1. introduction and background

Aesthetic minimally invasive procedures are becoming increasingly popular and are now mainstream. According to the annually published Aesthetic Plastic Surgery Statistics, injections increased by 44% in 2021 compared to the previous year [1]. Wrinkle injections with hyaluronic acid and botulinum toxin injections have also been ranked first and second in the German Society for Aesthetic Plastic Surgery (DGÄPC) for years, ahead of surgical procedures [2]. In the area of buttock augmentation alone, statistics from the American Society of Plastic Surgery for 2019 show an increase in treatments of 90.3% [3]. In addition to established aesthetic treatments, there is also a strong increase in interest in biostimulants such as poly-L-lactic acid (PLLA) or calcium hydroxyapatite [4].

Due to trends and social networks, treatment with derma fillers and biostimulators outside the face is increasingly in demand. As minimally invasive aesthetic treatments are usually performed on the face first, there can be an aesthetic imbalance between the youthful face and aged areas of the body, which gives patients an additional incentive for body treatments. For example, statistics from Aesthetic Plastic Surgery show that since 2020, aesthetic body procedures such as abdominoplasty, buttock augmentation and liposuction have increased by 63% [1]. As patients usually prefer minimally invasive treatment to surgery, the potential for biostimulators in the area of non-facial treatments is very high. This trend is reinforced above all by the significantly longer effect of biostimulants compared to filler substances such as hyaluronic acid [5].

Internationally, PLLA has been used for several years in various body indications [5]. The use of PLLA and the associated increase in experience has led to a steady improvement in the safety of the active ingredient. In recent years, new treatment recommendations for body treatments with PLLA have come from Brazil in particular [5]. However, a detailed and consistent German-language expert opinion has not yet existed.

With this publication, I would like to share my personal experience and working methods in the field of body indications with my German colleagues. The recommendation is primarily aimed at doctors who already have several years of experience with PLLA or other biostimulating agents and would like to offer their patients additional treatments.

My focus is primarily on PLLA-SCA (Poly-L-Lactic Acid – Sculptra Collagen Activator; trade name: Sculptra®, Galderma). Since the PLLA formulations sometimes differ significantly (integration, distribution and degradation behavior) [6]in the further course of this publication, a distinction is made between PLLA in general and PLLA-SCA.

Dr. Luiz Avelar is a certified specialist in plastic surgery. He became a specialist member of the Brazilian Society of Plastic Surgery in 1994 and a full member in 1999. He is also a member of the American Society of Plastic Surgery and a forensic anthropologist for the Minas Gerais State Police. This activity led him to write a book entitled “Atlas De Medicina Legal”. He is currently studying the “Physiopathology of Facial Aging” and its effects on aesthetics.

Dr. Avelar received his medical degree in 1989 from the Faculdade de Cléncias Médicas de Minas Gerais in Belo Horizonte, Brazil. He completed his first residency in general surgery in 1991 before moving to Rio de Janeiro in 1992, where he completed a second residency in plastic and cosmetic surgery. Dr. Avelar has extensive experience in hyaluronic acid filler, botulinum toxin and collagen stimulator treatments.

He has been a speaker and trainer for Galderma for more than 5 years, giving lectures at symposia and congresses as well as at a large number of workshops and master classes (more than 50 in 2016). As he is both a plastic surgeon and an anthropologist, he is particularly interested in anatomy, dissection and aesthetic procedures.

2. from implantology to esthetic medicine

Polylactic acid was discovered in 1932 by Wallace Hume Carothers during his work at the DuPont company and was synthesized for the first time by French scientists in 1954. Biodegradable materials have been the subject of research since the 1960s [7]. The first synthetically produced and completely biodegradable material was a polymer of polyhydroxyacetic acid and was used as a suture material. Polylactic acid was also used primarily as a component in absorbable suture materials such as Vicryl and Dexon, but was also used in fixation devices in orthopaedic surgery, in tracheal stents, in dental implants and as a carrier for vaccines [7, 8].

