LIPOSUCTION TEXTBOOK

Chapter 29:
Critique of Ultrasonic Liposuction

The term ultrasonic-assisted liposuction (UAL), or ultrasound liposuction, refers to any modified liposuction technique that delivers ultrasonic energy to subcutaneous fat to facilitate traditional negative-pressure liposuction. The concept of UAL is intuitively appealing. A piezoelectric crystal converts electric energy to rapid (ultrasonic) vibrations and heat, which are transmitted to a small metal rod or paddle. Ultrasonic energy delivers a combination of vibratory mechanical energy and thermal energy to subcutaneous fat and thus injures living tissue.

At present, any claim that UAL is safe and effective is controversial. One study of 250 consecutive UAL patients concluded that internal UAL is “both safe and effective” despite three cases of dermal necrosis (1.2%), 28 postoperative seromas (11.2%), and 35 patients with Reston foam blisters (14%).¹

The Safety Controversy

A 1998 annual scientific meeting dedicated to cosmetic surgery included a symposium on UAL. With no experts on the physics of acoustics, the technical discussions were elementary and featured graphic art illustration supplied by a UAL device manufacturer. The clinical presentations were anecdotal and based on speakers’ clinical experience.

No speaker presented data based on personal research projects. All the speakers were enthusiastic about the future of UAL. The symposium gave the overall impression that UAL represented a significant advance for cosmetic surgery.

No speaker mentioned that UAL might prove more dangerous than tumescent negative-pressure liposuction. Apparently no studies have compared the two techniques. Also, no speaker discussed UAL complications. The biologic effects of destructive ultrasonic energy on adipose tissue in vivo have not been well studied, and no in vivo animal studies have defined the safety limits of UAL.

UAL has many enthusiastic advocates among the world’s most prominent and well-respected liposuction surgeons. The literature reveals, however, that the incidence of seromas and prolonged postoperative induration is greater with UAL than with tumescent negative-pressure liposuction. Furthermore, the American enthusiasm for UAL is difficult to reconcile when many disappointed European liposuction surgeons have abandoned UAL because of unsatisfactory results.

Objective information is lacking about the safety of UAL. High-profile television interviews of surgeons who are publicly enthusiastic about UAL may provide the public with an unrealistic assessment. Promoting UAL at surgical meetings without a full discussion of its complications may lead surgeons to believe that UAL is relatively safe.

The purpose of this chapter is to point out the need for more objective and scientific studies of UAL. This chapter discusses the ethical and epidemiologic issues associated with UAL safety.

I believe that the enthusiasm about UAL may be based on fallacious reasoning, biased information, and misleading advertising. Ultimately, the benefits of UAL may outweigh its detriments, but this has yet to be established.

Biophysics of Ultrasound

Named after H.R. Hertz (1857-1894), a German physicist, the hertz (Hz) is a unit of frequency equal to one cycle per second. Ultrasound designates high-frequency sound waves exceeding 20 kilohertz (20,000 Hz = 20 kHz), which are not perceptible to the human ear.

The two types of UAL are internal and external. Internal UAL delivers ultrasonic energy directly to subcutaneous fat by a metal rod or cannula inserted through a skin incision. External UAL delivers ultrasonic energy to subcutaneous fat by applying a paddle-shaped instrument directly to the overlying skin.

Diagnostic ultrasound devices used in obstetrics to assess fetal growth and anatomy operate in the range of frequencies between 2 and 4 million Hz, or 2 to 4 megahertz (MHz). External UAL devices typically use 1 to 3 MHz, whereas internal UAL devices operate in the range of 22.5 kHz.

The power of ultrasound, expressed in watts (W), refers to the amount of work done through the ultrasound field as it interacts with the medium in which the sound waves are propagating (Box 29-1). Diagnostic ultrasound devices typically operate at 0.1 to 100 milliwatts (mW). Most therapeutic external ultrasound devices (external UAL) operate in the range of 1 to 50 W, and internal UAL devices deliver 150 W. The intensity (output) of an ultrasound device is the amount of energy it delivers per unit area, or watts per square centimeter (W/cm²).

Increased ultrasound frequency (decreasing wavelength) produces increased heating and decreased depth of penetration. Thus the shorter the sound waves, the greater is local heat production and the greater the risk of focal thermal injury. Clinical evidence indicates that thermal injury to the microcirculation causes microvascular thrombosis.²

Internal UAL

Internal UAL consists of the delivery of ultrasonic energy directly into subcutaneous fat via a metal rod inserted through a skin incision.

