Can We Standardize the Techniques for Fat Grafting?




Fat grafting still remains technique dependent with possible less favorable long-term results because there are no standardized techniques used by the surgeon to perform the procedure. In this article, the authors have tried to standardize the techniques for fat grafting as first proposed and popularized by Coleman. These techniques, supported by the most recent scientific studies and understandings of clinical course following autologous fat transplantation, emphasize proper fat harvesting, processing, and placement so that a predictable long-lasting result can be achieved.


Key points








  • The preferred donor sites include the low abdomen and inner thigh, especially in younger patients.



  • Fat grafts should be harvested with lower negative pressure via modified liposuction technique to ensure the integrity as well as the optimal level of cellular function.



  • Fat grafts should be processed with centrifugation that can reliably produce purified fat and concentrated growth factors and adipose-derived stem cells, all of which are beneficial to graft retention.



  • Fat grafts should be placed following certain principles with gentle injection of a small amount per pass in multiple tissue planes and levels with multiple passes to ensure maximal contact of the graft with vascularized tissue in the recipient site.






Introduction


Fat grafting can be a good option for soft tissue augmentation because fat is abundant, readily available, inexpensive, host compatible, and can be harvested easily and repeatedly. However, the overall survival rate of a fat graft is around 50% in most reported studies, which has not been considered ideal for clinical practice. The goal of improving graft retention has been, therefore, the constant driving force for scientists and clinicians to search for better techniques for fat grafting.


Refinement of fat grafting techniques has largely been investigated to maintain the fat graft’s viability and to create a better environment in the recipient site for fat graft survival. In this article, the authors primarily introduce one possible preferred technique for autologous fat grafting based on the most recent scientific studies by many investigators. The authors propose it as a standardized technique because this would be a more scientifically sound approach. The authors hope the readers will be able to use the information provided here to achieve the best possible outcome of fat grafting for their patients.




Introduction


Fat grafting can be a good option for soft tissue augmentation because fat is abundant, readily available, inexpensive, host compatible, and can be harvested easily and repeatedly. However, the overall survival rate of a fat graft is around 50% in most reported studies, which has not been considered ideal for clinical practice. The goal of improving graft retention has been, therefore, the constant driving force for scientists and clinicians to search for better techniques for fat grafting.


Refinement of fat grafting techniques has largely been investigated to maintain the fat graft’s viability and to create a better environment in the recipient site for fat graft survival. In this article, the authors primarily introduce one possible preferred technique for autologous fat grafting based on the most recent scientific studies by many investigators. The authors propose it as a standardized technique because this would be a more scientifically sound approach. The authors hope the readers will be able to use the information provided here to achieve the best possible outcome of fat grafting for their patients.




Classifications for fat grafting


The fat grafting technique can be arbitrarily classified into 5 essential components: how to select the donor sites, how to harvest the fat grafts, how to process the fat grafts, how to prepare the recipient sites, and how to inject the fat grafts. Fat grafting can also be arbitrarily divided into 3 categories based on the volume needed: Small-volume fat grafting (<100 mL) is performed primarily for facial rejuvenation or regenerative approach. Large-volume fat grafting (100–200 mL) is performed primarily for breast and body contouring. Mega-volume fat grafting (>300 mL) is performed primarily for buttock augmentation or breast augmentation or reconstruction. Each category may have its respective technique for the procedure.




Basic considerations for fat grafting


Donor Site Selection


A variety of body areas that uniformly have abundant or excess fat are suitable as donor sites for harvest of fat grafts, such as the abdomen, flanks, buttocks, medial and lateral thighs, or knees. As a general rule, donor sites are selected that enhance the body contour and are easily accessible in the supine position, which is the position that is used for almost all facial and body augmentation procedures. Although there is no evidence of a favorable donor site for harvest of fat grafts because the viability of adipocytes within the fat grafts from different donor sites may be considered equal, a higher concentration of adipose-derived stem cells (ADSCs) is found in the lower abdomen and inner thigh in one study. In addition, in a younger age group (<45 years old), fat grafts harvested from both the lower abdomen and inner thigh have higher viability based on a single assay test. With what we know about the potential role of ADSCs in fat grafting, the lower abdomen and inner thighs should, therefore, be chosen as the better donor sites for fat transplantation ( Fig. 1 ). These donor sites are not only easily accessible by the surgeons with patients in the supine position but also scientifically sound as long as patients have an adequate amount of adipose tissue in those areas. If patients are placed in the prone position, the posterior medial thigh, lateral thigh, and flank areas can be the primary donor sites for harvest of more fat grafts. The palm and pinch test should be performed in the donor tissue to determine if there is adequate fat reserve and to quickly estimate the amount of fat that can be harvested. A palm size is roughly measured as 200 cm 2 , whereas a pinch test predicts the layer thickness of the fat graft to be harvested. For example, even in a thin patient, a 0.25-cm layer thickness of fat harvested over the surface area of a palm will yield 50 mL of fat graft (200 cm 2 × 0.25 cm = 50 mL). Therefore, we can harvest 250 mL of fat solely from the anterior surface of a woman’s thigh that has 5 palm measures.




Fig. 1


Lower abdomen as a commonly selected donor site for small-volume fat grafting.


Anesthesia


Anesthesia for harvest of fat grafts can be performed under general anesthesia, epidural anesthesia, or local anesthesia with or without sedation. Intravenous sedation is routinely used in conjunction with regional or local anesthesia if requested by patients. The tumescent solution used for donor site analgesia or hemostasis should contain the lowest concentration of lidocaine possible because its high concentration may have a detrimental effect on the adipocyte function and viability. In general, the authors often use 0.01% to 0.02% of lidocaine in Ringer lactate if the fat grafting procedure is performed under general anesthesia and 0.04% if the procedure is under local anesthesia with or without sedation. The tumescent solution also contains epinephrine with a concentration of 1:1,000,000. Epinephrine can precipitate vasoconstriction in the donor sites as well as the recipient sites, which may decrease blood loss, bruising, hematoma, and the possibility of intra-arterial injection of the transplanted fat, especially when injecting around periorbital areas or in the face.


