Form and dimension of the gluteus in the population is highly variable. Small asymmetries and the variety concerning shape and volume is immense. Form and shape depend  on size and shape of the muscle, fat distribution and configuration of the pelvis. Terminology in terms of surgical procedures addressing the aesthetic appearance varies reference10 from gluteoplasty, buttock- or gluteal enhancement, augmentation or lift. Buttock augmentation via autologous fat transfer from area of the body into the subcutaneous layers of the buttock is also known as Brazilian Butt lift. Recently, the term composite or hybrid gluteal surgery was brought up, describing procedures in which gluteal implants and autologous fat grafting was combined reference11. Goal of all mentioned procedures is improvement of the buttocks contour, size and or shape; however, there is no exact definition concerning quantity of added volume, gain in terms of projection or changing ratios to other landmarks. Over the last decades, the professional knowledge around gluteoplasty, its relevant anatomical structures, technical mandatory refinements and specific instruments have been investigated and developed to a high expert level, which is reflected in the number of evidenced based literature, masterclasses and congresses about this field. Gluteal augmentation has moved mainstream among today's plastic surgery procedures.

Due to severe malpractice related morbidity and mortality of gluteoplasty, familiarity with relevant clinical anatomy is mandatory! Besides, precise evaluation of shape, volume, specific superficial anatomical landmarks and tissue quality is key to choose the right technique, analyze limitations and receive the postoperative appearance of desire. 

A buttocks projection is influenced by three factors: thickness of the gluteus maximus muscle, quantity of subcutaneous fat and degree of lumbar lordosis. The amount of subcutaneous fat is usually greater in females versus males, varies among ethical groups and is strongly influenced by weight changes, aging and genetics.

Two distinct indentations that are superficial to the sacroiliac joints formed by a fascial cutaneous insertion to the PSIS (posterior superior iliac spines), which represent attractiveness.

The sacral space is defined as the area between the lumbar-sacral junction and the upper end of the intergluteal crease length; male skeletons present a sacral triangle, female skeletons a rhomb. The female rhomb/ diamond shapes basic points corelate to the following structures: lateral to Venusian dimples, caudal to the anal rim /third to fourth coccygeal vertebras and cranial to the third to fourth lumbar vertebras. Lengths of the sacral space ideally is 50% to 100% of the intergluteal crease length.

Reflects the inferior border of the buttock; this well-defined sulcus is formed by thick fascial insertions from the femur and pelvis through the intermuscular fascia to the skin reference12reference13. Length and definition strongly influence aesthetic of the buttocks: medially positioned, short and sharp infragluteal folds contribute to full tight and youthful buttocks reference14 . Aging causes an increase in buttock height and lengthens the infragluteal fold, additional weight gain causes drooping of the infragluteal fold reference12.

Palpable, sometimes visible landmarks concerning the superior border of the buttock.

Is formed by the greater trochanter and insertion of thigh and buttocks muscles. The existence of lateral trochanteric depressions may be desired in males, where it contributes to an athletic look. 

The ideal intergluteal crease measures ideally less than the hight of the sacral space and  half of the gluteus muscle height, with more volume above the end of the crease reference18 . 

There are three gluteal compartments: the gluteus maximus compartment, the gluteus medius-minimus compartment and the tensor fascia lata compartment. The gluteus maximus muscle origins at the lateral sacrum/ coccyx and posterior superior iliac spine (PSIS), is attached to the iliac crest and inserts at the iliotibial tract and lateral rim of the greater trochanter. Delicate neurovascular structures (superior and inferior gluteal vessels and sciatic nerve) are part of the medius- minimus compartment. Cadaver dissections addressing vessel diameters of veins in different tissue layers of the buttocks determined vein sizes of 1.05 +/- 0.22mm, inside the gluteus maximus of 1.3 +/- 0.3mm and inside the submuscular space of up to 13.65 +/- 6.55mm (Inferior gluteal vein) reference07