Europeans were the first to embrace internal UAL. After initial enthusiasm for internal UAL, most European liposuction surgeons eventually rejected it because of an unacceptable incidence of complications. Despite this, internal UAL was subsequently introduced into North America.

The following factors have contributed to the initial success of internal UAL in North America:

1. Consumers believe that “high-tech” is synonymous with high quality.
2. News media were eager to showcase UAL because of the widespread interest in liposuction.
3. Many surgeons purchased UAL devices because UAL was “cutting-edge” cosmetic surgical technology and might attract new patients (customers) in a competitive marketplace.

Thus, despite no objective data showing that internal UAL was superior to tumescent liposuction, and despite the negative European experience, internal UAL acquired an initial marketing success in the United States.

The reality of internal UAL has subsequently become more discernible. Internal UAL is not necessary for the best results; it is more time consuming; UAL equipment is very expensive; and internal UAL is associated with a more prolonged recovery. Most importantly, I believe the risks of UAL complications outweigh any benefits of UAL. The emerging consensus seems to be that microcannular tumescent liposuction is safer and achieves better results than UAL.

Microcannular Liposuction

Internal UAL has few indications because of the risks of cutaneous necrosis. Even for treating relatively fibrous fatty tissue, the most common indication for internal UAL, safer and more efficient ways using microcannulas accomplish the same goals. Fibrous areas of fat are efficiently treated by the skillful use of progressively larger microcannulas.

Patients who are not overweight and who require only limited liposuction in well-defined areas are generally not regarded as good candidates for UAL. UAL is unnecessary in these patients, and the prolonged postoperative healing time with internal UAL is unacceptable.

Most surgeons who advocate UAL may have little or no experience with microcannular tumescent liposuction. One comparison of UAL and traditional liposuction did not employ tumescent liposuction and did not use microcannulas.³ For any given form of anesthesia, microcannular tumescent liposuction will allow an experienced surgeon to do liposuction more quickly and more completely than with UAL.

Hemostasis

Less bleeding and less bruising occur with UAL compared with the dry technique, wet technique, or superwet technique. It is not the ultrasound that reduces the blood loss, however, but rather the copious tumescent infiltration required for internal UAL.

Liposuction by systemic anesthesia does not demand complete local anesthesia, and therefore the degree of the infiltration and the subsequent degree of hemostasis are rarely maximal. In contrast, internal UAL demands a compulsively high volume of subcutaneous infiltration, which in turn produces profound hemostasis.

Symbolic logic helps explain the spurious correlation between UAL and hemostasis. For example, suppose U is ultrasound liposuction; M, microcannula liposuction, S, syringe liposuction; T, tumescent technique; and B, better results. If U + 1 T, M + 1 T, and S + 1 T all produce B, but neither U nor M nor S alone produces B, the critically important factor must be T. It would be illogical to conclude that U or M or S is responsible for B.

The same analysis can be applied to superficial liposuction. For example, superficial liposuction would not be possible without the use of small cannulas, which in turn would not be possible without the tumescent technique (see Chapter 27).

Thermal Trauma

Microvascular Thrombosis. Relatively mild temperature elevations of 41° to 43° C (105.8° to 109.4° F) can disturb the delicate intravascular balance between procoagulant and anticoagulant biochemical reactions, which can precipitate thrombosis. Mild hyperthermal stress in humans, such as 3-minute immersion in a 47°-C (116°-F) bath, decreases fibrinolytic capacity and leads to thrombosis.⁴ Heat stroke in humans is associated with coagulopathy.^5,6 In one epidemic of heat stroke, 17 of 55 patients had evidence of disseminated intravascular coagulation (DIC). ⁷

Elevation of intravascular temperature precipitates intravascular thrombosis and associated tissue necrosis.^8,9 Heating cultured endothelial cells to 42° C (107.6° F) stimulates release of plasmin inhibitor, which is produced by the endothelial cells, and may contribute to postburn vascular occlusion, leading to secondary progressive tissue necrosis.¹⁰

Platelet thromboembolism appears to be the major factor causing this progression of postburn dermal ischemia.¹¹ Thermal trauma causes acute thrombosis and occlusion of vessels in the dermis that is directly injured by thermal energy. A vascular response also occurs in the uninjured dermis bordering the site of injury. Diminished blood flow leads to progressive ischemia and necrosis in the dermis beneath and surrounding the burn.¹² Thermal trauma induces hypercoagulability and hyperfibrinolysis related to organ failure.¹³

Early liposuction surgeons said that liposuction creates a large subcutaneous wound that affects the patient in a manner analogous to a thermal burn. Internal UAL literally creates a large area of subcutaneous microvascular thermal trauma.

