13.1 History of PAL

Liposuction as a procedure has always been a balance between the need to maximize tissue penetration and minimize tissue damage. PAL was developed in the 1990s in response to the need for improved fat penetration and control without the generation of excessive heat and the complications associated with ultrasound-based devices. ¹

13.2 Equipment

The first power-assisted devices incorporated a blade within a cannula drawing from orthopedic and otolaryngologic instruments and were primarily intended for submental use. ² Concerns about increased blood loss using cannulas with internal blades led manufacturers away from blades in favor of reciprocating cannulas. ² These instruments were designed to vibrate at a rate of 800 to 10,000 movements per minute and the vibration allowed easier tissue penetration. ² The power-assisted devices were also designed to work with a variety of cannula shapes and sizes.

The early powered devices were driven by compressed gas and were very noisy. ^{2 , 3} They also required the expense and inconvenience of maintaining large tanks of medical-grade compressed gas. Byron Surgical (Mentor, Irvine CA) developed a disposable power-assisted handle that was driven by the air discharged from the aspirator. ² However, this was fraught with increased noise and cost. Quieter electrical sources were soon developed. ³

A small variable speed motor generates a forward and backward reciprocating motion to produce a 2 mm to 12 mm excursion at the tip. ^{4 , 5 , 6} At the tissue level, the reciprocating movements of the powered cannula mirror that of the manual movements but the standard stroke distance and limited lateral movements help to reduce tissue trauma. Vigorous movements are replaced by slower manual passes of the powered cannula, maximizing fat extraction with less exertion. The mechanism of action has not been clearly defined. Two possibilities have been proposed: (1) a jackhammer-type motion of the cannula tip breaks up fat or (2) the fat is suctioned into the cannula and then avulsed by the reciprocating motion. ⁴

Studies have demonstrated the largest increase in fat extraction using the PAL system previously produced by Byron Surgical (Mentor, Irvine CA). ² Some systems rely on electricity and others are gas driven. ⁶ Differences in efficacy may be attributable to differences in the rate of vibration though it is unclear whether slower or faster vibration provides optimal efficiency for removing fat. ² The extent of radial movement may also contribute to efficacy. Choice among competing PAL devices is generally based upon warrantee, preference of electrical versus pneumatic, vibration, and noise. ⁶ In the United States, the PAL LipoSculptor by MicroAire (Charlottesville, VA) is the only PAL system that is currently being manufactured. The device is electric and operates with a 2 mm reciprocating stroke at 4,000 cycles per minute. Per report from the manufacturer in 2016, the system costs approximately US$20,000. Other companies that have previously manufactured PAL systems include Wells-Johnson (Tucson AZ), Byron Surgical (Mentor, Irvine CA), and Medtronic (Minneapolis MN), but these products are no longer on the market.

Powered systems incorporate cannulas of comparable length and diameter to suction-assisted lipoplasty cannulas, allowing for the use of small incisions. The powered cannulas have been shown to create larger tunnels in the subcutaneous tissue than traditional liposuction cannulas. ^{2 , 7} In other words, a 3 mm cannula may produce tunnels of 4 mm or larger. ^{2 , 7} Therefore, surgeons should consider choosing a smaller size cannula than that to which they are usually accustomed. This also allows surgeons to make smaller access incisions than they would typically require for a given tunnel size. When the power is on, the cannula can be held in one place and still remove fat. Caution must be used for this same reason to avoid creating contour irregularities.

13.3 Advantages for the Surgeon

The improved tissue penetration of the power-assisted devices reduces operator fatigue by allowing for more rapid aspiration and decreased muscle strain. This is particularly helpful in revision cases as well as fibrous areas such as the back, flanks, and male breast. By reducing the physical exertion required by the surgeon, longer or more numerous surgeries can potentially be performed in a given session. Furthermore, decreasing the fatigue and monotony associated with traditional liposuction likely improves surgeon attention and precision. ^{2 , 7 , 8}

A multicenter study performed by Coleman et al demonstrated an average increase in fat extraction of 30% (range 20 to 45%) with PAL, as compared to traditional liposuction. ⁵ Traditional liposuction was simulated in their study by using PAL devices in their non-powered modes. The greatest increase in fat extraction was seen in the hip area (62%), compared to the upper thighs (48%) and the abdomen (36%), which supports the observation that PAL is particularly advantageous in fibrous areas where traditional liposuction can be more challenging.

Katz et al compared traditional liposuction and PAL in a group of patients who served as their own controls. ⁷ They found that PAL was associated with 35% shorter operative times, 31% greater fat aspiration per minute, and 49% less surgeon fatigue than traditional liposuction. ⁷ The authors also reported that, because of the greater ease with which the powered cannula moves within the subcutaneous tissue, together with the increased patient comfort associated with PAL (see section 13.4), they were able to fine-tune difficult areas at the end of the case with the patient standing. ^{2 , 7} They believe that this opportunity allows for a degree of final symmetry and contour that could not otherwise be achieved with traditional liposuction and a lower incidence of revision procedures. ⁷

In an attempt to assess skin tightening following PAL, Sasaki et al measured surface area changes in three patients who underwent both PAL and traditional liposuction of their abdomen. ⁹ While their results did not reach statistical significance, they reported a greater reduction in skin surface area with PAL (average 5.8%) than with traditional liposuction (average 4.2%) six months postoperatively. ⁹ Their study was limited by its small sample size, but should encourage further research into the potential skin tightening advantages of PAL over traditional liposuction.

The overall increase in fat extraction reported by Coleman et al, as discussed above, was only significant for surgeons who had performed eight or more PAL cases. ⁵ For surgeons who had performed seven or fewer PAL cases, there was no significant difference in fat extraction between powered and non-powered liposuction. The study draws attention to the short but real learning curve associated with the powered devices. Surgeons must become accustomed to moving the cannula more slowly than in traditional liposuction in order to maximize the fat extraction benefits of PAL. While temporary, this learning curve may be considered a small disadvantage of PAL.