In a Brazilian Butt Lift is the Fat Injected Under the Muscle or Above the Muscle?

True on not.... I can only guess.  There is no way to know.  The Brazilian Butt Lift is extremely popular and because of this popularity, there is a great deal of scientific investigation taking place trying to figure out what is the best way to get consistently good results and to figure out what is really going on.  
I have performed this procedure for about 15 years now, and there is no question that the majority of the fat is injected into the fatty tissue on top of the muscle.  The muscle layer is relatively thin compared with the fat layer and can only hold a smaller percentage of the fat.  Also, although the fat is thought to have a greater chance of surviving in the muscle on th short term, I believe that in the long term, this fat will be injured and die with use of the muscle, especially if large volumes are injected there.  The fatty layer or the body is under great study and has been found to have a very rich blood supply.  The fat does quite well when grafted to this layer.  
The biggest questions in cases where patients had the BBL done and their fat "went away" is....  How much fat was really injected?  What technique was used?  What did you do afterwards? 
I'd be  interested in knowing these answers. 
Thank you
Dr M

In my experience the best long-term volume results from fat injections into the buttocks is when it is placed into both the gluteal maximus muscle and the subcutaneous space. If all of the fat is put into the buttock fat tissue only, there is much higher chance of it being completely resorbed. While not all fat injections can be placed entirely into the muscle, the more the better. There is no such thing as placing the fat behind the muscle. It is either placed into it or above it.