BY LAKHDAR BELHAOUARI
Proposing a new vertical classification system, Lakhdar Belhaouari, Pierre Quinodoz, Camille Belhaouari, and Ignacio Garrido describe their injection techniques for…
Proposing a new vertical classification system, Lakhdar Belhaouari, Pierre Quinodoz, Camille Belhaouari, and Ignacio Garrido describe their injection techniques for rejuvenating the facial contour
The symmetrical symbol of beauty and youth, the oval of the face is more than just a detail. Loss of this ‘oval’ can be a distressing experience. Few people are insensitive to the passing of time, the first sign of which can be noticeable facial slackening. Improvement and rejuvenation of the facial contour is a daily request in our aesthetic clinics, either through surgical or non‑surgical means. In order to offer the best advice, a sound understanding of the anatomy and physiology of the ageing process, mastery of the required techniques, and knowledge of the latest products are essential. As a result of our experience and to aid amelioration of the facial contour, an original classification of this zone of the face will be proposed.
Relevant anatomical and physiological considerations
Classically, the cervicofacial area is divided into the upper, middle, and lower face, with the upper part of the neck often included in the lower face. Here we present a different approach not using horizontal divisions, but vertical. We have divided the face into three vertical segments from medial to lateral: the proface, the mesoface, and the metaface (Figure 1). This original method of segmentation accounts for the sliding planes of the face, movement dynamics and time-related changes (Figure 2–3), especially useful for the mid and lower floor of the face.
The mesoface
The intermediate part of the face is the main subject of this article.
Its subcutaneous tissue varies in thickness but is firmly attached to the covering skin. In contrast, it adheres little to the deeper layers that it covers. The mesoface is mobile and expressive and is thus susceptible to slackening, or ptosis, with time. In contrast, because the posterior metaface adheres to the deep layers that it covers (masseter), it does not have the same freedom to become flaccid over time.
In our opinion, the mesoface should not be divided into the mid and lower thirds of the face since these two parts are linked. Age-related slackening occurs across the whole area, and thus for treatment purposes, changes to this zone should be considered over its total height (Figure 3).
In the upper part of the mesoface, around the mid-face, the primary motor element is the orbicularis oculi muscle which mobilises and raises the superficial subcutaneous malar fat pad of the mid-face during movement, while the deep malar fat pad remains attached to the underlying supporting bone. Age-related sagging only occurs in this mobile part and creates the three main grooves of the mid-face: the palpebromalar groove with the tear trough, the midcheek groove, and the nasolabial fold (Figure 3)1.
In the lower part, the contour sagging only occurs around the mesoface, forming a ‘jowl’. By contrast, sagging does not occur in the proface (chin) or the metaface. This heterogeneity in the sagging disrupts the regularity of the jawline of the face, causing loss of definition of the contour. Once the contour is broken, the more youthful appearance is lost, and it is this which we strive to restore. The retaining ligaments such as the mandibular cutaneous ligament and the mandibular septum provide a deep anchorage in this zone2.
Metaface
The metaface is posterior to the mesoface, on the lateral part of the face. It covers and adheres to the muscles of mastication (masseter). As a consequence of the adherence to the underlying tissues, very little to no sagging can occur in this area. Moreover, the subcutaneous tissue of the metaface is often thinner than that of the mesoface. However, since sagging occurs in the mesoface, a disparity is created that breaks the contour lines along the border of the mandible, disrupting the oval shape.
A sound knowledge of the anatomical structures that cover the insertion of the masseter is essential because injections to re-shape the contour are performed on the edge of the mandible. The masseter muscle is thick, in the order of 3 to 8 mm. Its fibres pass inferiorly to insert into the first 3–4 cm of the posterior part of the horizontal branch of the mandible — the angle — and 1 cm of the vertical branch of the mandible. Hypertrophy of the masseter is uncommon, but when it occurs, it gives a ‘square’ appearance to the face. There is no precise aetiology; however, it may be associated with parafunctional habits such as bruxism, forced occlusion tics or frequent chewing of gum.
¤ The parotid gland partially overlies the angle of the mandible, as much as 1 cm anterior to the angle. Injections in the mandibular angle area therefore carry the risk of also injecting the parotid gland. It is imperative that the injection has to be deep into the masseter muscle (which is around 4 mm thick in this area), sufficiently close to the bone, to avoid any implantation in the parotid gland.