Pathophysiology. According to manufacturers’ claims, UAL devices simply deliver mechanical (acoustic) energy in a way that lyses adipose tissue cells and thus facilitates the aspiration of the resultant detritus. The amount of heat produced by UAL is not discussed, suggesting that manufacturers believe it is unimportant.

Clearly the risk of thermal trauma is a direct function of (1) the amount of acoustic energy delivered per unit of time (energy intensity) and (2) the amount of energy per unit volume per unit time (energy density). Thus using internal UAL at a low energy per unit time is safer than when UAL delivers a higher energy per unit time; in other words, the less ultrasonic energy, the safer the liposuction. UAL delivers significantly more energy (thermal and acoustic) to subcutaneous fat than microcannular tumescent liposuction.

The relative amount of mechanical energy versus thermal energy delivered to the fat is a function of wavelength. Internal UAL and external UAL operate at different wavelengths. Thus, when internal and external UAL devices are adjusted to deliver the same amount of acoustic energy per unit time, they will not deliver the same amount of heat per unit time.

Based on the fundamental laws of thermodynamics (e.g., conservation of energy, heat flows from hot to cold), the excess energy delivered by ultrasonic liposuction must augment the risk of unwanted tissue damage and surgical complications. Studies estimate that the temperature of a given fat compartment (e.g., thigh, flank, abdomen) infused with 1 L of tumescent fluid rises 1° F for each minute of ultrasonic energy.¹⁴ Tissue temperatures after internal UAL therefore may correlate with incidence of complications.

In a study of tissue temperatures during UAL the maximum subcutaneous temperature in one of 55 patients was 41° C. The authors state, “The heat generated is a byproduct of the energy transfer, and no heat emanates from the probe tip itself.”¹⁵ Analagously, one could state that the heat generated from a carbon dioxide (CO₂) laser is the product of energy transfer, and that no heat emanates from the laser handpiece itself. In either case the ultimate consequence of too much heat is tissue necrosis.

Potential Mutagenicity. High-intensity ultrasonic energy generates high-energy chemical reactions that may have adverse long-term effects on living tissue. The destructive mechanical effects of UAL should be differentiated from the potentially mutagenic chemical effects of free radicals generated by ultrasound. The true oncogenic risk of prolonged exposure to high-intensity ultrasonic energy associated with the use of UAL is not known.¹⁶

Thermal Relaxation Time. UAL and the CO₂ laser interact with biologic tissue in similar ways. Both are capable of a focused delivery of energy that produces an intense spike in local tissue temperature. The UAL cannula focuses the delivery of its electromechanical energy with 1 to 2 mm of the cannula tip. The CO₂ laser beam focuses the delivery of its electromagnetic energy within a 1-mm to 2-mm spot.

In both cases the concept of thermal relaxation time explains the risk of thermal trauma if the energy is delivered over a prolonged time. Either form of energy can produce a thermal burn or small vessel coagulation.

With either internal UAL or external UAL, the probe that delivers the ultrasonic energy to the subcutaneous fat must not be allowed to linger too long in one location. The probe must be kept in constant motion. The transfer of energy to a local area of tissue over a prolonged interval will lead to thermal trauma and tissue damage.

Burns and Necrosis. Appropriate training and experience are prerequisites for safe internal UAL. Clearly, however, unknown factors increase the risk for UAL-associated skin necrosis. For example, in the patient with a clinically undetected hypercoagulable state, focal areas of excessive UAL-induced high temperatures may precipitate focal vascular compromise and local full-thickness skin necrosis. Among such patients, no amount of UAL training can eliminate increased the risks of a “UAL burn.”

The incidence of burns and skin necrosis from thermal trauma or vascular compromise has been reported to be as high as 4%.¹⁷ Advocates of UAL state that temperature increases are negligible if the technique is performed correctly.¹⁸ Training and experience, however, do not always guarantee proper technique (Figures 29-1 and 29-2).

Mechanical Versus Thermal. Traditional liposuction involves the use of a vacuum inside a hollow cannula to aspirate fat. The mechanical trauma of microcannular liposuction is essentially localized to tissue in direct contact with the cannula. In contrast, UAL delivers mechanical (ultrasonic) and thermal (heat) energy that literally radiates beyond the fatty tissue in direct contact with the ultrasonic cannula.

