“Is power-assisted liposuction (PAL) really superior to handmade (SAL)?” — A surgeon's record of delving into a landmark liposuction paper to the end
The standard medical name in the title is ‘Powered liposuction (PAL)’and ‘Traditional negative pressure liposuction (SAL)’ instead '기계식 지방흡입'and ‘Handmade’The reason why the expression is included is because it is a familiar term that is currently widely spread among patients in private practice for marketing purposes. However, what you should not misunderstand is that there is no such thing as an automated method where a machine performs surgery on its own. Both PAL and SAL methods are ultimately surgeries performed from start to finish by the doctor holding the handpiece and stroking it.It is true.
As a surgeon who performs liposuction surgery and as a clinician who must promise the safest and most precise results to patients, there is a fundamental question I always ask myself.
“Between Power-Assisted Liposuction (PAL, Power-Assisted Liposuction), which uses the power of a motor to finely vibrate the tube, and traditional Negative Pressure Liposuction (SAL, Suction-Assisted Liposuction), which involves suctioning using only the doctor’s touch without a vibration motor, is there really a scientific paper designed well enough to change the patient’s final surgical outcome?”
Today, many hospitals advertise specific expensive equipment (such as PAL) or, alternatively, specific techniques, as if one guarantees superior results. However, when we open the original text of the actual medical academic database (PubMed), not just a marketing phrase, and verify the design step by step, we come across loopholes behind the paper that we believed to be 'scientific evidence'. In today's column, I looked for and read comparative papers between PAL and SAL. 5-step critical verification processWe would like to share this transparently with our dear Chaebi readers.
PAL vs SAL landmark paper verification process at a glance
Even if it is a paper published in a famous academic journal, a completely different truth is revealed when the research design, sample, and interests are dismantled step by step from the perspective of a surgeon.
• Question: “What representative randomized controlled trials (RCTs) have demonstrated significant differences between PAL and SAL?”
• Surface area reported: increased suction rate (mL/min), reduced surgical time, and reduced surgeon arm fatigue (Katz et al., 2001)
• Question: “What is the body mass index (BMI) of the patients studied? Weren’t they mainly selected for overweight and obesity?”
• Limitations found: Individual height, weight, and BMI values are not indicated → A defect in ‘generalization (external validity)’ in which the mechanical time reduction effect is exaggerated when focusing on the obese group
• Question: “After checking the original text, isn’t the total number of patients only 18?”
• Limitations found: Minimum statistics were obtained through symmetrical comparison (split-body), but actual safety could not be verified due to skin necrosis, discoloration, and asymmetry with a sample of 18 people.
• Insight: “Aren’t the authors of the paper themselves commercial stakeholders in the organizations and techniques they promote?”
• Academic evidence: bias in positive conclusions due to financial interests (Lopez et al., 2015) and lack of independent reproducibility review by opposing experts.
• Linguistic analysis: Excessive superiority framing (Spin phenomenon) compared to the restrained description of orthodox medical and surgical papers
• Surgeon's conclusion: ① Fat lobule hydrodynamics, ② Microvascular preservation, and ③ The delicate tactile sense of the opposite hand (guide hand) that is taken away by vibration, and the risk of vibration damage to the surgeon (Wu et al., 2021)
1. The superficial results presented in the paper and the limitations of the ‘hidden BMI distribution’
In academia, the most widely cited early literature comparing PAL and SAL as a prospective randomized controlled trial (RCT) was published in 2001. Dermatologic SurgeryThis is a multicenter study by Katz et al. published in [1. PAL vs SAL prospective comparative study]. The researchers used a split-body design, dividing the left and right symmetrical parts of a patient's body and inhaling on one side with the PAL and the other with the SAL.
If you read this far, it seems like PAL is superior in every way. But as a surgeon, the next question I asked was: “Is the BMI (body mass index) distribution of the patients who participated in the study provided?”It was.
