In the last recent years the buttock area has received much media attention which has produced an increased patient demand for buttock contouring and augmentation. The statistics of the American Society of Aesthetic Plastic Surgery (ASAPS) are reflecting this phenomenon and shows that there is an increasing of buttock augmentation procedures from 2015 to 2019 by 90,3% and also an increasing buttock lift procedures by 102,9% in the same time [1]. However, as the number of interventions increased, possible risks and complications became evident. The worst complications were fat embolism and infection, some of which were fatal. The increasing number of complicated treatment processes, regardless of whether after operations such as augmentation using silicone inlays [7]. fat crafting operations [4-10]. silicone injections [2,3]. or injections with other materials [8]. led to the establishment of the Gluteal Fat Grafting Task Force (GFGTF) of the Aesthetic Surgery Education and Research Foundation (ASERF) to scientifically work on these risks and ultimately to formulate treatment recommendations from the findings [10]. The findings of the GFGTF have been that there is an 403% increase in the risk of fatal and nonfatal pulmonary fat embolism when injecting fat into the deep muscular tissue [10]. So mid to superficial muscle and subcutaneous injections are recommended, though it is likely that some risks remains with them [10]. An expert opinion survey [31]. performed by board certified Brazilian plastic surgeons showed complication rates in gluteal fat grafting such as necrosis (23.63%), seroma [17,75%], infection [13,5%], oil cysts [11,25%], haematoma [9,38%], paraesthesia [5,13%], fat embolisms [2,25%], pulmonary embolism [2,13%], deep venous thromboembolism [1,88%], and death [1,5%]. The fatal complication of this survey have been strongly correlated with injection of fat into the deep highly vascularised muscular tissue, so the recommendation was that fat should be injected in the subcutaneous plane only [17]. A less invasive and simple method for gluteal augmentation and recontouring should be the augmentation with filler materials such as hyaluronic acid, liquid injectable silicone, poly-L-lactic acid, polymethylmethylacrylate or polyacryamid to prevent most of the possible complications after fat grafting such as necrosis, seroma, oil cysts, fat embolism and deep venous thromboembolism. Despite long term use of the filler there have been few reports of it to date in buttock augmentation. Severe complications are known to occur [19-22] with nonhuman filling materials and it is recommended to avoid these materials until proven safety and efficiency in good scientific studies is reached [23]. The effectiveness and safety of the use of Hyaluronic acid (HA) Fillers for buttock augmentation has been investigated and published [17,18,24]. The patient satisfaction have been high and the complications low [24,28,29]. Due to the high costs and limited duration HA fillers have been withdrawn from the market. With the development of new HA fillers it is possible that their use in body contouring will be reintroduced in the future. This study will report on the safety and efficiency of a new hyaluronic acid gel (Variofill®, Adoderm, Germany) for buttocks augmentation and recontouring.

Started in 1969 by the use of breast silicone implants to achieve volume restoration in buttocks with atrophy of the gluteal muscle[11]. Later the breast silicon implants were followed by gluteal implants [12]. With the introduction of liposuction for body contouring in the 1980s autologous fat grafting was developed for buttock augmentation [13]. All these methods of buttock enhacement are surgical procedures which can produce surgical problems such as poor wound healing, scarring, infection or dehiscence of the scars. The procedures have to be performed under general, regional or local anesthesia. They mostly requires hospitalization and have longer recovery times. Studies over fat grafting has shown that the technique is relatively safe and effective [14-16] but there was still a risk for partially fatal complications after fat transfer operations [4,5,6,7,9]. Also this technique is not suitable in patients with an insufficient amount of body fat and many patients want to be treated with other less invasive procedures.  That is the reason why injectables have been developed for the treatment of body contouring, or rather said: as injectables have been developed for facial treatments they have been used for body contouring and buttock treatments also. Due to the high costs of the HA fillers they have been withdrawn from the market.