The sciatic nerve originates from L3 to S4 has no gluteal branch except one to the hip joint. It emerges throught the greater sciatic foramen between piriformis and superior gemellus muscle and enters theposterior compartment of the thigh. Compromising the sciatic nerve is followed by inactive thigh muscles of the posterior thigh compartment and all muscles of the rest of the leg, as well as lateral leg and complete foot sensation. Cutaneous sensation of the Buttock: the superior clunial nerves (L1 – 3), medial - (S1 – 3) and lateral clunial nerves, which innervate the superior, medial and caudal area of every side of the gluteus; the superolateral unit is innervated by the lateral cutaneous branch of the iliohypogastric (L1) and the lateral femoral cutaneous nerves (L2, 3). After autologous gluteal augmentation, protective cutaneous sensation is likely to be impaired!  

Gluteoplasty is suitable for 

Gluteoplasty is contraindicated for 

Relative contraindications are patients with ASAII health status; if comorbidities are under control and und a specialist’s therapy, surgery can be discussed together with the anesthesiologist

Patients who underwent previous liposuction sometimes present with severe fibrotic subcutaneous tissue; harvesting and quantity of aspirated material may become less and more difficult than expected

Mendieta described 10 aesthetic units  to the posterior region reference18  . Additionally, he and Sood classified four different basic frame types: A-shaped (30%), V- shaped (15%), Square (40%) and round (15%).

The buttocks height can be tall, intermediate or short; square shapes, which present with a short hight (width to height ratio of the gluteus muscle from 1:1) are a typical male feature. The round shaped buttock bears the risk of unpleasant, excess fat in the lower-inner (transition between the intergluteal and intragluteal folds) gluteal fold area. V- shape buttocks tend to have a tall pelvis, thin legs, and a tendency toward central obesity. 

The inferior gluteal base width can also be narrow (0% beyond the central vertical line), normal (10 – 30% beyond the central, mid- buttck line), or wide (40 – 50% beyond the central line). Characteristic of a young aesthetic buttock is the short clear defined ending at the mid-buttock line and a downward slope . 

Concerning volume- analysis of tissue above the greater gluteus muscle it helps to devide the buttock into four quadrants (vertical and horizontal midbuttock line): in the perfect buttock, volume distribution is equal in all four quadrants with the apex of projection where both lines cross each other .

Finally, the lateral buttock presents 3 zones: upper, central, and lower zone. This division helps determine where most of the buttock bulk or volume is and/or should be located. 

Mostly in weight loss or patients of advanced age, gluteal ptosis may play an important role in choosing the most suitable buttock reshaping technique: Ptosis exists, when skin droops over the infragluteal fold and the fold is appreciated at the lateral view between grade I and III according to the skinfolds angle .

Make sure that patients avoid medications and nutrition supplements that influence rheology (keep the risk for bleeding low). A hemoglobin level of at least 12 g/dl should be checked beforehand. Patients getting implants need to be informed about the specific risk of seroma, implant displacement, temporary sciatic nerve affection, capsular dehiscence, infection till implant exposure, asymmetry and anaplastic large cell lymphoma reference19. In transgender patients, pause hormone- therapy two weeks before and two weeks after surgery reference20.Work under general anesthesia or intravenous sedation! For patients getting implants: we highly recommend additional epidural anesthesia.

Predicting fat graft volume resorption remains challenging and varies from 20 – 90%; it is influenced by a large number of variables including graft size, procedure techniques, graft microenvironment etc. reference21. Mechanisms concerning adipose tissue graft survival remain subject of scientific studies, however well supported theories exist.

Earlier investigations have shown that lidocaine has potential cytotoxic effects on adipocyte stem cells in vitro, which is crucial in terms of transplant survival reference22 . Other investigations found no evidence for banning lidocaine from its use in lipotranser reference23 as it had no adverse effect on the relative distribution, cell number, or viability of adipocyte stem cells, preadipocytes, mature adipocytes, or leukocytes in the stromal- vascular fraction. However, the dosage of lidocaine depends on patient’s bodyweight as well as well as the additional use of epinephrine and often is maxed out in large volume lipoaspiration. 

