The evolution of dermal fillers has resulted in numerous products with different qualities and specifications. This is a testament to the fact that no one product is suited to meet the needs of each patient. Soft tissue fillers provide correction by two general mechanisms: the filler occupies a space, or the filler material stimulates collagen production. Adjustment of variables such as viscosity, elasticity and plasticity determines how the filler behaves during and after injection. Different HA concentrations, particle size, hydrophilicity and percentage of cross-linking are additional factors that contribute to diverse clinical outcomes and allow for selection that is best suited for a specific goal. Products with higher elasticity increase tissue projection by providing firmness and resistance to muscular and gravitational forces. Cohesivity confers more three-dimensional tissue expansion. Science-based selection of filler products and injection techniques allows a more evidence-based approach toward safety and efficacy.
As our knowledge and understanding of the physiology of aging has evolved, so has our use of dermal fillers, shifting from an early focus on the treatment of superficial lines, to the current focus of facial areas in a three-dimensional manner. The aging process of the face is a complex interplay of numerous factors. These include the redistribution, atrophy and hypertrophy of the facial fat, dermal thinning, bone resorption, the loss of elasticity and collagen in the skin, loss of muscle tone, and finally, gravity.
The perception of an attractive female face is largely subjective, influenced by ethnicity, age, culture and personality. The fundamental aspects that should be evaluated are facial topography, morphology, balance and symmetry, irrespective of whether the goal is to restore a more youthful appearance, or enhance the features of a younger face.
In the youthful face, the superficial and deep fat pads are distributed evenly, creating homogeneous topographical appearance, with smooth transitions between facial areas and appropriate convexities that reflect light. As the fat distribution becomes altered with age, hills and valleys develop and demarcation with shadowing between the cosmetic units becomes more pronounced. Glasgold et al. (2008) have suggested that a detailed examination of the shadow patterns will lead to a better understanding of how to apply volumetric techniques to create natural-looking results. Although not every person develops every shadow as they age the typical patterns are consistent.Appreciating these concepts is critical because seemingly subtle changes in light and shadow can have significant impact on our perception of a face.
Fundamental steps in evaluation and decision-making principles:
- Facial Morphology
Most individuals have a shorter and fuller side of the face and a longer, thinner side. The fuller side is usually the more attractive side in youth and the younger appearing side with age. Figure comparing and analyzing two sides
The traditional regional approach to facial assessment is to divide the face into upper, middle and lower thirds vertically and equal fifths horizontally. A youthful face has an ovalized upside-down-egg shape, an anterior convexity, and an oval frame. When assessing a face, it is useful to consider what causes that face to deviate from ideal proportions. Early changes in the cheeks and temples are often not noticed by the patients, until features become more concave, with increased shadowing among the hills and valleys and the excess skin begins to sag. This becomes most apparent to patients in the areas of the nasolabial folds, flatter lips, and the mandibular areas in the form of marionette lines and jowls.
In the upper face, the orbital aperture increases with age, both in area and width. Resorption, is site-specific and uneven, with the superomedial and inferolateral aspects receding more. The eccentric shadow of the medial upper orbit leads to A-frame changes of the upper eyelid (figure).
In the midface, the rate of bony resorption is not uniform. The maxilla is more susceptible to age-related loss than the zygoma. These changes manifest as loss of maxillary projection and reduction of the maxillary angle.
Aging changes in the nose include lengthening and drooping of the nasal tip, as well as posterior displacement of the collumella and the lateral crurae. The piriform aperture enlarges with preferential bone loss in its lower aspect. This manifests clinically as posterior displacement of the alar base. Deepening of the maxilla results in posterior positioning and deepening of the nasolabial folds and adjacent upper lip.
Earlier studies reported that the dentate mandible expands continuously with aging. However, more recent studies on aging of the lower face found that although certain measurements increased significantly with aging, some measurements decreased. Bone loss in the prejowl area of the mandible contributes to the appearance of jowls. Bony changes affect the location of the attachments of facial retaining ligaments. As the volume of the face diminishes, these structures may lose the effect on the tissue that they act upon and the attachment points define most of the shadows that are seen in an aged face.
