Fat grafting to the face for volume restoration or augmentation has become very popular in the past five years. The appeal of it to plastic surgeons and patients alike is irresistible given that it is not only a natural substance but that it is relatively easy to administer by injection. Fat grafting just seems like it should work since it is one’s own bodily tissue and there is no chance of any immunologic rejection. But despite all of fat’s apparent charms, it unfortunately is highly unpredictable. It does not always take and how much of the injected fat that does take can not be precisely predicted.
Despite what is written or purported as medical fact, much of the science of fat grafting is unknown. This can be seen in the large number of fat grafting techniques used that propose numerous methods for harvesting, processing and injection techniques. Manufacturers have a vast array of devices that are now available to aid in every step of these techniques. Some of these preparatory devices are automated machines that can cost close to six figures while others are simple mechanical devices that cost but a few hundred dollars. While some of the basic concepts behind these devices certainly seem like they should be true (e.g., fat concentration and isolation), how useful any of these devices are is not yet conclusively clear.
In clinical use, the amount of fat injection graft take is hard to measure other than by gross visual assessment. So claims as to how well anyone’s injection methods works are level 5 evidence based otherwise known as anecodal or observational. Unless one is looking at a minimum of six months follow-up or, even better, a year, the evidence of fat volume retention is not convincing. Does the take of a fat graft mean that the transplanted adopicytes have survived or that stem cells or preadipocytes have converted and ‘volumized’? Or is it some combination?
Because there are many variables in fat injection grafting, most of which are not well understood, I prefer to keep the technique simple using the basics of DPI. (donor, processing and injection) Facial fat is both structurally and physiologically different than body fat. It is unknown what body donor areas would provide the best match for survival in the face. On a practical level, donor sources are the abdomen, flanks, thighs and knees. Based on cell size, one would assume that smaller-sized adipocytes from the inner thighs, knees or flank are a better donor source for use in the face. Grafting like to like would seem to make the most sense. But that supposition has yet to be proven. The face requires considerably less volume than the breast or buttocks so the inner thighs and knees usually offer an adequate donor source.
Preparation of fat has been done multiple ways and better isolation of viable cells vs fluid is the goal. Whether it should be done by centrifugation or simple washing through a sieve or filter is a matter of debate. I still prefer sieve preparation over centrifugation as it eliminates steps and time from donor site to the face. The shortest time between harvest and implantation reduces the anoxic (lack of oxygen) period of the graft, which is an often overlooked factor in fat graft survival. It is critical for every other tissue in the body that is transferred so why would free fat be any different? It should be but a few minutes out of the body for the graft.
Injection into the face is known to be best in small aliquots (droplets) but despite this technique survival varies all over the face. We know by a lot of experience that fat injections do not work well, for example, in the lip and nasolabial folds but works much better in the cheeks. This may be because there are no discrete fat pockets in the lips and nasolabial folds naturally unlike the cheeks and temporal regions. This makes volume restoration of lost fat pockets likely more effective than trying to fill subcutaneous or submucosal areas for a pure augmentation effect. Selecting the facial problem being treated is just as important as the injection technique in getting good take of the fat graft.
Dr. Barry Eppley
Indianapolis, Indiana