Because microcannulas are designed to be thin walled, they are more delicate and bend easily. This bend of the microcannulas increases with cannula length and higher cannula gauge. Owing to cannula flexibility and bend, movement in a straight line is necessary. These cannulas cannot be utilized to lift or move tissue. To redirect the cannula, it should removed until just the tip remains under the skin and then redirected. The cannulas are not designed to be forced through areas of dense resistance. In that case, a smaller-diameter or shorter cannula should be chosen. Microcannula liposuction should be a smooth process, with the cannula slipping between fibrous septa without imposing excessive traction through resistant tissue. Microcannula liposuction is a two handed procedure, with one hand squeezing and gripping the tissue to immobilize and compress fat and the other gently moving the cannula through the tissue tunnel created. Liposuction will not occur with a stationary cannula and minimal fat is aspirated without a hand grasping, pinching, compressing, or otherwise immobilizing tissue. The fat compartment should not move back and forth with the cannula but must remain stationary for efficient liposuction to occur. A fully tumesced compartment with increased tissue tension has less tendency to move as the cannula traverses the area. Therefore, tumescence of the area is important for microcannula liposuction to be fully effective.
Care should be taken to avoid repeatedly pushing the hub into the skin in order to avoid tissue trauma that could result in dyspigmentation. Change in cannula direction occurs by withdrawing and redirecting the microcannula. The compressing hand can also move the fat around between strokes by manipulating the fat vertically or laterally. When using a cannula with holes on only one side, small rotations between strokes allow more complete aspiration. The key surgical technique is the concept of multiple aspiration sites and the fanning pattern between incision sites. A pattern of tunnels thus radiates from each adjacent incision site. There is overlap, interdigitation, and intersection of the various tunnels from multiple incision sites. Thus, the incision sites are close enough such that overlap from adjacent aspiration sites occurs during the liposuction procedure. It is important to remember to remove only limited amounts of fat from each incision site before moving onto the next site and eventually returning to the original site to continue the process. The procedure requires use of multiple aspiration sites over an area sequentially with repeated aspiration from the same port on several occasions throughout the liposuction. A fanning technique of liposuction is employed with anywhere from five to 25 strokes from each port, all at the same depth. The liposuction surgery involves small removals from any incision site so that fat is uniformly taken throughout the field.
The process is then repeated several times from the various aspiration sites until an end point is reached. Continually switching aspiration sites affords the cosmetic surgeon the opportunity to achieve a smooth and uniform result. Fat is thus removed in small sequential steps in that 10–20% of fat is removed uniformly over the entire area, such as the abdomen, with each series of passes. The procedure is continued until the desired clinical end point is attained. The deeper fat is approached first. Once the deeper fat has been addressed from all the aspiration ports, the process is repeated in the middle depth of the fat pocket and finally the various ports are utilized for aspirating the more superficial level of fat. It is essential to address the deeper compartment first. A cleavage plane at the muscle level must be established in order for accurate liposuction to occur. Clinically, only a small amount of liposuction at the deepest fat level adjacent to muscle is needed for establishing the desired cleavage plane and the initial cannula strokes establish that cleavage plane. If this cleavage plane is too superficial, then the surface hand squeezing the tissue will only be working with mobilized tissue above that cleavage plane and the deeper fat will be obscured and not removed, ultimately producing suboptimal results. After the deep and superficial compartments have been appropriately aspirated, microcannulas are used to feather the periphery. This enhances symmetry and blending to produce optimal skin contouring. Liposuction of the most superficial aspect of the subcutaneous compartment must be completed carefully to avoid damaging the undersurface of skin. Injury to the dermis may injure the skin’s vascular supply, resulting in cutaneous necrosis and undesirable sequelae such as ulceration, scarring, and dyspigmentation. Liposuction cannulas should not scrape the dermis.
When working at the most superficial compartment, cannulas with apertures on the underside only should be utilized. It may seem counterintuitive, but the initial stages of the liposuction procedure should be accomplished with the smallest cannula. These are less uncomfortable than larger cannulas. The larger microcannulas can then be utilized subsequently. The concept involves creating extensive tunnels with the smaller cannula and then enlarging those holes with a larger cannula. In this concept developed by Klein in utilizing the smallest cannula first, the emphasis is on maintaining uniformity throughout the procedure by gradually working up to the larger cannula. When larger cannulas are used first, it is more difficult to direct the small cannula into new pathways, whereas larger cannulas follow the least-resistance direction by entering existing holes. Using the smallest size first avoids the issue of excess liposuction occurring in discrete locations resulting in irregularities that may be visible and difficult to completely even out. Furthermore, the smallest microcannulas are most effective initially in the fibrous areas such as periumbilical, upper abdomen, male breast, male flank, and back.
Details of utilizing microcannulas in various anatomic areas are discussed in the remainder of the article. In general, larger cannulas should be used when debulking large fat volumes in the deeper planes, while smaller cannulas can be used in the more superficial plane where fine contouring is required. In treating the deeper fat planes of the flanks, saddlebags, and abdomen, 10–12-gauge cannulas are frequently utilized. Fourteen-gauge cannulas are probably the most versatile in our experience and fit through a small 1.5-mm skin opening with little residual scarring. In fibrous areas such as the periumbilical area, breasts, and abdomen, 16-gauge cannulas are effective in fenestrating the fibrous tissue. Subsequently, a larger 12- or 14-gauge cannula can be introduced. Determining when to introduce larger cannulas is a clinical decision. Often, less resistance is noted after repeated sweeps through an area, prompting an empiric trial of a larger size. Finer cannulas, including the 16-, 18-, and 20-gauge cannulas, are the instruments of choice in treating more delicate areas on the lower face such as the nasolabial region. Twenty-gauge cannulas are extremely fragile and must be handled with care. Surgeons may prefer lightweight aspiration tubing for more precision when using the smallest cannulas.
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