Several studies have been made studying the influence of the lipoaspiration- cannulas diameter on fat graft viability and found out: fat cell viability increases according to the diameter of the cannula reference24reference25reference26. And blunt bore cannulas of 4 to 5mm should be used for fat harvesting. 

Autologous fat grafting for gluteoplasty affords infiltrating graft amounts of 300 to more than 1000cc per side; for this maneuver, manual graft preparation and injection is not advisable: roller pumps provide even application in “no touch”- technique using a closed system. Additionally, a roller pump shortens the procedure time and the risk for thromboembolic complications reference28

Accurate Pocket preparation is key in implant-based buttocks augmentation; besides light hooks, instruments such as a Bayonet dissector and spatulas ease muscle dissection and keep it less traumatic reference11.

Patient anatomy dictates implant selection reference29; likewise in breast surgery, there are various forms of silicone implants approved for gluteoplasty: round, anatomical and spherical; they vary in terms of projection, diameter, width and surface. In 2019 the first case of ALCL after implant based gluteoplasty had been described reference19, proofing that gluteal implants require identical precautions as silicone breast implants.

Temperature management is key to lower the thromboembolic risk to a minimum: Control the temperature management and make sure patients do not cool down: heating blankets/ prewarmed warmed tumescence fluid and or preheating the patient is essential, as a majority of the body will not be coverable during the procedure addressing the entire core and if necessary extremities during lipoaspiration

Gluteal Lipoinjection performed in a systematized manner, following protocols will provide predictable and standardized results: 

Markings, identifying the zones of liposuction and lipofilling are obvious.

Additionally, danger triangles (content: major gluteal vessels and sciatic nerve) can be useful, when drawn on each buttock side: apex of the triangle ist the posterior superior iliac spine. The inferior lateral point is located at the greater  trochanter and the inferior medial post is at the ischial tuberosity reference09. 

When performing larger volume (>100 cc) fat transfer, there is no significant difference in adipose cell viability and later take rates among donor sites such as abdomen, flank, thighs, or knees. reference64 

Lipoharvest will be performed according to zones in various positions: supine, lateral prone and or decubitus ensure that the patient is quite mobile on the operation table. Access incisions next to the buttocks should be placed suitable for later infiltration: in the gluteal crease, natal cleft and posterior iliac crest.

Many ways of conventional liposuction exist. No matter which method is used, it should be fast, sterile, gentle to the donor site and gentle to the harvested fat cells, leave no irregularities and it should be less exhausting for the surgeon. 

Simultaneous separation and tumescence of fat reference31 reference65 or "SAFE- Lipo" - Separation, Aspiration and Fat Equalization - Liposuction Technique is the recommended technique of preparing the donor site before liposuction: Separation of the subcutaneous fat layer emulsifies the target fat without injuring the stromal blood vessel network. After aspiration, the remaining fat emulsion prevents adherence or collapse of the dermis down to the fascia. The act of liposuction can be performed in various ways, waterjet- assisted, ultrasound assisted, pure manually or power assisted; altogether, larger bore multi-whole cannulas (>4,1mm) and low-pressure suction is recommended to minimize blood loss and improve adipocyte viability reference66 .There is no evidenced based knowledge concerning a superior method for fat processing reference67 .However, closed systems, such as large sterile canisters with fluid taps are highly recommended as they prevent contamination, enable simultaneous separation and tumescence of fat and keep the quantity of manipulation and potential damage to the transplant tissue as low as possible. 

Once the fat layer and excess liquid (blood and tumescence) separate, the liquid is decanted off and the lipoaspirate is transferred to injection cannulas, ideally power assisted. Centrifugation in large volume lipo- transfer cases is uncommon, neither is there enough data support to recommend adding antibiotics to the harvested fat reference37.   