In 1999, the product New-Fill® received CE certification in Europe and was approved for the treatment of small volume deficits in the face. At that time, the product was prepared with a reconstitution volume of 3 mL. From November 2004, the product was approved in Europe (under the trade name Sculptra®) for the augmentation of soft tissue in HIV-associated facial lipoatrophy [9]. The original reconstitution volume in the study was 4 to 6 mL aqua ad iniectabile (without further additives). The analgesic effect was mediated by an ectopically applied preparation containing lidocaine. Treatments were repeated every 3 to 6 weeks (up to 4 treatments in total). In the pivotal study by Narins and colleagues published in 2009, the same PLLA formulation was used to treat nasolabial folds [10]. The dilution was carried out with 5 mL aqua ad iniectabilie (without further additives), and the time interval between each of the 4 treatments was 3 weeks.

Against the background of a comparatively increased incidence of adverse events, the reconstitution procedures were reassessed. In 2014, several expert panels developed treatment recommendations to further improve the safety profile of PLLA-SCA for facial treatment [11, 12]. These are reflected in the current EU instructions for use: a reconstitution volume of at least 5 to 8 mL aqua ad iniectabilie [13] with optional addition of 1 mL of 2% lidocaine, treatment intervals of at least 4 weeks and subdermal placement of the product (Sculptra® EU Instructions for Use; December 2020). These measures led to a significant reduction in lump formation and granuloma formation when applied to the face.

In their 2022 review, Christen and colleagues summarized the evidence to date for PLLA applications in body indications [5]. It is interesting to note that the majority of the publications include studies on PLLA-SCA or studies in which PLLA-SCA is used. This indicates a solid evidence base and an extensive publication history:

-Neck and décolleté [14, 15, 16, 17, 18, 19, 20, 21, 22]

-Gluteal region [14, 23, 24, 25, 26, 27]

-Abdomen [25, 27, 28]

-upper arms [25]

-thigh [24, 25, 29, 27]

-knee [27, 30, 31]

-Hands [21, 32, 33, 34, 35]

In summary, the reconstitution volumes vary between 10 and 20 mL (usually with the addition of 2% lidocaine) and the treatment intervals last between about 4 and 6 weeks. The safety profile is classified as good for all PLLA formulations described.

In addition to PLLA-SCA and other PLLA formulations, there are currently other biostimulating substances on the aesthetic market that are also used in the area of body indications. These include hyaluronic acid, calcium hydroxyapatite (e.g. Radiesse®, Merz), combination preparations of hyaluronic acid and calcium hydroxyapatite (e.g. HArmonyCa®, Abbvie) and polycaprolactone (e.g. Ellansé®, Sinclair Pharma), as well as other PLLA formulations (e.g. Elleva®, Rennova; AestheFill®, Regen Bio Global). From his clinical experience with various biostimulants, the author reports that the different substances integrate very differently into the tissue. This observation is supported by two publications. In 2023, Casabona and colleagues sonographically examined the product distribution in the abdomen of human cadavers and came to the conclusion that the PLLA preparations integrate best in the desired tissue area. They attributed this to the water-like flow properties of the suspension (reconstituted PLLA-SCA is technically assessed as a non-viscous suspension) and concluded that such distribution behavior may have a beneficial effect on the aesthetic outcome and safety profile [36]. A year earlier, Sigrist et al. conducted a similar study. They investigated the tissue integration of different PLLA formulations in the gluteal region. It is interesting to note that the authors showed that the various PLLA formulations differ from each other in their rheological properties. PLLA-SCA in particular showed rapid and uniform tissue integration [6].

3. molecular mechanism, duration of action and degradation of PLLA

PLLA-SCA is applied with a carrier fluid (aqua ad iniectabilie with 2% lidocaine). This initially leads to visible changes (e.g. slight smoothing, hydration) in the skin. After about two to three days, the surrounding tissue absorbs the carrier fluid of the suspension. Although the tissue initially returns to its original state, the PLLA-SCA particles remain subdermal and are in direct contact with the tissue. There they unfold their biostimulating effect via two coupled mechanisms.

