Due to the unpredictable high absorption rate and low survival rate of transplanted fat, there has been no breakthrough in autologous fat transplantation for more than half a century. However, as an ideal soft tissue filling material, autologous fat tissue is more biocompatible than artificial tissue substitutes, allogeneic or xenogeneic collagen and other materials, and there is no immune rejection phenomenon. Autologous fat transplantation by injection does not leave scars and is reproducible, so it has great potential and application prospects in cosmetic surgery.
The fat obtained by aspiration is no longer a complete piece of adipose tissue, but a mass of fat cells separated from each other, a significant portion of which remains intact. When these cells are injected into the body, they are able to remain viable through the permeation of the surrounding tissue fluid and plasma, as if in cell culture, until blood flow is established. Therefore, the fat particles can be viable after transplantation. The survival rate is affected by various factors. If the fat cells are less damaged, the blood supply in the basal bed of the recipient tissue is abundant, and blood flow is established as early as possible, the survival rate of the fat particles after transplantation will be high.
Fat particles acquisition and treatment.
1.Liposuction site.
It is generally advocated to extract deep fat. It has been found that the subcutaneous fat is divided into two layers, deep and shallow, by a loose fascia, i.e. superficial fascia. In general, the deep layer of fat is very thin, and some parts of the body have a proper ratio between the shallow and deep layers of fat, but some specific areas have a well-developed deep layer of fat, which is called localized fat deposition (LFD), such as the abdomen, buttocks, lateral femur, posterior lumbar region, and the inner and upper thighs. Because deep fat is metabolically inactive fat cells, once formed, it is difficult to disappear. The parts where deep fat exists are the parts where local fat accumulation is likely to occur, and they are also the best parts to get more fat for breast augmentation.
2.Liposuction technique.
The amount of fat particles needed for breast augmentation is large, and the structure is required to be intact, so there are special requirements for liposuction devices and technology. Ultrasonic liposuction can selectively destroy and liquefy fat tissue due to its tiny mechanical movement, cavity phenomenon and thermal effect, so the fat tissue sucked out by this device cannot be used as filling material for granular fat injection for breast augmentation.
Although the dry technique can accurately determine the amount of fat extracted and shape well, it bleeds a lot and the patient suffers from significant pain. The wet technique attempts to dissolve the fat cell membrane with hypotonic infiltrating solution, which is unfavorable for the transplantation of fat cells. Therefore, most of them now use the swelling technique of negative pressure suction tube liposuction, and a large amount of saline containing low concentration of lidocaine and epinephrine to perform local subcutaneous fat layer infiltration, which avoids the potential danger of general anesthesia surgery, and at the same time can play the role of local anesthesia, reduce intraoperative bleeding and postoperative pain, and if the suction negative pressure is appropriate, a considerable amount of structurally intact fat particles can be retained.
Some people also advocate that the fat aspiration swelling solution used for breast augmentation under general anesthesia should only use 4oC cold saline and epinephrine.
3. Fat particle treatment.
The purpose is to remove as much blood, anesthetic fluid, intertissue fluid, broken fat and fibrous tissue fragments mixed with intact fat particles as possible. The stratified debridement method, floating retrieval method and suction removal method are commonly used for fat processing of small amounts of fat grafts in the face, but not for purification of large amounts of fat for injectable breast augmentation. It has been reported in the literature that the flushing and filtration method is simple and faster to operate.
The aspirated fat particle suspension is properly rinsed and filtered through a single layer of mesh gauze with physiological saline containing antibiotics, and the pure fat particles are reserved. The antibiotic saline rinsing solution can be added with gentamicin, or gentamicin and dexamethasone or insulin.
4.Fat pellet injection.
The purpose of using granular fat grafting is to increase the contact area between the fat cells and the basal bed, so that the transplanted fat cells can get nutrition from the basal bed under the early ischemia and hypoxia, thus increasing the number of viable cells. It is generally accepted that in breast augmentation, fat should be injected in a “dot” or “line” shape to avoid injecting into large masses, which may result in poor blood supply and liquefied fat absorption.
There are three main methods of operation.
(1) Multi-site multi-level dot injection method;
(2) Single point entry multi-level linear injection method;
(3) subcutaneous fat layer injection method of the breast.