UAL causes thermal damage to cells beyond the range of mechanical trauma. This thermal trauma is not “harmless” and may be associated with delayed healing, excessive inflammation, seromas, prolonged induration, and full-thickness dermal necrosis.

Marketing Conflict. In general, manufacturers of UAL devices do not provide graphic illustrations of the biologic effects of thermal energy that emanates from a UAL cannula. Deemphasizing the deleterious effects of the heat generated by UAL presents an unrealistic picture.

An uninformed audience might confuse marketing hyperbole with scientific fact. I believe that the surgeon who gives a lecture with illustrations provided by a manufacturer is essentially acting as that manufacturer’s spokesperson. This situation could represent a potential conflict of interest. The conflict of interest is real unless the lecturer makes an effort to provide evidence of the potentially harmful effects of UAL (see later discussion).

Seromas

Experts have stated that UAL has a 15% to 70% incidence of seromas. Experience has shown that advancing the internal UAL cannula too slowly or delivering too much ultrasonic energy can result in an unacceptable degree of collateral tissue damage and a high incidence of seromas.

In response to this unprecedented incidence of seromas, one manufacturer has modified its recommendations. The manufacturer has “solved the problem” by recommending that surgeons reduce the amount of internal ultrasonic energy that is delivered to subcutaneous fat. In other words, do less ultrasonic liposuction to reduce the incidence of problems.

External UAL

External UAL is a sequential process involving the following:

1. Infiltration of tumescent local anesthesia
2. Percutaneous delivery of ultrasound energy to subcutaneous fat
3. Traditional negative-pressure liposuction

External UAL is the topical application of ultrasound to the skin under the assumption that the transmission of ultrasonic energy into the subcutaneous fat will improve liposuction.

No convincing data show that external ultrasound provides any clinical benefit. If using external UAL is ineffective, however, at least it is less dangerous than internal UAL.

The external ultrasound machine is essentially the same type of device that has been used for years in rehabilitation medicine and physical therapy. Many surgeons became interested in external UAL after becoming disillusioned with internal UAL.

Typically, external ultrasound is applied after infiltrating the tumescent local anesthetic and immediately before beginning liposuction of an area. For each area treated, applying external ultrasound typically consumes about 10 minutes. Thus, if external UAL on two hips and two outer thighs is planned, an additional 40 minutes of surgical time is necessary for the application of external ultrasound.

Unsubstantiated Benefits

No objective studies support claims that external ultrasound makes liposuction safer, better, or easier. Unsubstantiated claims include that external UAL (1) allows easier penetration of larger liposuction cannulas, (2) promotes dispersion of the tumescent anesthetic solution throughout the targeted fat, (3) is associated with less intraoperative bleeding, and (4) reduces postoperative pain.

All information in favor of external UAL has been anecdotal, with no publication of well-designed, unbiased clinical studies. Presentations at cosmetic surgery meetings consist mainly of enthusiastic testimonials, such as “I’ve tried this and I’m convinced it is easier” or “it seems that patients like it better.”

External ultrasound has also been promoted for postoperative use. Some claim that postoperative applications of external ultrasound, when used repeatedly over several weeks, can decrease postoperative edema and soreness. No unbiased studies, however, have compared the effects of postoperative treatment with external UAL on one side of the body with a sham treatment on the contralateral side.

Manufacturer’s Warnings

The external UAL device is the same ultrasound apparatus traditionally used by physical therapists. These ultrasound machines are associated with definite risks and dangers. For example, allowing the device to linger over one area of skin can produce a second-degree burn. Also, if the device is applied for too long over a bone, it can blister the periosteum. Surgeons who promote external UAL from the podium at national surgical meetings rarely discuss these risks.

The manufacturers of external ultrasound devices provide instructions that state these devices should not be used over the heart, ovaries, or large arteries (e.g., carotid). Thus manufacturers’ warnings would seem to preclude the use of external ultrasound for liposuction of the male chest, the female abdomen, or the submental chin area. If these warnings were followed, external ultrasound would have few applications for liposuction. A surgeon who uses external UAL on the female abdomen probably does not include the manufacturer’s warnings when providing the patient with informed consent.

No evidence indicates that external UAL is of any benefit for liposuction of the submental chin and neck. On the other hand, the risk of a carotid embolism after thermal trauma from a local application of external ultrasound is unknown. Is any risk justified with no evidence of objective benefit?

Ethics and Placebo Effect. Without objective evidence that external ultrasound is beneficial, one must assume that it is no more than a placebo. Therefore promoting external UAL may be an unethical conflict of interest. In a elective situation such as cosmetic surgery, deriving financial benefit and profits from promoting a placebo would seem to indicate a financial conflict of interest.