Firstly, contact with PLLA-SCA causes fibroblasts (without the additional influence of immune cells) to start synthesizing collagen type I, elastin (cross-linking for collagen) and matrix metalloprotease inhibitors (slowing down the degradation of the extracellular matrix) [37, 38]. On the other hand, the injection of PLLA-SCA causes a direct immunological response via a wound healing reaction. Activated macrophages (M2 polarization) secrete TGF-β (transforming growth factor-β), among others, which strongly stimulates fibroblast proliferation [39]. This leads to a significant increase in collagen production, as a higher number of active fibroblasts are present in the tissue.

An interesting observation by the author is that PLLA-SCA only has a volumizing effect on the face and in the gluteal region. In all body indications, the effect is associated with collagen formation, which counteracts skin laxity.

There are various data in the literature on the duration of the therapeutic effect: In a study on the treatment of nasolabial folds, the effect lasted for up to 25 months [10].

The degradation of PLLA-SCA is mainly hydrolytic. The hydrophobic molecular chains break down into oligomers and monomers and these are metabolized to CO₂ and water. Although the pure hydrolysis of PLLA-SCA (under laboratory conditions / in vitro) would take about two years, it can be assumed that cellular and enzymatic processes in the skin significantly accelerate the degradation process [4]. Lifestyle (e.g. competitive athletes, smokers) also plays a significant role in the rate of degradation.

4 The ideal patient: criteria for the selection of body regions for treatment

The decision to undergo PLLA-SCA treatment in the context of body indications requires a thorough investigation of the patient’s suitability for this therapy. In this selection process, it is crucial to have a good understanding of the limitations of the treatment, as well as taking into account individual patient preferences. Therefore, patients may need to consider other treatment options or additional measures may be recommended to achieve the desired results.

As PLLA-SCA stimulates collagen neogenesis, the primary physiological effect is a tightening of sagging skin. Therefore, the most important consideration is whether the indication is excess tissue or sagging skin. Patients with excess tissue should be treated surgically. However, surgery does not compete with PLLA-SCA treatment. In fact, in the author’s experience, PLLA-SCA treatment can significantly improve and support the results of surgical intervention. Injectors who have no surgical experience should therefore discuss such therapies with the patient and the patient’s surgeon.

Another contraindication is the body mass index (BMI). For successful PLLA-SCA treatment, the patient must be at most of normal weight or have a BMI of 25 or less. Overweight or obese patients will not benefit much from collagen neogenesis, as the effects are less visible in these specific cases. This view is also confirmed by other experts [40].

Although a number of other factors are not contraindications, they must be taken into account when selecting and informing patients. Metabolism and the fibroblast population decrease with increasing age, which is why patients over the age of 60 require more frequent treatments or larger quantities of product for corresponding success. Lifestyle also plays a role. Athletes and smokers are more likely to experience weaker treatment success. Another important factor is gender. Although men generally have stronger muscles and therefore deeper wrinkles, the author’s experience shows that men tend to respond better to PLLA-SCA treatment than women.

5. patient comfort: communication, pre- and aftercare

The decisive factor for patient satisfaction lies in effective communication, which begins long before the decision for treatment is made. The treating physician’s task is to precisely understand the patient’s exact wishes and to clarify whether these can be realized with a PLLA-SCA treatment. An illustrative example of this is the so-called “hip dips” (trochanteric dips). While hip dips are not always perceived as aesthetic in the USA and Brazil, they are often seen as an indication of athleticism in German-speaking countries. Treatment without the patient’s express wish can lead to considerable dissatisfaction in such cases. In other situations, a patient may expect unrealistic results. These may include rapid changes within a few days or the complete removal of severe excess tissue (see Chapter 4). In such cases, it is up to the practitioner to show the limits of the treatment and regulate unrealistic expectations.

