Basic knowledge on facial fat grafting (autologous fat transfer)
Facial fat grafting (autologous fat transfer) is a widely practiced technique in cosmetic medicine and reconstructive surgery aimed at restoring lost volume, shaping facial contours, and promoting skin tissue regeneration (rejuvenation). This article explains the basic mechanisms of fat grafting, the evolution to the latest nanofat technology, anatomical injection compartments, the latest scientific data on graft survival rates, differences from fillers such as hyaluronic acid, and serious risks and complications based on provided medical literature.
1. How fat grafting works
Autologous fat is considered an ideal filler material because it has abundant supply sources, high biocompatibility, and low risk of allergy or rejection (Lv 2020). However, the mechanism by which transplanted fat survives long-term (integrates) is extremely complex.
Transplanted fat tissue immediately after injection lacks a reliable blood supply network, relying solely on osmotic absorption from surrounding tissue fluid for nutrition. If a dedicated blood supply is not rapidly established, fat tissue in the center of the graft may experience sustained ischemia and hypoxia, potentially leading to necrosis and liquefaction. According to the "borderland concept" proposed by Carpaneda et al., only 40% (Wei 2017) of tissue within a 1.5±0.5 mm range from the periphery of a transplanted fat mass survives.
The key to solving this graft survival challenge isfat aspiratederived stromal vascular fraction (SVF). SVF contains not only mature adipocytes but also diverse cells including adipose-derived stem cells (ASCs), vascular endothelial cells, fibroblasts, and pericytes, which have been confirmed to promote rapid neovascularization of the graft and dramatically improve survival rates. Furthermore, when used in combination with platelet-rich fibrin (PRF) generated by centrifugation from autologous blood, growth factors such as PDGF, VEGF, TGF-β1, TGF-β2, and EGF are continuously released, powerfully promoting tissue repair and regeneration. Conventionally, 20% to 90% (Wei 2017) of transplanted fat is absorbed, but the use of SVF and PRF plays a critical role in preventing ischemia in the graft center and achieving long-term integration.
2. Evolution from Coleman method to nanofat
The history of fat grafting is long; since Neuber first reported fat transplantation in 1893 (Lv 2020), numerous technical innovations have been made (Chou 2017).
Coleman method (structural fat grafting)
Dr. Coleman greatly contributed to standardizing fat grafting. In 1998, he proposed "Structural fat grafting," which involves delicate fat harvesting, centrifugation purification, and injection of fine fat parcels in multiple layers. Coleman argued that in areas with thin skin such as around the eyes, the volume of each injected parcel should be 1/30–1/50 mL (0.020–0.033 mL) (Chou 2017) to prevent necrosis in the center of the fat mass.
Birth of MAFT (Micro-Autologous Fat Transplantation)
Subsequently, in 2006, Dr. Lin et al. proposed MAFT (Micro-Autologous Fat Transplantation). The MAFT concept emphasizes reducing injected fat parcels to less than 1/100 mL (0.01 mL)—a sphere with a radius of 1.3 mm—to avoid complications (cyst formation, nodulation, calcification, etc.) and ensure graft survival to the center of the fat. Using dedicated precision injection devices such as the MAFT-GUN allows consistent, controlled transplantation of extremely small amounts of fat, ranging from 1/120 mL (0.0083 mL) to 1/240 mL (Chou 2017).
Arrival of nanofat (Nanofat)
In 2013, Tonnard et al. reported "nanofat." This is a microparticle obtained by mechanically emulsifying harvested fat between syringes and passing it through a dedicated filter. Nanofat particles are 100 μm (Wei 2017) or smaller (or 800 microns or less) in diameter and are rich in stem cells (ASCs) and SVF. Nanofat is used not for physical volume augmentation but for skin rejuvenation, fine line improvement, and regeneration of radiation-damaged tissue (Crowley 2021).
Currently, within the concept of Injectable Tissue Replacement and Regeneration (ITR2), fat is classified into the following 3 types (Crowley 2021) based on size and applied according to anatomical use:
- Millifat:2.4 mm or larger (Crowley 2021). Used for deep fat compartments and foundation formation over bone.
- Microfat:1.2 mm or larger (Crowley 2021). Used in shallow fat compartments and subcutaneous tissue.
- Nanofat (Nanofat): 800 microns or smaller (Crowley 2021). Injected into the subcutaneous or dermal layer (via microneedling, etc.) and used for skin quality improvement and tissue regeneration.