Surprisingly, the original paper did not specify the patients' individual height or BMI values, but only presented basic epidemiological summary values such as the average range of weight, age, and gender. [1. Limitations of patient group epidemiological data]. If individual height and weight had been recorded, BMI ($\text{Weight (kg)} / \text{Height (m)}^2$) could have been back-estimated, but the summarized statistics alone cannot tell whether these patients are slim body shape correction patients or severely overweight and obese patients who require large-dose inhalation.
① Disparity between internal validity (accuracy within the study) and external validity (generalizability)
Since the left and right sides of one person were compared, the internal causal relationship (internal validity) that “PAL was faster in this experiment” is established regardless of obesity level. But What if the research team had selected samples mainly from obese and overweight patients with a large amount of fat to extract in order to maximize the time-saving effect of PAL?
The thicker the fat layer and the greater the suction volume, the greater the effect of reducing time and doctor fatigue caused by the machine's reciprocating vibration. On the other hand, in normal weight to slightly overweight patients who want detailed line sculpting, the time difference between PAL and SAL may be clinically insignificant. The fact that epidemiological summary values are lumped together so that they cannot be distinguished is an obvious limitation that makes it difficult to generalize the study results to all patients.
2. Sample of only 18 people ($N=18$), and structural conflict of interest in plastic surgery papers
The bigger shock I encountered when I read the original text of the paper directly was The total number of study subjects is only 18 (1 male, 17 female).was true [1. Limitations of very small sample design].
The very small sample of 18 people was only an initial exploratory study (pilot study) to gauge the operating speed of the device. With such a small sample, patients are really worried. It is completely statistically impossible to verify differences in serious side effects, such as skin necrosis, severe bruising and hematomas, uneven skin asymmetry, and permanent pigmentation.I do. In fact, a plastic surgery journal PRS Global OpenA study by Swanson (2014) published in also sharply criticized the fact that many clinical papers comparing expensive liposuction equipment are being used as a tool for purchasing and marketing expensive equipment, even though their reliability is low due to sample design flaws and failure to control confounding variables. [3. [Criticism of the level of evidence in cosmetic plastic surgery clinical papers].
In my opinion, plastic surgery papers are better than other medical and surgical departments. The relationship is so strong that the authors themselves are direct commercial stakeholders of the research results. This is because the moment you prove your surgical ability and publish a paper on the superiority of the procedure or equipment you are advertising, enormous commercial benefits follow, including hospital publicity, increased surgical costs, and consulting fees for equipment manufacturers.
In fact, researchers at Johns Hopkins University (Lopez et al., 2015), the most authoritative journal in plastic surgery, Plastic and Reconstructive SurgeryAccording to an analysis published in Plastic surgery papers written by researchers with financial conflicts of interest (COI) from equipment companies, etc. had a statistically significantly higher probability of reaching a 'positive and superior conclusion' about a specific device or procedure compared to papers by researchers without a conflict of interest. [4. [Financial conflicts of interest and conclusion bias in plastic surgery papers].
Moreover, surgical research is different from drug research, where the doctor's 'manual skill and skill' itself determines the results. We cannot rule out the risk that authors trying to promote PAL are already proficient in PAL, and may unconsciously perceive higher levels of fatigue or manipulate it in less detail when performing SAL, which is the control group. Therefore, what is more important than the design of the paper itself is: Will the same results be obtained when an opposing expert (traditional SAL master) or an independent third party whose interests conflict with the content of the paper examines reproducibility under the same conditions?It is.
MicroAire® PAL® (Power-Assisted Liposuction) Handpiece
It is an electric handpiece equipment that reduces fiber passage resistance and operator's arm fatigue with thousands of microscopic reciprocating strokes per minute.
Medela® Precision Liposuction Cannula & Surgical Negative Pressure Suction System
Based on Swiss Medela®'s precision-processed cannula and stable vacuum negative pressure (Dominant Flex, etc.), this is a standard SAL system that reads tissue resistance and blood vessel running surface and suctions in detail using only tactile feedback from the tips of the surgeon's hands without vibration of the motor.
