Is fat necrosis more likely if the harvested fat is just allowed to settle in the syringes before injection, rather than washing or filtering the fat?

Fat Grafting: There are many opinions when it comes to treating fat to be used for injection. Some believe that washing or filtering helps select the viable fat cells while others feel that allowing the fat to settle in the syringes is less traumatic. Either way, minimizing the fat's exposure to air and using proper microdrop injection techniques will assure the greatest fat survival.

Necrosis: Fat necrosis increases the longer the fat tissue stays outside the body.

There are various ways to prepare the fat for injection.: Preparation of the fat that is harvested with liposuction is done to separate the extra fluid and the oil which represents damaged fat cells, so that just fat cells are injected. A common way to do this is to allow gravity to separate the liposuction aspirate. This is very atraumatic which is good. The problem is that some fluid remains in the fat and in order to remove this more completely a centrifuge is needed. Centrifuging is somewhat traumatic however. A low-speed centrifuge is ideal. Centrifuging is also important when the fat needs to be concentrated maximally such as in the face of the breasts where there is limited room for injection and the volume is generally low.