For lipo-infiltrating the gluteus, the patient is placed in a prone position, “jackknife” position (hips flexed in about 30 degrees) by placing silicone roles underneath the anterior superior iliac spines.  Additional knee bending avoids lower extremity venous stasis and venous thrombosis. The buttocks being the punctum maximum in this position in combination with an angled infiltration canula eases the surgeon control of the canula tip and remaining strictly above the muscle.  

After numerous reports of fatal and nonfatal pulmonary fat embolism resulting from gluteal lipofilling, the Aesthetic Surgery Education and Research Foundation (ASERF) formed a Task Force and worked out nine major recommendation for a safe procedure reference38:  

The following key principles need to be respected during the process of gluteal fat infiltration: working with rigid, angulated large-bore (4- to 5 mm) blunt cannulas minimizes the risk of venous injury reference39 or penetration into the musculature due to better control. Additionally, viability of adipocytes is improved reference68.

Injecting only while cannula is in motion has two reasons: it prevents direct and continuous injection into a vessel and spreads the fat grafts even into the subcutaneous tissue scaffold with a higher chance of adequate lobular diffusion and graft take. The risk of Bolus infiltration and consecutive oil cysts is minimized. By using a power-assisted liposuction device and automated roller pump in an off-label manner Expansion, Vibration and automated Lipofilling reference33 has become safer compared with manual axial grafting! Instead of wasting muscular energy, the nondominant hand remains free to continually palpate and control the injection cannulas exact position and tip reference09 reference33. 

Overfilling the recipient site with excessive graft pressure should be avoided reference41reference42reference43 ! Overfilling theoretically bears the risk of fat embolism: it can lead to pressure gradients that favor fat entrance into a possibly injured lower pressure vein lumen. Besides, overfilling can reduce oxygen diffusion capabilities, decreases the amount of graft survival, impairs skin perfusion and leads to oil cysts. However, there is no formula for optimal fill volumes as quantities applied depend on individual tissue characteristics and tissue compliance. 

Compression garments need to be placed postoperatively reference37 supporting the liposuction donor sites and minimizing the risk for bleeding. 

Standard postoperative deep venous thrombosis prophylaxis depending on the patients Caprini Score is as evident as early mobilization reference69. In terms of postoperative positioning, again, there is not enough data support to confirm keeping the patient away from sitting in order to avoid pressure off the grafted zones; nevertheless no direct sitting is strongly recommended for a minimum of 2 weeks reference44reference45.

Aesthetic buttocks augmentation started as “implant dominant” procedure; the reason why aesthetic approaches recently favored fat transplantations was the high complication rate resulting from early trial and error methods used for gluteal implants reference51referece52 : Especially superficial augmentation planes (subcutaneous and subfascial planes) are prone to dislocation, visibility, late seroma and discomfort(48), sometimes after some years, when connective tissue including the fascia loosens. A recent Metanalysis investigating differences in complication rates showed buttock implants having the highest complication rate of 31.4%, whereas fat grafting had the lowest 6.8% amongst gluteoplasty procedures(53). Nevertheless, implants do have a value set, especially in thin patients with a BMI from under 20 to 25kg/m2, not providing enough transplant material or patients with flat buttocks particularly asking for projection. Therefore, sophisticated methods, mostly with intramuscular muscle pocket positioning have been developed and deep sub- and intramuscular pocket dissection for implant based buttock augmentation optimized reference48referece52reference54. Similar to breast augmentation surgeons lately started combining both techniques, alloplastic and autologous gluteus augmentation, called hybrid or composite buttock augmentation; this guarantees reliable core projection and surrounding the implant by autologous fat for the natural feeling, appearance and if desired hip management reference11.