A placebo would also be unethical if its potential complications were not fully disclosed.

Objective Evaluation

An objective evaluation of the external UAL demands an unbiased experimental design in which all participants are unaware of the treatment dose. Thus the patient, the surgeon, and the person who applies the external ultrasound should not know the amount of ultrasound energy applied to any specific area.

In such a “triple-blind” study involving 11 patients, we tested the hypothesis that external UAL has no significant clinical benefit compared with routine microcannular tumescent liposuction. After completion of liposuction, the following information was elicited:

1. The patient indicated which of two treated sides was the most uncomfortable during liposuction.
2. The surgeon indicated the side where liposuction was easiest to perform.
3. The nurse who applied the ultrasound made a visual assessment of the supranatant fat and decided which of two containers of aspirated fat had the greatest amount of blood.

Each patient had ultrasound applied to one symmetric pair of areas, such as both hips or both lateral thighs. Treatments were randomly allocated to either the left or the right side and consisted of 10-minute applications of an external ultrasound device.

One side received a relatively high dose (30 W/cm²) and the opposite side a very low dose (5 W/cm²) of ultrasound. This differential protocol was used to prevent the participants from guessing which side received the significant dosage. If one side received ultrasound and the other did not, the nurse or patient might detect a difference in sensation from the ultrasound.

Results. Two of 11 patients said the high dose of ultrasound was associated with more pain on liposuction than the low dose. Nine patients indicated no difference.

The surgeon judged liposuction to be easier in two areas treated with high-dose ultrasound and in one with low-dose ultrasound, with no difference in eight patients.

On visual assessment of supranatant fat for evidence of unequal surgical bleeding, the side that received the high dose of topical ultrasound was darker (contained more blood) in one patient. No difference was seen in the remaining patients.

Burn Complication. Our study of external UAL was terminated when a patient encountered a second-degree burn 2.5 cm in diameter on her hip (Figure 29-3). This burn resolved without significant dyschromia.

Although this burn might have been avoided with a more fastidious technique, a burn is an obvious risk that should not be ignored. With no objective evidence that external UAL provides any benefit, it was concluded that the risk of an inadvertent second-degree cutaneous burn outweighs any possible benefit of external UAL.

Assessment

With inadequate or suboptimal tumescent infiltration, external UAL might accelerate the diffusion of the local anesthesia. The increased tissue temperatures might facilitate diffusion. However, this might also increase the rate of systemic absorption.

Tumescent anesthesia is complete with proper infiltration, and thus external UAL would be unnecessary. External UAL provides no significant benefit for liposuction.

Complications and Conflicts

Cosmetic surgeons should be obligated to test the hypothesis that the benefits of UAL outweigh its risks. In principle, establishing that UAL has more risks than tumescent liposuction totally by local anesthesia should be rather straightforward. With the excellent safety record of tumescent liposuction, several reports of significant UAL complications should suffice. I believe, however, that advocates of UAL tend to avoid disclosure of UAL complications.

Reasons for Underreporting

No reliable system exists for reporting adverse events and complications associated with cosmetic surgical procedures (see Chapter 6). Surgeons should be highly skeptical about claims that a UAL device is “safe.” UAL complications might not be reported to government agencies or in surgical journals for various reasons (Box 29-2).

Reputation. Possible harm to one’s reputation and exposure to litigation are obvious reasons for surgeons and manufacturers of UAL devices to avoid voluntarily reporting significant surgical complications. This self-protection might be a strong deterrent for candid reporting of UAL complications. Also, as occurred in Europe, if UAL produces too many complications, it will be rejected. To protect the reputation of UAL, manufacturers might downplay reports of UAL complications.

Investigation. The U.S. Food and Drug Administration (FDA) regulates the manufacturers of medical devices and equipment. If a manufacturer has FDA approval to market a surgical device and receives a written report of a serious surgical complication associated with the device, law requires the manufacturer to notify the FDA.

This may result in a time-consuming FDA investigation, a reassessment of the device’s safety, and a restriction in sales. Thus a self-serving UAL device manufacturer might attempt to avoid any knowledge of reports about UAL complications.

Definition. To justify not reporting UAL complications, a manufacturer could adopt a policy that (1) a UAL complication need not be reported unless it is “truly significant,” and (2) death is the only truly significant UAL complication.