Furthermore, the patient’s immediate expectations must correspond to the possibilities of the treatment. The effect of the treatment occurs gradually over several weeks (approx. 3 – 6) after the treatment. It is therefore important to convey to the patient that collagen neogenesis is a process that takes time, but generates a natural appearance. In this context, it is important to mention that several millilitres of water are injected into the tissue during a PLLA-SCA treatment, which temporarily volumizes the tissue. The volume will usually return to its original state after three days, which should not unsettle the patient.

Another important aspect of communication with the patient concerns the treatment intervals. It is crucial to distinguish between the initial treatment and the refresher treatment. The initial treatment usually consists of a series of therapy sessions that are carried out approximately 4-6 weeks apart

It is important to make it clear to the patient that the success of treatment is individual. Single sessions may be sufficient for the initial treatment, particularly depending on the age and lifestyle of the patient and the area of the body being treated. However, it is also possible that some patients may require at least three sessions with above average amounts of material. It is also worth noting that the evidence and studies indicate that the duration of effect of PLLA-SCA can be up to 25 months. However, there is expert opinion suggesting that refresher treatments for the body indications are recommended every 1 to 1.5 years to maintain the desired results. This is based on an individualized assessment and adjustment of treatment plans to ensure long-lasting effectiveness.

Once the patient and injector have decided on the treatment, some technical aspects must be taken into account. To support the effect, I recommend that the patient takes nutritional supplements containing protein or collagen a few days before the treatment.

All make-up should be removed and the skin disinfected immediately before treatment begins. Local anesthetics can be administered in the form of a cream or as an injection. However, the author’s experience shows that the puncture and application of 2% lidocaine generally cause greater discomfort than a direct injection (this observation only relates to work with a blunt cannula).

It is recommended to cool the area immediately after the injection. After a few minutes of cooling, the applied material should be massaged in for about 5 minutes. The author also recommends using a soothing skin cream.

To ensure an even distribution of the material, it is recommended that the patient continues the massages at home over several days. The massages should be uniform in order to prevent possible PLLA aggregation.

Although the patient can return to their normal routine shortly after the treatment, Dr. Avelar recommends avoiding saunas and excessive exercise for the first few days.

The injector should consult the patient again in person approximately 4 to 6 weeks after the first session to plan further therapy. This may require a second or even third session, depending on the patient’s response to the initial treatment. Thereafter, the patient should be offered the prospect of booster treatments.

6. general treatment instructions

For the treatment of body indications with PLLA-SCA, it is recommended to first gain experience in the use of the product in the facial area.

In addition to the patient selection described above (see chapter 4.), some important technical aspects must be taken into account. Although the author is not critical of the use of a pointed needle, he recommends the use of a 7 cm long, blunt, atraumatic cannula. He recognizes the advantages of this method in that only a few puncture points are required, which considerably reduces the risk of infection and haematoma. In addition, precise placement in the correct tissue layer and adherence to this layer is much easier.

Dilution is another important aspect. In principle, PLLA-SCA should be diluted significantly more for use on the body than is known for facial indications. The author’s recommendation for a safe yet effective treatment is between 16 and 20 mL (total volume; incl. lidocaine) per vial [13]. A greater dilution when using PLLA-SCA in the body indications than in the face is associated with a very good safety profile. I share this experience with other experts [40]. I myself work with a total dilution of 20 mL (18 mL aqua ad iniectabilie and 2 mL 2% lidocaine) per vial, regardless of the body region. Regardless of the dilution (16 or 20 mL), the rule of thumb is that one vial is sufficient for an area of approx. one DIN A4 page.

I also recommend combining a PLLA-SCA treatment with other procedures. Laser, microneedle therapy and subcision [24, 29] are procedures with which I and other colleagues have had very good experiences.

