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An expert consensus report on the clinical use of the Vycross® hyaluronic acid VYC‐25 L filler

Abstract Background The portfolio of hyaluronic acid (HA) fillers and the techniques of administration have evolved in recent years. The latest innovation in the Vycross® range was the introduction of VYC‐25L (Juvéderm Volux®; Allergan plc), a first‐in‐class filler effective for chin and facial lower third remodeling. The aim here was to provide clinicians who are starting to use VYC‐25L with key advice, and to standardize procedures so that optimal and predictable outcomes can be obtained. Methods A multidisciplinary group of experts in esthetic medicine from Spain and Portugal reviewed the properties, treatment paradigms, administration techniques, and potential complications of VYC‐25L, on the basis of which they drafted consensus recommendations for its clinical use. Results The consensus panel provided specific recommendations focusing on the patient profile, dose, administration techniques, and the complications of VYC‐25L and their management. The panel identified five different profiles of patients who may benefit from VYC‐25L, and they drafted recommendations aimed to facilitate the treatment of these patients, namely, microgenia (women/men), masculinization (men), rejuvenation (women/men), facial laxity (women/men), and submental convexity (women/men). In terms of their safety, no specific recommendations were made beyond those established for other HA fillers. Conclusions The evolution of esthetic medicine makes it necessary to update the clinical recommendations that guide patient assessment and treatment with the new HA fillers developed. The current consensus document addresses relevant issues related to the use of VYC‐25L on different types of patient, in an attempt to standardize procedures and help specialists obtain predictable results.


| INTRODUC TI ON
Esthetic medicine is continuously evolving, providing specialists with constant challenges. The development of new classes of products, new indications and procedures, and the evolution of treatment paradigms, in conjunction with a better understanding of facial anatomy and its aging, make it necessary to adopt more comprehensive approaches to facial rejuvenation, and to update guidelines.
Over the past few years, the number of minimally invasive esthetic procedures has increased dramatically. 1 Based on a survey conducted by the International Society of Aesthetic Plastic Surgery, more than 13.6 million non-surgical procedures were performed Hyaluronic acid fillers are mainly used to fill rhytides and folds, or to restore/correct soft tissue loss caused by either disease or aging. [2][3][4] HA is a high molecular weight, natural, and linear glycosaminoglycan that is present in all mammals. 5,6 Due to its physicochemical properties, HA is one of the most hygroscopic molecules in nature and hydrated HA can contain up to 1000-fold more water than its own weight. 7 Some specific features of HA influence its properties as a filler, such as polymer chain length, HA concentration, degree of cross-linking, or the cross-linking technology used, which affect its duration, extrusion force, and elastic Modulus (G').
These phenomena define the distinct products and the indications for which they may be employed. 6,[8][9][10][11][12] One of the most recent generation of fillers was created using the patented Vycross® technology (Allergan, Inc.), which utilizes a proprietary mixture of high and lower molecular weight HA. 13 VYC-25L (Juvéderm Volux®; Allergan plc) represents the latest innovation in the Vycross® range, combining high G' (resistance to deformation) and high cohesivity HA, 14 properties that make it an ideal filler to create and restore facial volume. In clinical practice, VYC-25L has been successfully used to restore and create facial volume in patients with chin retrusion 15,16 and for other esthetic indications. 17 Moreover, when used for chin augmentation in patients with chin retrusion, its effects persist for at least 18 months. 16 It is not only effectiveness but also the safety of new HA products that must be considered. Thus, it is particularly important to study the bio-integration and tolerability of HA fillers after their injection. 18 Tissue bio-integration of VYC-25L was assessed recently in a prospective, non-comparative, open-label, and multicenter study carried out on subjects who underwent facial rejuvenation treatment of the lower third of the face. 19 According to this study, partial bio-integration of VYC-25L was evident 48 h after treatment and the HA had fully integrated into the tissue 30 days after injection.
Although we have data from clinical studies about the good efficacy and safety profile of VYC-25L, there is only limited knowledge about its use in daily practice. This manuscript aims to provide guidelines for the best way to use VYC-25L in clinical practice, focusing mainly on three issues: (1) the best patient profile; (2) patienttailored treatment approaches to improve esthetic outcomes; and (3) the prevention of adverse events and potential complications.
Thus, in this article we shall establish consensus-based recommendations to provide doctors with a reference framework extracted from the available data and the panel's clinical experience.

