The use of granulated fat as a filler material for one’s own soft tissues has long been a source of anticipation for plastic surgeons, but there are still major questions about the effectiveness of injectable grafts, especially the survival rate of larger amounts of granulated fat in a single graft. A review of a large amount of foreign clinical data in recent years found that the buttocks, as the next hot spot in cosmetic surgery, has the potential to become one of the most ideal areas for granular fat injection and the best fat survival.
1. History and current situation.
The earliest report of autologous granular fat transplantation for buttocks was in 1990, proposed by Chajchir years but no details of the case situation. 1991 Toledo reported syringe fat aspiration (syringing, liposculpture), in which there were some cases of buttock augmentation. thereafter there were successive reports of less volume of fat buttock augmentation, generally 100 ~ 300 cc per side. ~Analysis of the data from these reports by Peren et al. found that although the buttocks were slightly augmented after fat injection, the main effect was produced by fat aspiration to the hips, thighs and lower back and abdomen, with the buttocks appearing relatively garden-shaped and proportionally larger. Reports of successful injections of larger volumes of fat into the buttocks began in the early part of the new century, with an average injection volume of 400 cc or more per side, a volume that produced a significant degree of buttock augmentation, clearly excluding the effect of fat aspiration from the surrounding area alone.
Recent data from a group of 261 cases by Roberts showed that after the first 50 cases, in which an average of 490 cc was injected on one side and good results were achieved, the volume was increased to 670 cc in the second 50 cases, and by the last 100 cases the average volume injected on one side reached 825 cc. Among the 261 cases in this group, there were Caucasians with a minimum of 205 cc unilateral fat injections, Caucasians with 1430 cc unilateral fat injections, Hispanics with 1478 cc unilateral fat injections, and African Americans with a maximum of 1880 cc unilateral fat injections, which are by far the largest number of one-time fat injection cases reported. This large number of successful one-time granular fat injections has never been experienced before in any other part of the body, indicating that the buttocks is an area that is particularly well suited for fat injections.
The success of the large number of fat injections is supported by sufficient clinical cases and preliminary confirmation by imaging data from the follow-up survey. 6 cases of fat injections for buttock augmentation were examined by MRI before and after the procedure, and MRI 12 months after the procedure clearly showed good survival of the fat injected into the buttocks in the subcutaneous and muscular areas. Clinical experience estimates that 20-40% of the injected fat is absorbed, and the imaging results are approximately the same as this. In a recent prospective study by Fontdevila, et al. (2008) on facial fat graft survival in HIV patients, CT data from 26 cases (52 sides) preoperatively, two months postoperatively and one year postoperatively showed that fat grafting gives a good clinical outcome with no trend of reabsorption at 12 months postoperatively. This study used objective measurements, the information and was statistically processed, and the results supported the achievement of good long-term survival rate of fat grafting from different aspects.
2. Surgical operation characteristics: The method of fat granulation in the buttocks is not different from that in other areas, but still has its unique requirements, which are described as follows.
(1) Selection of the donor area: fat from any part of the body can be used for buttock injection and no difference in the survival rate of different sites has been observed so far. In order to show better results of buttock augmentation, the areas near the buttocks, such as the lower back, iliac region, outer thighs and abdomen, are generally considered first. Emphasis is placed on fat aspiration in the sacral triangle, not only for the need of the granular fat donor area, but also to restore the important aesthetic features of the buttocks, revealing the smooth inward slope of the sacral dorsum and lumbar region. Estimating the amount of fat to be taken, if 825 cc is needed for injection on one side and 1650 cc on both sides in total, plus the fat that may be damaged and discarded, usually more than 2000 cc has to be aspirated to be sufficient, marking out sufficient areas for fat aspiration before surgery. It is cautioned not to aspirate the subgluteal fold in some cases where there is a horizontal mass of fat, also known as a “banana strip” (, banana, roll), which has a poor appearance before surgery. It provides the support structure of the buttocks, and aspiration may deepen and lengthen the subgluteal groove, causing the buttocks to sag and sometimes even requiring filling in this area.
(2) Suction pressure: Since buttock augmentation surgery needs to provide a larger amount of fat, the syringe method of suction is not generally applicable. The negative pressure of fat aspiration machines available on the market can reach 630-710 mmHg, but there is evidence that too high a pressure can damage fat cells and affect survival, so it is generally advocated that the negative pressure level should be controlled below 560 mmHg. One study found that medical negative pressure machines and syringe aspiration generate negative pressures of 630-710 mmHg, and in this negative pressure state, bubbles can be seen in the adipose tissue. Although boiling of water at pressures greater than 760 mmHg can be produced under room temperature conditions, this cannot explain the situation at negative pressures of 630-710 mmHg. The most likely explanation is the phenomenon of gas overflow (gasging, out), which is the overflow of dissolved oxygen and hydrogen into gas. This can occur within the intercellular matrix and certainly within the cell, the latter leading to the destruction of intracellular organs and cell membranes and reducing the viability of the transplanted cells. Microscopic observation of the volume change of adipocytes confirmed a 41% increase in volume at a high negative pressure of 710 mmHg, environment, compared to a low negative pressure of 380 mmHg, environment. The authors also observed that blistering disappeared at pressures less than 560 mmHg, which is consistent with the concept of gas spillage, and for this reason the authors advocate controlling the negative pressure for fat aspiration below 560 mmHg, which is also supported by other authors.