¤ The jugular vein lies deep within this area. Circumventing the mandible, it then ascends in front of the anterior border of the masseter muscle. If the insertion of the masseter is marked out during tooth clenching, there is little danger of damaging or injecting the jugular vein as it is in front of the muscle. Nevertheless, aspiration should always be performed before any injection. Unlike the jugular vein, the facial artery is more anterior, on the posterior border of the depressor anguli oris.
¤ The mandibular branch of the facial nerve is cervical at this level: it runs deep to the platysma muscle, 1 or 2 cm below the mandible and should be too inferior to be at risk of accidental injury.
Accordingly, deep injection at the level of the insertion of the masseter to the horizontal branch of the mandible should carry little danger of injuring nearby important structures provided that the masseter, particularly the anterior border, is localised and marked during tooth-clenching. Superficial injection fanning in the subcutaneous cellular tissue should also be safe in this region provided injections are carried out in the subcutaneous layer, although ecchymosis may still occur.
Proface
This is the middle part of the face also containing the chin.
Sagging does not occur over the chin as it does on the jowl; however, it is mobile because of the action of the mentalis muscle. The depressor anguli oris and the depressor labii inferioris muscles act on the mouth.
As sagging of the jowl occurs with no ptosis of the chin, a disparity between the two appears as an indentation in the prejowl. This breaks the contour of the facial oval, making the jawline irregular, similar to that which occurs in the mesoface and metaface.
Differences may occur in the thickness of the subcutaneous tissue between the chin and the cheek, with the tissue thicker around the cheek area compared with the chin. When sagging occurs, this difference in thickness accentuates the pre-jowl sulcus.
There are several options available to restore the contour and jawline. At the time of writing, the most popular technique is the surgical face-lift and patients will often spend time in front of the mirror mimicking the effect of facial lifting. A non-surgical option, the implantation of fillers, essentially hyaluronic acid, is also effective. The aim of filling injections is to erase the difference between the chin and the jugal areas.
Two main anatomical structures, which must be respected during injection of the pre-jowl sulcus, are:
¤ The facial artery, posterior to the area of interest and running superiorly along the posterior border of the depressor anguli oris.
¤ The mental nerve, higher than the region of interest, and more medial as it exits the mental foramen. It is important not to ‘scrape’ this nerve with the cannula or needle.
The neck
The neck ages like any other region. Its skin loses its elasticity due to a reduction in collagen and elastin fibres. Sagging of the neck follows the slackening of the lower jugal zone, bringing with it the skin, subcutaneous adipose, and the platysma muscle. As a consequence, the neck, the cervicomental angle, and the jawline lose their definition. The oval outline of the face and well-defined cervicomental angle are replaced by a double chin, jowls, a dewlap and wrinkled, sagging skin (‘turkey neck’).
Improvement and rejuvenation using hyaluronic acid
What to inject?
Even if there is currently no universally-agreed ideal product, hyaluronic acid3 is considered to be the gold standard, particularly since the development of more volumising formulations.
As plastic and aesthetic surgeons, we have considerable experience with techniques that involve fat grafting and have found that they can produce remarkable results. However, the flexibility, ease of injection, quality of results, and the light follow-up required still argue in favour of the use of hyaluronic acids. Many factors guide the choice of this product.
¤ Safety: hyaluronic acid has a strong record of patient safety.
¤ Medical criteria: there are few risks of secondary reactions and undesirable side-effects associated with hyaluronic acid. For example, a low risk of immunogenicity and granuloma. Hyaluronic acid also integrates well into human tissues and is compatible with other techniques, which facilitates combined treatments.
¤ Technical criteria: hyaluronic acid produces predictable, durable and high-quality results. The injected zone is stable without secondary migration of the product.
¤ Formulation: cohesivity, elasticity, viscosity and integration into tissues differ between formulations of hyaluronic acid from different manufacturers; each product has its own characteristics, and their quality is improving continuously.
¤ Cost: certainly a factor but it does not compare with safety and quality.
As a consequence, we no longer use non-resorbable or semi-resorbable products. Injectable, resorbable products are preferred to avoid compromising the future health of the patient with complications, such as foreign body reactions, granulomas, scar tissue or other functional and/or aesthetic side-effects.