3. Abuse of “Significantly” and “Than”: Language gap with orthodox medical and surgical papers
Throughout the paper, sentences and vocabulary that emphasize the superiority of surgery—especially 'Significantly'Wow 'Than (superior to)'If we compare the use of — with similar orthodox internal medicine or essential surgery papers, we can see that it is a so-called verbal exaggeration for commercial persuasion. ‘Spin’ phenomenonThis is clearly revealed [5. Verbal exaggeration and spin phenomenon in clinical papers].
| Lexical and descriptive analysis items | Academic norms for orthodox internal medicine/essential surgery papers | Description of the relevant plastic surgery instrument comparison paper (Katz et al.) |
|---|---|---|
| Framing of the Title | "Comparative Evaluation of A and B..." Adopt a value-neutral comparison structure |
"The Benefits of Powered Liposuction..." Promotional title that puts the ‘benefits’ of a specific device at the forefront |
| Usage of "Significantly" | Strictly limited to predefined primary endpoints only. When $N=18$ level Immediately add the proviso that “the sample is small and interpretation requires caution.” | Throughout the abstract and conclusion "Significantly faster", "Significantly less fatigue"By repeatedly arranging Exaggerated as ‘clinical overwhelmingness’ |
| Comparative composition using “Than” | "Relative to", "Compared with" Confidence interval (CI) values are calmly presented along with neutral phrases such as | "Faster than", "Easier than", "Superior to"By using in succession Traditional handwriting method (SAL) downgraded to an outdated standard |
| Subjective Indicators and Conclusion Tone | Physician fatigue, which cannot be blinded, is reduced to an auxiliary indicator and the need for large-scale follow-up verification is specified. | “Effortless” Conclusively recommend the justification for introducing the organization by mobilizing tangible modifiers such as |
Surgeon's conclusion: 'Physics of skin', 'preservation of blood vessels', and 'tactile sensation of the opposite hand' that motor vibration can never replace
In the end, whether PAL or SAL, the passage through which fat is suctioned is a thin tube (cannula) with a diameter of several millimeters, and the place through which the tube passes is the living patient's skin. What determines the success or failure of surgery is not the vibration motor attached to the handle. Basic principles of human physics and physiology and the surgeon's sense of both handsIt is.
The fat in our body is not a flowing liquid like water, but a lump (fat lobules, 1-4 mm) tightly bound together with a collagen net like small grapes. [6, 7, 8. Size of fat lobules and cannula hydrodynamics]. As the diameter of the tube becomes too thin, the internal flow resistance rapidly increases ($R \propto 1/r^4$), and grape cluster grains may get caught in the hole and block the tube, or large fat lobules may be skipped without being absorbed. [6. Mechanism of occlusion of fatty lobules within the lateral foramen]. At this time, if you use force with machine vibration or excessive sound pressure, only the surrounding flesh tissue will be injured, so only the surgeon's delicate handling of selecting an appropriate tube according to the size of the fat lobule and reading the tissue resistance with his fingertips can create a smooth line.
Even if the surgery time was shortened by 20 to 30 minutes with the power of the machine, what would happen if the thin blood vessel network under the skin was injured through rough manipulation relying on fast vibration? The oxygen path to the skin is blocked skin necrosiscomes, or the blood that leaks out accumulates Hematoma and infection, long swellingcauses the iron content in the blood to seep into the skin. Permanent dark skin staining (pigmentation) due to hemosiderin depositionwill leave behind [9, 10. Preservation of subcutaneous vascular network and prevention of complications].
