Review of Coleman, SR et. al. Clinical Efficacy of Noninvasive Cryolipolysis and Its Effects on Peripheral Nerves

May 3, 2009

Aesthetic Plast Surg. 2009 Mar 19

Clinical Efficacy of Noninvasive Cryolipolysis and Its Effects on Peripheral Nerves

Coleman SR, Sachdeva K, Egbert BM, Preciado J, Allison J.

Review copyright 2009

Coleman and colleagues present the first clinical report on the ‘love handles’ of 10 patients using the Zeltiq non-invasive fat reduction device.  The investigators used repeatable data collection methods, and proper data analysis procedures, resulting in a highly credible paper.

During a single patient visit, the Zeltiq treatment was administered to one of two love handles, with two to three applications of the cooling device, so as to sufficiently cover the area to be treated.  The opposite love handle was left untreated and used as the control. Follow up visits for fat thickness measurements were performed at 2 months and 6 months.

Fat thickness reduction (from ultrasound images) was used as an quantitative measure of efficacy, at various follow-up points compared to baseline.  The investigators went to great lengths to ensure measurement accuracy, using a transparency to align ultrasound measurements at the various time points, and collecting up to 12 evenly spaced ultrasound measurements at each location.  Generous amounts of ultrasound coupling gel were used to prevent the ultrasound probe from compressing the dermis and fat.  Overall fat layer thickness reduction was calculated by subtracting the ‘fat thickness change on the control side’ from the ‘fat thickness change on the treated side,’  where the fat thickness change for each patient was the average of the up-to-12 individual measurements.  The authors properly used this internal control, unlike so many papers in this field.

Additionally, efficacy was also measured by photographic assessment of treated versus control area, using standardized photography setup at a series of viewing angles every 22.5 degrees from 0 degrees to 360 degrees.  Three blinded reviewers compared baseline and 4-month post-treatment photos for five subjects for whom four month follow-up was available.  Again the investigators used blinding properly, to produce reliable results.

Transient numbness is a common, non-serious complication of the Zeltiq treatment.  Sensory neurologic assessment of the treated area was performed in nine patients at baseline and weekly post-treatment for 2 months. In one patient, nerve biopsies were collected at 3 weeks and 6 weeks post-treatment, at the treated site and a contralateral control, and evaluated for signs of sensory impairment.

There were no serious adverse events.  One patient had a non-serious adverse event during treatment.  After treating the median area of the love handle, the applicator was applied to the left anterior area.  After several minutes the subject reported pain and the treatment was aborted.  Other than redness that lasted six hours there was no other effect.  This subject did not complete the treatment, so no follow-ups were performed.

Erythema was observed in all 25 treatment locations of 9 patients who completed study. Numbness was reported at 24 of 25 treatment locations, which improved at a 1-week phone follow-up and resolved completely by the 2 month follow-up visit. Three of nine subjects did not complete the 6 month follow-up ultrasound, and two subjects did not complete the 6-month follow-up photographs.

Unlike prior reports of non-invasive body contouring, the authors in this paper present their results as a percent reduction, rather than a centimeter reduction.  AestheticDeviceReview speculates that the authors found a correlation between starting fat thickness and the amount of reduction, and so chose to report a percentage rather than an absolute amount.  In the six patients with six-month data, ultrasound fat thickness reduction was 20.4% +/- 4.9% in the treated side versus control at two months, and 25.5% +/- 9.5% at six months.  All patients had at least 11.5% reduction at 2 months, and 10.7% reduction at 6 months.  These are impressive results for a single treatment,demonstrating that results last for at least six months. 

For the blinded photographic assessment, the blinded reviewers were able to correctly pick the follow-up versus the baseline image 93% of the time.  If there were no treatment effect, we would expect the reviewers to be correct 50% of the time.  Again, these are impressive results, and objectively indicate cosmetic improvement.

For the nine subjects who completed the battery of sensory tests, 3 subjects had no change from baseline during the study on any test, and the other 6 showed steady improvement over six weeks with full resolution at week seven.  Nerve biopsy results on one patient showed completely normal nerves at 6 weeks, suggesting cryolipolysis does not cause any long-term damage.  Given the small number of patients, these results do not completely rule out the possibility of long-term nerve damage in a larger population of patients.  We need to await further results.

