The popularity of gluteal fat transplantation is in conflict with its dismal safety profile. Breast augmentation growth from 2014 to 2016 was 0 percent, whereas gluteal fat grafting posted an average annual growth of 28 percent.1
Options for surgical buttock augmentation include large-volume fat grafting or silicone implants. Although gluteal surgery began as an “implant-dominant” procedure, high complication rates were reported, especially among U.S. surgeons.2 Despite successful implant series,3,4 buttock aesthetic approaches have recently favored fat transplantation.
The reality is that neither strategy is ideal. If we are frustrated by implant complications and lack of hip width management, we are equally challenged by a lack of reliable posterior projection and the risk of massive pulmonary fat embolism that is associated with fat. These observations, coupled with lessons learned in aesthetic surgery of the breast,5,6 have led to the concept of composite buttock augmentation as a potential strategy.
Composite buttock augmentation, defined in this article, seeks to use the reliability of the implant’s core volume projection, drawing on the natural appearance and feel of fat for transitional fill and lateral hip management. The purpose of this article is to describe the authors’ experience with, indications for, and technique of composite buttock augmentation and to introduce this concept as a likely future direction in aesthetic gluteal surgery.
PATIENTS AND METHODS
One hundred forty-seven consecutive patients were treated with composite buttock augmentation between 2013 and 2016. One hundred thirty-seven women and 10 transgender patients ranged in age from 21 to 47 years, with an average age of 28.7 years. Periprosthetic fat grafting was used in all patients. Periprosthetic fat grafting is defined as fat grafting from separate incisions other than the implant surgical incision into distinct, subcutaneous planes around the implant, as opposed to fat grafting by means of the gluteal implant access incisions. Patient follow-up ranged from 6 months to 3.3 years, with an average follow-up of 1.5 years.
Description of Technique
Patients are marked standing. The most important landmarks are the natal cleft and the posterior superior iliac crest. A vertical line is drawn from the superiormost portion of the posterior iliac crest to the infragluteal crease line, called the vertical buttock line. A second line is drawn horizontally through the midpoint of the natal cleft, called the horizontal buttock line. These lines intersect at the most projecting portion of the gluteus maximus muscle and mark the center of the desired implant pocket, referred to as the desired point of maximum projection (Fig. 1). Implant size was chosen to optimize projection and at the same time respect the soft-tissue limitations of the patient’s gluteus muscle.
The horizontal buttock line is extended laterally to the midaxillary line. The point at which the horizontal buttock line intersects the midaxillary line defines the point of maximum hip widening, which we call the C-point, first described by Mendieta as an arbitrary soft-tissue point between the iliac crest and the trochanter.7 A diagonal line is drawn from the posterior iliac crest to the C-point. A second diagonal is drawn from the C-point to a meeting point of the vertical buttock line with the inferior gluteal crease. Joining these three points results in a triangle that is the target zone of fat grafting in the upper outer and lower outer quadrants. Using a marking pen, these lateral limbs of the ensuing triangle can be curved laterally in a convex shape (Fig. 2).
Paramedian incisions are marked on each side of the apex of the natal cleft, starting at the coccyx, extending cephalad 5 to 6 cm. Care is taken to ensure that there is a minimum tissue bridge of 2 cm between the two incisions.
Surgical Technique for Fat Harvesting and Processing
All procedures are performed under general anesthesia with supplemental epidural block. The usual sequence is as follows:
- Donor fat harvest, supine.
- Flip patient.
- Donor fat harvest, prone.
- Perform implant pocket dissection and placement of a sizer.
- Perform periprosthetic fat transplantation.
- Final implant placement and closure.
Fat harvest is performed using WaterJet-assisted liposuction (BodyJet; HumanMed Schwerin, Germany) with 3.7- and 4.8-mm cannulas at a jet range setting of 2 to 3. The tumescent infiltration solution consists of 1000 ml of saline together with a 1-cc ampule of adrenaline.