| ME THODS
A multidisciplinary group of experts in esthetic medicine from Spain and Portugal convened to discuss the use of VYC-25L in clinical practice. Meetings took place using a virtual platform from April 3 to May 26, 2020.
Different topics emerged as core concerns, including patient profiles, injection techniques, indications, and potential complications (Table 1). As a result, the authors drafted this consensus document based on their experience and opinions, and on a literature search of PubMed conducted in using the search terms "Hyaluronic acid" OR "Dermal Fillers" OR "Aesthetics" OR "Tissue bio-integration" OR "complications." Articles on human subjects in English, French, Portuguese, or Spanish were selected. Moreover, the references cited in the selected articles were also reviewed to identify additional relevant reports. In addition, relevant national and international guidelines were also reviewed.
Consensus was achieved by discussing the expert panel's opinions, and considering their clinical experiences and the currently available scientific evidence. An initial document was drafted as a result of these meetings, and it was reviewed by the members of TA B L E 1 The session's objectives and the issues considered as key points for the Consensus document about the use of VYC-25L (Juvéderm Volux ® ; Allergan plc) in clinical practice

Session objectives and key points
Patient profile: • To identify and understand the different types of patients who can benefit from VYC-25L treatment. • To determine how specialists can readily diagnose these patients in private clinical practice. • To identify other possible indications that can be treated with VYC-25L.
Tailored treatment approach • To understand and select the best treatment approach to be used for each patient profile based on their characteristics and needs. • To understand and evaluate the best way to administer the treatment. • To understand the possibility to combine VYC-25L with other esthetic treatments in these patients.

Safety
• To develop treatment strategies, recommendations and/or advice for the correct and safe use of VYC-25L. • To establish potential risks or "warnings signs" that should be borne in mind based on the patient's baseline characteristics (medical and/or family history). • To understand and to determine when and how it is appropriate and/or convenient to make recommendations to the patient (psychological profile, educational level, etc.

| Patient profile
Choosing the appropriate patients for treatment with VYC-25L is essential to obtain optimal esthetic results. Prior to any treatment, it is crucial to perform an exhaustive examination to determine why the patient wants to undergo esthetic treatment and to establish "realistic" treatment goals. 20 According to the expert opinion, the first step is to identify whether the patient is a suitable candidate for a lower third intervention.
• Recommendation 1 (Strong consensus): It is essential to establish whether the facial proportions and facial angles make the patient a good candidate for treatment. Evaluating the different measurements and characteristics of the jaw is crucial to determine the best patient profile to be treated.
An individual's facial beauty is determined by the harmony of its proportions and symmetry. 21 Symmetry and balance are two relevant aspects that should be taken into consideration during the patient's facial assessment and diagnosis. 22 Among the different facial angles, the glabella-subnasale-pogonion angle may be considered as the most important one. The mean value of the glabella-subnasalepogonion angle ranges from 165º to 175º. 23 In addition, the "WAY" paradigm may be a valuable tool to diagnose and treat aging in the mid-and lower third of the face. 24 This paradigm takes into consideration different aspects of facial aging, including the appearance of the jaw contour ("W"); the prejowl ("A"); and the tear trough, palpebromalar area, and nasojugal groove ("Y") regions. Table 3 summarizes the most important measurements to take into account.
• Recommendation 2 (Strong consensus): The most suitable patients for an intervention with VYC-25L in the lower third are patients with microgenia (women and men), and those undergoing masculinization (men) or rejuvenation of the lower third, mainly the jawline (women and men).
In addition to those profiles mentioned above, other patients that may obtain significant benefit from such a procedure are as follows:

| Treatment
The introduction of new products onto the market often requires new treatment paradigms to be devised. These new paradigms aim to establish comprehensive approaches focused more on achieving patient beautification than on treating individual facial deficiencies.
Due to the increasing popularity of minimally invasive esthetic procedures, it is necessary to create a "common language" that can be used not only to describe treatment approaches but also to communicate among specialists around the world. The medical codes  (Table 4).

