Energy devices in aesthetic surgery

Preoperative preparation

Preoperative markings are made with the patient in the standing position. As in traditional liposuction, there are five distinct anatomical zones that should be avoided in UAL. These areas are the “zones of adherence” and include the gluteal crease, the lower lateral thigh area of the iliotibial tract, the posterior distal thigh above the popliteal crease, mid-medial thigh area, and the area of the lateral gluteal depression. Contour deformities frequently result following attempts to treat these areas. Careful planning of skin incisions is important prior to the procedure because UAL requires a greater number of slightly longer access incisions to accommodate the skin protectors. Furthermore, carefully planned incisions avoid torque on the ultrasonic probe, particularly over curved anatomical areas.

The characteristics of localized fat in the area to be treated must be considered when selecting the appropriate VASER probe. Fat cells differ in various regions of the body with respect to collagen structure and septi among the fat cells, as described by de Souza Pinto. In order to achieve the best outcome, knowledge of these differences is essential.

Tissue penetration is influenced by the diameter of the probe, as well as the number of rings at the tip of the probe. A probe of a given diameter with more rings will emulsify fat tissue more efficiently than one with fewer rings. However, a probe with more rings will not penetrate fibrous tissues as easily due to vibratory energy that is dispersed to the sides of the probe as opposed to the front surface. In general, fibrous tissues are better addressed with probes with fewer rings as the energy is more concentrated. Furthermore, when addressing fibrous tissue, smaller-diameter probes penetrate the tissue more easily. The 3.7 mm probes can achieve efficient debulking and contouring of medium to large volumes of soft to fibrous tissues. The number of rings at the tip of the probe should correspond to the fibrous nature of the tissue. Fine contouring of smaller, soft to extremely fibrous localized fat deposits is achieved with 2.9 mm probes.

As a general rule, continuous mode is frequently used for fibrous tissue, faster fragmentation, and, in instances where tissue emulsification is not readily achieved, in the pulsed VASER mode. VASER mode is typically suited for finer, more delicate sculpting or softer tissues. Smooth movement of the probe through tissues is ideal, and settings must be adjusted in order to achieve this end.

Application times have been delineated through practice and experience. Generally, 1 min of application time in VASER or continuous mode can be applied for every 100 mL of infused wetting solution. The surgical endpoint is loss of resistance to probe movement in all intended areas. Aspiration can then be performed with suction-assisted or power-assisted liposuction.

In the past, there has been concern that ultrasound emulsified adipose tissue would be inappropriate for fat grafting as it could affect cell viability. However, the third-generation VASER system has been proven to be produce highly viable adipose tissue for grafting in both laboratory and clinical evaluations.

Surgical technique

General endotracheal anesthesia is preferable, particularly if prone positioning is required, as well as for large-volume aspirations. The back, flanks, lateral thighs, and superior posterior thighs are easily accessed in the prone position. Many surgeons also prefer the lateral decubitus position. Despite the fact that additional repositioning is required, some surgeons maintain that the lateral decubitus position offers better access and facilitates large-volume evacuations from the flanks and back in order to achieve more aesthetic waistlines. To access the abdomen, anterior and medial thighs, knees, calves, arms, ankles, breasts, and face, the supine position is used.

Core body temperature maintenance is essential and is accomplished by infusing warmed intravenous (IV) fluids as well as the use of forced warm air with a Bair Hugger (Arizent Inc., Eden Prairie, MN). The access incisions are made using a No. 11 blade and must accommodate the fluid-infiltrating cannula. In general, the wetting solution is prepared with 1 mL of epinephrine added to a 1 L bag of Ringer's lactate at room temperature (1 : 1,000,000 dilution). Lidocaine may be added to the wetting solution for an additional local anesthetic effect. Lidocaine dosing should typically not exceed 35 mg/kg, although some authors routinely use doses exceeding 50 mg/kg while maintaining a safety margin. Tranexamic acid can also be given intravenously or added to the wetting solution for additional hemostatic effects.

Wetting solution is first infused using a fine cannula or can also be accomplished with a power-assisted basket cannula. Then, for most areas of the body, pretreatment is completed with a 3.7 mm two-ring probe set to continuous mode at 80% power. We have found this to be safe in most regions when applied for approximately 1 minute per 100 mL of infused wetting solution. The endpoint of treatment should be a loss of resistance to passage of the cannula. For areas with more fibrous tissue (including gynecomastia), we would recommend using a one-ring probe as the energy is more concentrated and allows for easier penetration of these tissues. For thinner or smaller areas, the 2.9 mm diameter probe can also be used. The emulsified fat can then be aspirated with either standard suction or power-assisted liposuction cannulas. All treated areas should be checked for evenness of resection and can be equalized using a basket cannula without suction.