3. Anatomical Compartments and Indications
To perform facial fat grafting safely and effectively, a deep understanding of anatomical compartments (divisions) is essential. For example, the forehead (frontal region) is composed of the following 3 major layers (Chou 2017), and appropriately sized fat is injected into each:
- Deep layer (on the periosteum/posterior frontal muscle surface): Space between the frontal bone and frontal muscle. Millifat is used in this layer to build the foundation and create the basic contour of the face.
- Middle layer (within the frontal muscle): A layer with rich blood flow within the frontal muscle; microfat and similar materials are injected to maintain volume.
- Superficial layer (subcutaneous tissue): The layer between the dermis and frontal muscle, where micro-sized fat is placed to smooth and refine the contour.
In Asian culture, forehead roundness and fullness (Frontal fullness) are considered to indicate social popularity and leadership qualities, and aesthetic demand for forehead volume augmentation is notably high (Chou 2017).
Indications for facial fat grafting include age-related facial volume loss, asymmetry, congenital or acquired deformity, progressive hemifacial atrophy (Romberg's disease), and post-traumatic depression, among others (Lv 2020). By replenishing tissue of the same nature as the lost tissue (fat) to the appropriate anatomical layer, natural three-dimensional structure restoration becomes possible, rather than merely filling wrinkles.
4. Graft Survival Rate (Lv 2020)
The greatest challenge in facial fat grafting is the difficulty in predicting the graft survival rate. A systematic review and meta-analysis by Lv et al. (Lv 2020) provides important data objectively and quantitatively evaluating this survival rate.
This study analyzed 27 studies including 1,011 patients who underwent facial fat grafting. The postoperative follow-up period was 3–24 months, and the graft survival rate in objective measurements showed wide variation ranging from 26% to 83%. The average graft survival rate across all studies combined was 47% (95% CI 41–53%) (Lv 2020).
The following data demonstrates factors affecting graft survival rate:
- Differences by measurement method: The graft survival rate was 43% using 3D scanning, 57% on CT, and 40% on high-resolution ultrasound (HRUS). A significant difference was found between 3D scanning and CT (p=0.01 (Lv 2020)), suggesting that CT tends to overestimate the survival rate.
- Fat processing method: The graft survival rate was 47% using centrifugation, 36% with filtration, and 46% with sedimentation (Lv 2020). No clear statistical evidence was found that any one method was superior among these.
- Number of injections: While the first injection had a graft survival rate of 45%, the second injection (secondary injection) had a survival rate of 63% (Lv 2020), confirming that multiple injections significantly improve engraftment.
- Indications:In patients with congenital deformities, the engraftment rate was 51%, and in cosmetic augmentation, it was 42% (Lv 2020).
Additionally, the incidence of complications in this meta-analysis was only 2.8% (Lv 2020), confirming that facial fat grafting has high safety overall.
5. Difference from fillers
As options for restoring facial volume, synthetic fillers such as hyaluronic acid (HA), calcium hydroxyapatite (CAHA), and poly-L-lactic acid (PLLA) are widely used. The main differences between fat grafting and these fillers are as follows.
Convenience and reversibility
Synthetic fillers are pre-made products that can immediately restore volume without the burden of harvesting. In particular, HA fillers have an extremely significant advantage: if results are unsatisfactory or complications such as vascular occlusion occur, they can be safely dissolved (reset) using an enzyme called hyaluronidase. Additionally, in some areas such as the nose, HA may last 2–3 years. In contrast, if fat enters blood vessels after injection, there is no safe antidote to dissolve it (Moellhoff 2023).
Biostimulation effect
Fillers also have tissue-stimulating effects. HA stimulates fibroblasts by physically stretching the extracellular matrix (ECM), promoting collagen production. CAHA and PLLA act as biostimulators that strongly promote long-term collagen generation through microinjury-induced foreign body reactions (Crowley 2021).
Safety of autologous tissue and cellular regeneration
Because fat is the patient's own tissue (autologous tissue), there is no risk of foreign body reaction, allergy, or rejection (Crowley 2021). Additionally, fat grafting is not merely a "physical filler." Through the action of SVF and adipose-derived stem cells (ASCs) mentioned earlier, it improves blood flow at the cellular level and has the effect of fundamentally regenerating the thickness and texture of the dermis. However, fat has less predictable engraftment rates compared to fillers, and fat that does not engraft carries unique risks of causing cysts, calcification, and nodules (Lv 2020).
