History of the Procedure
Although the popularity of fat transplantation is a relatively recent development in plastic surgery, the concept of fat transfer is not new. As early as 1893, free fat autografts were used to fill a soft tissue defect. The use of autogenous abdominal fat to correct deficits in the malar area and chin was reported in 1909. Throughout the early part of the 20th century, attempts were made to correct other conditions, including hemifacial atrophy and breast defects, but modern fat grafting did not develop until the early 1980s with the popularity of liposuction.
Illouz reported the transfer of liposuction aspirate fat in 1984.  In 1986, Ellenbogen reported the use of free pearl fat autografts in a variety of atrophic and posttraumatic facial deficits.  With refinements in technique, fat grafting has become the procedure of choice for an array of problems, including facial scarring, lip augmentation, and facial rhytids (such as several otherwise difficult-to-address areas such as the nasolabial fold and glabellar furrows).
Methods of addressing rhytids range from excision and re-draping of excess skin to methods of skin resurfacing including dermabrasion, laser ablation, and chemical peels. Each of these modalities has limitations.
Implantation of a filler substance into a deficient area is another solution. Whereas facial resurfacing can be thought of as leveling the mountains, use of an implantable substance fills in the valleys.  Many materials have been tried for the correction of soft tissue defects and deficits. However, the use of most of these substances has met with difficulties, including impermanence, foreign body reaction, unnatural texture, and possible disease transmission. In addition, most of the products currently available remain relatively expensive.
Collagen has been used to address rhytids. Available collagen consists of purified bovine collagen. Zyderm is 95% type I collagen and 5% type III collagen. The addition of glutaraldehyde cross-linking (Zyplast) slows resorption; however, the substance nonetheless eventually is degraded by the host. While collagen works well for the correction of fine lines, results for deeper furrows are less impressive. The major drawback to the use of collagen is the short duration of the response. Within 3-6 months, the collagen is resorbed completely and the improvement is lost. In addition, because the collagen is bovine-derived, pretesting for an allergic response is required. The test spot should be observed for 1 full month prior to treatment.
The Food and Drug Administration (FDA) approved Gore-Tex (solid polytetrafluoroethylene) for facial plastic surgery in 1993. The result is generally predictable because the substance is nonreactive, but the resulting feel of the tissue is somewhat unnatural. The substance is rigid and is not available in an injectable form. In addition, infection remains a potential problem because the substance is a foreign body. Because this substance does not become integrated into the host tissue, it is generally easy to remove.
Newer substances are being marketed. Sheets of human dermis (AlloDerm) are also available and produce a more natural result. Again, the form of this substance limits its use. Although it is derived from a human source and becomes revascularized by the host, it is not autogenous. Concerns about possible disease transmission have been expressed, although processing appears to control for this. A micronized form of human dermis has been available since 2000. While the semiliquid form of the substance gives it the versatility of collagen, the substance does not have the longevity of the sheet form. The major impediments to use of this substance remain the high cost and, although initially touted as a permanent solution, the substance is eventually degraded by the host.
Use of injectable poly-L-lactic acid (PLLA) has gained widespread popularity in Europe since its approval for cosmetic correction in 1999. PLLA is a synthetic polymer of lactic acid that is biodegradable, resorbable, and biocompatible. The large particle size of PLLA (40-63 µm) prevents it from being phagocytosed by macrophages, but it can still be used in needles as fine as 26–gauge (ga). The outcome in patients with a loss of facial volume and contours appears to be very good as judged by physicians and patients, with satisfaction rates reaching as high as 70% and 75%, respectively. One multicenter trial conducted by Laglenne and colleagues involving 110 patients reported minor adverse effects, with only 10% of patients experiencing nonspecific ecchymoses and no patients experiencing allergic reactions.  However, others have reported many cases of granulomas and inflammatoryreactions, which are difficult to treat.
Hyaluronic acid (HA) is a carbohydrate polymer and one of the major components of the extracellular matrix. It is found extensively in neural, connective, and epithelial tissues. Although pure HA is not biocompatible with dermal tissues, the cross-linked form is biocompatible. HA was initially extracted from cock combs but, possible allergic reactions limited its use.  This problem was overcome by the compound Restylane, which is produced from nonanimal cells through a process of fermentation and filtration.  A study conducted at 6 medical centers in the United States showed similar outcomes to Zyplast as a filler in wrinkles.  The FDA approved its use in 2003. Complications are usually related to local inflammatory responses.  According to the American Society for Aesthetic Plastic Surgery 2012 Statistics, HA was the second most commonly performed nonsurgical cosmetic procedure, with botulinum toxin A the most commonly performed. 