Transient hypo-esthesia seems to be a common complication of the Zeltiq technique.  It is not explained why one patient felt pain and could not complete treatment.  Fat thickness measurements were performed in a well controlled manner, and the treatment side was properly analyzed versus controls.  Unusually, fat thickness reductions were reported as a percentage reduction, and centimeter reduction was not reported.  There was no correlation between the fat thickness change and weight change in this group.  Blinded photographic assessment shows that the clinical changes are visible to trained observers.  It is not clear if the clinical changes are evident to patients, especially since the changes take a long time to become visible. Patient satisfaction was not measured, and it is not known if the patients were offered subsequent treatment of the contralateral side.  It is not known why there were so many drop-outs for follow-up; possibilities include the large number of follow-up visits, the long duration between the treatment and the 4 and 6 month follow-up visits, or a lack of subject interest in the result.  Nevertheless, the main results – sustained fat thickness reduction and cosmetic improvement – are credible and compelling.

Review of Brown S. et. a. Characterization of Non-thermal Focused Ultrasound for Non-invasive Selective Fat Cell Disruption (lysis): Technical and Pre-clinical Assessment

March 15, 2009

S. Brown, PhD et al

Characterization of Non-thermal Focused Ultrasound for Non-invasive Selective Fat Cell Disruption (lysis): Technical and Pre-clinical Assessment

currently available on PRS Advance Online at

In this new paper, Spencer Brown MD et. al. performs four pre-clinical experiments to elucidate the acute biological effects of the Ultrashape device for non-invasive fat cell disruption.  Brown’s five co-authors are Ultrashape employees.  In general, the presented work appears to be careful and the results accurate.  Unlike the previously reviewed Zeltiq pre-clinical study, however, several important pre-clinical experiments were not performed, so we still do not know how the acute biological effects of the Ultrashape device are related to ultimate clinical outcomes.

In the first two experiments, the authors characterize the energy delivery of the UltraShape probe in water, which is a standard method for characterizing ultrasound energy fields.  Brown shows that the device focuses the ultrasound energy in a volume that has a diameter of about 8mm, and a depth that ranges from about 5mm to about 25mm from the probe.  Brown shows that the energy density (power per cm2) at the probe-water interface is very small, as desired.  Further, the authors showed that the ultrasonic energy created air bubbles in the focal region, consistent with a non-thermal cavitation effect.  Quantitative measures of ultrasonic power density were performed at 0mm and 14mm depth, and showed an absence of “hot spots.”  An improvement to the study would have included power density measurements at 1.5-2mm (approximately the depth of the dermal-fat junction) and 25mm (to characterize the extent of the ultrasonic energy transmission).

In the third experiment, the UltraShape probe was characterized in a gel phantom intended to simulate the ultrasound transmission properties of skin and fat.  In this case the focal volume was 9mm in diameter (slightly less focused than in water) and extended about 18mm in depth (the distance from the surface was not reported, but appears to extend from about 4mm to 22mm from the probe according to the figure).  Again, bubbles were seen in the focal region in this model, consistent with a non-thermal cavitation effect. 

In the fourth experiment, porcine skin was treated and then immediately evaluated with both frozen sections and histologically stained sections.  Untreated control skin was also evaluated to ensure that results were not due to processing artifact.  Importantly, no effect on skin color or skin appearance was seen on the animals receiving this treatment, and histology showed that the dermis and epidermis appeared to be completely unaffected by the treatment.  The subcutaneous fat, however, showed evidence of tissue injury in both the frozen sections and the histology.  Histological staining for LDH activity using NTBC (elevated levels of LDH indicate tissue breakdown) demonstrated a layer of adipocyte cell breakdown extending from about 15mm to 25mm of tissue depth.  In the treated tissue, but not the control tissue, frozen sections and two other histological stains (H&E and Masson’s Trichrome) indicated a “defined area of tissue destruction” extending from approximately 8mm to 18mm of tissue depth.  This region showed clear disruption of fat cells, while connective tissue, blood vessels and nerves remained intact.  No evidence of any thermal damage was seen in any treated tissue, again “consistent with initial cavitation followed by the mechanical destruction of cells.”  The authors state that fourteen animals were treated in this study, and the results were “consistent over time” despite the use of “multiple devices, [and] multiple transducers [by] numerous users.”  No quantification of subject-to-subject variability was provided.  For example, the authors should have measured the zone of tissue damage in each animal, and presented the results as averages with 95% confidence intervals.

