For over a century, surgeons have struggled to apply autologous fat grafting in plastic, reconstructive, and esthetic surgery with variable results. In 1893, the grand surgeon, Neuber,7 became the first to reconstruct a facial defect. Thereafter, several reports have described fat grafting: Kanavel21 stated that “fat cells are the best friend of the surgeon,” Peer8 described an approximately 55% fat-graft retention rate, and Bames9 reported convincing results regarding fat grafting for breast augmentation. In 1977, Illouz10 reported on “liposuction” and developed the related medical instruments. Subsequently, fat grafting was fine-tuned and applied in plastic surgery; for example, Fournier11 used fat grafting to fill involuted facial tissues, and Chajchir and Benzaquen12 used fat grafting for rejuvenation of facial wrinkles and treatment of hemifacial atrophy. In addition, various endeavors have been attempted for recipient site preparation; for example, Asken13 performed subcision to prepare a pocket for fat grafting, and Nguyen et al14 reported muscle as the optimal recipient site for fat grafting. In the past 2 decades, prominent surgeons have illustrated numerous principal theories. Carpaneda and Ribeiro15,16 postulated higher fat graft survival, and in 1993 and 1994, they experimentally proved that the graft survival is higher when the grafting is within 1 to 2 mm from the margin. In 1994, Coleman17 presented the structure fat graft method and emphasized that in special locations, such as periorbital areas, each fat parcel must be between 1/30 and 1/50 mL. Based on the review of the aforementioned literature, experts and scientists in the field have demonstrated various fat-grafting techniques; however, no conclusive strategy has yet been developed.22
Evidence-based Medicine in Fat Grafting
Evidence-based medicine applies the most reliable evidence gained from scientific methods to clinical decision making.23 In autologous fat grafting, 2 theories were proposed by Carpaneda and Coleman, which demonstrate the importance of evidence-based medicine.
Theory by Carpaneda
Carpaneda and Ribeiro15 demonstrated only 40% graft survival at 1.5 ± 0.5 mm peripheral to the graft margin. Furthermore, they reported that thickness and geometrical shape are the keys to successful fat transplantation and concluded that the diameter of the fat graft (either spherical or cylindroid shaped) should be < 3 mm to achieve higher graft survival rates.16
Coleman17 proposed the concept of structure fat grafting and emphasized that the fat parcels should be manually arranged in layers with a volume of < 1/10 mL per injection for each parcel; in special sites such as periorbital areas, each fat parcel should be 1/30–1/50 mL. Moreover, the complications and morbidities can be minimized by avoiding the central necrosis of a fat graft that can be induced through overinjection when each parcel is placed.
Disadvantages of Commercialized Medical Devices: Ratchet Guns
For several years, commercially available ratchet guns have been clinically applied in fat grafting with variable results. The advantages of ratchet guns include the accurate control of fat parcels by pulling of the trigger, and the ergonomic design. However, the disadvantages are the relatively large volume injected per triggering (1/10 mL, 1/2 mL, and up to 1 mL) and the potential exposure of the fat graft inside the syringe to ambient air because of repeated manipulation of the plunger. Although some surgeons have reported favorable results, most surgeons are hesitant in using these instruments. Accordingly, in addition to accuracy, fat grafting also necessitates delicate, precise, and consistent control of the placement of each fat parcel.
The aforementioned evidence-based medicine indicates the necessity for precise, accurate, and consistent delivery of each parcel, as insisted by Coleman and Carpaneda. However, commercial devices have not yet satisfied all the requirements for precise delivery. Moreover, manual operation is not only physically difficult; it is also scientifically impossible to deliver each fat parcel at minute volumes between 1/30 and 1/50 mL when using this method.
Myths Regarding Overinjection with Massage
Previous studies have emphasized the requirements for optimal fat grafting at recipient sites, such as the periorbital area, wherein a fat droplet should be as minute as 1/30 to 1/50 mL.17 The delicate placement of fat graft relies on the surgeon’s manual skills; however, even an experienced surgeon cannot expect to inject each minute fat parcel with accuracy and consistency, particularly in the case of tissue resistance inside the donor area. Therefore, instances of overinjection or abrupt placement of fat are frequently observed and unavoidable.