In liposuction, the movement of the main hand holding the suction device (handpiece) is also important, The sensation and role of the ‘opposite hand (pinching & sensing hand)’ that judges the thickness and roughness of the remaining tissue on the skin in real time and secondarily adjusts the suction pressure by gently pressing it.This is no less decisive. If PAL is fully adopted during surgery, the continuous mechanical vibration (approximately 74 Hz, acceleration $5.69\text{ m/s}^2$) generated by the cannula and handpiece at tens of times per second will fatigue and dull the fine tactile receptors in the fingertips, resulting in loss of precise thickness discrimination sensation. [11, 12. Tactile nerve dullness and sensory loss due to mechanical vibration].
In fact, it is an authority on cosmetic plastic surgery. Aesthetic Surgery JournalIn a paper by Wu et al. (2021) published in When performing surgery using the vibrating mechanical method (PAL), the actual measured vibration intensity is significantly higher than the manufacturer's published value ($p < 0.001$), and when used for more than 1 hour and 30 minutes a day, the vibration exposure caution limit (action value) has already been reached, which can cause 'Hand-Arm Vibration Syndrome (HAVS)', which causes permanent loss of sensation, peripheral nerve damage, and blood vessel constriction in the operator. Be very careful of damage to the surgeon.has warned safety guidelines [11. Risk of exposure to vibration of surgeon when using PAL and HAVS caution recommendation]. We must calmly ask ourselves whether strong mechanical vibrations, which can dull the senses of the surgeon's fingertips and cause cumulative damage to the nerves of the hand, are really unconditionally beneficial to delicate body sculpting.
Surgeon Dr. Han Gru (Chief Surgeon)’s medical principles: Principles of truthful treatment without exaggeration“We do not rely on the names of expensive expensive equipment, commercially inflated numbers of papers, or promotional slogans from provocative YouTubers. We honestly diagnose the patient’s body condition as it is, transparently explain the limitations of the surgery, and prove it only with the results in the operating room.”
4. Frequently asked questions about liposuction equipment (PAL vs SAL) and medical literature
In the consultation room, we will organize in an easy-to-understand manner the four questions dear Chaebi readers are most curious about regarding liposuction equipment advertisements and thesis evidence.
Q1. If you look at hospital advertisements, they say that you should use vibration equipment (PAL) to reduce bruising and swelling and to prevent sagging skin. Is this true?
Not necessarily so. The key advantages of PAL demonstrated in the paper are ‘It reduces arm fatigue for surgeons and passes through hard fibers quickly.’The point is. The real key to determining bruising, swelling, and skin discoloration after surgery is not whether the machine vibrates, but rather how accurately the surgeon suctions at a precise depth and angle without damaging the thin blood vessels under the skin (vascular preservation technique).
Q2. So is PAL equipment bad equipment? When does it help?
PAL itself is by no means a bad device. In areas where the skin is particularly hard and tough, such as the back or gynecomastia areas, or in reoperation areas where scar tissue has hardened from previous surgery, it is an excellent 'auxiliary tool' that reduces the doctor's physical expenditure. However, if you rely solely on vibration, even the delicate sense of the other hand, which measures the thickness of the skin, may become dull, so in the end, the doctor's sense of both hands and detailed hand skills are essential to controlling the machine.
Q3. Is PAL better if you have a slim body type and want to precisely trim the flab in some areas?
For those of normal weight or seeking partial body sculpting, there is little difference in surgical time between PAL and traditional manipulation (SAL) because the absolute volume of fat to be extracted is not large. Rather, authentic manual handling, in which the thickness of fat grains and skin is directly felt in 1mm increments with the fingertips through a thin tube and delicately refined, is very advantageous in producing smooth results.
Q4. How should we accept the phrase ‘SCI-level thesis proof’ posted by plastic surgery clinics or clinics on their websites?
Rather than the fact that there is a thesis itself, ‘Is this a poorly based paper in terms of research design or data?’, and ‘Isn’t this a promotional paper written with support from an equipment company?’You should doubt it at least once. Even the famous paper we looked at today was an early study with only 18 patients. It is wiser to choose a doctor who can honestly explain your body's anatomical condition and the limitations of surgery, rather than a screenshot of a flashy English paper or a popular machine name.