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Vectors are significant to a BBL because they can limit what I can do in the operating room and even make or break whether a patient is a suitable candidate for surgery. Understanding these different parameters before you have surgery is crucial because it will help you align your expectations with more realistic results.

Based on the butt, pelvis and spine, patients will fall into one of three categories of vector – negative, neutral and positive. During a consultation, I examine your body from the front, back and sides to determine your category.


A neutral vector is the most common, and it’s when your spine comes down very straight, and the butt comes out just a little. That’s what I’d consider a normal relationship between the spine and butt.


People with a positive vector tend to be a bit curvier and often appear a bit more athletic. They have more of a tilt to their pelvis, and their butt pokes out a little more than someone neutral. The positive vector is seen less frequently than neutral.


Patients with a negative vector are the most challenging patients to operate on, and they are also the rarest – instead of the butt coming out in a positive or neutral vector, the top of their butt projects out more than the bottom. It’s almost like the pelvis tilts inward, and there is little to no volume.

If a patient starts in a negative vector and does not have soft tissue  – those are red flags for surgery. This combination creates a big challenge, and sometimes these patients are even better off not having a BBL because there won’t be a significant change.

How Are Vectors Created?

As mentioned above, vectors are created by the interaction between the spine and the pelvis. Consider the spine and pelvis as two separate but connected components.

First, the spine can tilt in all directions (and 100% of the time, there is often at least a slight tilt forward, backward, side to side, or even on the angles), and it can also be bent or arched.

Next, the pelvis (what the butt sits on) connects to the spine, and it can be straight or bent based on how it interacts with the spin. Further yet, the body isn’t symmetrical, and the pelvis can also interact with the legs. Sometimes we even see patients with one leg a little longer than another, so they have a specific tilt to their pelvis for that reason.

The ultimate goal for anyone coming in for a BBL is volume and projection. That’s understandable, as it’s the whole point of the surgery. However, your results will depend mainly on your vector category. That’s why understanding your vector is so vital before surgery. These are things I will go over with you during a consultation. Still, if you understand what category you fall into ahead of time together, you’ll better understand what we can accomplish during surgery.

Dr. William Miami

Author Dr. William Miami

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