Based on a study conducted by Peer that indicated approximately 55% graft survival after fat grafting, some surgeons prefer to perform fat grafting through overinjection at the recipient site, followed by vigorous manual massage exerted by the operator to even out and flatten the skin surface. However, as illustrated in Figure 7, overinjection can eventfully induce several complications as described previously.24
Concept of MAFT
Similar to the acceptance of skin grafts, a fat graft regains its blood circulation 48 h after implantation (neovascularization formation).25 However, the inflow of nutrients and outflow of metabolites (adipocytes) depend on the initial diffusion and plasmatic imbibition after grafting. Carpaneda and Ribeiro15 demonstrated that the central area eventually necrotizes and only the marginal zone survives at a rate of approximately 40% at 1.5 ± 0.5 mm from the grafted margin, regardless of the shape of the fat graft (spherical or cylindrical).
Previous studies have reported several postoperative complications associated with the large size of an implanted fat parcel, including absorption, cyst formation, fibrosis, calcification, ossification, and asymmetry.24 This phenomenon of “central necrosis” induces a cascade of aggressive chain reactions, leading to numerous unavoidable complications including unpredictable graft survival and fat retention. Therefore, it is highly recommended that the size of the implanted fat droplets be as small as possible.11
Based on the theory postulated by Carpaneda, the mathematical formula for determining the optimal volume of fat parcels (here, the fat graft is presumed to be spherical in shape) is calculated as follows: the volume of a globe is (4/3)πr3, where r is the global radius and π is the ratio of any circle’s circumference to its diameter in Euclidean space. Table 1 presents the information regarding the volume of each fat parcel at the radii of 1, 1.5, and 2 mm. We concluded that the injection frequency of 1-mL fat parcels for a spherical graft with a 2-mm radius can be calculated by dividing 1000 mm3 (1 mL) by (4/3) π (2 mm)3. Therefore, a minimal injection frequency of 30 was set for each 1 mL fat-graft parcel to achieve superior graft survival rates.
What MAFT Emphasizes and How It Works
Precise, Accurate, and Consistent Placement
The subcutaneous tissue overlying the skin where fat grafts are primarily placed possesses a strong longitudinal adherence to the fibrous septa, with strong fascia or ligaments. For placement of minute parcels, a tunneling maneuver of the injection needle is required by moving it back and forth to loosen the tough subcutaneous tissues and place as small a parcel as possible. Such a maneuver in fat placement results in more tissue injury and necessitates a longer healing time. Moreover, severe ecchymosis and swelling in the first 2 weeks after grafting embarrassed and frustrated the patients with an unattractive or bruised appearance.26 Some swelling persisted even 16 weeks after grafting.
Alternative to Overinjection with Manual Massage
As observed in Figure 7, an irregular depression (Fig. 7A) was observed as a soft-tissue defect (mimicking soft-tissue depression or grooves). Surgeons often overinjected the sunken areas (Fig. 7B), followed by vigorous massage to remold and flatten them evenly (Fig. 7C). However, after vigorous massage, the fat parcels formed a confluent mass. Although the skin surface appeared smooth and full after operation for days to weeks, the remolding processes including absorption and fibrosis continued and evolved because of central necrosis (Fig. 7D). Eventually, as shown in Figure 7E, irregular skin and uneven surface over the graft area appeared as unavoidable morbidities.
An Instrument to Reflect the Concept of MAFT
The innovative transmission system of the MAFT-Gun was designed to minimize the injecting volume to 1/240 mL per parcel (Fig. 1D). This microdelivery mechanism ensured that the radius of each injected droplet was approximately 1 mm, which has been documented in the literature as essential to decreasing the severity of the inevitable central necrosis of the fat parcel.15 Therefore, the graft survival rate improved when the fat droplet resided in the tissue with no potential central necrosis, which was the primary reason for impairing the transmission of nutrients inside and the metabolites outside the adipocyte (or preadipocyte).
