Residency · Residency · Plastic Surgery
Fat Grafting: Science and Technique
Overview
Autologous fat grafting is one of the most versatile procedures in plastic surgery, used for volume restoration, contour correction, and increasingly recognized for its regenerative properties. Despite its widespread adoption, fat graft survival remains unpredictable, and technique standardization continues to evolve. ---
Biology of Fat Graft Survival
Cell Survival Theory (Peer, 1950)
Transplanted adipocytes survive only if they receive adequate blood supply within 48 hours. Cells beyond approximately 1.5 mm from a vascular source undergo ischemic necrosis. Graft survival depends on rapid revascularization from the recipient bed.
Three-Zone Model of Fat Graft Survival
Surviving zone (outermost): adipocytes closest to recipient vasculature survive intact. Regenerating zone (middle): adipocytes die but adipose-derived stem cells (ADSCs) survive and differentiate into new adipocytes. Necrotic zone (central): all cells die; replaced by oil cysts, calcification, or fibrous tissue. Small aliquot placement maximizes the surviving and regenerating zones.
Adipose-Derived Stem Cells (ADSCs)
Multipotent mesenchymal stem cells residing in the stromal vascular fraction (SVF). Capable of differentiating into adipocytes, osteoblasts, chondrocytes, and endothelial cells. Paracrine effects: secrete VEGF, HGF, IGF-1, SDF-1 promoting angiogenesis and cell survival. Form the basis for cell-assisted lipotransfer (CAL) -- enrichment of fat grafts with ADSCs. ---
Harvesting Techniques
Donor Site Selection
Common sites: abdomen, flanks, inner thighs, lateral thighs, inner knees. No definitive evidence that one donor site produces superior graft survival. Avoid areas with previous liposuction (fibrotic, fewer viable cells). Lower extremity fat may have higher ADSC density (some studies suggest).
Tumescent Infiltration
Standard tumescent solution: lactated Ringer with 1:400,000-1:500,000 epinephrine and lidocaine. Infiltration-to-aspiration ratio: typically 1:1 (super-wet technique). Wait 10-15 minutes after infiltration for epinephrine effect.
Harvest Methods
Manual aspiration with syringe (Coleman technique): 10 mL syringe with 2-hole blunt cannula at low negative pressure; considered gentlest method. Low-pressure machine-assisted suction: wall suction at < -500 mmHg; may reduce cell viability at high pressures. Power-assisted liposuction (PAL): comparable cell viability to manual harvest. Ultrasound-assisted liposuction (VASER): controversial; may damage adipocytes but preserves SVF. Laser-assisted liposuction: thermal damage to adipocytes; NOT recommended for fat grafting harvest.
Cannula Considerations
Larger bore cannulas (3-4 mm) preserve more intact adipocytes. Smaller cannulas produce smaller fat parcels better suited for facial grafting. Blunt-tipped, multi-hole designs reduce trauma.
<image>Step-by-step medical illustration of the Coleman fat grafting technique showing four panels: (1) harvesting with a 10 mL syringe and blunt 2-hole cannula from the abdomen, (2) centrifugation at 3000 rpm for 3 minutes separating the aspirate into three layers (oil supernatant, purified fat, and blood/tumescent infranatant), (3) decanting the oil and draining the infranatant to isolate the middle fat layer, and (4) injection through a 1 mL syringe with blunt cannula using retrograde linear threading technique into the recipient site.</image>
Processing Techniques
Centrifugation (Coleman Technique)
3,000 rpm for 3 minutes (1,200 g). Separates aspirate into three layers: Top: oil from lysed adipocytes (discarded). Middle: concentrated viable fat (used for grafting).
Bottom: blood, tumescent fluid, cell debris (discarded). Most studied and widely adopted technique. Concern: excessive centrifugation may damage adipocytes.
Gravity Sedimentation
Fat allowed to settle by gravity over 10-30 minutes. Less processing trauma than centrifugation. May retain more ADSCs. Comparable graft survival in some studies.
Filtration
Washing and filtering through mesh or closed systems (Revolve, Puregraft). Removes blood, oil, and free lipid. Rapid processing time. Standardized and reproducible.
Decanting (Cotton Gauze Rolling)
Fat placed on absorbent material (Telfa, gauze) to wick away fluid and oil. Simple, rapid technique. Some concern about loss of SVF cells.
Head-to-Head Comparisons
No definitive evidence that one processing method is clearly superior. Key principle: gentle handling and removal of non-viable components. ---
Injection Technique
Principles
Small aliquots: inject in 0.1-0.3 mL ribbons to maximize surface area for diffusion. Multiple passes and planes: fan-shaped retrograde injection through multiple tissue planes. Low pressure: gentle, steady injection pressure. Multiple tunnels: create a three-dimensional lattice of small fat parcels.
Recipient Site Preparation
Pre-expansion with external devices (e.g., BRAVA) may improve fat retention in breast augmentation. Rigid scar or irradiated tissue may need release or conditioning before grafting. Infiltration of recipient site with tumescent solution to expand space and reduce trauma.
Volume Considerations
Overcorrection by 20-30% is traditionally recommended (though evidence is limited). Expected resorption: 30-70% over 6-12 months (highly variable). Multiple sessions may be needed for optimal results.
Site-Specific Applications
Face: 1 mL syringes, small cannulas (18-gauge blunt), inject in periosteal, sub-SMAS, subcutaneous, and intradermal planes. Breast: careful technique to avoid large bolus injection; fat necrosis and calcification may confound mammographic screening. Buttocks (BBL): subcutaneous plane ONLY (intramuscular injection associated with fatal fat embolism). Hands: dorsal subcutaneous plane. ---
Fat Grafting in Specific Applications
Facial Rejuvenation
Volumetric restoration of deflated fat compartments. Common areas: periorbital hollow, malar region, nasolabial fold, temples, lips, jawline. Addresses the "deflation" component of aging complementary to lifting procedures. Reported skin quality improvement (regenerative effect of ADSCs).
