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Mechanisms of Action of External Volume Expansion Devices

Swanson, Eric M.D.

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Plastic and Reconstructive Surgery: March 2014 - Volume 133 - Issue 3 - p 425e-426e
doi: 10.1097/01.prs.0000438452.52851.c3
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Lancerotto et al.1 in their experimental study conclude that “epidermal and dermal cell proliferation and vascular density were significantly increased” only 2 days after a 2-hour external skin expansion in mice. The authors do not attempt to reconcile this finding with well-documented wound healing physiology.2,3 Angiogenesis and fibroplasia take place during the proliferative phase (4 to 14 days) of wound healing.2 Monocytes must first transform into macrophages before they can release growth factors that attract fibroblasts and initiate angiogenesis, a process that requires 48 to 96 hours.2 Once they arrive, fibroblasts start forming the collagen matrix that is needed for neovascularization.2,3 Consequently, new tissue and formed blood vessels cannot develop within 48 hours. Only inflammatory cells, the “first responders,” can account for cellular hyperplasia during the first 2 days. Moreover, hypoxia, documented in this study,1 impedes collagen production and angiogenesis.3

Dr. Orgill’s group published a study in mice4 with a 28-day follow-up period and concluded that new adipose tissue was created in the hypodermis. However, these investigators also conceded that recruitment of mouse skin, which is looser and more mobile than human skin,1,4 into the expander could account for some of the increased tissue thickness. This important confounder is not mentioned in the present study.1 The photograph and magnetic resonance scan in the authors’ previous study demonstrate this tissue recruitment, with bunching of tension-free redundant skin within the expander.4 Because of its tiny base, only 1 cm in diameter1,4 (the size of the device relative to the mouse is enlarged in an artist’s illustration4), it is easy to double the tissue volume within the expander, which is not hemispherical but rather thimble-shaped, permitting a volume of 1 cm3 of tissue to be drawn in. A similar tissue recruitment, on a percentage basis, would be unlikely in women wearing much larger, lower-profile devices. Notably, the mice in the previous study were expanded constantly for 28 days.4 In women, the expander is worn for 6 to 10 hours each day.1,4–6 Whether any benefits from tissue stretching are lost during these daily relaxation periods is unknown.

Because subcutaneous fat is pulled into the device with the skin, it is not surprising that the tissue thickness would increase simply from bunching of tissue. The fact that adipocyte counts4 rise proportionately with subcutaneous thickness suggests that there is no production of new fat cells.

The cellular proliferation rate reportedly increased 1.4-fold in the epidermis and 1.7-fold in the deep dermis/hypodermis. At 2 days after stimulus, there is insufficient time for this finding to represent new tissue growth, as discussed above. The fact that these ratios were only slightly higher (1.9-fold and 2.0-fold) after another 28 days of expansion4 casts doubt on whether these counts truly signal the formation of new tissue.

The authors provide evidence of edema, not adipogenesis. They reference studies of chronic lymphedema in which lymphatic fluid stasis is believed to cause abnormal fat deposition.7 Tissue expansion bears little physiological resemblance to chronic lymphedema; it does not create a barrier to lymphatic drainage, and the authors report no evidence of venous stasis.1

Adams8 reports, “the track record of the BRAVA device has not been good” and its claims “were never realized by those not associated with the product.” Clearly, if the device were effective, there would be no need for fat grafting to enlarge breasts. More recently, the same device has been advocated to improve results after breast fat grafting. Despite recent publications,5,6 no published study compares the results of fat grafting in women treated with and without this device. Khouri et al.5 compared their results to pooled data from six other published studies, which is of limited usefulness because of differences in fat harvesting and preparation techniques and measuring devices. The promoted advantages of this method remain largely based on first principles. Khouri et al. liken the process to preparation of soil before planting seeds.5

The creation of new breast parenchyma5 or adipose tissue (as opposed to skin) by intermittently stretching the breasts is an extraordinary claim and one that should not be accepted by practitioners too easily. Our reaction as evidence-based clinicians should be, “let me see a prospective controlled study with measurements in consecutive patients.” It is entirely possible that similar results might be achieved with fat injection and no preexpansion. In fact, a finding of no hyperplastic response in these tissues (particularly breast) may be a more favorable one from an oncologic standpoint. Financial conflicts are relevant.1,5 Investigators are not immune to the effects of commercial bias, particularly when a manufacturer provides funding.1

Magnetic resonance imaging is impractical for studying large numbers of patients because of its expense and noncompliance.6 Breast preexpansion may be best investigated using a level 2 study design comparing (1) women who are willing to undergo preexpansion with (2) women who are not interested in this pretreatment. Consecutive patients with a high inclusion rate are required. Standardized measurements need to be quick and easy9 to ensure patient cooperation.

As always, our first responsibility is to our patients. We should avoid overstating any purported benefits (i.e., the creation of new space and tissue) of an extremely onerous8 and costly pretreatment. Most patients’ concerns about the safety of breast implants may be assuaged by a candid discussion of the pros and cons. Although breast implants are sometimes (perhaps negatively, but accurately) called a lifetime device,5 they also consistently provide a high level of patient satisfaction and an improved quality of life10 that may also last a lifetime. No prospective outcome study of consecutive patients is available yet to support fat injection. Published photographs show results that fall short of what can be achieved using breast implants.8 Of course, saline-filled implants are an option for women who are concerned about silicone gel. Very few properly informed women will choose fat injection, with or without preexpansion, if implants are a feasible alternative.


The author has no financial interest to declare in relation to the content of this communiation. There was no outside funding for this study.

Eric Swanson, M.D.

Swanson Center

11413 Ash Street

Leawood, Kans. 66211

[email protected]


1. Lancerotto L, Chin MS, Freniere B, et al. Mechanisms of action of external volume expansion devices. Plast Reconstr Surg. 2013;132:569–578
2. Broughton G, Janis JE, Attinger CE. The basic science of wound healing. Plast Reconstr Surg. 2006;117(Suppl):12S–34S
3. Ueno C, Hunt TK, Hopf HW. Using physiology to improve surgical wound outcomes. Plast Reconstr Surg. 2006;117(7 Suppl):59S–71S
4. Heit YI, Lancerotto L, Mesteri I, et al. External volume expansion increases subcutaneous thickness, cell proliferation, and vascular remodeling in a murine model. Plast Reconstr Surg. 2012;130:541–547
5. Khouri RK, Eisenmann-Klein M, Cardoso E, et al. Brava and autologous fat transfer is a safe and effective breast augmentation alternative: Results of a 6-year, 81-patient, prospective multicenter study. Plast Reconstr Surg. 2012;129:1173–1187
6. Del Vecchio DA, Bucky LP. Breast augmentation using preexpansion and autologous fat transplantation: A clinical radiographic study. Plast Reconstr Surg. 2011;127:2441–2450
7. Aschen S, Zampell JC, Elhadad S, Weitman E, De Brot M, Mehrara BJ. Regulation of adipogenesis by lymphatic fluid stasis: Part II. Expression of adipose differentiation genes. Plast Reconstr Surg. 2012;129:838–847
8. Adams WP Jr. Discussion: Breast augmentation using preexpansion and autologous fat transplantation: A clinical radiographic study. Plast Reconstr Surg. 2011;127:2453–2454
9. Swanson E. A measurement system for evaluation of shape changes and proportions after cosmetic breast surgery. Plast Reconstr Surg. 2012;129:982–992; discussion 993
10. Swanson E. Prospective outcome study of 225 cases of breast augmentation. Plast Reconstr Surg. 2013;131:1158–1166; discussion 1167–1168


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