No Excess Swelling and Long Healing Time Compared with Other Traditional Modalities
Even when performed by the most experienced surgeons, postoperative swelling and edema are unavoidable, which often frustrates patients.26 Severe bruising and swelling develop in the recipient areas in the first week after fat grafting, and this is primarily attributed to the to-and-fro movements of the injection cannula during the injection procedure.26 However, the strong and tough adherent subcutaneous tissue in some recipient areas needs to be loosened by using such a maneuver to place the fine fat parcel and avoid the dislodgement of huge droplets by abrupt overinjection. The patented microcontrolling system of MAFT-Gun ensured that the injection volume of each parcel was predetermined and thus controlled in the procedure. A steady and accurate volume was transmitted at each trigger pull, regardless of the strength exerted by surgeons or the tempo of the injection. Therefore, by reducing the frequency of the back-and-forth tunneling movements used to loosen the recipient area, postoperative healing time was reduced, and the swelling and edematous appearance was minimal when compared with traditional techniques.
Enhanced Performance of Surgeons
Surgeons have to turn their hands often because the fixed pinhole of commercial injection needles requires changing for various grafting sites. The inconstant and labor-intensive turning of the surgeons’ hands impedes efficacious performance during the grafting procedure. A clear marking with 360° multirange adjustability of the MAFT instrument provided precise control of the direction of injection. With this innovation, surgeons were able to change the pinhole of the injection needle freely, comfortably, and accurately. The user-friendly trigger system based on the pulling maneuver enabled a predetermined volume of each parcel to be precisely delivered. Right- or left-handed use of the handpiece was set in advance, which is therefore adaptable for use by all surgeons.
Innovation of MAFT-Gun
The MAFT-Gun provided an innovative operating system to deliver fat grafts with a flexible volume of 1/60, 1/90, 1/120, 1/150, 1/180, or 1/240 mL per injection (by rotating the adjustable dial to 60, 90, 120, 150, 180, or 240, respectively), which was suitable for the needs of the surgeons performing the grafting procedure at various areas. Ease of use and ergonomics in application defined the characteristics of this state-of-the-art device as a preferential assisting device.
Problems with Sunken Upper Eyelids
Sunken upper eyelids, particularly in Oriental people, are a common occurrence and often present a weak and tired appearance. Based on racial and physiognomic considerations, Asian people might wish to enhance the facial appearance caused by sunken upper eyelids, not only for beautification but also for luck. Several operative strategies, including fascia, dermal grafts, and derma-fat-fascia grafts, have been documented in the literature.1–5 However, no satisfactory long-term results have been reported. Commercial soft-tissue fillers such as hyaluronic acid, collagen, or other synthetic biocompatible/degradable materials are popular in the cosmetic market. However, because of the high cost, short duration, and risk of allergies and other complications, an ideal filler is yet to be defined regarding persistency, no allergy reactions, and lower morbidity.22 In this study, the sunken upper eyelids were recontoured using the MAFT concept and by employing the MAFT-Gun, which enabled an accurate and precise transplantation of each fat droplet. In addition to the recontouring of the hollow-looking eyes, most patients observed that after MAFT, their skin texture and appearance was more youthful and rejuvenated, which implied the existence of stem cells or stromal vascular fractions in the transplanted fat.27, 28 Because fat grafts play an essential role as “more than a permanent filler,” as advocated by Coleman,29 they occupy the future stage in regenerative medicine. Therefore, the success of completion of a fat grafting procedure has promising applications not only in cosmetic surgery but also in reconstructive surgery.
The evolutionary era of fat grafting is the result of the continuous endeavors of various plastic surgeons. All the strategies of fat grafting, including harvesting, processing, refinement, and transplantation, exhibit promising progress. MAFT is introduced as a novel approach in fat grafting, and its execution can be accomplished using the innovative MAFT-Gun instrument. Using this technique, sunken upper eyelids with multiple folds, which present as hollow eyes, can be reconstructed with favorable long-term follow-up results.
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