(3), suction tube and fat treatment: with 3.0~3.5mm (, Kell, tip, cannula), boat-shaped opening suction tube, fat particles of about 2mm diameter can be aspirated. Most authors believe that survival is highest with fat particles less than 3 mm in diameter. Another reason is that any particle larger than this diameter cannot be passed through the syringe connecting tip (Luer-lock, tipped, syringe) without fragmentation, and a large number of fat transfers and implants are performed with this device.
After the fat aspirate is left to settle, the lower layer of fluid is removed and the upper layer of fat is placed into a 60 ml syringe and centrifuged at 2000 rpm for three minutes to remove the water and free fat, leaving the pellet fat, which is injected into a 3 cc syringe ready for implantation using a completely closed method. Some people also advocate static separation of fat, believing that this method causes the least damage to fat.
(4), Injection level: Roberts [9,10] operated with a 2 mm diameter, 15 cm long, pure-tipped, open side port (Byron, Medical) injection syringe through 3-5 small skin incisions on the lateral gluteal area. Fat is injected first into the muscles and fat of the deep bone surface of the medial buttock, but it is important to note that the sciatic nerve is located just lateral to the sciatic tuberosity. Only 0.3cc can be injected per pass, so if 825cc of fat is injected per side, 3000 passes are required. The procedure generally begins in the lower medial gluteal area, which is usually flat below the sciatic bone and where years of sitting pressure have resulted in denser tissue fibrosis that may limit the degree of augmentation that can be achieved, then moves to the medial mid gluteal area and then the upper medial area, producing the largest augmentation in the upper middle third of the gluteal area. Because the fat easily follows the injection syringe as it exits, when the injection is complete on the medial side, most of the lateral area is also partially filled and eventually the outer buttocks and outer thighs are injected. For patients who need to significantly increase the fullness of the outer thighs, the injections are done in the anterior thighs first before being placed in the prone position to ensure a smooth anterior-posterior transition. Sometimes the buttocks cannot be fully injected to achieve the ideal garden shape and become square or flat after injection. In this case, fat aspiration around the circumference of the buttocks can be used to make it hemispherical, with the inner side of the upper buttocks showing an inward low slope transition to the low back. It is also injected through the skin incision on the inner side of the upper buttocks and the skin incision in the intergluteal groove.
Two major features are highlighted here: intramuscular injections and very multiple access punctures. The thickness of a single gluteus maximus muscle can be 6-7 cm, and the blood supply of the muscle is rich, which is very conducive to the survival of the injected fat. The fact that the buttocks can receive more fat injections than any other part of the body is probably related to the abundance of thick muscles in this area. Injecting into every layer of the buttocks, including the intramuscular and subcutaneous layers, whereas injecting at a single level in other parts of the body may mean that the blood supply to the recipient area is inadequate. Injections are insistently performed in a drop-by-drop fashion and were used primarily in the early days for the face, but are now becoming the mainstream method of fat injection for grafting.
This method ensures that each injected fat particle has a blood supply surrounded by nutrients, but is extremely time consuming and requires a significant amount of surgical time to perform the implantation. Some authors also believe that the amount of fat injection is not as important as the site of injection, it injects 2mm, x 10cm fat strips into different levels of the buttock muscle, it can achieve satisfactory results with a follow-up of up to 5 years, but the average injection volume of this author is only 180ml (120-240ml), whether such a volume of fat injection does not have to be too small and too fine is not known.
3. Complication prevention and management.
Early articles and individual recent articles rarely mention complications after fat injection, or even say that there are no complications; in fact, they inject very little fat, about 30-210 cc per side, thus ensuring fewer complications, but such a small amount of fat injection rarely plays a role in buttock augmentation or visible buttock augmentation.Cardenas-Camerena (1999) first reported gluteal complications of fat injections, although in a total of 66 cases, the volume injected per side was only 210 cc, the incidence of complications was 18% for fasciitis, 6% for seroma, 12% for tissue unevenness, and one case of fat embolism.