Finally, two warnings should be noted. As with the face, hyperdynamic regions should be avoided, as material can accumulate in these areas, which can lead to the formation of lumps. I also warn against general overtreatment. An excessive number of injections and an excessive volume administered (and the associated amount of PLLA) can lead to a strong immune reaction in the form of fever. It is therefore advisable to treat the patient with restraint, caution and care.

The exact treatment recommendations for the selected body regions are summarized in Tables 1-7 and Figures 1-12.

7. treatment recommendations of the author by body region

7.1 Neck

The indication for the use of PLLA-SCA on the neck is sagging skin. The therapy can also improve skin quality and smooth out wrinkles.

Patient selection is particularly important in the neck region. A clear distinction must be made between laxity (skin laxity) and excess skin. The treatment is most effective in slim to normal weight patients who suffer from skin laxity. For patients with a large amount of excess tissue or fat, surgery would be the better choice. Based on my experience, a PLLA treatment can support the results of a surgical procedure by tightening the skin.

The neck region is one of the more difficult indications and requires some experience. The neck is injected only laterally. Even if the skin laxity is present in the larynx area, the effect of lateral application is strong enough to improve it appropriately. The submental region should also be taken into account. It is applied above the curvature of the larynx and the underside of the chin. 4 mL per side are injected submentally and 6 mL per side laterally using an atraumatic (blunt) cannula. Working with a cannula helps with the application in the deep dermis, especially with regard to the sometimes very thin tissue coverage on the neck. Working with a cannula also reduces pain and the risk of hematomas.

The initial treatment is carried out in 2 – 3 sessions, with an interval of around 4 to 6 weeks between sessions. Based on my experience, the effect can last for several years. A refresher treatment is recommended every 1 to 1.5 years.

7.2 Decolleté

The use of PLLA-SCA on the décolleté is primarily aimed at improving skin quality and smoothing wrinkles.

The treatment of the décolleté is easier than that of the neck and can also be considered by beginners in the field of body indications. One of the most important aspects is injecting only into the deep dermis, which is why I recommend using an atraumatic cannula here too. Intradermal injections should be strictly avoided as this can increase the risk of lump formation.

As results can vary from patient to patient, I recommend waiting around 4 to 6 weeks after the first injection and only planning further treatments after an examination. In many cases, one session with one vial is sufficient to achieve good and long-lasting results.

It is interesting to note that there is no good surgical alternative to décolleté treatment. A possible, but limited, treatment in terms of skin quality would be skin booster preparations (based on cross-linked hyaluronic acid). They are primarily aimed at improving skin hydration.

7.3 Upper arms

Treatment of the upper arms focuses primarily on the sagging skin in the triceps region. However, the biceps region can be injected if necessary. If necessary, the treatment can also be extended to the frontal armpit area. This can result in a more harmonious overall appearance. As with the neck, it is important to differentiate whether the patient suffers from sagging skin or excess tissue in the upper arms. The latter should be treated surgically. I recommend a PLLA-SCA accompanying therapy for a possible surgical procedure.

Although PLLA-SCA is used to generate volume in other areas of the body, this effect does not occur in the upper arm area. On the contrary, my experience even shows a reduction in circumference after a successful treatment.

The treatment requires advanced skills and a certain amount of experience. It is injected exclusively into the deep dermis. To achieve good results, I recommend at least one full vial per arm per session. For the initial treatment, 1 – 3 sessions should be scheduled.

7.4 Abdomen

The abdomen is a beginner-friendly body indication for therapists who do not yet have much experience outside of using PLLA-SCA on the face. Whether a patient is suitable for treatment in this case also depends on the excess tissue. If there is excess tissue, surgical intervention should be the first priority. Following surgical tissue removal, however, a PLLA-SCA treatment is recommended to tighten the tissue. The best indications are mild to moderate skin laxity without excess tissue. Body fat percentage also plays an important role in patient selection. Patients with up to 4 cm on the adipometer scale are suitable, patients with less than 2 cm on the scale are considered ideal.