Other Injectabels for Buttock (Body Shaping/Volume Restoration) Augmentation

Injectable Silicone: Injectable liquid silicone has been used off label as a soft tissue filler in cosmetic procedures for decades. However, there is still a lack of well documented controlled trials in the usage of injectable liquid silicone but there have been multiple reports about complications of its use, such as abscess, ulceration [35], foreign body migration [35,37], granuloma [33,37], acute and late onset pneumonitis and pulmonary embolism [34,36].

Polyalkylimide Gel: Polyalkylimide Gel (Bio-Alcamid®; Polymekon Laboratories, Italy) came onto the market in 2001. It received a CE mark for the use of volume therapy in body and face aesthetic procedures. Initially it was very popular due to its resistance to hydrolysis, non-migration and longevity. Bio-Alcamid® has never received the FDA approval. In 2012 Nadarajah et al. [39] published first long-term results on 267 patients treated with Bio-Alcamid®. He showed that 19% of treated persons developed infection associated with the implant. Since the international meeting on adverse drug reactions and co-morbidities in HIV of 2010 Bio-Alcamid is no longer recommended in the treatment for facial lipoatrophy in HIV patients. In a report of 18 cases of treatments with polyalkylimide there have been shown migration in 12 cases, infection in 8 cases [40]. The onset of the complications ranged from 1 months to 3 years (mean 15 months). We have not found any publication on the use of Bio-Alcamid® in the gluteal region.

Polyacrylamide Gel: Polyacrylamide hydrogel is a non-resorbable gel (Aquamid®; Contura, Soeborg, Denmark). It received CE mark for the use of a soft tissue augmentation in the face in 2001. in 2003 this mark was extended to include soft tissue corrections of the body. However, the gel has no FDA approval. After initial very positive reports with high rates of patient satisfaction [41,42] several studies with clear complications of the nondegradable filler were published over the course of the year these showed product migration, breast deformity, spontaneous extrusion and capsular contracture [44,45,46,47], especially in very flexible tissues such as muscles [48].

Polymethylmethylacrylate (PMMA): Artecoll® (Artes Medical Inc. San Diego, USA) renamed Artefill® received FDA approvel in 2006 and rebranded to Bellafill® (Suneva Medical, San Diego, USA) in 2015. PMMA is recommended fo the use in the face and we did not find any study with the use in the buttock. Salles et al published a case report over 32 cases with Complications after PMMA-Filler treatment [49]. They reported about tissue necrosis (5 cases), granulomas (10 cases), chronic inflammatory reaction (10 cases), lip complications (6 cases) and infection (1 case). The outers conclude that complications with PMMA-fillers are “rare, but often permanent and difficult or even impossible to treat”.

This was a retrospective study performed using 12 treated subjects with the wish to be treated on their buttock volume loss or volume deficit. Patients were excluded from the treatment if they were pregnant or lactating or if they reported autoimmune diseases, coagulation disorders or anticoagulant medications. Also patients were excluded if they had any other treatment before in the gluteal region. A total of 12 patients were included. All the patients received an injection treatment of the buttock with a new hyaluronic acid gel Variofill®, Adoderm, Germany.

Planning the Buttock Treatment

All patient received a medical consultation to assess if the patient is suitable for Variofill®, Adoderm, Germany for a gluteal augmentation procedure. During the consultation the procedure and potential risks have been explained. The patients were asked to rate their satisfaction with their buttocks according to three sizes (very dissatisfied, dissatisfied, neutral). It was checked if there is any contraindication for having the treatment including if there have been any other treatment in the gluteal region before. No pretreatment was recommended. A local examination of the skin with a checking of the integrity of the skin was done. The exact treatment region and the treatment volume were determined. The treatment region were signed on the buttock upright standing. Before injection, informed consent had to be signed. Before photographs were taken.