Both patients and practitioners desire safe, quality treatments — it gives patients confidence and makes practitioners credible. As an alternative to autologous fat, the use of hyaluronic acid fulfils these criteria and their usage adheres to the philosophy of ‘primum non nocere’, in accordance with the demands of current society.
Furthermore, as the quality of the hyaluronic acids is continually improving, it would seem likely that the future of injectable products can only be further optimised by research and development.
Hyaluronic acid implantation technique?
The aim of hyaluronic acid injections is to attenuate, or even eliminate, the disparity in the contour. Softening of this jawline restores the contour of the oval, which is broken by the sagging of the mesoface.
There are two solutions:
¤ Tighten the sagging of the mesoface: the face-lift or improvement by laser lipolysis
¤ Provide support over the edge of the mandible of the metaface: filling
The second solution will be discussed here.
Our approach to the treatment of the outline and the pre-jowl is similar to techniques we have developed and published for the mid-face1,4, i.e. deep injection on the edge of the bone to provide stable support, and subcutaneous, superficial injection to perfect and complete. In practice, however, only one of the two techniques may be necessary to restore the outline. A logical, coherent, and effective technical approach can be applied to different zones.
Deep implantation
Deep implantation provides better support, similarly to injection in the deep malar fat pad of the mid-face. This deep support is stable and fixed because it is solidly attached to the structural support. Two or three deep aliquots (0.2 or 0.3 ml each) in the metaface, on the posterior part of the horizontal branch of the mandible project the injected zone away from the edge of the mandible, erasing the disparity between the meta and mesoface. The injection is in the masseter muscle at its bone insertion, just above the inferior bony edge of the posterior part of the horizontal branch of the mandible, as described above.
To perform the injection:
¤ Mark the posterior and anterior limits of the masseter muscle during tooth clenching.
¤ Mark the angle of the maxillary bone (between the vertical and horizontal branches of the mandible).
¤ Mark the number of points to inject, usually three, between the bone angle and the anterior border of the masseter, about 5–10 mm above the inferior border of the bone.
¤ Inject 2 or 3 boluses (0.1 to 0.3 ml each) perpendicularly into the thick area of the muscle near its insertion (Figure 4), with or without bony contact (depending on experience). It is usual to aspirate before injecting to avoid intravascular injection. The injection is thus deep, slow and modest, with an average of 0.2 ml per bolus. The product should be a volumising, cohesive hyaluronic acid with high elasticity (G’) to ensure projection, and a moderate viscous module (G”) to avoid spreading.
¤ Soft moulding may be carried out, avoiding firm massage.
¤ The quantity injected may vary: on average 0.6 ml in each side.
This injection carries practically no risk of injuring important structures, despite inherent risks of complications in any medical procedure. The facial vein is anterior to the anterior border of the masseter. The mandibular branch of the facial nerve is below the horizontal branch of the mandible; it runs under the platysma, 1 or 2 cm below the mandible. Only the parotid gland is close to the posterior bolus as it partially covers the angle of the mandible. Nevertheless, the injection is deep, the masseter is thick, and the injection is performed on the edge of the bone in the thick part of the masseter.
This deep, fixed, non-mobile implantation provides a stable support that should not sag. It does not disturb the function of the masseter. On the contrary, it can modulate it or even improve the symptomatology of bruxism as an alternative to botulinum toxin (myomodulation replaces myorelaxation). It can also improve post-maxillo-facial surgery symptomatology by its modulating function, bringing relief to patients.
Deep implantation is often sufficient to produce a satisfactory result. If necessary, it can be complemented by a superficial injection (Figure 5).
Superficial fanning injection
This may also be sufficient to produce a satisfactory result; however, we often associate it with deep injection. The injection is subcutaneous, and it should be remembered that the subcutaneous tissue of the metaface is relatively thin. There is no danger of injection into other important structures, as long as the injection is subcutaneous, because there are none nearby to be injured — all structures being deeper than the platysma muscle.
If the aim of this injection is to reduce the difference between the meta and mesoface, it should be performed in the posterior part of the jawline. However, the field can be increased towards the ear, over the masseter to restructure the entire metaface (Figure 7), or extended forwards in order to recreate the whole oval; it can also cover the entire cheek to improve the skin trophicity, hydration, and radiance.
To perform the injection:
¤ Draw the zone to be restructured.