Particular attention should be paid to possible hernias. A hernia should always be ruled out before the procedure.

The product is applied exclusively to the deep dermis. The initial treatment can be carried out in one to three sessions. For optimal results, the author recommends distributing a total of 3 vials over all treatments. Depending on the patient’s wishes, all three vials can be used during one treatment or spread over up to two further treatments at intervals of 4 to 6 weeks. Booster treatments should be considered approximately every one to one and a half years.

7.5 Hands

For the treatment of sagging skin on the back of the hand, I recommend using half a vial per side in one to three sessions. As the back of the hand is quite delicate, the injector should already have some experience. A refresher treatment is carried out as required, as the results can vary greatly.

If a PLLA-SCA treatment does not produce the desired results, treatment with hyaluronic acid preparations is possible. Skin boosters to improve skin quality and fillers to add volume are recommended.

7.6 Gluteal region

Alongside the face, the buttocks are the body region that experiences a significant increase in volume through the use of PLLA-SCA. Accordingly, four (partly overlapping) indications can be treated depending on the area of application:

• Lifting
• Projection and volume
• Skin quality / mild to moderate cellulite
• Contouring

This is also reflected in patient selection. Although very good results can be achieved in the gluteal region with PLLA-SCA, the practitioner is always called upon to set clear limits and, if necessary, suggest alternative therapies to the patient. In particular, the Subcision™ technique (against cellulite [24, 29]) and liposuction are such alternatives, but they can also be effectively combined with PLLA-SCA treatment.

Although there are other opinions, I recommend – from years of experience – injecting most of the volume into the upper and outer part of the gluteal region. The area or frame of the basic treatment thus resembles the number 7 (right side of the patient) or a mirrored 7 (left side of the patient). The application to achieve one or more of the four effects requires very good anatomy and product knowledge and should only be carried out by experienced injectors.

For good effects, it is recommended to use at least one vial per side per session. In the author’s experience, the increase in volume can lead to good results after just one application, so it is advisable to schedule an evaluation about 6 weeks after the first treatment and only then make further treatment decisions.

During treatment, it is important to always inject above the gluteal fascia. Larger blood vessels run underneath it, which should remain intact.

7.7 Knee

The aim of PLLA SCA treatment on the knee is to reduce skin laxity and smooth out wrinkles above the kneecap. As with other indications, a clear distinction must be made here between skin laxity and excess skin, as excess skin should also be surgically removed from the knee.

For the treatment of the knees, the injector should already have experience with PLLA-SCA in the area of body indications. As a rule, one vial is used for both knees. The injection site is 5 – 10 cm above the kneecap.

The effect can vary depending on the patient, so the author recommends discussing the results with the patient about 6 weeks after the first treatment and only continuing with further treatment if necessary.

8. conclusion

When used correctly, PLLA-SCA is a well-tolerated and effective therapy against skin laxity and improvement of skin quality. It is characterized by a long-lasting effect and a slow and therefore natural-looking increase in collagen. In the author’s experience, in addition to correct technical implementation, patient selection and communication are the most important pillars for ensuring patient satisfaction. It is essential to take sufficient time to plan the treatment and to discuss the possible results with the patient.

The most important point is that the injector understands the patient’s wishes and plans and designs the treatment accordingly with the patient. Unrealistic patient wishes must be clearly addressed and, if necessary, realized via alternative therapies. It must be clear to the patient that the slight volumizing and hydrating effect that occurs immediately after treatment due to the volume administered will subside within a few days and that collagen neogenesis may take several weeks. The extent of collagen neogenesis can also vary, which is why it is generally recommended not to plan too far in advance. The results of the first treatment should first be discussed with the patient. Only then, and only if necessary, should further injections be carried out.

Understanding the effect of the preparation, strong anatomical knowledge and robust and clear patient communication are key to patient satisfaction and safe use of PLLA-SCA.