Material

Variofill®, Adoderm, Germany is a sterile resorbable cross-linked pyrogen free CE marked medical HA filler for gluteal augmentation of nonanimal origin. The product is 100% designed and made in Germany. The degree of cross linking is 80%. The cross-linking agent is Devinylsulfone (DVS). The concentration is 33 mg/ml. One syringe of Variofill®, Adoderm, Germany contains 10ml of HA gel.  Due to the high viscoelasticity of Variofill®, Adoderm, Germany and its higher concentration compared to other hyaluronic acids on the market, it is recommended to use 30 to 50% less Variofill® than other products. Variofill® can be injected pure or in some cases it can also be injected diluted. The dilution preparation must be done just before the treatment in a sterile environment to avoid bacterial contamination.

Treatment Preparation/Dilution Process

To prepare the injection solution the 10 ml syringe of Variofill® is connected to and other empty 10ml syringe through a luer-lock connector. The 10ml of HA gel is divided in the two syringes each one with 5ml of HA gel. Then 3,5ml of saline solution and 1,5ml of lidocaine 1% is added to each syringe. After that an empty 10ml syringe is connected to the mixed 10ml injecting solution and the injecting solution is homogenized by going back and forward between both syringes several times to correctly homogenize the mixture (Figure 1).

Figure 1: Treatment Preparation/Dilution Process.

Treatment

The buttock markings were drawn while the patient is in an upstanding position. Then the patient must lie down on the bed on stomach position. In some but not in all cases an anaesthetic cream was been used for about 20-30 minutes before the disinfection and injection of the gluteal region was performed. This time can be used to fulfill the dilution process. No antibiotic treatment was recommended. The treatment area was sterilized with Cutasept® (Paul Hartmann AG, Germany).

There Are Basically Two Different Injection Techniques available

Injection Technique with blunt Cannula (More Subcutaneous Injection): The recommended size of the Blunt cannula is from 16G to 18G and from 12 to 18cm in length. The entry point for the Blunt cannula is about 5cm on either side of the median axis from the top of the buttock (Figure 1). More injection points are possible infra-gluteal or lateral. A small subcutaneous injection of pure with a small incision of only about 1mm wide to avoid a suture should be done. The mixed lidocaine injection solution is then injected in a retrograde fanning technique for augmentation of the subcutaneous area of the buttock (Figure 1). To achieve an aesthetic outcome the injection solution must be injected homogeneously. When finished the treatment area has to be cleaned and a deep but soft massage should be done to avoid lumps and nodules. The entry points should be closed by suture-strips. Afterwards the injection points should be covered by a tape for 7 days.

Injection Technique with Sharp Needles (Subcutaneous and Superficial Muscular Injection): The recommended size of the sharp needles is from 18G to 19G and from 40mm in length. Before laying down on the bed on the stomach position a grid with 2cm side squares in the area to be treated have to be drawn on the buttock (Figure 1). After intensive desinfection a small amount of local anesthesia should be paddled into each great field that is to be injected. There would be between 20 to 30 injections on each side of the buttock and afterwards again a desinfection step. Once again disinfection. The needle is then  inserted with an angle of 90° and only a few millimeters into the subcutaneous area. Under aspiration the needle is then pulled forward up to a depth of about 3 to 4cm under constant aspiration. When blood is aspirated no product is to be injected! The treatment solution is then injected through the tower technique [25]. The same process is repeated in each square to be treated. When finished the treatment area has to be cleaned and a deep but soft massage should be done to avoid lumps and nodules. Afterwards the injection points should be covered by a tape for 7 days.After the treatment, the patients were asked about the pain of the treatment on an analog scale (visual analogue scale, VIS) [26] and the answer was documented. Overcorrection or overtreatment must be avoided in both techniques.

Post Treatment Recommendations

For the first 14 days hot bath, sauna or solarium or direct exposure to sun has to be also avoided. For the first couple nights the patients were asked to sleep on their Probably it is meant "on their stomach" back. No physical activity for 7 days was recommended. Patients were asked to get in contact to the practice immediately if possible side effects such as redness, hematoma, pain, heat and edema occur.