Composite buttock augmentation is said to de- risk the complication rate of both methods as smaller implants for core projection and less amounts of fat are needed than in a procedure using only alloplastic or autologous implants reference11

Markings depend on the implant pocket and if planned, additional fat grafting in terms of composite buttock augmentation:

In case of intramuscular implant positioning, only incisions need to be marked, pocket location is determined by course and dimension of the gluteal muscles. If composite buttock augmentation is planned, Aslani recommends marking not only the implant incisions, but also the target zone of autologous lipofilling:  

Various access options have been reported: The choice of incision is either single intergluteal or bilateral paramedian. Also inverted heart shaped incisions with the base of the heart being the most cranial ending of the natal crease have been described, as it exposes the muscle reference48. In a 2013 survey by Mofid and colleagues of US and international surgeons, 53% preferred a single midline incision(55). Using two separate incisions prevents soft tissue dehiscence and unpleasant pterygium development inside the natal cleft; additionally potential communication between both pockets is impossible in case one side develops seroma, infection etc.. In case two separate incisions are planned: paramedian markings, approximately 1cm lateral to both sides of the natal cleft running vertical for five to six centimeters are drawn reference11.

We kindly refer to chapter "Gluteoplasty by autologous fat harvesting".

Choice of plane: Buttock implants have been placed deep (sub- or intramuscular) or superficial (subfascial or subcutaneous). 

Deep placement is least likely to present implant visibility and is best suited for thin patients that lack enough autologous fat and depend on alloplastic buttocks augmentation: Incisions are made where marked and dissection towards the muscle is completed; make sure to leave enough tissue on the natal crease to prevent perfusion impairment. If available, ease pocket dissection by hydrodissection using temeszenz fluid. Using a sequence of different instruments (Progressive instrument dissection) enables define a proper pocket.  Before blunt pocket dissection: Paramedial cut the gluteus muscle vertical to a depth of 2- 4 cm about 2 cm lateral from its sacral/ coccyx origin. Important is a thick muscle flap plane to perfectly cover the implant and primarily close the incision after implant positioning. This step is followed by even horizontal undermining along the course of the muscle fibers in terms of muscle splitting leaving the same amount of muscle above and behind the future implant comparable to a sandwich reference48. 

Periprosthetic fat grafting is defined as fat infiltration through separate incisions other than the implant, into distinct, subcutaneous planes around the implant reference11. During the infiltration process, soaked towels serve as spacer inside the intramuscular pockets, hemostasis- control and as discrete blunt pocket enlargement. 

Drains are placed into pockets after meticulous hemostasis. Inserting gluteal implants is comparable to breast implants and the same rules need to be respected

Implant size is limited by anatomy of the muscle: if the muscle coverage is too thin or the implant to big, superficial muscle fibers will spread apart at the weakest point “implant show” will occur (often laterally). If the muscle base is too thin ischiatic neurapraxia may occur. In 2019 the expert published a level 4 evidence based retrospective study of a series of 147 implant based composite buttock augmentations: a trend towards the end of this series demonstrated a clear preference towards round implants (volumes from 180 to 370 cc) due to malrotation of anatomical implants reference11. 

Key to proper healing and pocket stability is meticulous closure of a dry pocket via readdressing muscle, fascia and skin by.

Postoperatively, patients are dressed in compression garments, drains should remain 5- 7 days and buttocks offload is strictly recommended 4 to 6 weeks.

Similar to cosmetic patients, management of postbariatric patients is described in literature and includes completion of certain conditions: weight loss with a stable body mass index of ideally less than 32, smoking cessation, nutritional assessment, anemia screening, usage of mechanical prophylaxis against thromboembolism and consideration for usage of chemoprophylaxis with low molecular weight or unfractionated heparin. Facilities need to be accredited and special attention needs to be payed concerning positioning and patients body temperature. Massive weight loss patients have excess skin and fat between the iliac crest and superior gluteal margin, in extreme cases sagging down towards the posterior thigh. Like cosmetic patients they are seeking for a round harmonic buttock contour not just losing the excess of skin. All procedures common is the resection of excessive skin for a buttock lift. However methods vary in, how projection is gained: either autologous pedicled flaps, autologous fat grafting or alloplastic augmentation is described reference17. Focus of the following description is the pedicled flap based autologous gluteoplasty: various methods of adipocutaneous gluteal flaps (mostly superiorly based) exist as profound knowledge concerning soft tissue perfusion of the gluteal region is present in form of : 20 to 25 perforating branches reference57reference58. The ideal flap should be versatile, rely on a constant vascularization, give good projection. Scars need to be covered easy by apparel.

