The Science of Liposuction

Liposuction, after 25 years since its introduction in the United States in 1981, remains one of the most popular plastic surgeries for both men and women. How it works seems simple enough...'stick a tube and suck it out' to paraphrase what many patients say. And while it is conceptually simple mechanical process, there is more to it than meets the eye.

At its simplist, liposuction is a two-steo process for removing fat. A hollow tube (cannula) is put under the skin, the tube is moved back and forth until the fat is dislodged, and the attached vacuum source draws the fat back through the cannula into the tubing and finally into the plastic bottle.

Despite this apparent simplicity, there is more science to it than that. There are three interesting components about liposuction, all of which contribute to its safety and effectiveness. These include the concept of tumescence, water vaporization and suction, and tubing size and design.

An integral part of the oepration is the placing of fluid into the areas where the fat will be suctioned. I frequently get asked by patients if I do tumescent liposuction. Patients think that this is a special method of liposuction, when in fact, it is used in every liposuction procedure. Putting large amounts of fluid into the fat areas to be suctioned beforehand is known as tumescent infiltration. This achieves two fundamental things, substantially reduces bleeding (from the fat being broken up by the liposuction tube and it distends the fat compartments which make the tube easier to pass through the fat being suctioned. Without tumescent infiltration, liposuction would quite bloody, give patients more pain, and have them bruised for a month, if not longer.

The amount of suction generated by the liposuction machine, in short, makes liposuction possible. At the accepted amount of suction needed for liposuction (-20 cms of water or -1 atmosphere of pressure), the pulling of fat through the tubing certainly occurs. But it also causes the vaporization of water. If you have ever witnessed an actual liposuction procedure, you may have seen bubbles in the fat or bubbling in the plastic cannister. To some degree, this is actually water boiling....or the vacuum pressure exceeding the vapor pressure of the water in the fat being removed. It is this vaporization that makes the viscosity (how thick it is) of fat, which is actually a combination of fat, blood, and infiltration fluid, less to improve its ease of flow through the tubing. From a flow standpoint, water that is vaporized ( a gas) flows 100 times faster than liquid water. This is also why liposuction done at higher altitudes, where the water vapor of pressure is less, is somewhat easier to do. (takes less suction from the machine)

The tube (cannula) that is actually used under the skin differs in diameter and the holes at the tip. In days gone by, the cannulas were quite large but left a lot of depressions in the overlying skin after due to removing too much fat too fast and in large pieces. Today, small cannulas are used which removes fat more carefully and in smaller pieces, decreasing the problem of skin irregularities after surgery. The tip of the cannula is rounded so that it travels through the fat easier with less chance of penetrating something you shouldn't. The holes at the tip are where fat sticks to and then gets sucked into the cannula. The more holes there are at the tip achieves two effects; increases the shearing effect (like a blade) on fat and makes more cross-sectional area through which fat can be suctioned.

Currently, there are newer methods of liposuction or to be accurate, methods of loosening up the fat. These include internal and external ultrasonic and laser probe-assisted. While they sound quite advanced (and they are), there is no convincing evidence at this time that they are actually better than traditional liposuction. Better meaning....you get more fat oout, smoother skin, and heal faster. Manufacturers market them as such but no study has yet proven it. And suction is still required to pull out loosened fat.