¤ Inject subcutaneously using a conventional fanning technique. The fanning should be even. We prefer to use a 25 or 23-gauge non-flexible cannula because, in the authors’ experience, they cause less ecchymosis than needles. Moreover, because they provoke greater tissue resistance than needles, they can increase stimulation of fibroblasts cells and thus further improve the trophicity of the skin (‘skin booster’ effect)1. We do not use flexible cannula because they tend to bend during placement, making the trajectory difficult to control and leading to possible misplacement
¤ The injection should be slow and gentle, and the product should be well spread in the marked-out zone
¤ Moulding and even soft massage can be carried out to facilitate penetration and integration of the hyaluronic acid into the surrounding tissues
¤ The vector follows the body of the maxilla to improve the curve of the contour. The whole metaface can thus be restructured using a more vertical vector, and fanning may be carried out over the whole cheek
¤ The product must be cohesive, with moderate elasticity (G’) because the aim is not projection. It must have an excellent viscous module (G”) to ensure good spreading, and short chains to improve integration and tissue penetration
¤ The quantity injected depends on the surface and the extent of the problem treated. It is always best to undertreat than to over treat.
The result will be immediately visible although there may be temporary ecchymosis. The skin trophicity and hydration effect, resulting from the rheological properties of the product and the stimulation of fibroblasts, takes around two weeks to become apparent.
This tissue response is created by the trauma-related stimulation of fibroblasts, as well as the hydrating properties of the hyaluronic acid integrated into the tissues. Elastin, collagen, proteoglycans and structural glycoproteins are produced in the dermis by fibroblasts5,6. Any local reaction, inflammatory response or healing process provoked by stimulation, whether surgical or following the injection of a product, stimulates fibroblast proliferation1,5,6. The injection of any product will thus induce a reaction because all superficial trauma stimulates the fibroblasts. This stimulation is the result of the deposit of the product itself, as well as the mechanical, traumatic phenomenon of tunnelling in the subdermis, whether using a cannula or needle (skin booster effect). It can be assumed that a cannula provokes a more significant reaction than a needle, due to the greater resistance of blunt cannula than a sharp needle and a 22-gauge cannula will produce a more significant response than 25 or 27-gauge because of the greater resistance associated with fanning.
Cannula or needle?
This is the subject of much debate among experts. Clinicians should choose the technique with which they are most comfortable. However, evidence suggests that use of a fine needle is preferable for a deep bolus and a non-flexible cannula is better for superficial subcutaneous fanning injections.
We can imagine the concept of superficial stimulation to describe a vector technique, highlighting the importance of the orientation of the vector. According to this concept, the superficial injection of products that follows a similar vector to that of a surgical lifting procedure, produces a tension effect in the same magnitude as surgical lifting.
We do not believe that a potential tensile effect created by fibroblast stimulation can have any vector since a fibroblastic response itself has no vector. Over and above the injection technique (vertical, in the direction of surgical lifting or horizontal, like a hammock), it is the zone of fibroblastic stimulation that is important to create a light tensile effect. The effect is multi-directional, like the ripples generated by a stone thrown into a pool of water, they travel in all directions, not just one1.
This mechanism also explains why superficial injections of hyaluronic acid improve the skin. As well as the slight tensioning effect described above, the skin acquires better trophicity and so appears hydrated, smoother, and more radiant.
Lifting effect?
The recreation of a continuous contour by the attenuation or elimination of the disparity between the meso– and metaface, as well as the restoration of the outline of the jawline by the provision of better support and skin tension, all contribute to the rejuvenating effect and produce a ‘lifting effect’.
The improvement of the skin texture by the superficial fanning and the skin booster effect add to the rejuvenating effect. Thus, we can use the terms ‘lifting effect’ or ‘medical lifting’ although it is not a true lifting in the surgical sense.
The pre-jowl sulcus
The anterior part of the contour corresponds to the chin. In contrast with the mesoface in which sagging occurs, creating jowls, there is no sagging in the proface zone. This interrupts the contour of the anterior mandibular transitional zone outline between the mesoface and proface. The pre-jowl sulcus extends the ‘bitterness’ folds.
Correction for this area is the same as the treatment of the metaface as described above: the injection can be deep or superficial.
Deep injection
A deep injection in contact with the periosteum provides a filling and projection effect that erases the disparity in the levels around the drooping jowl. Our technique involves injection of 1 to 2 deep boluses.