In a strictly scientific group of 261 American cases, every complication after buttock augmentation was closely documented. In the early years, between 1998 and 2002, the high rate of infection in the recipient area of the graft and the accumulation of body fluids in the donor area were often plagued by a desperate search for ways to overcome them, and the data after 2002 showed that the major complications in the last 100 cases of this group were reduced from 17.6% to 7%. With the current measures, the incidence of serious complications is reduced to a low 2.7% if larger volumes (>1000cc) are excluded. The following is a comprehensive list of various possible complications, the corresponding prevention and treatment methods.
(1) Infection: The causes are multiple: (1) the surgical site is close to the anus and is easily contaminated; (2) the various processes of fat extraction, processing and implantation can be contaminated, especially during long surgical procedures; (3) the large amount of fat implanted is an ideal medium before vascular growth (at least 4-7 days) because of the warm, moist and traumatic environment, where a very small amount of bacteria can cause infection; ④ the skin at the injection site has a reduced barrier function to bacteria due to repeated abrasion damage. Preventive measures: ① use systemic antibiotics for common flora; ② prepare the skin without a razor, using only scissors; ③ disinfect with iodophor ring while standing preoperatively; ④ fill the intergluteal sulcus with iodophor ring pads to reduce contamination from swelling fluid and anus; ⑤ minimize damage to the fat, such as by completing the entire process from aspiration to injection in an airtight manner without rinsing; ⑥ the authors believe the single most important measure is to suction bottle with multiple antibiotic solutions, a method that makes the fat particles bathed in a solution three times the concentration of systemic antibiotic administration.
(2) Fluid accumulation in the fat donor area: This problem is particularly prominent in the lumbosacral region. In order to produce the curvy female form of the back and the upper hip bifurcation, good shaping is needed in this area. Even with only 100-240 cc of fat to be aspirated and injected, the Cardenas-Camarena data showed a 6% incidence and Peren et al. 10%. Murillo reported a 40% incidence of seroma for an average unilateral 700 cc injection. Placing a drain in the fat aspiration area is an effective approach. Aspiration is required in 45% of cases in the early stages before a drain is placed. Initially, there was concern that the placement of drains and sacral pressure would affect the local blood supply, but later it was found that even with the placement of two drains there was no need to worry about skin ischemia and injury, and the incidence of fluid accumulation was only 2% in cases after that.
(3) Transient sciatic nerve sensory abnormalities: usually mildly symptomatic, with discomfort, tingling and numbness along the sciatic nerve pathway; Mendieta reported a 1% incidence and Roberts reported a 4% incidence. In two cases, there was temporary loss of sciatic nerve motor function, but no sciatic nerve hematoma or other visible injury was seen on MRI. Motor function recovered within 1 to 2 weeks, and sensory abnormalities recovered within 1 to 3 months. Nerve stab injury is unlikely to occur with a 2 mm diameter garden blunt injection needle; the likely causes are physical contact with the injection tube, local inflammation and swelling. Dexamethasone is routinely used prior to surgery, and gabapentin and anti-inflammatory drugs are used if symptoms are significant.
(4) Small amount of liquefaction of the incision in the recipient area: Several drops to 1-3 mL of fluid are injected into the incision daily and there is always damage to the skin of the incision, no matter how carefully it is protected. Attempting to reduce the damage with a small protector, increasing to five injection incisions on one side, has the potential to reduce the skin damage of the injection incision.
(5), aseptic abscess (fat necrosis): once it occurs promptly drainage treatment.
(6), other complications: can also see the donor area minor cellulitis, diffuse intravascular coagulation, mild metabolic disorders and other very rare complications.
4.Summary.
Compared with the method of buttock prosthesis implantation, granular fat injection buttock augmentation has the following advantages: ①, no series of problems caused by the presence of the prosthesis itself: such as prosthesis rupture, displacement, exposure and contracture of the envelope; ② good texture and elasticity of the augmented buttocks, avoiding the poor palpability and elasticity of the implanted prosthesis, especially when solid prosthesis is used and implanted to a shallow level; ③ adequate overall augmentation of the buttocks (2) the overall augmentation of the buttocks is adequate, including the outer hip and outer thigh, while implantation of prosthesis is commonly insufficient to fill the lower hip and difficult to implant to a low enough position in order to avoid injury to the sciatic nerve and important blood vessels; (3) there are no intractable complications such as incisional splitting; and (4) at the same time, the fat extracted from oneself is used to save from waste, and there is no need to purchase prosthesis, which reduces the cost of surgery.
In addition to the aforementioned possible complications, the procedure takes longer (about 5 to 8 hours), which is about double the time required for implantation of a prosthesis, and the body must be able to provide a sufficient amount of fat extraction. Further observations are needed to confirm the long-term effects of fat implantation, whether there will be hardening, calcification and absorption.