Once sufficient fat is harvested in the supine position, the patient is placed prone to continue fat harvest. Fat is washed in a 1:1 ratio (fat volume to wash volume) by means of the off-label use of Poloxamer 188, created by mixing one 20-cc ampule of Poloxamer 188 (Surclens; Cardinal Health, Dublin, Ohio) in 1 liter of saline. Polaxamer-188 has been shown to improve volume maintenance of transferred fat grafts in an animal model.8
Access to the Gluteal Fascia
Approximately 1 cm lateral to the coccyx, two paramedian incisions are made. This approach ensures having a minimum 2-cm skin bridge between the two pocket incisions. The scalpel is beveled 45 degrees laterally to preserve a bulk of soft tissue centrally. When reaching the subcutaneous level, electrocautery dissection is used to reach the fascia of the gluteus maximus muscle (Fig. 3).
Rather than dissect the pocket from beginning to end with one instrument, we describe a series of dissection steps using a sequence of different instruments, intended to most accurately, consistently, and safely define proper pocket dimensions. Each step sets up the optimal instrument for the subsequent step. We refer to this surgical strategy as progressive instrument dissection.
Progressive Instrument Dissection
Part 1: Water Jet Dissection
The gluteal fascia is incised perpendicular to the direction of the gluteus muscle fibers, and dissection through the muscle is performed to a depth of 2 to 4 cm, ensuring a thick muscle flap overlying the implant. A dense whitish septal structure, often observed at this level, heralds adequate depth (Fig. 4).
Once this thickness is reached, a high-pressure water jet tumescent infusion cannula (Body Jet; Human Med, Schwerin, Germany) is advanced axially, parallel to the gluteus maximus muscle fibers in a blunt manner, to establish the proper depth of the intramuscular plane. It is important to keep the angle of the cannula parallel to the muscle, which curves anteriorly (downward), to maintain consistent muscle thickness and to avoid passage of the cannula through the muscle laterally. In a fan-like pattern, a 2.5-mm cannula is used to hydrodissect the muscle fibers and to vasoconstrict small intraseptal vessels, setting up ensuing blunt dissection.
Part 2: Axial Muscle Separation
A curved spatula is introduced into the intramuscular space. Following the previous hydrodissection plane, “to-and-fro” axial movements delineate the thickness of the muscle overlying the planned pocket. At this point, lateral maneuvers with this spatula are not used (Fig. 5).
Part 3: Intramuscular Fiber Spreading
A duckbill-type spreader is introduced into the pocket with the blades oriented perpendicular to the dissection plane. After introduction, the spreader is rotated 90 degrees until the blades are oriented parallel to the pocket dissection plane, and dissection continues in spreading movements. The 90-degree rotation achieves spreading the muscle fibers in a controlled manner rather than tearing fibers apart (Fig. 6).
Part 4: Blunt Septal Dissection
A blunt tip club-type (bayonet) dissector is placed into the pocket to dissect remaining deep intraseptal fibers and to round out the pocket. It is important to keep the instrument angled parallel to the muscle, as stated previously (Fig. 7).
Part 5: Sizer Dissection
An towel soaked with epinephrine-saline (five ampules of epinephrine in 50 cc of normal saline) (Texpol, Barcelona, Spain) is placed into the pocket. This towel connotes a volume of approximately 300 cc. If necessary, the pocket can be enlarged by blunt finger dissection or by using the bayonet dissector. It is important that additional blunt dissection at this point be performed beneath the towel and not superficial to it. The frictional force afforded by the towel allows for a broader, less traumatic expansion of the pocket, whereas use of the instrument above the towel directly on the muscle can lead to disruption of muscle fibers (Fig. 8).
Fat transplantation is performed before final implant placement, using a saline-soaked towel as a sizer to occupy the pocket space. Access incisions are made in the gluteal crease, natal cleft, and posterior iliac crest area. The Coleman technique of fat injection was performed subcutaneously in 98 cases (10-cc syringes, 14-gauge Luer-Lock cannula); in 49 cases, expansion vibration lipofilling (Microaire, Inc. Charlottesville, Va.)9 was used.
Placement of Permanent Implant and Postoperative Management
After removal of the towel sizer and after drain placement, permanent implants are placed into the intramuscular pocket. Before skin closure, meticulous muscle and fascial closure is performed using three interrupted figure-of-eight sutures of no. 1 Prolene (Ethicon, Inc., Somerville, N.J.). Patients are mobilized on the first postoperative morning. Drains are left in place for 7 days. Postoperative compression garments are worn, and buttock offloading is recommended for 4 to 6 weeks.