Our understanding that fat exists in discrete compartments rather than a homogeneous sheet over the face (Rohrich & Pessa, 2007) has been critical in how we approach facial rejuvenation. The adipose tissue of the face can be divided into superficial and deep compartments, which are separated by the superficial musculoaponeurotic system (SMAS). (figure) It has been shown the adipocytes in the deep compartment are different morphologically, metabolically, and smaller in size than those in the superficial one (Cotofana, 2016). It is also possible that the compartments behave differently during the aging process. There are 5 deep fat compartments: the deep nasolabial fat located in the premaxillary space, the deep pyriform fat located in the deep pyriform space, the deep medial cheek fat, the deep lateral cheek fat, and the sub-orbicularis oculi fat, which is further divided into medial and lateral compartments. A recent imaging-based investigation of the deep facial fat compartments concluded that there does not seem to be age-related inferior displacement. (Schenck, 2018).
There are 7 distinct superficial (subcutaneous) facial fat compartments: superficial nasolabial, superficial medial cheek, superficial middle cheek, superficial lateral cheek, jowl, and superficial temporal and inferior temporal (Cotofana, 2018). Increased age was shown result in significant inferior displacement of the superficial nasolabial, and jowl compartments. Not only do the superficial and deep compartments behave differently when injected with dermal fillers, but there are differences within the superficial compartments themselves. Filling of the superficial nasolabial, middle cheek and jowl compartments resulted in their descent, which was not observed with injection of the medial and lateral cheek, or the temporal compartments. These differences could be due to greater stability of the fat pads that are bounded by stronger ligamentous and fascial attachments.
Preferential loss of each compartment results in various clinical appearance. In the cheek, loss of the superficial fat with intact deep compartments retains the convex midfacial appearance. Alternatively, loss of the deep midfacial fat reveals ligamentous attachments points and the shadows that develop with age. Understanding of the behaviors of the deep and superficial fat compartments translates into clinical practice. Deep, supra-periosteal injection of soft-tissue fillers in areas of the deep fat compartments provides support for the overlying structures, increases anterior projection and induces a lifting effect of the more inferiorly located adjacent facial soft tissues. Re-volumization of the deep medial cheek fat helps improve with V deformity, reduces the size of the nasolabial fold (NLF) and diminishes the appearance of the tear trough. Care must be taken when injecting into the subcutaneous plane in the superficial nasolabial fat, middle cheek and the jowl, as this can result in an effect opposite to that desired.
The muscles of facial expression have been shown to contribute to the formation of boundaries of the deep midfacial fat compartments. MRI studies found no difference in muscle length, thickness, volume, or location of origin with age. Age-related changes in facial muscles may include increase in the muscle tone and shorter amplitude of movement. This may lead to contractures that, with shifting of the fat and accentuation of skin creases, transform dynamic wrinkles to static lines.
Of the facial ligaments, the zygomatic ligament (ZL) has been shown to be the “stiffest”, followed by the orbital retaining ligament (ORL) and the mandibular ligament (OL). The ZL extends from the zygomatic arch toward the orbital rim and connects with the ORL medial to the mid-pupillary line. From there, the ORL becomes the tear trough ligament. The ZL forms the hammock for the SOOF. The most posterior part of it is called the McGregor patch and is regarded by some as the zygomatic ligament. Although it is possible that the ligaments themselves do not undergo age-related changes, the changes in the underlying bone and overlying skin have an effect on their position and course.
Skin appearance is a primary indicator of age. This includes elasticity, smooth texture, clarity and evenness of color and the absence of wrinkles. In addition to age-related collagen loss, UV light and smoking are two major factors that have a negative impact on the skin. It is important to recognize that in patients with significant skin laxity, fillers alone may not be able to achieve the desired results, unless paired with a skin tightening procedure. The converse is true in patients with healthy skin, where mild-moderate volume loss can be less visible and conservative filler treatments achieves good results.
Chronological age is one factor that a clinician should consider when selecting a soft tissue filler. Because the face continues to age following procedures, temporary effects are preferred, especially in younger patients, so the face can be periodically re-assessed and treated to accommodate the ongoing changes. Although there is no age beyond which patients no longer benefit from volume restoration with fillers, declining tissue quality and skin laxity are limiting factors that may require combination treatments with other modalities such as lasers or surgery. Older patients are more likely to require treatments with products that correct the results of more significant fat atrophy and replace volume, addressing the loss of the foundation and underlying structure of the face. In younger patients, age-related disharmonies are not yet prominent and emphasis is typically on modification and improvement of congenital features. Younger patients are better candidates for dermal fillers in certain areas, such as the lower eyelids, due to adequate skin tone and tissue support to keep the filler in place. Once herniation of orbital fat becomes more pronounced, and/or significant skin laxity is seen, surgical procedures are more successful. In younger patients, the typical goal of lip augmentation is to make the lips appear fuller, whereas in older patients, the goal is to restore structure and volume.