To perform the injection:
¤ Define and mark the depressed part of the pre-jowl
¤ Mark 1 or 2 points in the pre-jowl sulcus, 5 to 10 mm above the bony border
¤ Inject a bolus perpendicularly, avoiding contact with the bone (withdraw the needle slightly if it occurs). The point of the needle should be just above the insertion of the depressor labii inferioris and depressor anguli oris muscles and is often in the muscle bellies
¤ Aspirate before injecting to avoid intravascular injection. The injection should be deep, small and slow, on average 0.1 ml. The product should be cohesive and volumising with high elasticity (G’) to have a projection effect
¤ Gentle moulding can be carried out without massage to avoid demolishing the projection effect
¤ The quantity injected is variable, around 0.2 ml for each side.
The facial artery is more posterior, following the posterior border of the depressor anguli oris muscle, but care must be taken with its chin branches (always aspirate before any injection). The foramen of the mental nerve is higher and more medial.
This deep implantation, in contact with the bone, produces a fixed, non-mobile filling that is not susceptible to sag and provides stable support that is often sufficient for a satisfactory result. The indentation is thus erased, and there is no longer a difference in levels. It can be complemented by superficial injection.
Superficial fanning injection
This may be sufficient by itself, or it can be associated with a deeper injection.
The injection is subcutaneous, into the space between the skin and the depressor anguli oris and labii inferioris muscles. Remember to aspirate due to the chin vessels.
To perform the superficial injection:
¤ Define and mark the area to be restructured.
¤ Using a cannula, inject subcutaneously using a conventional fanning technique. Our preference is a 25 or 27 gauge cannula for this zone.
¤ The injection must be gentle, and the product should be well-distributed in the marked area.
¤ Moulding and even massage can be carried out to facilitate spreading and integration of the hyaluronic acid in the other tissues.
¤ The vector is fanned to cover the whole area, perhaps even beyond it towards the bitterness folds.
¤ The product should have good cohesivity, provide little volume, have moderate elasticity (G’) and a moderate viscous module (G”) to ensure good spreading, and short chains to ensure good integration and penetration in the tissues.
¤ Remember the position of the mental artery, which is a terminal branch of the inferior alveolar artery as this may become cannulated when injecting in the pre-jowl or marionette region of the lower face.
A five-stage classification
Classifications and scales are useful as learning, understanding, and teaching tools. We have previously designed a scale for the midface1,7, the lips1,8, and the dark circles of the eyes1. Here, we propose a five-step classification for the facial oval.
Two elements are important to classify the harmony of the facial oval:
¤ Firstly, the degree of sagging. This can be described as a four-point scale where 1 = no sagging, 2 = mild, 3 = moderate or 4 = severe ptosis.
¤ Secondly, the thickness of the subcutaneous tissue. Differences occur in the thickness of the mesoface, even in the absence of ptosis if the thickness of the subcutaneous tissue is not uniform. The mesoface can contain thicker fatty tissue, causing a visible difference, a sulcus. Thus, even in the case of no ptosis, two situations may occur: either a regular jawline if the thickness of the subcutaneous tissue is uniform across the meta, meso– and preface, or an irregular jawline if the subcutaneous tissue is thicker in the mesoface, producing a small indentation.
¤ Accordingly, our classification has five stages, including two stages where sagging is absent:
– Stage 1: no sagging of the mesoface. The outline of the oval curve is regular, and the outline of the mandibular border is regular and smooth.
-Stage 2: no sagging but the outline is irregular with a small indentation due to a difference in thickness of the subcutaneous tissue; the subcutaneous tissue of the mesoface contains more fat and is thicker.
-Stage 3: mild sagging with a slight indentation.
-Stage 4: moderate sagging with moderate indentation.
-Stage 5: severe sagging with a large indentation.
Conclusion
In our clinic, the loss of the contour definition is a cause for distress in our patients since it is one of the first signs of ageing. The demand for improvement and rejuvenation is increasing, we believe, as a consequence of the efficacy of our results and the quality and safety of our products. A sound understanding of anatomy and physiology and use of the ‘right product in the right place’ by qualified and experienced professionals are all essential factors. To achieve this, we have presented our method of dividing the face using vertical divisions into metaface, mesoface, and proface and proposed an original classification to aid fellow professionals to undertake similar cosmetic procedures.