With such definitions, if a complication is not associated with a fatality, it does not qualify as a reportable complication. A manufacturer can plausibly deny knowledge of any “reported UAL complications.”

Notification. If the event is not officially reported in writing, it may be regarded as hearsay. Thus, if a manufacturer never receives written notification but merely “hears” about complications from its UAL device, these cases might not be reported to the FDA.

No Surveys. Manufacturers of UAL devices are not required to actively seek data on adverse outcomes involving their products.

A manufacturer usually has a list of all surgeons who have bought its UAL device. To my knowledge, however, no manufacturer of UAL devices has conducted a survey of customers seeking information about UAL complications. If a complication is not voluntarily reported to the manufacturer, it may never be reported to the FDA.

No Reporting Requirements. Even if a manufacturer does report a UAL complication to the FDA, the manufacturer is not required to disclose the complication to the public or medical community. The FDA can require public notification, but only under exceptional circumstances. The public remains ignorant about many complications.

Litigation. When a significant UAL complication has occurred, the case will likely be in litigation. Legal constraints thus prevent the surgeon from reporting the event.

Recently, a patient of a nationally prominent advocate of internal UAL developed multiple areas of full-thickness dermal necrosis as a result of UAL. Pending litigation prevented the surgeon from informing his colleagues of this significant UAL complication (see Figure 29-1).

This discrepancy between enthusiastic advocacy of UAL and the underreporting of severe UAL complications highlights the need for caution when judging the safety of UAL.

Results. Even if a surgeon or surgical society wanted to alert the public about surgical complications associated with UAL, the information is simply not available. Based on the previous discussion, surgeons have ample reason to be skeptical when evaluating the safety of UAL.

Anecdotal Data

Case reports of successful applications of UAL are of little statistical value in establishing the procedure’s merits and safety relative to other liposuction techniques. A report of one clinician’s experience with UAL proves nothing about its long-term safety. In contrast, a few anecdotal reports of severe UAL complications may be sufficient to condemn the procedure.

Reporting Bias. Because of reporting bias, a surgeon’s report of no UAL complications is never sufficient to prove that UAL is safe.

Suppose that 10 surgeons have each performed 300 cases of UAL and that one enthusiastic surgeon has had “no serious complications” with UAL. The remaining nine surgeons have discontinued using UAL because of disappointing results, such as local areas of skin necrosis or a higher frequency of seromas, prolonged indurations, or painful recoveries.

The enthusiastic surgeon would likely publish a paper on the benefits and safety of UAL. The nine disillusioned colleagues would want to forget about UAL. Few surgeons are motivated to report their poor results in a journal article.

Thus, without organized epidemiologic surveillance, anecdotal reports may yield an overenthusiastic impression about UAL safety. An unrealistically optimistic view of UAL safety based on insufficient data is not in the best interest of patients.

Cautious Approach. Most evidence presented in favor of UAL is anecdotal in nature. By definition, anecdotal data are statistically biased. In evaluating UAL, these data may be unreliable and susceptible to economic influences.

When the results of a scientific study conflict with an influential group’s self-interest, anecdotal data can be used to obscure the facts. If a group’s economic interests depend on the successful marketing of UAL, the group might have difficulty being candid about UAL safety.

Thus, again, the surgeon should be cautious in considering anecdotal data in decisions that affect patient safety.

Lack of Studies. The popularity of UAL in the United States is extraordinary, but this is based on marketing rather than objective scientific data. No prospective studies have compared risks and benefits. Instead, the driving force for UAL popularity is media hyperbole and the public’s passion for anything “high tech.” Rather than relying on convincing scientific data, many surgeons offer UAL merely because patients ask for it.

At cosmetic surgery meetings, discussions are biased. The theoretic effects of cavitation waves on adipose tissue are presented as established fact, whereas comprehensive discussions of the serious complications associated with UAL are usually nonexistent. Complications are dismissed as the result of inexperience and poor training rather than the expected traumatic effects of acoustic and thermal energy.

Typically, after developing a new medical device, the manufacturer provides clinical studies to support the product’s safety. Published results of multicenter studies define the types and incidence of complications. This information should allow a physician to decide if the product is safe and effective. In the case of UAL, manufacturers have not presented such information.

Salesperson Versus Scientist

Whenever the person providing information about the safety and efficacy of UAL is also in a position to profit from the successful marketing of UAL, the profit motive may bias the information. A potential conflict of interest does not rule out that a presenter may provide well-balanced and accurate information. Surgeons must be skeptical, however, and critically examine information about UAL for potential sources of conflicts of interest.

