Chapter 5 SNIF: Sharp Needle Intradermal Fat Grafting
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Treating facial sagging, deterioration of the skin surface, and deflation of facial volumes can rejuvenate the face. Modern facial rejuvenation requires that all these aspects be addressed. Sagging can be treated by face-lift techniques. The deflation can be treated with classic lipofilling techniques (volumetric build-up). Wrinkles can be treated by filling subdermal or intradermal planes. Filling in the subdermal plane is used to treat folds or deep wrinkles that result from underlying volume depletion. Conversely, fine wrinkles are treated with intradermal injections because they result from changes in the skin itself. The damaged skin surface can be treated by skin resurfacing techniques (laser, peelings, dermabrasion) or by intradermal filler injections. These injections can be performed alone or as an adjunct to the facial rejuvenation surgery. Dermal filling is an increasingly popular method for reversing the effects of skin aging in a minimally invasive way, often sought at a relatively young age (30 to 40 years).
Off-the-shelf dermal fillers can generally be categorized as permanent or resorbable. Permanent fillers have a higher complication rate than their resorbable counterparts.1 Moreover these complications are often more dramatic, irreversible, and intractable. However, patients typically consider the temporary nature of resorbable fillers a disadvantage, so the pressure on practitioners to use permanent fillers is high. Permanent fillers often show a deceiving early problem-free interval, which lures inexperienced practitioners into continu ing to use them. However, complications such as granulomas, migration, and infection may occur only years after implantation, because every permanent filler is considered a foreign body that the human immune mechanism tries to remove. Our opinion is that every permanent filler potentially leads to a permanent problem.
The quest to find the ideal dermal filler is ongoing. In 2008 we started using fine-particle microfat for intradermal injection into facial rhytids with the intent of achieving a permanent correction without the perils of a synthetic permanent filler. This sharp needle intradermal fat injection method was published under the acronym SNIF. 2
PATIENT EVALUATION AND SELECTION
Aging of the skin is a multifactorial phenomenon that involves intrinsic and extrinsic factors. The major intrinsic factor is an attenuation of dermal thickness caused by a decrease of collagen, elastin, and hyaluronic acid content.3 The major extrinsic factor is sun exposure, but other environmental factors (such as smoking and pollution) also play an important role. Mechanical factors such as repetitive facial movements and gravity also play a role in the development of wrinkles.
Like a hinge always folding at the same place, mimetic muscle action during facial expression causes the appearance of lines on the surface of the skin. Initially, those lines are seen only during facial muscle contraction (dynamic wrinkles), but the repetitive nature of the movements causes the lines to become permanent over time (static wrinkles).
Whether the targeted wrinkle is treatable with SNIF depends on the skin thickness, mobility, and quality. Dynamic wrinkles in the glabella will primarily need chemodenervation by botulinum toxin. Residual rhytids can later be additionally treated with SNIF.
Atrophic craquelé of the skin of the lower eyelids is usually not a good indication for a filler nor for SNIF. Skin enhancement with tretinoin, possibly followed by resurfacing, is the treatment of choice for this condition. Deep folds such as the nasolabial folds and marionette grooves are more amenable to blunt-cannula microfat grafting with or without subcision.
Thus the gross indications for SNIF are quite similar to those for superficial resorbable synthetic filler treatment.
INDICATIONS AND CONTRAINDICATIONS
SNIF is typically a technique for correcting superficial dermal damage or deformities such as rhytids, acne scars, and atrophic scars, but not for deep volume correction. We still use hyaluronic acid dermal fillers as an initial treatment for facial rhytids, but after a while some patients request a more permanent correction with a safe filler material. SNIF fulfills most characteristics of the “ideal dermal filler.” It is nonteratogenic, noncarcinogenic, and biocompatible and has very few side effects. It has a superior longevity to all resorbable fillers and is available in large amounts for a limited cost (Fig. 5-1). The availability and the cost of the filler material are an important issue. An advantage of pharmaceutical filler materials is obviously that an off-the-shelf use is possible, but unfortunately those are quite expensive and the cost increases as more filler material is used.