However, some scholars emphasize that
(1) Each injection volume should preferably not exceed 50 ml (unilateral);
(2) The injection level should be chosen in the posterior space of the breast, if the injection is in the breast tissue, it is easy to develop hard knots;
(3) Strictly observe the rules of aseptic operation.
5.Fat particles are absorbed.
The absorption rate of fat particles after transplantation is quite high. Clinical practice has proved that the absorption rate of human fat particles after transplantation is significantly lower than the absorption rate of animals, generally 30%-40%.
The volume reduction of fat particles after transplantation is mainly related to the following factors.
(1) Damage to adipocytes during transplantation;
(2) The condition of early blood circulation establishment in the recipient area;
(3) Contraction of the fibrous tissue around the graft, which causes the volume of the lax adipose tissue to contract and accumulate toward the center
(4) Influence of the number of grafts and the area of the recipient area;
(5) Influence of basal conditions. In order to reduce absorption and compensate for the unsatisfactory surgical results due to absorption, attention should be paid to proper surgical methods, reasonable postoperative disposition, overuse correction and repeated injection.
6.Prevention and treatment of complications.
Fat particle injection for breast augmentation is an extremely promising surgical method, but because a considerable part of the fat is absorbed after transplantation, in addition, complications such as fat liquefaction, intra-breast lump formation, infection and hematoma formation can occur, resulting in unstable surgical results. For these major complications, clinical countermeasures are proposed to prevent and solve them.
(1) Fat liquefaction and intra-mammary mass formation: The key to graft survival lies in the reconstruction of blood circulation. The use of fat particles for transplantation increases the contact area between the graft and the basal bed, which is conducive to the survival of the implanted tissue that can absorb sufficient nutrients. If the amount of transplanted fat is too large and loses the ratio to the basal bed that depends on survival, it will liquefy due to ischemia and hypoxia. In the early stages, when the necrotic foci are not liquefied, they may appear as hard solid masses with pain due to inflammation and fibrous encapsulation reactions. When the necrotic foci liquefy to form a cystic cavity, they may be cystic in nature. The cystic membrane contains yellow oily fluid and pearly fat globules, and the cystic cavity is formed about 3 months after surgery. The key to preventing liquefaction is to keep the early nutritional requirements of the grafted fat within the range of what the basal bed can provide. This is accomplished by controlling the total amount of fat grafted and by aligning the injected graft in a linear or punctate pattern. In order to solve the contradiction between the high fat requirement of the recipient area and the insufficient capacity of the basal bed, some advocate treating the fat particles with insulin or taking vitamin E orally to increase the tolerance of fat cells to ischemia and hypoxia. It is also advocated to freeze and store the fat that is not finished in one injection and re-inject it after 3-6 months. Fat liquefaction and intra-breast masses have been formed and can be treated with negative pressure aspiration.
(2) Infection and hematoma: Generally speaking, infection and hematoma are possible in all surgical procedures, but due to the characteristics of fat injection breast augmentation itself, infection and hematoma will directly lead to the failure of the procedure, so special attention should be paid to this problem. In the process of obtaining and processing fat, the fat has to pass through suction tubes, negative pressure vials and other containers, and the operation of removing mixed components from the fat is also exposed to air, so there are many possible contamination points.
Therefore, the concept of asepsis and skilled operation must be strongly emphasized during the procedure, and antibiotics are routinely used during the perioperative period. In addition, the injection process is a blind operation, which may cause lacerations of different degrees of soft tissues at the site involved in the injection syringe, and this injury is further aggravated by the shaping massage, resulting in capillary or even small vessel rupture and hematoma. Therefore, the operation should be performed gently and avoid violent operation.
Once a large hematoma is detected, it should be removed by aspiration as soon as possible, with pressure bandaging and complemented by anti-inflammatory, hemostatic and symptomatic treatment. For moderate and small hematomas, hemostasis, anti-inflammatory and symptomatic treatment should be given, and the decision of whether to puncture and aspirate should be made depending on the situation. It is generally believed that the success or failure of fat granule injection for breast augmentation depends entirely on the fat handling and injection techniques obtained by aspiration. Proper resolution of technical problems and proper management of postoperative complications will help to promote the application of this procedure.