The recent October 2015 issue of Plastic and Reconstructive Surgery Journal had an article which reviewed studies which looked at how is it best to harvest, process, and inject fat to help it survive. They did a systematic review of the current state of the literature. “The Current State of Fat Grafting: A Review of Harvesting, Processing, and Injection Techniques.”
They looked at studies investigating the effect of the harvest site. Is there a “best” place to harvest fat from?
- multiple studies have looked at this from 2004-2014. Some were in vitro studies, some in animals, and some in humans.
- most of these studies found no difference in volume retention from different body donor sites. Two studies find a little difference. ONe thought lower abdomen was better than thigh, which was better than knee. Another found thigh resulted in the best overall graft in mice, with the best structureal integrity.
Is there a difference with how you prep the donor site?
- tumnescent (which is where we blow up the area with fluid prior to harvesting the fat to decrease pain and bleeding) has been found to not be detrimental, and may help fat graft survival.
- This didn’t include a recent study where they added something to the tumnescent which let the fat “go to sleep” and seemed to improve fat survival.
How do you get the fat out? Here is a place where you see lots of variability. Do you use a hand held syringe? suction assist? ultrasound assist?
- No difference was found with the techniques when tumnescent was used. They looked at histology and leakage of fat enzymes to assess for cellular damage.
- None of these studies were carried past 12 weeks, so there may be differences when looking at long term survival.
- None of these looked at laser liposuction. From what I know, laser liposuction is found to harm the fat and stem cells.
Liposuction cannulas. These are those metal long tubes we use to harvest fat. There is some controversy here. Is it better to use a large cannula, to not harm the fat as we get it? Or does that give us fat globules which are too large, so when we graft the fat, the inner part of the fat doesn’t get blood supply and dies?
- There is a study which shows aspirates from a 6mm cannula are more viable than smaller aspirates. For those in the know, that is a huge cannula size. I don’t use that size on my patients for liposuction because your risk of irregularities or grooves is high. They also in this review did not include studies I have read which talk about ideal fat globule size for revascularization, and that size is much smaller than 6mm. Many of the studies cited were done dry – no tumnescent- so it is thought that may have affected the outcome.
How do you process the fat? Do you centrifuge? Gravity separate? Use a strainer of filter? Wash it? A current survey shows 34$ of us centrifuge, 45% do gravity separation, and 11% roll in gauze.
- Here there is conflicting information. In animal studies, they found gauze processing did better. In humans, they found centrifuge was better than gravity separation, and other studies showed no difference between the techniques. One study found filtration had a higher nodule formation than centrifuge.
- Confused yet?
- There were many studies on the optimal centrifuge speed.
- Here there was some evidence when using suction assist to remove the fat (as opposed to hand held suctioning to remove the fat) there is more risk of centrifuge hurting the fat when spinning. They found hand held fat removed actually did better with higher centrifuge forces, which they attribute to removing more of the blood and debris. And they propose hand held suction may be less traumatic to the fat cells.
- Then there is the density of processed fat. After centrifuge, there is difference in the density of the fat within the syringe. The stuff at the bottom layer seems to be better: more retention, angiogenesis, growth factors, etc.
Then there is how fast do you inject the fat? Slow injection speeds are shown to result in larger fat survival than fast speeds.
Where are you injecting into? Muscle has more blood supply, so some studies show fat survives better here, but then other studies show areas of high movement- the glabella and the lips- have less survival than stationary areas like the cheek. Some studies indicate you may be able to prep the site (like BRAVA for the breast) to make the area more receptive to the fat.
Other variables in fat survival?
- age
- trauma to overlying skin (is it burned? fibrous? radiated?)
- severity of defect
- vascularity (as you age, it may be harder to form new vessels)
SO WHAT DOES THIS ALL MEAN?
I have to admit, I was excited to see the title of this article. I thought, AHA! Now we will know THE answer to this question. I do a ton of fat grafting, and I crave being able to predict fat survival better. There is so much variability between people. So I go to my meetings, go to fat grafting talks with people from all over the country, read the countless studies on experiments in the lab and nude mice and people, and I continuously refine my technique to make it better.
And this article tells me in their summary, “There has been a substantial increase in research interest to identify methodologies for optimizing fat graft survival. Despite some differences in harvest and implantation technique in the laboratory, these findings have not translated into a universal protocol for fat grafting. Therefore additional human studies are necessary to aid in the development of a universal protocol for clinical practice.”
Urg. There is no clear better way yet.