The estimated final scar is marked after the patient is asked for her/ his favorable under- and swimwear habits for future scar concealing. By moving the central gluteal tissue upwards, one can estimate the curvilinear upper border of the buttocks, which is fused at the sacrum to an aesthetically pleasing V- shape crease. Then, the pinch method is used to estimate the amount of possible skin resection.

Similar to abdominoplasty, the upper and lower resection lines may meet slightly ventral at the flanks to avoid dog ears. Additional liposuction of the transitory zone around the waist and sacrum may be helpful in patients still providing accumulated fat deposits in the flanks, so called love handles. Besides, lipofilling may be the ideal tool to camouflage irregularities or slightly visible borders of the flaps.   

Whether additional projection needs to be reconstructed has to be discussed with the patient; Schmitt et al published a Classification of the gluteus initial situationreference59 as well as an additional algorithm for operative planning (see table and algorithm concerning patient classification after massive weight loss focusing on back fat distribution and buttock augmentation) : 

Patients should be placed in a prone “jackknife” (hips flexed in about 30 degrees) position, by placing silicone roles underneath the anterior superior iliac spines and ankles avoiding lower extremity venous stasis.

There are various techniques for simultaneously addressing not only the loose and ptotic skin excess, but also regain natural projection after weight loss by pedicled tissue augmentation: All have in common the auto- implant based creation of buttock projection via perforator-, a random or perforator based pedicled flaps reference72: in general, the marked flap is deepithelialized dissected down to the fascia and fixed epimuscular into an undermined pocket; partial splitting of the muscle to ease flap mobilization has been described reference56. Depending on the rigidity of the subcutaneous tissues, it is sometimes favorable to transpose the flap as a turn-down flap rather than to rotate the flap inferiorly. Coverage of the flaps is gained by pulling the mobile buttock skin together.

Seroma is the most common complication of postbariatric buttock- surgery and can be prevented by avoiding dead space, using progressive tension sutures and use drains. Fibrin glue or preservation of a thin fat layer is also described to reduce the incidence of seroma without scientific proof reference70 . Minimizing skin tension, respecting tissue perfusion and modifying the procedure to the patient anatomy allows a safe gluteal augmentation!

Postoperative care is similar to other gluteal procedures including compression garments, drainages, positioning restrictions and antithrombotic prophylaxis; most important: early mobilisation is key. However it may vary from surgeon to surgeon. 

Gluteoplasty used to be underestimated and had a simple procedure reputation; with increasing demand, simultaneously increasing nontolerable complications such as lethal pulmonary embolism after intramuscular fat infiltration occurred; buttock augmentation was about to be banned and forbidden. Thanks to meticulous investigation, experimental and clinical studies, task forces, and published papers the technical error is well-known: intramuscular fat embolism bears high risk of venous vessel damage and direct or indirect fat embolism: as a consequence, sophisticated maneuvers and mandatory safety recommendations have been developed; in terms of techniques, operative strategies and respect for deep anatomic structures and proper patient positioning besides industry catched up and specialists have grown as well as gluteoplasty societies and educational and congress meetings started. Bodycontouring, large Volume Fat harvesting and Fat grafting are fields that are key to a successful management of the entire spectrum of gluteoplasties and need to be mastered as well as implant handling or experience in Flap surgery: However key to successful buttock surgery is understanding the buttocks anatomy and concomitant appearance and tissue behavior of this region. Performing gluteoplasty requires proper instrumentation, knowledge and training reference33. With respect and a repertoire of various techniques for various conditions highly pleasant results can be achieved and rewarded by the patient.