Breast Augmentation and Reconstruction
Autologous alternative to implants (limited augmentation of 100-200 cc per session). Useful for contour refinement after implant-based or flap reconstruction. Concern: fat necrosis, oil cysts, and calcifications can mimic malignancy on imaging. ASPS Fat Graft Task Force: fat grafting does not increase breast cancer risk (2012).
Brazilian Butt Lift (BBL)
Highest mortality rate of any cosmetic procedure (~1:3,000 historically). Cause of death: fat embolism to pulmonary vasculature via gluteal veins. Critical safety measures: Inject ONLY into subcutaneous fat (NOT intramuscular or submuscular).
Use blunt cannulas. Avoid cannula tip directed toward deep muscle. Ultrasound guidance gaining adoption. Multi-society task force safety guidelines (2018).
Regenerative Applications
Fat grafting to irradiated tissue, chronic wounds, and scars. Lipofilling of painful neuromas. Improvement of burn scar pliability and appearance. Mechanism: ADSC paracrine effects promoting neovascularization and anti-fibrotic remodeling.
<image>Medical illustration showing fat grafting injection technique in the face with a cross-sectional view demonstrating the concept of multi-planar injection: small 0.1 mL ribbons of fat being deposited in a retrograde fashion through a blunt cannula at different tissue depths (periosteal, deep fat compartment, superficial fat compartment, and subdermal planes). The cross-section shows how small aliquots maximize surface area contact with surrounding vascularized tissue for graft survival.</image>
Complications
Early
Ecchymosis and edema (expected). Overcorrection and contour irregularity. Infection (rare). Fat embolism (rare but potentially fatal, especially in BBL). Hematoma at donor or recipient site.
Late
Resorption (30-70%) requiring repeat sessions. Fat necrosis: palpable firm nodules, oil cysts. Calcification: may require biopsy to exclude malignancy (breast). Contour irregularity, asymmetry. Cyst formation. Blindness from retrograde arterial embolization (periorbital injection -- extremely rare).
Fat Embolism Prevention (BBL)
Inject in subcutaneous plane only. Use large-bore blunt cannulas. Avoid deep penetration into or below the gluteus maximus. Patient positioning: prone or lateral. Limit injection pressures. ---
Emerging Concepts
Cell-Assisted Lipotransfer (CAL)
Enrichment of fat grafts with additional ADSCs from the stromal vascular fraction. Enzymatic (collagenase) digestion of fat to isolate SVF, then recombine with fat graft. Theoretical improvement in graft survival. Regulatory concerns regarding cell manipulation (FDA considers enzymatic processing as more than minimal manipulation).
Nanofat
Mechanically emulsified fat processed through small connectors to create a liquid fat emulsion. Contains ADSCs and growth factors but no viable adipocytes. Used for intradermal injection for skin rejuvenation, scar treatment, and pigmentary changes. Not a volumizing technique.
Stromal Vascular Fraction (SVF) Therapy
SVF contains ADSCs, endothelial progenitor cells, pericytes, and immune cells. Point-of-care devices for SVF isolation. Regulatory landscape evolving. ---
Clinical Pearls
The key to fat graft survival is small aliquot placement -- each fat parcel must be within 1.5 mm of a vascular source for diffusion-based nutrition. Gentle handling at every step (harvest, process, inject) maximizes adipocyte viability. The Coleman technique (manual syringe aspiration, centrifugation, small aliquot injection) remains the gold standard, though no processing method has been proven definitively superior. Fat grafting to the breast does not increase cancer risk, but patients should be counseled about potential radiographic findings (fat necrosis, calcification, oil cysts).
BBL carries the highest mortality of any cosmetic procedure -- strict adherence to subcutaneous-only injection is non-negotiable. Expect 30-70% volume loss over the first year; patients should be counseled about the need for multiple sessions. The regenerative properties of fat grafting (via ADSCs) extend beyond simple volume replacement -- improvement of irradiated tissue, scars, and chronic wounds is well-documented. Avoid harvesting fat with laser-assisted liposuction -- thermal damage destroys adipocyte viability. ---.
References
- Coleman SR. Structural fat grafting: more than a permanent filler. Plast Reconstr Surg. 2006;118(3 Suppl):108S-120S.
- Peer LA. Loss of weight and volume in human fat grafts with postulation of a "cell survival theory." Plast Reconstr Surg. 1950;5(3):217-230.
- Yoshimura K, Sato K, Aoi N, et al. Cell-assisted lipotransfer for cosmetic breast augmentation: supportive use of adipose-derived stem/stromal cells. Aesthetic Plast Surg. 2008;32(1):48-55.
- Khouri RK, Rigotti G, Cardoso E, et al. Megavolume autologous fat transfer: part I. Theory and principles. Plast Reconstr Surg. 2014;133(3):550-557.
- Mofid MM, Teitelbaum S, Suissa D, et al. Report on mortality from gluteal fat grafting: recommendations from the ASERF Task Force. Aesthet Surg J. 2017;37(7):796-806.
- ASPS Fat Graft Task Force. Fat grafting to the breast: an assessment of oncological concerns. Plast Reconstr Surg. 2012;129(1):169e-173e.
- Tonnard P, Verpaele A, Peeters G, et al. Nanofat grafting: basic research and clinical applications. Plast Reconstr Surg. 2013;132(4):1017-1026.