Follow Up

Follow up visits were arranged for day 2 and day 14 after the treatment procedure. The patients received a clinical examination with documentation of the side effects. In addition, there was photo documentation and a questionnaire on satisfaction with the result of the treatment. They were asked to rate their satisfaction with their buttocks after the treatment procedure according to four sizes (dissatisfied, neutral, satisfied, very satisfied).

Long-Term Follow-Up

The survey on the long-term results was carried out by telephone in December 2020. only two of the 12 patients were asked about other treatments in the practice and therefore asked here. The patients received once again a clinical examination with documentation of the side effects. In addition a questionary on satisfaction with the result of the treatment. They were asked to rate their satisfaction once again after the treatment procedure according to the four sizes (dissatisfied, neutral, satisfied, very satisfied).

Results

From February 2020 to October 2020, there have been 12 patients, 11 female and one male, treated with Variofill®. All 12 patients were included retrospectively in this study. No patient suffered? on any preexisting illness. The average age of the patient was 30,1 years (range: 21-37years). The average body mass index (BMI) was at 21,06 kg/m² (range: 18,4-24,2 kg/m²) (Tab.1). The average injected volume of Variofill® was 85ml total injected? per side? (range: 60-100ml). All patients were injected by the injecting technique with the sharp needles as described above in the subcutaneous and superficial muscular plane. The evaluation of the described painfulness of the treatment showed an average of 2.83 (range: 2-4).

Table 1: Demographic Characteristics.

At day two after the treatment several side effects have been reported, such as redness [3/12;25%], swelling [4/12;30%], pain [10/12;83,3%], haematoma [12/12;100%], overheat [6/12;50%], itching [1/12; 8,3%] and palpable knots [12/12;100%]. There were no patient without any side effect. At the 2nd follow up appointment on day 14 after the treatment much less side effects have been reported: redness [1/12;8,3%], swelling [1/12;8,3%], pain [3/12;25%], haematoma [7/12;58,3%], overheat [1/12;8,3%], itching [3/12; 25%] and palpable knots [12/12;100%].The long-term follow-up as described was done by a telephone survey. The average time after procedure was 22,7 weeks [range 8-40weeks]. the only long-term side effect reported was palpable knots in 8 out of the 12 patients [66.7%].No case of non-thrombotic embolism, necrosis or pressure on any nerve have been seen [Tab.2].All patients [100%] reported an improvement in satisfaction with their gluteal region. The average improvement showed 2,92 steps forward on survey table of very dissatisfied to very satisfied. It should be Menschen@ that delivers satisfaction Rate ist strictly correlated Wo ist Laura infection Volume auf HA gel. Patients with an injected volume of only 60ml showed an average improvement in their ranking of only 2 steps. Even with 80ml, there was only an improvement of 2 steps. The average improvement rate for an injection volume of 100ml was 4 steps.

One Case of Infection

Patient number 8, a 31 year old female patient [BMI: 19,8kg/m²], who received a buttock augmentation with 100ml of Variofill® developed an infection therefore her case needs to be described in more detail here. At the first follow-up appointment on the second day after the treatment, the patient presented significant warming and swelling of the left buttocks. Antibiotic treatment with Amoclav 875/125mg twice daily was started immediately. After a short symptom improvement on day 3, there was a further deterioration on the fourth postoperative day. A sonographic examination carried out on the left buttocks then showed a subcutaneous abscess formation, because of that an incision treatment with pulling the flap was carried out immediately under local anesthesia. Down here and under the antibiotic treatment appropriate to the smear, the symptoms quickly improved and the abscesses healed within 10 days. The lying delete? could be removed on the 8th day after pulling through. In the further course the patient was surprisingly extremely satisfied with the results of her treatment and would recommend such a treatment to a friend. Three slightly pigmented scar about one centimeter long remained. This case will be reported in a Case-Report.