An objective presentation about UAL ought to provide a thorough discussion of its pros and cons. A lecturer who is a salesman would devote most time to enthusiastic support of the product. A lecturer who is a scientist would devote much of any general discussion about UAL to the subject of complications. An audience of liposuction surgeons listening to a lecture about UAL can judge the speaker’s objectivity by comparing the amount of time devoted to the benefits and to the risks of UAL.

Any discussion of UAL mechanisms using the applied physics of advanced acoustics must also present information about the thermodynamic inefficiency of ultrasound transmission and its natural conversion to heat energy. A salesperson might attribute the effects of UAL to ultrasonic cavitation and never mention the first law of thermodynamics. A scientist might demonstrate how UAL produces enough thermal energy to cause necrosis.

Because surgeons and manufacturers are naturally reluctant to disclose their complications voluntarily, the scientist must aggressively seek information about UAL complications. The salesperson might avoid a balanced discussion of UAL complications with the statement that UAL complications can be avoided with adequate training and experience.

Potential Conflicts of Interest. As mentioned, in financial aspects of patient care, unethical conflict of interest might arise when profit motives are allowed to outweigh concerns about patient safety.

Manufacturers of UAL devices do not always have FDA approval to market ultrasonic machines for liposuction.¹⁹ It may be contrary to FDA regulations for a manufacturer or its paid representatives to market UAL machines specifically for liposuction, but it is not illegal for one physician to talk to another physician about the UAL machine.

I believe that many surgeons who promote UAL from the lecture podium or teach UAL courses are intentionally or unintentionally acting as surrogates for the manufacturers in promoting the sale of UAL machines. It is ethical for a physician to act as a spokesperson for a manufacturer provided that (1) all financial incentives are disclosed and (2) patient well-being is given precedence over the profit motive.

A surgeon who has a reputation as an expert or innovator in UAL and travels internationally to surgical meetings as a featured speaker is unlikely to criticize the safety of UAL. If such an influential surgeon downplays the risks of UAL, a professional conflict of interest becomes evident.

If lecturers advocate UAL but avoid a detailed discussion of UAL complications, the audience may receive distorted and prejudicial information that indicates UAL is a relatively benign procedure. Unless equal emphasis is given to the advantages and disadvantages of UAL, the information might create a conflict of interest regarding patient safety.

If money is spent on advertising and promoting UAL, without budgeting for research into the safety of UAL, a financial conflict of interest may result. Surgical societies charging tuition for UAL instructional courses have an obligation to provide prospective epidemiologic data about UAL safety.

It is hoped that UAL will be shown to provide benefits that far outweigh its risks. Unfortunately, no data support this hope at present.

Ethical Considerations

The ethics of promoting UAL in North America is open to discussion, especially since UAL has previously been rejected by many European liposuction surgeons. UAL may or may not be more dangerous than traditional liposuction.

Is it ethical to promote UAL as a significant innovation without making an effort to document the safety of UAL relative to liposuction without ultrasound?

Many surgeons have embraced UAL without sufficient knowledge to make an informed decision about its safety. As noted, those who extol its benefits rely on plausible but unsubstantiated arguments.

An internal UAL cannula inserted through a small skin incision delivers enough acoustic and thermal energy to subcutaneous fat that it can cause widespread damage to blood and lymphatic vessels, nerves, and collagenous stroma, as well as adipocytes. An external UAL paddle applied to skin can readily cause a second-degree burn. If the paddle is applied to skin overlying a bony prominence, blistering of the periosteum may occur.

Clearly, external UAL and internal UAL are not entirely benign. The ethical promotion of UAL demands a complete discussion of UAL complications.

Author’s Conclusion

The European experience has shown that internal UAL is less safe than tumescent liposuction. The present state of the art of UAL may not offer sufficient clinical benefits to warrant the significant risks of thermal trauma, seromas, and prolonged healing. Even in the hands of experienced surgeons, serious complications may be associated with UAL and cannot be ignored.

A consensus gentium is a consensus of the people. The consensus gentium fallacy is concluding that a proposition must be true simply because so many people believe it is true (see Chapter 7). Many cosmetic surgeons are enthusiastic about the benefits of ultrasonic UAL. This does not prove that UAL is safe, however, or that UAL is more effective than microcannular liposuction. The liposuction surgeon should remain skeptical until objective evidence confirms the safety of UAL.