The amount of microfat required for intradermal fat injections is very small (ranging from 0.5 to 5 cc). If intradermal fat transfer is performed without deep lipofilling, harvesting the fat is not time consuming (2.5 to 25 cc of lipoaspirate is sufficient in most cases). Hence donor-site availability is rarely a problem, even in lean patients.
However, SNIF usually is applied as a supplementary and final act after blunt-cannula microfat grafting of the deep folds (such as nasolabial folds) or in conjunction with any surgical facial rejuvenation procedure. In some cases intradermal fat injection is combined with laser resurfacing or croton oil peeling during the same procedure. Some patients underwent intradermal fat injections with subsequent skin resurfacing (Erbium-YAG laser or croton oil chemical peeling). The advantage of this strategy is that the wrinkle is elevated from the inside and flattened from the outside. This reduces the required resurfacing depth, resulting in a safer procedure and quicker recovery, and less risk for hypopigmentation and scar formation.
When resurfacing is combined with intradermal fat injections, the effects are synergistic. This stands in contrast to the knowledge that laser resurfacing of skin recently treated with a heterologous dermal filler may cause degradation or liquefaction of the underlying filler material, and hence is contraindicated.
In some cases SNIF can be a viable alternative for patients who seek skin rejuvenation but refuse skin resurfacing.
Contraindications for SNIF are atrophic skin conditions (such as result from steroid use and diabetes), bleeding disorders and anticoagulant use, and smoking.
PREOPERATIVE PLANNING AND PREPARATION
Preoperative standardized photographs are taken during the intake consultation. In preparation patients should quit smoking at least 3 weeks before surgery and interrupt oral anticoagulants 2 weeks preoperatively. Herpes prophylaxis is prescribed for any procedure around the lips.
TECHNIQUE
Anesthesia
When treating the face, we always prepare the surgical area with infiltration with a local anesthetic injection containing adrenaline, both for patients receiving local and general anesthesia (lidocaine 0.3%, adrenaline 1:650,000). This is important because the vasoconstriction caused by adrenaline minimizes the risk of intravascular injection and, to some degree, the bruising. The donor areas are anesthetized with a classic Klein solution.
Markings
Before injection the facial rhytids are marked with a fine permanent marker while the patient stands and makes exaggerated facial expressions (Fig. 5-2). It is important to mark before any injection of a local anaesthetic solution as this will obliterate the fine wrinkles to be treated.
Donor areas are marked with the patient in standing position. Classical donor areas are the lower abdomen, love handles, inner thighs and knees.
Patient Positioning
The patient is usually positioned supine to allow harvesting and grafting without repositioning.
Technique
A major concern of sharp injection of soft tissue fillers in the face is the risk of intravascular injection with embolization of certain vascular territories. This can lead to adjacent skin necrosis but also to more catastrophic problems such as blindness or cerebral stroke.1,4–9
Injection is always performed in a very superficial dermal plane, while withdrawing the needle, again to minimize the risk of intravascular injection. Squeezing the skin with the wrinkle between the index finger and thumb during fat injection will occlude any vessel in the injection trajectory (Figs. 5-3 and 5-4). Finally, a low pressure on the plunger will diminish the risk for embolization. If a high resistance is observed, the pressure on the plunger should not be increased, because this may lead to a bolus injection of too large a volume. Instead the needle should be changed; it occasionally can be blocked by residual fibrous strands in the micro-fat, depending on the quality and consistency of the fat. Box 5-1 provides safety pearls for SNIF injection.
Box 5-1 Safety Pearls for Sharp Needle Intradermal Fat Graft Injection
The receptor area should be infiltrated with a local adrenalin-containing solution.
Injection should be made in a superficial dermal plane, never in the subcutaneous plane.
Injection should occur during withdrawal of the needle.
The wrinkle should be squeezed between the index finger and thumb.
Low pressure should be used for the injection.
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