Variofill®, Adoderm, Germany is a sterile resorbable cross-linked pyrogen free CE marked medical HA filler of nonanimal origin used for gluteal augmentation. In the current study, we were able to show that most of the problems of invasive procedures such as operations and fat graftings like transplant necrosis, oil cysts, seroma, deep venous thromboembolism do not occur [9,10]. The number of expected mild side effects such as redness, swelling, hematoma, pain, overheat, itching and palpable knots was comparable to that of other procedures () and disappeared within several weeks. One case of infection [8,3%] happened. This is comparable to the number of infection symptoms in other approaches to HA gel for body shaping [10,87%] [24]. No other serious complications could otherwise be described.

Patients: Our patient baseline characteristics are comparable to those of other studies [24)]. Among our treated patients, the proportion of women is far superior at 91,7%. The average BMI was 21,06kg/m². The patients are therefore underweight [BMI<20 kg/m²] or low normal weight, who are not good eligible for lipotransfer due the lack of fat reserves. High normal weight or overweight patients were not treated in the present study, although their treatment was not an exclusion criterion. Treatments of such patients should be carried out and evaluated with the question of whether they are just as satisfied with the same injection volume as leaner patients and whether higher injection volumes are accompanied by a higher rate of complications.

Injection Technique: As described above there are essentially two different methods to inject the HA gel. The one with the sharp needle or the other one with the blunt cannula [29]. However, the angle at which the injection is made is very important because this, together with the length of the needle or cannula determines the depth of the injection. Possible, sometimes fatal complications, such as nonthrombotic embolism or nerval injury are described not only in fat grafting procedures [4,6,8,9,10,31]. The Brazilian survey [31] and an anatomical study in cadavers [32] showed that the plane of injection influence the risk of nonthrombotic fat embolism and death dramatic. Analyzes by the ASERF Task Force showed that injecting fat into deep muscle plane increases the risk of fatal or nonfatal fat embolism by 403% [32]. It was strongly recommended that practitioners performing this procedure avoid deep muscle injections [32]. The Brazilian survey recommended strongly only to inject in the subcutaneous plane [31]. These recommendations apply to fat grafting but one case of non-thrombotic pulmonary embolism with Polyacrylamid Hydrogel in 2016 [8] and others with liquid injectable silicone were also reported [34,36]. In the current study all patients [n=12] have been injected with sharp needles in 90° angle to the skin. The length of the needle was 40 millimeters, the injection depth was into the superior muscle and subcutaneous plane in the described tower technique. The needle was always advanced under aspiration. I recommend to rephrase...

No case of nonthrombotic pulmonary embolism was reported within our patients. We felt very safe with our approach up to the intensive research on the publications for this article and will now reduce our injection depth a little.

Injected Volume: In the present study the volume injected was between 60 and 100ml, that means in maximum 50ml per side. In the treatment guidelines of Variofill®, Adoderm, Germany [29] volumes up to 125ml per side are recommended. Despite the low injection volume a high level of patient satisfaction could be documented in the present study in slim patients [100%]. In other studies there are volumes up to 400ml (200ml each side) of HA gel (Macrolane®) reported [17,18]. In buttock augmentation procedures with other materials especially fat grafting procedures there are much higher volumes up to 800ml per buttock described [30,31].Once again treatments with Variofill® of patients with higher BMIs should be carried out and evaluated with the question of whether they are just as satisfied volume as leaner patients and whether higher injection volumes are accompanied by a higher rate of complications.

As expected, we were able to show in this study that this filler can be used safely and efficiently to augment the gluteal region. Nevertheless, the practitioner should reflect very carefully on the anatomy and injection technique before use. Further studies should be carried out to provide better recommendations on injection volume and perioperative antibiotic administration. Nonbiodegradable filler materials are strictly not recommended.

Steffen Giesse is a advisor for Adoderm, but has no financial intrest in the company or its products. No fundings was provided for this study or other activities. Jason Webb has no conflicts to declare.

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