6. Risks and complications (Moellhoff 2023)
Although fat grafting is generally considered a safe procedure, "arterial embolism (AE)" caused by accidentally injecting fat into blood vessels is an extremely serious and catastrophic complication that can lead to blindness, stroke, and even death.
In a systematic review by Moellhoff et al., data from 61 patients who developed arterial embolism after facial fat grafting were analyzed. The mean age of affected patients was 33.56±11.45 years, relatively young, and the mean injection volume was 21.5±21.5 mL (Moellhoff 2023).
High-risk injection sites
The injection sites most frequently associated with arterial embolism were the glabella or multiple facial regions, affecting 16 of 61 patients (26.2%). This was followed by the temple in 10 patients (16.4%) and the forehead in 9 patients (14.8%) (Moellhoff 2023). These areas are extremely high-risk regions because branches of the ophthalmic artery and internal and external carotid arteries form complex anastomotic networks.
Symptoms and occluded vessels
Among 58 patients with recorded initial symptoms, 24 patients (41.4%) reported neurological symptoms, 20 patients (34.5%) reported visual symptoms, and 13 patients (22.4%) reported both (Moellhoff 2023).
The breakdown of vessels with confirmed occlusion (60 patients with data) was: ophthalmic artery (OA) occlusion in 26 patients (43.3%), cerebral artery (CA) occlusion (including anterior and middle cerebral arteries) in 11 patients (18.3%), and occlusion of both OA and CA in 14 patients (23.3%) (Moellhoff 2023).
Serious outcomes and prevention measures
The outcomes were extremely severe. 100% of patients (26 people) with ophthalmic artery (OA) occlusion resulted in permanent vision loss (blindness). Of 10 patients with cerebral artery (CA) occlusion, 80% (8 people) suffered neurological deficits, and of 11 patients with concurrent involvement of both, 63.6% (7 people) suffered both vision loss and neurological deficits. Furthermore, 6 patients (Moellhoff 2023) died as a result of embolism.
Because fat embolism has no specific antidote like hyaluronidase, prevention before occurrence is absolutely critical. As preventive measures, it is recommended to use thick blunt needles (cannulas) of 18G or larger to avoid high arterial penetration force, and to inject slowly in small amounts at low pressure using a 1 mL syringe (retrograde injection) (Moellhoff 2023). Meticulous attention to micro-doses of 0.1 mL or less per site is essential.
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7. Summary
Summary of this article
- Fat grafting has evolved from the Coleman technique → MAFT → Nanofat, expanding its role from "filling" to "tissue regeneration"
- By using different fat sizes—millimeter, micrometer, and nanometer scales—we can replenish anatomically appropriate layers from deep tissue to the dermis
- Average engraftment rate is 47% (Lv 2020) with significant individual variation, improving to 63% with a second injection
- The advantages are the safety and regenerative effects unique to autologous tissue, but the risk of arterial occlusion leading to blindness and stroke must never be underestimated
- The practitioner's anatomical knowledge and strict adherence to low-pressure, low-volume injection are key to maximizing benefits and minimizing risks
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References
- Azoury S, Shakir S, Bucky L, et al. Modern Fat Grafting Techniques to the Face and Neck. Plastic & Reconstructive Surgery. 2021DOI
- Coleman S. Structural Fat Grafting: More Than a Permanent Filler. Plastic & Reconstructive Surgery. 2006DOI
- Egro F, Roy E, Rubin J, et al. Evolution of the Coleman Technique. Plastic & Reconstructive Surgery. 2022DOI
- Trevidic P, Sykes J, Criollo-Lamilla G, et al. Filler Complications and the Role of Hyaluronidase. Aesthetic Surgery Journal. 2022DOI
- Wei H, Gu S, Liang Y, et al. Nanofat-Derived Stem Cells with Platelet-Rich Fibrin for Facial Rejuvenation. Oncotarget. 2017DOI
- Lv Q, Li Y, Fan Y, et al. Fat Grafting for Facial Rejuvenation: A Systematic Review and Meta-analysis of Volume Retention. Aesthetic Plastic Surgery. 2020DOI
Author of this article
Hiromitsu NakamuraPhysician
Zetith Beauty Clinic Ginza, Osaka, Fukuoka
He has a track record of research presentations at domestic and international academic conferences and is involved in technical guidance and education across Zetith Beauty Clinic. He specializes in precision aesthetic medicine based on anatomical foundations, pursuing natural results tailored to each individual's skeletal structure and tissue composition.