Factors that affect fat graft survival

Why is fat survival difficult to predict?

Fat survival refers to transplanted fat staying alive in its new location by receiving a blood supply there. Autologous fat grafting is widely used to rejuvenate soft tissue, restore volume, and reshape the body, but the difficulty of predicting how much of the fat will be absorbed after grafting is recognized as a major challenge ^[1].

A 2020 review stated that making use of the biology of fat tissue could theoretically improve fat survival, but that there is still no consensus on the best technique ^[1]. Another review also noted that although fat grafting is a biocompatible and natural method, the lack of standardized methods and the difficulty of predicting how much fat will be absorbed limit how much volume is maintained ^[3].

Losses at each stage

During fat grafting, a substantial number of fat cells are lost and absorbed, so in some cases the volume decreases and the procedure needs to be repeated ^[2]. The literature notes that fat cells can be lost at all four stages of grafting ^[2]. There are also reports that new techniques, such as different methods of harvesting fat, fat processing, and grafting combined with supplementary substances, have improved fat cell survival and the restoration of blood supply (revascularization) ^[2].

However, it was pointed out that there is very little published evidence on the techniques used to inject fat, that these techniques are mostly based on the surgeon's experience, and that standardized techniques and training are also lacking ^[2]. The methods developed so far differ in the following respects ^[3].

• The area where fat is harvested
• Whether a solution is injected before harvesting, and how much
• The harvesting method, the size of the tube, and the suction pressure
• How the fat is processed and how it is injected

Evidence on harvesting methods

A 2018 review examined the most suitable harvesting site, the differences between cutting out tissue directly, suctioning by hand, and liposuction techniques, and the recommended tube size, pressure, and volume of solution injected in advance ^[3]. However, the results of comparisons between methods varied depending on the outcome measured, making it difficult to determine the most efficient method ^[3].

The lack of a standard test for determining fat survival or volume gain was also cited as a limitation ^[3]. Claims that a particular method is best for fat survival should be weighed with these limitations in mind.

The environment of the recipient site

According to the literature, what becomes of the stem cells in fat is determined by the microenvironment of the site that receives the fat ^[4]. Based on the idea that the condition of the recipient site matters for fat survival, breast reconstruction surgeons have also tried expanding the tissue externally before surgery to create a foundation in which large volumes of fat can survive ^[5].

The authors of the review on this method stated that they summarized multicenter experience with 488 patients over 7 years ^[5]. However, the research summary does not give specific outcome figures such as survival rates, so the size of the effect is difficult to judge from this source alone.

What role do stem cells play?

It has been clearly confirmed that grafted fat contains living adipose-derived stem cells, and in animal studies, a considerable portion of these cells survived after grafting ^[4]. In clinical studies, scar scores and scar stiffness improved after fat was grafted into burn scars, and the quality of tissue that had received radiation therapy also improved ^[4].

However, the same source stated that it is not yet clear whether these effects are due to the stem cells, and that there is no evidence to support the routine use of fat grafting enriched with stem cells ^[4]. Meanwhile, regarding fat grafting after breast cancer surgery, the literature notes that although clinical studies have shown no clear evidence of an increased risk of recurrence, there is preclinical evidence that fat cells can promote tumor growth, so questions remain to be resolved ^[6].

What to check during your consultation

Fat survival depends not only on the technique but also on the condition of the recipient site and the characteristics of your tissue, so results can differ from person to person even with the same method. It is a good idea to check the following and align your expectations with the specialist who examines you in person.

• The area where fat will be harvested and how it will be processed
• The plan for additional procedures if the volume decreases
• The condition of the recipient site, such as scarring or previous radiation therapy
• If stem cells or additives are used, the evidence behind them and their limitations