The selection of a filler is based on the indication and site of placement:
- For improving the structural foundation and facial contours by restoring volume, a high-density (high G’, ç*) filler is injected deep into the supraperiosteal space.
- For treating medium-deep depressions, a mid-density filler is injected subdermally
- For the periorbital and perioral areas, a low-density, less hydrophilic filler is best
Patient Positioning and Procedural Approach
As most tissues of the face are relatively mobile and gravity-dependent, it is best to have the patient’s head in an upright position during evaluation and treatment. Treatment of the temple and the lips maybe done with the patient supine but the injector must be able to move around the treatment chair freely and evaluate the outcome progressively from different viewpoints for a better 3-dimentional outcome.
The method of filler delivery, whether it is via a microcannula or a needle, is injector-dependent. More precision can be obtained when using a needle, while using a cannula allows less trauma and access to larger areas through a single entry. (expand)
Preinjection aspiration for HA fillers has utility as a safety checkpoint. Waiting times to visualize flashback may be affected by physiochemical and rheological properties.(expand)
Approach to the upper third
One of the earliest sites to see fat atrophy in the face, are the temples. In a youthful female face, the temples should be flat, or slightly concave, with a smooth transition into the lateral cheek inferiorly and the central forehead medially. Baseline characteristics of the patient dictate treatment goals. The temples of an individual with bony structures of the face and thin skin should have more of a concavity than an individual with a rounder face and thicker skin. In thin skin, the product could become visible, if not placed appropriately. Fillers with high elasticity (G’) that bestow firmness and resistance to force, as well as higher viscosity (η*), conferring resistance to spread, are best suited for deep volumization. Products with lower elasticity and viscosity are more appropriate for superficial subdermal placement. Alternatively, Poly-L-lactic acid (Sculptra) can be used for deep placement to restore volume. The quantity injected should be a balance between noticeable improvement, but not over-treatment. A conservative approach, not injecting more than 1mL per site, is preferred.
Approach to the midface
The midface region tends to be the primary area affected by age-related volume loss and undergoes the most complex soft tissue changes. Clinically, these changes present as tear trough deformity with orbital fat herniation, malar mounts, a double convexity, deepening of the nasolabial folds, and loss of cheek definition. Adding volume to the midface with dermal filler provides a means of addressing these signs. Unlike the temple, there are less structural boundaries in the cheek, but it can be divided into three zones: the zygomaticomalar region, the anteromedial cheek, and the submalar region. (Hinderer’s lines diagram). The injector should pay attention to each zone, the transitions between the regions, and the transitions between the midface and the surrounding aesthetic units.
The goal of midface treatment may range from enhancing the cheeks, giving more width to balance other features, to restoring age-related volume loss. A certain degree of facial asymmetry is common and slight asymmetry provides a more natural appearance. When significant asymmetry exists, it is best to correct the more asymmetric side first, using the more youthful side as the template. Once close symmetry is achieved, further injections can continue to enhance bilateral structures.
Discuss specific filler selection: Voluma younger patients, Lyft/Radiesse when need more lift, lower G’ to blend the upper and mid-cheek, depth and filler choice to avoid exacerbation of premolar edema, etc.
Approach to the lower face
The lower face has 2 anatomic variables that need to be considered when planning treatment: the jawline and the perioral region. The labiomental hollow creates a U-shaped shadow that separates the lower lip from the chin, and the labiomental fold creates a distinct shadow that characterizes the frown.
- Position and prominence of the mandibular angle
- Length of the mandible
- Thickness of the skin and subcutaneous tissue
- Height, projection, and width of the chin
- Cervicomental angle
In addition, age-related changes and relative degrees of fat atrophy vs. fat hypertrophy guide treatment.
A youthful female jawline consists of a smooth transition from the mentum transecting an imaginary line parallel to the angle of the auricle adjacent to the tragus. The objective of treatment is to restore those transitions.
Overvolumization is best avoided by assessing the patients before, during and after injection – not only at rest, but also in animation. A conservative approach is always preferred, especially with newer, longer lasting HA fillers. It may be valuable to counsel patients about the philosophy of more frequent visits to achieve and maintain consistent results, rather than be unnatural and overdone.The use of one filler is not exclusive to the use of another filler. The best outcomes are often achieved with combination treatments, taking advantages of the attributes of each product.
To achieve meaningful and natural results, the clinician must take a comprehensive approach that treats the aging face from the “inside out”. Products and treatment techniques should be tailored to the individual needs of the patient.