Fat Graft Harvesting


The syringe aspiration, as a relatively less traumatic method for harvest of fat grafts, is supported by the more recent studies and should be considered as a standardized technique of choice for harvest of fat grafts. However, this technique can be time consuming even for experienced surgeons; the large quantity of fat grafts may not be easily obtained with this technique. Several manufactures have attempted to develop an ideal device that combines the fat harvest, process, and transfer. Unfortunately, only a few such devices have been studied comprehensively for their reliability; their usefulness is still debatable even among the experts in the field.


Small-volume harvesting technique


Placement of incisions can be done with a No. 11 blade in the locations where the future scar can be easily concealed. Fat grafts can be harvested through the same incision made for infiltration of the aesthetic solution. The size of the incision is about 2 to 3 mm. A tenotomy scissor is used to dilate the underlying subcutaneous tissue through the incision to allow insertion of the harvesting cannula with ease. The aesthetic solution is then infiltrated to the donor site 10 to 15 minutes before fat extraction, which makes harvesting of the fat graft easier and less traumatic. The ratio of aspirated fat to tumescent solution should be about 1:1 so that each pass of fat extraction can be more efficient.


A 10-mL Luer-Lok syringe is used and connected with a harvesting cannula. The authors prefer a 10-mL syringe to a larger one because the 10-mL syringe is less cumbersome in hand. The harvesting cannula is 15 cm long with a blunt tip and has dual openings like the shape of a bucket handle ( Fig. 2 ). Gently pulling back on the plunger creates a 2-mL space vacuum of negative pressure in the syringe. With a gentle back-and-forth movement of the syringe, the fat is gradually collected inside the syringe ( Fig. 3 ). If little fat with too much fluid is present within the syringe, the fluid can be easily pushed out from the bottom of the syringe in a vertical position and fat extraction can be continued. After harvest, all incision sites are closed with interrupted sutures once excess tumescent fluid or blood has been milked out.




Fig. 2


The instruments used for fat injection: Different size and shape of cannulas are used as needed. The forked-tip cannula can be used to release fibrotic tissue, scar, or adhesion.



Fig. 3


Fat graft harvesting: back-and-forth movement with a 10-mL syringe, and fat grafts are easily aspirated into the syringe.


Large- or mega-volume harvesting technique


For large-volume fat grafting, one well-conducted study has showed that fat harvested with low aspiration pressure (<250 mm Hg) has a more viable adipocyte count than that harvested with high aspiration pressure (>760 mm Hg). Several devices have shown their potentials for large- or mega-volume fat graft harvesting with reliability in yielding a greater number of viable adipocytes and a higher level of cellular function within fat graft compared with the standard liposuction technique. One of the examples is the LipiVage fat harvest, wash, and transfer device (Genesis Biosystems, Inc, Lewisville, TX). It may have certain benefits for less-experienced surgeons to use the device for harvesting and processing fat grafts so that such fat grafts can be more consistent in terms of their viability and intact structure. Khouri and colleagues advocated a low-pressure vacuum (300 mm Hg) liposuction with a specially designed device (KVAC-Syringe; Lipocosm, Key Biscayne, FL) to harvest the fat graft with constant low pressure and place it to low G force (15 g, 2 to 3 minutes) using a hand-cranked centrifugation for mega-volume graft harvest and processing. A newly designed harvesting cannula by Khouri may have many advantages because of its efficiency and less trauma to adipocytes. Such a cannula can be incorporated into a large-volume fat grafting instrument set and be used in conjunction with lower suction pressure for large-volume fat graft harvest ( Fig. 4 ).




Fig. 4


A newly designed cannula with multiple side holes for large- or mega-volume fat graft harvest.


Fat Graft Processing


Several methods have been proposed to effectively remove the infiltrated solution and cell debris within the lipoaspirates and to obtain more concentrated fat grafts. However, it is actually the most controversial and disagreeable issue in fat grafting even among many experts in the field. Common methods for processing fat grafts include centrifugation, filtration, or gravity sedimentation.


Centrifugation, as proposed by Coleman , is the authors’ preferred method to process fat grafts. There are several advantages of centrifugation of fat grafts. More viable adipocytes are found at the bottom of the middle layer after centrifugation even with a force of 50 g for 2 minutes based on viable cell counts, and this makes manipulation of the fat graft for use easier and with reliable viability. Recent studies have shown that proper centrifugation can concentrate not only adipocytes and ADSCs but also several angiogenic growth factors within the processed fat grafts. Because a higher content of stem cells or angiogenic growth factor positively correlated with fat graft survival both in experimental and clinical studies, centrifugation at 3000 rpm (about 1200 g) for 3 minutes seems to offer more benefits for this effectively concentrating adipocytes and ADSCs and should be a valid method of choice for processing fat grafts, especially for small-volume fat grafting.


Processing of fat with centrifugation


The Luer-Lok aperture of the 10-mL syringe locked with a plug at completion of harvest is ready for centrifugation ( Fig. 5 ). After careful removal of the plunger, all lipoaspirate-filled 10-mL syringes are placed into a centrifuge and are then centrifuged with 3000 rpm (about 1200 g) for 3 minutes. Greater G force or longer duration of centrifugation may be harmful to adipocytes and is, therefore, not recommended.


Nov 20, 2017 | Posted by in General Surgery | Comments Off on Can We Standardize the Techniques for Fat Grafting?

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