Fat grafting

What is fat grafting?

Fat grafting is a procedure which removes excess fat cells from one area of the body, commonly the abdomen or thighs, and then reimplants it where needed.

Other names for fat grafting include autologous fat transfer (AFT) and lipofilling.

What is fat grafting used for and what are the techniques used?

Fat grafting can be used for correcting or improving:

• Scarring
• Volume
• Sunken cheeks and facial lines.

There are different types of fat grafting based on the particle size of transferred fat:

Macrofat grafting

• Fat particle diameter >2.4 mm
• Involves harvesting large volumes of fat, typically through more extensive liposuction, followed by processing and injection into the targeted area.
• This is commonly used for larger volume restoration eg, breast augmentation/reconstruction, buttock augmentation, hemifacial atrophy, or other lipodystrophies.

Microfat grafting

• Fat particle diameter <1 mm
• Involves harvesting small amounts of fat using a gentle liposuction technique, followed by processing and injection into the targeted areas.
• Primarily used for facial enhancement and rejuvenation due to its smaller particle size.
• Areas targeted include sunken cheeks, under eye hollows, facial rhytides, and the dorsum of hands.

Nanofat grafting

• Fat particle diameter <0.1 mm
• This is a similar technique to microfat grafting, but the harvested fat is further emulsified to create nanofat.
• Used for regeneration and rejuvenation without a volumising effect.
• Ideal for improving skin texture, fine lines, and scars (eg, acne scarring and lupus panniculitis).
• Nanofat is an ultra-purified suspension and, unlike macrofat and microfat, is devoid of mature adipocytes. It is composed of adipose-derived stem cells, other cells, microvascular fragments, growth factors, and cytokines.

In addition to adding volume, fat grafting is also utilised to improve tissue quality or reduce pain and other functional complaints eg, in radiation dermatitis, burns, post-mastectomy pain syndrome, and breast implant capsular contraction.

What are the contraindications with fat grafting?

Contraindications:

• High likelihood of graft volume loss eg, planned weight loss
• Active infection in the donor or recipient site.

Cautions:

• Conditions that impair blood flow or wound healing eg, diabetes mellitus, peripheral vascular disease, coagulopathy, smoking
• Patients with low body fat
• Psychological factors eg, body dysmorphic disorder, unrealistic expectations.

How is fat grafting performed?

The fat grafting procedure can last a few hours and is typically completed as an outpatient day case. If fat grafting is performed as part of a larger surgical procedure, an overnight hospital stay may be required. If large areas are being treated, the process can be split across multiple sessions.

Fat grafting consists of three main stages:

1. Harvesting

This step involves preparation of the site of fat removal using a local anaesthetic and removal of the fat via suction through a small incision.

There are several harvesting methods, but a common approach utilises liposuction with a wetting solution — a mix of a crystalloid fluid, local anaesthetic, and vasoconstrictor. The most common method is called tumescent liposuction, which infiltrates tissue with large volumes of wetting solution.

• The wetting solution is injected into the donor area to minimise pain, bruising, and blood loss.
• A cannula (thin tube) is inserted through a small incision to suck out fat under low pressure (via syringe aspiration or a suction machine).
• Following fat removal, the incisions are closed, either with stitches or a simple dressing.

Emerging techniques are exploring direct fat excision, where fat is surgically removed rather than suctioned. While early trials show promise, these methods are not widely adopted at present.

2. Processing/purification

The harvested fat undergoes processing to eliminate impurities (eg, free oils, cellular debris, blood, and fluid) as these can induce inflammation at the recipient site and undermine graft survival. Common processing techniques include centrifugation, filtration, washing, and sedimentation.

The degree of processing depends on whether macrofat, microfat, or nanofat grafting is utilised.

3. Injection

The recipient site is prepped and fat is injected in small aliquots using another cannula or needle into the area. This process is repeated until the desired correction has been achieved.

After the procedure

• Avoid massage and excessive movement of the treated area (minimises risk of fat migration).
• Ice compresses may be used for 24-48 hours to reduce inflammation.
• Simple, over-the-counter analgesics should be sufficient for any postoperative discomfort.

A follow-up visit is arranged approximately one week after the procedure to assess both the donor and recipient sites. Most of the swelling is expected to resolve within 6–8 weeks, at which point early results may be visible. A revision procedure may be required if the desired outcome has not been achieved, but this should not be performed within 3 months of the first graft.

What are the benefits of fat grafting?

A key advantage of fat grafting over other soft-tissue fillers is its biocompatibility. By using fat that is autologous (comes from your own body), the risk of hypersensitivity or foreign body reactions is minimised.

Other benefits:

• Easily accessible filler
• Gives more natural-looking results
• Favourable safety profile
• Minimally invasive.

Emerging evidence suggests that adipose-derived stem cells (ADSCs) within the grafted may enhance and promote regeneration of tissues.

What are the complications of fat grafting?

Like any surgery, fat grafting carries potential risks.

General surgical risks

• Bleeding — risk increases for patients taking anticoagulant or antiplatelet medications. While usually controlled intraoperatively, ongoing oozing can lead to a haematoma which may require drainage.
• Infection — can occur at the donor site or recipient site. It can be extensive, affecting large areas of skin or underlying muscle, potentially requiring further significant surgery.
• Pain — typically improves as the site heals and is manageable with simple analgesics.
• Scarring — unlikely to be a major concern as fat grafting is typically performed using a minimal-access approach.
• Seroma — similar to haematomas, a seroma is a build-up of tissue fluid after an operation. These may be reabsorbed naturally (often aided by compression garments) or require drainage with a needle or incision. Seromas can become infected.
• Swelling and bruising — expected and usually resolves within two weeks post-procedure.

Risks specific to fat grafting

• Graft failure — typically refers to grafted fat being absorbed by the body, causing a diminished contouring effect over time. Some degree of reabsorption is inevitable, but the amount will vary among individuals.
• Fat necrosis — when fat cells die and liquify. Will sometimes resolve on its own, but larger areas may require another procedure to drain the unhealthy fat.
• Oil cyst formation — part of the graft fails and forms a small pocket (cyst) that may need intervention.
• Calcification — calcium deposits can form within the graft, leading to hard lumps, contour irregularities, or discomfort. Calcification in breast tissue grafts has been reported to complicate breast cancer screening. Whilst there is no clear evidence as to whether breast fat grafting lowers cancer detection rates, it is widely accepted that additional imaging may be required for detection.
• Fat embolism — a rare but serious and potentially life-threatening complication where a fat globule enters the bloodstream and lodges in another organ, typically the lungs or the brain.
• Delayed wound healing — if complications occur, the site may take longer to heal and could require long-term dressings.
• Donor site morbidity — there is the additional risk of damage to local skin structures like nerves and blood vessels. In severe cases, the harvesting device can damage abdominal organs.
• Cosmesis — fat grafts may not produce a perfect contour match due to undercorrection (not enough fat injected), overcorrection (too much fat injected), or clumping of the fat from an uneven injection pattern.

Retention of fat grafts

The exact survival rate of fat grafts is not definitively known. During the first year, anywhere from 30% to 70% of the grafted fat can be reabsorbed by the body.

Fat grafts generally last longer in larger areas with limited movement. For example, fat grafting can effectively correct undereye grooves and sunken cheeks, but it may not be a suitable technique for lip augmentation due to the area’s high mobility.

The amount resorbed and therefore the longevity appear to depend heavily on the grafting technique used. Newer techniques, such as cell-assisted lipotransfer (CAL), are being developed to increase longevity. For longer-lasting results, patients may receive three or four treatments over a period of six months to a year.