Implant size ranged from 180 to 370 cc, with a mean size of 300 cc. In the first half of this series, implants averaged 340 cc; in the latter half of the series, average implant sized trended down to 240 cc. Anatomical implants were used in 97 cases (66 percent); in 50 cases, round implants were used (34 percent). A trend toward the end of this series demonstrated 100 percent round implants. Grafted volumes range from 80 to 900 cc on each side, with an average grafted volume of 380 cc. The mean surgery time was 115 minutes, and the mean hospital stay was 2.7 days. A trend toward the latter half of the series showed a shorter operative time when expansion vibration lipofilling was used (90 minutes versus 140 minutes).
The overall complication rate was 11.6 percent. The most common complications requiring additional surgical intervention were implant dislocation and palpability caused by inadequate soft-tissue coverage/muscular atrophy in 10 patients (6.8 percent), and early postoperative infection in seven patients (4.8 percent). All cases of infection were related to the implant pocket and were treated with either implant removal and delayed implant placement, additional fat grafting, or both. No cases of infection involved cellulitis or abscess of the area of the grafted fat. Dislocation of anatomical implants and palpability of its narrower, tapered tip was treated with pocket exploration and capsulorraphy. Because of its polar nature, implant malrotation occurred only when using anatomical implants. Adjusted for the denominator of anatomical implants alone as opposed to all implants, the incidence of rotational complications rose to 10.3 percent. In all cases of implant pocket infection (n = 7), fat grafting cannulas were introduced through the same access incisions used to place the gluteal implants.
This is the first description of using gluteal implants and fat for primary gluteal enhancement surgery in over 100 consecutive patients. However, the concept of gluteal fat grafting in conjunction with implants has recently been described by others, consistent with Gruber’s “cryptomnesia” concept.10 Munoz and Godoy, in their 17-patient series, used a composite approach for primary and revision gluteal implant cases.11 They suggested an efficient way to identify the proper depth of the gluteus maximus intramuscular pocket using calibrated scissors as a depth gauge. A second recent publication of implants and fat focused on revision implant surgery.12
First described for manufacturing and defense,13,14 the use of water jet technology in surgery is well described, having precedence as an atraumatic and bloodless means of dissection in hepatic and orthopedic surgery.15,16 Water jets allow intramuscular dissection through smaller intramuscular access channels without the need for large dissection approaches to gain pocket access, resulting in shorter surgery times, less surface area of muscle dissection, and lower potential for postoperative seroma.
The strategy for targeted fat transplantation addresses transitional irregularities and trochanteric depressions, and provides lateral expansion and roundness, all of which are not possible with implants alone. Although implants may be ideal for providing stable and reliable core volume projection, fat is necessary, especially lateral to the implant (Fig. 9).
Indications for Composite Gluteal Augmentation
Patients with Inadequate Fat
In thin patients, the indication for composite buttock augmentation is one of necessity, not of choice. These patients made up the majority of the patients in this series, with body mass indexes ranging from 20 to 26 kg/m2 (mean, 22.8 kg/m2) (Fig. 10).
Patients with Inadequate Projection
Some patients already exhibit good roundness and posterior projection on lateral view and may not necessarily require the projection afforded by an implant. If, however, the patient, regardless of the amount of fat available, has inadequate central mound projection, this may only be accomplished with multiple rounds of fat transplantation or by a composite approach in one session (Fig. 11).
De-Risking the Procedure and the Aesthetic Result.
Large amounts (800 to 2000 cc/side) of fat and multiple sessions may be required to achieve the posterior projection and roundness that is sometimes desired. This can result is excessively large buttocks and fat necrosis. Conversely, in implant-only procedures, large implant strategies, seeking to obtain both posterior projection and hip widening, can result in inadequate soft-tissue coverage and unacceptably high complication rates. By seeking the core mound projection from a small round implant (180 to 250 cc), and using smaller volumes of fat for transitional fill and hip widening, composite buttock augmentation seeks to “de-risk” the procedure of complications that are historically associated with either large-volume implants or large volumes of fat alone. Composite approaches may make anatomical implants less necessary, using round silicone implants with the potential for fewer anatomical implant-related complications.
Larger buttock implants may cause a greater likelihood of soft-tissue complications, and implant placement must respect the individual anatomy to avoid overstressing the tissues.17,18 Similar drawbacks of excessively large implants have been reported in the breast implant literature.19,20 In an “implant-only” world, surgeon and patient wish to achieve greater volumes through larger implants, which may lead both down a path of excessive implant size.