An ideal substance would be readily available, inexpensive, long-lasting, natural-feeling, and would not cause adverse immunologic reactions. Autologous tissue meets these requirements.  Several types of tissue can be transferred. Fascia and dermis require longer scars for harvesting. Ideally, dermis can be harvested from the area of a previous incision, such as a Cesarean delivery or abdominal scar, to avoid a new donor site defect. Strips of these tissues can be useful for larger areas and deeper defects but do not have the flexibility of a liquid or semiliquid substance. Fat can be harvested through inconspicuous access incisions. The harvesting does not leave a defect, and the removal of fat is often desirable. Fat tissue is soft and feels natural. It can be introduced to correct various deficiencies, it is not immunogenic, and it is readily available and inexpensive.
Autologous fat transfer has been used for correction of facial scarring, including acne scars. Enhancement of facial volume also can be achieved for disease processes such as hemifacial atrophy and for patients with aesthetic concerns, such as those who request lip augmentation. Signs of facial aging can be improved.  Rhytides that are too deep to be addressed by resurfacing modalities and areas poorly addressed by traditional lifting procedures (eg, nasolabial folds, glabellar creases, tear troughs) can also be treated with grafted fat.
Aging skin is characterized by decreased thickness, elasticity, and adherence to underlying tissue. In the epidermis, the number of melanocytes and Langerhans cells decreases. The rete pegs interconnecting the epidermis and dermis flatten, causing increased susceptibility to shear forces. The dermis atrophies as loss of ground substance, elastic fibers, and collagen occurs. Sun exposure leads to distinct damage to the skin. Elastosis (ie, deposition of thickened, irregular, partially degraded elastic fibers in the dermis) is characteristic of sun damage.
Cigarette smoking also is associated with changes in the skin. Post-traumatic scarring, acne, and the repetitive action of underlying muscle result in predictable histologic changes. Repeated weight fluctuations can contribute to wrinkling. Failure to properly evert skin edges during wound closure can result in a depressed scar. A genetic contribution also is present.
Older patients may present for correction of specific areas or for overall facial rejuvenation. The anatomic areas not addressed by traditional rhytidectomy, auxiliary suspensory procedures, or facial resurfacing often are ideal for fat grafting. Patients of all ages may present for facial enhancement; lip augmentation is the most common request. Often patients have obtained information from friends or media sources such as the Internet. Patient education and understanding are crucial to obtain optimal results. For information on aesthetic procedures, including news and CME activities, see Medscape’s Aesthetic Medicine Resource Center.
This procedure can be performed on an outpatient basis with local anesthesia. The preoperative consultation is crucial. By far, the most important part of the preoperative workup is an extensive discussion identifying areas to be treated. In addition, details of the procedure, postoperative care, expectations, and possible adverse outcomes should be discussed.
Photographic documentation is critical to planning and evaluation of this surgery. Lighting, angle, and expression should be standardized to allow for accurate delineation of detail and adequate comparison of preoperative and postoperative views. The patient should not wear makeup for preoperative or postoperative photographic documentation. Digital photography is useful for the patient to indicate areas of concern during the consultation. Photographs are also useful for postoperative comparisons.
Aging and scarring result in loss of subcutaneous tissue, which is amenable to replacement by fat grafting. Indications for fat grafting include correction of atrophy due to aging or scarring and enhancement of facial elements (eg, to correct glabellar frown lines or to provide a fuller, more voluptuous lip-). Areas of the face not addressed by procedures such as rhytidectomy include nasolabial folds, glabellar creases, and tear troughs. Lip augmentation may improve the appearance of fine perioral lines and increase the amount of vermilion show.
Despite early views that fat is a relatively inert and isolated tissue, fat has been demonstrated to be a well-vascularized tissue with high metabolic activity. In addition to its structural role, fat tissue serves as a reservoir for energy storage. The number of fat cells generally is assumed to be stable after the completion of adolescent growth. Changes in the volume of fatty tissue relate to the size of the cells and their overall lipid content. Cells removed by liposuction or other surgical procedures do not regenerate. Cells shrink with overall weight loss and, in fact, may dedifferentiate. However, subsequent weight gain causes re-differentiation of the cells with an increase in volume.
Fat tissue consists of fat cells, which have thin cell membranes enmeshed in a fibrous network. Without the supporting fibers, the cells tend to collapse. An additional supporting network of connective tissue structure creates the lobules of fat, which can be observed grossly. Harvesting fat while maintaining as much supporting structure as possible preserves structural integrity of the tissue and helps the tissue retain bulk in the transplanted site. Almost any site can be used for harvesting; however, the abdomen is easily accessible, and access incisions can be hidden within the umbilicus or in the hair-bearing skin of the pubic area.
Contraindications to fat grafting include the presence of any disease processes that adversely affect wound healing and of poor overall health status of the individual.
The use of free fat grafting for the treatment of contour abnormalities resulting from breast biopsy or for breast augmentation is generally contraindicated. The grafted fat can cause both palpable nodules and calcifications, situations that may hinder a diagnosis of breast cancer or cause unnecessary intervention.
Almost all candidates have some fat for harvesting; however, some individuals are unwilling to have a procedure performed at a distant site.
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