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14. Commons GW, Halperin B: Ultrasound-assisted lipoplasty: a clinical study of 250 consecutive patients, Plast Reconstr Surg 101:203-204, 1998.
15. Ablaza VJ, Gingrass MK, Perry LC, et al: Tissue temperatures during ultrasound-assisted lipoplasty, Plast Reconstr Surg 102:534-542, 1998.
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17. Scheflan M, Tazi H: Ultrasonic-assisted body contouring, Aesthetic Surg Q 16:117, 1996.
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Figure 29-1 A, Multiple areas of full-thickness dermal necrosis after internal ultrasonic-assisted liposuction (UAL). B, Results of surgical debridement of necrotic skin. C, Appearance of wound contractures after excision sites had healed by secondary intention.

Figure 29-2 Necrotizing fasciitis in 138-kg (304-pound) male after internal UAL of abdomen. Postoperative course was complicated by polymicrobial infection. A, Left lower abdomen and pubic areas with drains soon after surgical debridement of necrotic and infected subcutaneous tissue. B, Approximately 3 weeks after surgical debridement. Wide excision of multiple areas of skin and subcutaneous tissue was followed by prolonged hospitalization.

Figure 29-3 Second-degree burn after external ultrasound application on right hip of patient who received 3 watts/cm² with 10-cm² paddle (30 watts) after tumescent infiltration and before liposuction. The resulting 2.5-cm lesion resolved without significant postinflammatory hyperpigmentation.

BOX 29-1 Definitions: Acoustic Energy and Power

Sound waves consist of longitudinal oscillations of pressure within a conducting medium, such as a gas, liquid, or solid. As a sound wave travels through a medium, it is attenuated; that is, the sound wave’s intensity diminishes as it is absorbed by the medium. A sound wave’s ability to penetrate tissue decreases (attenuation increases) as its frequency increases; the higher the frequency, the smaller the depth of sound wave penetration. Ultrasound is an example of transforming electric energy into kinetic acoustic energy, which in turn is transformed into the thermal energy of the conducting medium as the sound wave is attenuated.

Energy, measured in units of joules (J), is a scalar quantity associated with a state or condition of one or more objects. The different forms of energy include kinetic energy and heat energy.

Kinetic energy is associated with an object’s state of motion. An object that has mass m and velocity v has kinetic energy K = mv2. In the case of kinetic energy:

1 joule = 1 J = 1 kg · (m/s)2

where m/s is meters per second. Kinetic energy is never a negative quantity because m and v2 are always positive. An object’s energy changes when an exchange of energy occurs between the object and its environment. A transfer of energy occurs when a force is exerted on the object or heat is exchanged. The process of transferring energy by means of a force is known as doing work.

Work is defined as the amount of energy transferred to or from an object by means of a force acting on the object. Work is positive when work is transferred to the object. Work is negative when energy is transferred from the object to its environment. A kinetic frictional force transforms kinetic energy to thermal energy (heat). Thermal energy is associated with the random motions of atoms and molecules within the object.

Power, measured in units of watts (W), is the rate of energy transfer. One watt is 1 joule/second (J/s). In the case of kinetic energy:

1 watt = 1 W = 1 kg · m2/s3

Intensity (I) of a sound wave at a surface is the average rate per unit area at which energy is transferred by a wave through or onto the surface. Thus:

I = P/A = W/m2

where P is the sound wave’s rate of energy transfer (power) and A is the area of the surface intercepting the sound.

Heat (Q) is the energy that is transferred between a system and its environment because of a temperature difference between them. Before the midnineteenth century, when physicists finally realized that heat was a form of energy (thermal energy), heat was measured in terms of the calorie (cal). One calorie of heat was defined as the amount of heat required to raise 1 g of water from 14.5° C to 15.5° C. As with work, heat is transferred energy. Thus:

1 cal = 4.1860 J

Data from Halliday D, Resnick R, Walker J: Fundamentals of physics, ed 5, New York, 1997, Wiley & Sons.

 

BOX 29-2 Disincentives to Reporting Complications of Ultrasonic-Assisted Liposuction (UAL)

1.   Surgeons and manufacturers want to maintain their reputations.

2.   Reports of complications may cause the U.S. Food and Drug Administration (FDA) to restrict sales.

3.   If the only significant complication is a death, all other complications are insignificant and need not be reported.

4.   Only written accounts of complications must be reported to the FDA.

5.   Manufacturers do not survey customers and surgical societies do not monitor members about UAL complications.

6.   Reports to the FDA are confidential and are not necessarily made public.

7.   Laws prevent voluntary reports of complications.

8.   The peer review process is secret.

9.   Malpractice settlements are often sealed.