In composite breast augmentation, the implant provides the core projection to push the nipple-areola complex forward, whereas the fat creates a natural softness to the transitions of the cleavage gap and the implant/lateral chest wall interface.21 In the buttock, we find the same analogue. There is less demand on either the implant or fat alone to achieve the entire shape/volumetric goals of any given case.
Progressive Instrument Dissection
Creating the intramuscular pocket is the most technically demanding and often intimidating maneuver in gluteal implant surgery. The surgeon, comfortable in dissecting between anatomical tissue planes, is confronted by the challenge of longitudinally clefting an artificial plane. Dissecting too superficially leaves insufficient muscle coverage over the implant; dissecting too deeply leads to misadventure, with potential damage to deep structures. Often, the prudent surgeon errs on the side of being too superficial in the muscle, generating implant “show” laterally.
Progressive instrument dissection affords the operative surgeon with the best attributes of each instrument—proper sounding of depth, blunt dissection, spreading, hemostasis, and circular “hand-in-glove” pocket creation of a pocket that is at the ideal muscle depth and is just large enough to hold the implant with minimal tissue trauma through the dissection channel (which could lead to seroma or neurovascular injury).
Limited amounts of fat can be transplanted using syringe-based techniques, largely because there is no intraoperative expansion of the recipient site and fat does not act as a tissue expander. Expansion vibration lipofilling has become a useful strategy for targeted transplantation of fat in larger volumes. It effectively reduces shear stress on the fat grafts, which is a key factor to fat survival.22
Fat transplantation was performed after pocket dissection and insertion of a temporary towel sizer, and before final implant placement. A saline sizer is a viable alternative. A sizer-based strategy eliminates the unlikely possibility of untoward damage of the permanent implant during cannula/fat insertion. In addition, a sizer placed before fat grafting gives the surgeon one last look at the implant pocket before permanent implant placement, to inspect for inadvertent fat deposition.
Patient Safety, Advisories, and the Future Role of Buttock Projection
A 2016 communication on massive pulmonary fat embolism caught the attention of surgeons in the United States.23 This led to an Aesthetic Surgery Education and Research Foundation survey24 estimating a one in 3000 mortality rate from gluteal fat grafting. In November of 2017, an intersociety advisory stated that injected fat should be limited to the “subcutaneous fat and superficial muscle only.”25
Despite this recommendation, there is no scientific or anatomical evidence regarding how one defines, identifies, and navigates the superficial versus deep gluteal maximus muscle. Pressure mounted over mandating a subcutaneous-only approach, based on the fact that no Brazilian butt lift deaths at autopsy have ever demonstrated fat only in the subcutaneous space. Six months later, in February of 2018, the intersociety advisory restated that fat should be placed in the “most superficial layers possible.” There was no mention or guidance on the muscle.26 Following the dissemination of additional experimental work showing deep intramuscular migration of fat when fat is placed just beneath the fascia of the gluteus maximus muscle,27 a most recent advisory in July of 2018 clearly prohibited the insertion of fat in the muscle,28 eliminating fat grafting as a means of obtaining intramuscular projection.
In adversity lies the opportunity for composite buttock augmentation. Using a small implant for projection placed intramuscularly provides stable and reliable projection and eliminates the potential risk of pulmonary fat embolism, relying on subcutaneous-only fat to gain transitional fill and hip widening.
Buttock augmentation using intramuscular implant placement, progressive instrument dissection, and targeted subcutaneous fat grafting is a powerful tool in body contouring surgery. Providing a standardized step-by-step approach toward accurate pocket dissection and avoidance of fat grafting through implant access incisions, the surgery has the potential to trend toward smaller implant volumes and smaller fat volumes. More efficient approaches to ensure consistent intramuscular depth and accuracy of the intramuscular plane will allow an average surgeon to safely and reliably create core volume projection without the historical risk of fatal fat embolization. What began as an implant-dominant procedure that shifted to fat, the strategic pendulum of gluteal aesthetic surgery may be stabilizing to a combination of both modalities. What emerged in the breast with composite combinations of fat and implants is repeating itself in the buttock, resulting in more predictable aesthetic outcomes in fewer sessions, and, most importantly, a safer approach for patients.
The patients provided written consent for the use of their images.
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