Buttock augmentation has become a part of mainstream body contouring plastic surgery. Creating a larger buttock has become desirous of those who have a normal size and just want to become bigger (ethnic buttock enhancement) to those who simply have never had one or ‘lost’ it at some point. Its popularity is largely due to the use of fat injections which offers a safe and natural method of increasing one’s buttock size even if fat survival is unpredictable and not everyone has enough fat to do the procedure.
But in increasing the buttock size with fat, we are only adding volume to the smallest component of what makes up a buttock. The greatest contributor is not fat but muscle, specifically the trio of the gluteus maximus, minimus and medius muscles. The gluteus maximus, as the name suggests, is by far the biggest of the three and occupies the lower 2/3s of the buttock. The medius is a pork chop-shaped muscle that is near the top of the hips and the minimus is sandwiched between the medius and the maximus. This composite large muscle mass is what keeps us upright as we walk, the bipedal feature which separates us from our primate ancestors.
The shape of the buttocks is largely a function of genetics which determines the size of the muscle and the amount and distribution of the overlying subcutaneous fat. Women almost always have more buttock tissue than men, regardless of race. One’s buttocks will also change with time as fat loss occurs with aging due to hormonal changes and a shift of where fat is preferentially stored. While exercise can certainly help shape and even slightly enlarge the gluteal muscles (up to a ½ to 1 inch), it can not simulate the size effect of a surgical buttock enlargement.
Despite what shape and size the gluteus muscles contribute to the buttock contour, it is fat that makes up the round or fuller buttock. Specifically this is a form of fibrofatty tissue and not the typical more gelatinuous fat that one finds in the stomach for example. The fibrous component is needed to keep the fat suspended over the buttocks not unlike that of the breasts.
With buttock augmentation by fat, most of the injectate goes into this subcutaneous fat layer. While the gluteus maximus muscle is a vascularized bed which more ideally supports fat survival, it is not possible to put all the injected fat into it. Most of the time the bulk of it goes into the fatty layer under the skin. The thicker the fat layer, the more fat that can be injected into it. This is why a really flat buttock has less of a chance for successful enlargement than a more full one. Without a certain amount of subcutaneous buttock fat, one may be better off considering a buttock implant as opposed to fat injections that does not have a sufficient reservoir in which to be placed.
Dr. Barry Eppley
Indianapolis, Indiana