Examination Description
Dental occlusion Pay special attention to class II malocclusion as this may be due to any combination of the jaw, tooth, and lip position. In these patients, the upper jaw (maxilla) can be too far forward or more usually, the lower jaw (mandible) is too far back. 34 Evaluation of facial angles Glabella-subnasale-pogonion angle: Describe the angle of facial convexity, which is formed by connecting the soft tissue glabella, subnasale and soft tissue pogonion. 35,36 This value ranges from 165º to 175º. 34,35 Evaluation of the effective jaw length Evaluate the distance between the condilion and gnation, or between the condilion and pogonion (both are acceptable). The mean (±standard deviation) of the effective jaw length from the condilion to gnation is 120.2 (±5.3) mm in women and 132.3 (±6.8) mm in men. 37 Evaluation of the chin Analyze the previously described facial angles.
Evaluation of muscle activity It is very important to assess the depressor anguli oris, mentalis and masseter muscle activity, in addition to that of the superficial musculoaponeurotic system.
Evaluation of skin laxity and submental fat Evaluating these aspects may be important when addressing combined treatments (neck + submental fat). It is important to maintain good skin integrity and structure. The "WAY" paradigm* may be a useful method to diagnose skin laxity and facial aging. 24 *WAY refers to the appearance of: the jaw contour ("W"); the prejowl ("A"); and the tear trough, palpebromalar area and nasojugal groove ("Y").

Other considerations
Besides the specific treatment strategies recommended for men and women, other issues that should be taken into consideration include dose/plane; learning curve; and warnings (

| Safety
According to panel's experience, no unexpected adverse events have been observed with VYC-25L. The data showed that VYC-25L achieved optimal esthetic outcomes with a good safety profile, making it an alternative to surgical interventions to increase chin projection and jaw volume. Moreover, the use of VYC-25L was associated with good patient and specialist satisfaction. 15,16 A retrospective, single-center study was also carried out on adult patients who underwent treatment of the lower third of the face with VYC-25L. 27 Again, this study showed a good safety profile and high patient satisfaction in terms of chin and jawline sculpting. 27 In Irrespective of the technique used, facial analysis is the cornerstone to achieve optimal outcomes, which critically depends on understanding the underlying anatomy and the clinical implications of facial aging. 28 Moreover, when considering facial muscles, it is important not only to focus on the treatment results at rest but also in movement. The effectiveness of the HA fillers in modulating muscle activity has been described previously. 29 It was proposed that the HA fillers can mechanically alter muscle contraction by either facilitating or blocking their action. 29 Although HA filler injection is considered a safe procedure, the rising popularity of dermal fillers has led to an increase in the number of complications associated with their use. 30 technical and placement errors, skin discoloration, and vascular conditions. [30][31][32] Finally, as a limitation of the current consensus, it should be noted that VYC-25L is a relatively new product, and thus, clinical experience with it is limited to the short-to mid-term. Nevertheless, there is evidence suggesting it has a good safety and efficacy profile [15][16][17] and that VYC-25L has a very good bio-integration profile as reflected by its partial tissue bio-integration 48 h after treatment and total integration 30 days after filler injection. 19 However, all consensus documents, and perhaps this one in particular, must be considered within an evolving environment, and therefore, this document should be regularly revised to implement novel findings as they occur and future evidence as it becomes available.

| CON CLUS IONS
To achieve optimal esthetic outcomes, clinicians must have an exhaustive knowledge of facial anatomy, filler characteristics, injection techniques, and, in particular, the patients best suited for an inter-

Rejuvenation
• The basic therapeutic strategy would be based on a 9-point pattern (See Figure 2). Nevertheless, a comprehensive approach that addresses the specific needs of each patient is the best treatment (Strong consensus b Do not inject into the cartilage or bone but rather at the level of the cartilage or bone.
c Aspiration is highly recommended when injecting with a needle at the level of the bone.
*Only in men. relevant points that may help professionals to undertake esthetic procedures with VYC-25L safely and effectively. Moreover, it could serve as a basis to standardize procedures, which may help achieve optimal and predictable esthetic results.

ACK N OWLED G M ENTS
Medical writing services were provided by Ciencia y Deporte S.L. and Editorial Assistance by BiomedRed S.L. Support for this assistance was funded by Allergan Aesthetic, an AbbVie company.

E TH I C A L A PPROVA L
Authors declare human ethics approval was not needed for this study.