Resorption of grafted fat is a natural, biological phenomenon. Resorption means that part of the injected fat will disappear. The rate of resorption is unpredictable but “in general” a 50% resorption rate is normal.
The lipofilling procedure is a “reversed approach” to treat soft tissue deficiencies. Cells, in particular adipocytes and their stromal counterparts are harvested in a traumatic manner through liposuction, centrifuged and injected in a recipient site or wound bed that is devoid of any supportive matrix.
The microenvironment of cells is from an embryological point of view the main director of cellular behaviour. This geometrical structure supports cellular migration, proliferation and differentiation and harbors the necessary nutrients and components that influence the cellular homeostatic system.
This explains why the main disadvantage of the lipofilling technique is the considerable resorption rate that occurs at the short term. Lipofilled material needs to survive initially through the process of (plasmatic) imbibition before angiogenic sprouting (development of new, young vessels) from the (micro)environment will nourish the transplanted cells with nutrients and oxygen.
Adequate tissue perfusion is necessary for the supply of oxygen, nutrients, and removal of metabolites from the tissue cells, and therefore is essential for tissue survival after transplantation.
In general, revascularization of the graft occurs already at day 1. Langer et al. observed vascular sprouts at the border of the graft at that time period in their in vivo skinfold chamber model in hamsters. They observed that the functional vessel density increased constantly and reached values that were, at day 12, comparable with those of the fat tissue in situ. At day 21 values were even higher than those of adipose tissue measured in situ. In the center of the graft, new vessels appeared on day 3 after transplantation.
Cells that are not revascularized in time will not survive. They will be removed by the defense mechanisms of the body or form oil cysts. The oil fraction within the death adipocytes will form local oil cysts.
On an average the resorption rate varies between 20 and 80% and depends on the quality of the wound bed, the lifestyle of the patient, the technique and the quality of the fat.