Autologous fat grafting has become a widely used technique in plastic surgery for both reconstructive problems and aesthetic concerns. Even though it is extensively used and touted, one of the realities of fat grafting is that it is not a completely predictable method of soft tissue augmentation. Volume loss occurs to variable degrees in almost all cases. There may be many reasons for its current unpredictability but one contributing factor is that it is not a standardized technique. There is no one single scientifically proven method of how to do fat grafting.
When it comes to fat grafting methods, how the fat is harvested, how it is prepared and the injection technique are all variables that are somewhat different amongst practitioners. How any of these fat grafting steps affects fat graft survival remains unclear. Injected fat grafts may not survive well due to failure to establish an early blood supply to the transplanted cells, overly traumatized cells in the graft, cell death due to a localized immune reaction or some combination of all of them.
One of the most focused on areas of fat grafting has been that of its preparation. Most surgeons feel that the harvesting and injection techniques, while important, are prone to less variability than how the graft is prepared. Graft preparation has been done using various methods, all of which are intended to remove extraneous non-cellular material and leave a concentrate of intact cells. Centrifugation was the initially described method and various spin times and rates have been advocated. Numerous mechanized and hand-held methods of centrifugation have been developed, each with its own advocates.
Other processing methods have included filtration or straining, again using a variety of devices to achieve it. With filtration the introduction of graft washing was introduced. Such washing, usually using isotonic saline, is designed to remove residual elements in the graft that may cause an inflammatory reaction such as red blood cells, free fatty acids and oils, lidocaine and epinephrine anesthetic solutions and cellular breakdown products such as lactate dehydrogenase. It is a simple step to perform that does not require any extra equipment or much extra time and adds no expense to the process. Several studies have shown that washed fat grafts have lower levels of triglycerides, lactate dehydrogenase and blood cells, all factors that are known to cause inflammation as well as restoration of physiologic graft osmolarity.
The other processing method is that of decanting. Harvesting the fat in syringes, or placing it into a large canister, and allowing it to sit for a period of time will allow a layering effect to take place in the graft due to differing densities of solid vs. liquid components of the harvest. The fat cell layer will develop its own distinct layer and it may then be extracted for injection. While extremely effective, the downside to decanting is time. Gravity is the driving force in fat graft decanting and some time is needed from harvesting to injection based on the speed of the layering effect. (centrifugation is just a faster method of doing decanting)
Raw fat grafts after harvest are known to be hyperosmolar and contain extraneous factors that are not conducive to to optimal post-transplantation survival. Centrifugation, filtering/washing and decanting are all methods that strive to remove the bad and retain the good. No one yet knows which one of these processing methods is best or if any one of them is really better than than the others.
Dr. Barry Eppley
Indianapolis, Indiana