So far, the results are promising, with clear evidence of non-invasive damage to subcutaneous fat and no apparent impact to the dermis.  Unfortunately, the analysis stops there.  For example, it is clear from the presented images that not all fat cells in the treated region were disrupted, but the authors do not quantify the percentage of the treatment volume that was disrupted.  Further, the response of the animal to this treatment was not studied.  Biopsies of treated and control areas were not performed at meaningful time durations subsequent to treatment (such a 1 day, 1 week, 1 month and 3 months post-treatment).  Unlike the recent Zeltiq study, we have no idea how the skin and subcutaneous fat respond to these injuries.  Does inflammation occur?  While no changes to the histology of the dermis were seen immediately post-treatment, could an inflammatory response occur over time?  Are non-viable cells removed or replaced?  Does this treatment cause meaningful changes in fat thickness compared to control volumes over time, and if so, when do these changes occur?  Lastly, blood lipid profiles were not analyzed in this study.  We cannot know if release of lipids from the disrupted adipocytes has any systemic effect, either on blood lipids or the liver.

The authors state that these study “observations do not directly lead to predict clinical results,” and they recommend further clinical evaluation.  However, the real need is for further pre-clinical evaluation.  Perhaps this partly explains why this device, widely available in Europe and Canada, is not yet cleared by the FDA.

Review of Manstein D, et. al. Selective cryolysis: a novel method of non-invasive fat removal

February 9, 2009

Lasers Surg Med. 2008 Nov;40(9):595-604

Selective cryolysis: a novel method of non-invasive fat removal.

Manstein D, Laubach H, Watanabe K, Farinelli W, Zurakowski D, Anderson RR.

Department of Dermatology, Wellman Center for Photomedicine , Massachusetts General Hospital , Harvard Medical School , Boston , Massachusetts , USA .

Manstein et. al. present the first animal study results with prototype  Zeltiq devices for non-invasive cold-induced fat destruction.   Note that Manstein is the inventor of the technology and receives royalties from Zeltiq. This report provides critical insight into the device-tissue interaction, the rationale for device parameter selection, and the mechanism of tissue response to the procedure.

Non- invasive surface cooling lowers the temperature of epidermis, dermis and subcutaneous fat via thermal conduction.  Because fat cells are more easily damaged by cold temperatures than are skin cells, this approach attempts to cool the subcutaneous fat below its damage threshold, while keeping the epidermis and dermis above their dermal damage thresholds.  Because cold is delivered from the surface through the dermal layers to the fat, the challenge is to make the dermis cold enough (for long enough) to adequately cool the fat, while keeping the dermal layers from frostbite.

Three animal studies (female black yucatan pigs, age 2-3, ca. 100 lb.) are presented in this paper.  All treatments were performed with the animals under general anesthesia, so treatment pain (e.g. signs of distress) could not be evaluated.

In the first study, a lab prototype was applied to eleven locations (abdomen, flank, buttock) on one animal.  This prototype provided contact cooling of the skin surface to -7C, and attempted to apply sufficient pressure to inhibit blood flow in the skin (which would warm the subcutaneous fat and thus prevent fat cooling below the damage threshold).  Durations varied from 5 to 21 minutes.  This pig was observed for 3.5 months, and except for some slight hyperpigmentation, no apparent skin injury was seen.  The highest degree of fat loss was seen as an easily visible indentation in the skin corresponding to the shape of the applicator.  This occurred at a buttock location with a cooling duration of 10 minutes, and where dermal blood flow was felt to be well inhibited.  By histology, 40% of the total fat layer thickness was removed in this area.  This n=1 experiment demonstrated initial feasibility of this approach.

