as opposed to improving folds through volume enhancement.

Results of filler injections can be long lasting. The paper recommends that practitioners use hyaluronic acid fillers because they can be reversed with hyaluronidase.

Maximising safety in the danger zones

Knowledge of the facial anatomy is essential to a safe and effective injection. As evidenced by numerous studies, the facial vasculature has many variations and can be found in various tissue planes, depending on location within the face. Anticipating the depth and course of vessels allows practitioners to develop techniques to avoid intravascular injection, vascular injury, and/or compression, the authors note.

With a thorough knowledge of the depth and the location of the vasculature within each zone, practitioners can tailor their injection techniques to prevent vessel injury and avoid cannulation.

Specifically, the six danger zones are the glabellar area, temporal region, lip and perioral area, nasolabial fold area, nasal area and the infraorbital area.

Brow and glabella area

In the brow and glabella area, the vasculature is initially deep, quickly transitioning to the intramuscular and subcutaneous level. Therefore, the authors recommended using a low-G filler injected intradermally to fill glabellar frown lines and bunny lines.

Apply digital pressure at the supraorbital rim during injection to occlude vessels. Intravascular injection at this level can travel retrograde through the anastomoses between the supraorbital, supratrochlear and ophthalmic arteries, leading to blindness and tissue loss. In multiple reviews, the glabella was the most common filler injection site leading to visual loss.

Temporal region

In the temporal region, fillers should be injected deeply or superficially. Deep filler injections in the temporal fossa should be in the preperiosteal plane. They should be injected within a fingerbreadth of the arch and/or greater than 25mm above it to avoid the middle temporal vein. In the preperiosteal plane, a high-G filler in greater amounts will be needed to translate results superficially.

It is recommended to inject filler in the superficial subcutaneous tissue, staying just below the dermis while applying pressure just superior to the peak of the brow. The frontal branch of the superficial temporal artery runs one layer deeper in the temporoparietal fascia and therefore is at less risk.

As the artery approaches the temporal fusion line, it transitions to the subcutaneous plane. Embolic phenomena occur when the cannulated artery propagates filler into the supraorbital system, or filler travels retrograde into the main superficial temporal artery system.

Either can lead to blindness. The authors caution against injecting at intermediate depths because it becomes nearly impossible to discern which layer is being injected.

Infraorbital region

When injecting deep into the midface, it is essential to be aware of the exact measurements to avoid intravascular cannulation or vascular injury.

Generally, the infraorbital foramen will be located approximately one-third of the distance between the medial and lateral canthi up to 11mm below the infraorbital rim.

Clinically, the infraorbital foramen lies slightly less than a fingerbreadth below the infraorbital rim in the vertical plane of the medial limbus, or immediately lateral to it.

It is recommended to avoid direct deep injections into this area, choosing to inject just lateral.

Injections more medial approaching the medial canthus should be avoided completely. If filler is needed in this area, it can be injected laterally and pushed medially.

Lips/Commissure

Injections into the upper lip should be less than 3mm deep, with an intermediate or low-G filler either at the vermillion cutaneous border or within the dry vermillion. The superior labial artery is typically posterior at the mucosal-muscular interface and several millimeters above the inferior border of the lip. Intravascular injection can lead to tissue necrosis.

Because the facial artery and the origin of the superior labial artery generally lie deep to or within the muscle, superficial subcutaneous injections in a linear crosshatching fashion safely addresses volume deficiency and laxity in this area.

Lower lip injections should be with an intermediate- or low-G filler either at the vermillion cutaneous border or within the dry vermillion, no greater than 3mm deep. The inferior labial artery is typically posterior at the mucosal-muscular interface and below the superior border of the lip. Intravascular injection in the area leads to tissue necrosis.

Nasolabial fold

In the lower two-thirds of the nasolabial fold, injections into the deep dermal and superficial subcutaneous plane are generally safe because most of the facial artery course lies beneath muscle and/or above it but in deeper planes; however, in the upper one-third, the artery can become very superficial. Near the alar base, the authors recommend injecting either intradermally or in the preperiosteal plane.

DESPITE PUBLISHED DESCRIPTIONS OF THE FACIAL VASCULATURE, THE ANATOMY CAN BE QUITE VARIABLE

Subcutaneous injections in this area can lead to alar and cheek necrosis if the facial artery or its branches are cannulated or injured. This is also a pathway for ocular embolism through propagation in the angular artery and its anastomoses with dorsal nasal branches.

In one review, the nasolabial fold was the second most common injection site leading to tissue necrosis, and, in another study, the third most common site leading to visual loss.

Nose

Given the shallow nature of the vasculature located within the nose, a misplaced injection can lead to disastrous results. Superficial injections compressing or injuring the superficial vasculature in the tip and alar facial groove can lead to tip and alar necrosis, respectively.

Likewise, given the tip, dorsal, and sidewall vessel anastomoses with the ophthalmic artery, intravascular injections in these areas can cause retrograde propagation of filler, leading to ocular ischemia and blindness.

Therefore, all lateral injections should be greater than 3mm above the alar groove and deep.

Injections to the tip and dorsum should be deep in the preperichondrial and preperiosteal planes. In several reviews analysing facial danger zones, nasal filler injections were documented as the leading cause of tissue necrosis and the second leading cause of visual loss after the glabella, the authors note.

Importance of anatomically based techniques

Facial filler injections continue to grow in popularity, however their complications can be even more impressive than their aesthetic results.

Having a thorough knowledge of the pertinent anatomy and knowing the six danger zones of the face means practitioners can tailor their injection techniques to maximise safety.

Despite detailed published descriptions of the facial vasculature, the anatomy can be quite variable, and vascular injuries can occur even after the best precautions are taken.

Likewise, actual needle depth can be difficult to track and at times unpredictable. Most importantly, practitioners need to recognise complications in a timely manner and take the appropriate measures to minimise what can be a devastating result. AMP