In the second study, two prototype Zeltiq devices were applied to a total of 60 locations on 4 animals, to test the effect of various device temperature settings and the need for blood-flow suppression.   The first device was a flat cold applicator that could be held against the skin surface (“flat” applicator) but would not inhibit blood flow.  The second device clamped a fold of skin between two cold plates (“fold” applicator), enabling compression of the skin fold, effective suppression of blood flow within the fold and an improved cooling geometry.  Ten control sites were treated with applicators set to skin temperature (20C).  At some treatment sites, thermocouples were used to measure in vivo tissue temperatures during the procedure, demonstrating that significantly colder fat temperatures were achieved with the “fold” applicator, even at the same temperature as the “flat” applicator.  In this study, no clinical or histological evidence of damage to the epidermis or dermis was found, thus demonstrating that it is possible to provide cooling to the fat without damaging the overlying skin layers.  By histology, fat damage was significantly greater at lower applicator temperatures, with the lowest temperature applicator (-7C) achieving the best results.  At 1 month post treatment, most of the “fold” applicator sites showed obvious visible skin indentation (up to 3mm reduction in fat thickness), while none of the “flat” applicator sites showed such indentations.  It is not known if 3mm reduction could be routinely obtained.

This study also provided data regarding the biological mechanism of fat destruction.  At one day post treatment, no damage was seen on histology at either control or treatment sites.  At two days, inflammation (clusters of neutrophils around the fat cells) was seen in the top 3-4 mm of the subcutaneous fat.  At 14 days, fat cell size was reduced, inflammation was more intense and occasional macrophages were observed.  At 30 days, fat cell size was further reduced, and multinucleated giant macrophage cells could be seen.  As mentioned above, no histological damage to overlying skin layers was seen.

The purpose of the third study, in six pigs, was to monitor blood lipids at six time points (1 hour, 1 day, 1 week, and 1, 2, and 3 months) following treatment of a very large portion (approximately 15%) of the body area. This treatment varied from prior studies in three ways.  First, the applicator was flat, had a more efficient cooling plate, and was weighted to apply 38mm Hg pressure to the skin (surface temperatures varied from -5C to -8C).  Second, ultrasound gel was applied to the skin beneath the applicator to enhance thermal conduction.   Third, a 1-minute vibrating massage was performed immediately after the cold exposure.   No significant changes in serum lipids associated with this treatment were seen, indicating the safety of the procedure despite the very large dose.  However, in this study, about 30% of the treatment sites suffered skin freezing, resulting in epidermal necrosis, transient hypopigmentation, but no scarring or ulceration.  It is unknown which of the three changes to the treatment above might have caused this freezing.

Together, these three studies showed that in pigs, it is possible to selectively cool fat below its damage threshold without damaging overlying skin.  While it is not surprising that lower applicator temperatures and effective blood flow suppression provide more cooling of fat and more effective fat destruction, it should be noted that these parameters also bring dermal temperatures closer to their damage thresholds.  The authors note that pig fat may be more sensitive to cold than human fat, because pigs have higher concentration of saturated fatty acids which may enable fat damage.

Because the approach appears to be operating close to the margin of skin damage, it may make sense to consider a study of multiple applications using a slightly lower cold dose (less likely to freeze overlying skin and slightly less damage to the fat).  Multiple applications of cold are likely to do additive damage to fat cells, while the overlying skin should be unharmed by each application.  The applications could be separated by just a few minutes, long enough for the treatment area to return to normal temperature, so that multiple applications could be applied in one treatment session.

If a 3mm fat thickness reduction could be routinely obtained, and the applicator was applied uniformly around the circumference of a body area, a circumference reduction of approximately a 2cm would be achieved.  These results would be considered clinically significant.  Of course, clinical techniques (e.g. layering) would need to be developed to provide cosmetically pleasing results.  No one wants a series of indentations in their skin.  Here again, multiple overlapping lower-dose applications may prove useful.

The need for 10-minute exposures may result in relatively long treatment times.  This would be increased if multiple applications of the device were needed in a single session.  The level of pain associated with this technique and the need for pain management techniques is also unknown.  While the prospect of holding a large piece of ice against the skin for 10 minutes may seem painful, simultaneous pressure on the skin is known to have analgesic effects.

While there are still many unknowns, this report provides critical insight into the device-tissue interaction, the rationale for device parameter selection, and the mechanism of tissue response to the procedure.  Aesthetic device users should demand analogous animal studies for every device that claims to have a novel tissue effect.  Subsequent to the performance of the studies in this paper, Zeltiq has carried out further device modifications and has begun two human clinical studies.