A Mechanomodulatory Device to Minimize Incisional Scar Formation

Abstract

Objective: To mechanically control the wound environment and prevent cutaneous scar formation.

Approach: We subjected various material substrates to biomechanical testing to investigate their ability to modulate skin behavior. Combinations of elastomeric materials, adhesives, and strain applicators were evaluated to develop topical stress-shielding devices. Noninvasive imaging modalities were utilized to characterize anatomic site-specific differences in skin biomechanical properties in humans. The devices were tested in a validated large animal model of hypertrophic scarring. Phase I within-patient controlled clinical trials were conducted to confirm their safety and efficacy in scar reduction in patients undergoing abdominoplasty surgery.

Results: Among the tested materials and device applicators, a polymer device was developed that effectively off-loaded high tension wounds and blocked pro-fibrotic pathways and excess scar formation in red Duroc swine. In humans, different anatomic sites exhibit unique biomechanical properties that may correlate with the propensity to form scars. In the clinical trial, utilization of this device significantly reduced incisional scar formation and improved scar appearance for up to 12 months compared with control incisions that underwent routine postoperative care.

Innovation: This is the first device that is able to precisely control the mechanical environment of incisional wounds and has been demonstrated in multiple clinical trials to significantly reduce scar formation after surgery.

Conclusion: Mechanomodulatory strategies to control the incisional wound environment can significantly reduce pathologic scarring and fibrosis after surgery.

Figures

Geoffrey C. Gurtner, MD, FACS

Figure 1.

Development of a hypertrophic-like scar model in red Duroc pigs. (A) Wounds of increasing dimensions were created and sutured closed to generate increasing levels of tension. Sutures were removed at postsurgery day 4, and wounds were followed for up to 8 weeks, resulting in varying degrees of gross and histological scar formation. (B) Calculated strains were significantly elevated with larger wound dimensions. *p<0.05. Figure reprinted with permission from Gurtner et al. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound

Figure 2.

Early-generation polymer device. Photographs of various applicators constructed during the development of the stress-shielding device. (A) A binder clip-based applicator. (B) A metal spring-loaded applicator. (C) A cam-driven applicator. (D–G) Various integrated foam stamper applicators. (H) A self-straining spring handle applicator. (I) A hinged self-release applicator. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound

Figure 3.

Device validation in a large animal model. Schematic of wound model (A–C), photographs (D–F), scar histology (G–I), and epithelial histology (J–L) of pig skin under different mechanical tension conditions. (A, D, G, J) Unwounded skin subjected to physiologic stresses. (B, E, H, K) Elevated stress incisions after closure of large excisional wounds. (C, F, I, L) The same elevated stress incision, but off-loaded with the stress-shielding device during repair. Note the recapitulation of unwounded epithelial architecture in stress-shielded wounds (J–L), suggesting that regenerative wound healing pathways may be activated. Figure reprinted with permission from Gurtner et al. Scale bars: (D–F) 5 mm; (G–I) 500 μm; (J–L) 50 μm. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound

Figure 4.

Biomechanical analyses of human skin behavior in vivo. (A, B) Strain analyses were conducted based on grid line displacement before (A) and after (B) device application. Red arrows indicate axis of device compression. (C) Digital image speckle correlation analysis was used to measure skin strains non-invasively. Red/white arrows indicate axis of device compression. (D) Tensile (red/orange color) and compressive (blue/purple color) skin strains were mapped after device application. (E) Measured strains and (F) calculated stresses on different anatomic sites. Data are means±standard deviations from three healthy adult men. Figure reprinted with permission from Wong et al. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound

Figure 5.

Phase I clinical trial in abdominal surgery patients. (A) Schematic of abdominoplasty surgery (i) involving the excision of skin and subcutaneous fat and surgical closure under high mechanical forces that predispose wounds to robust scar formation. Clinical study schematic (ii) demonstrates application of the stress-shielding polymer to one side of the incision, whereas the within-patient control side is left unshielded. (B) Photographs of paired abdominal incisions at 6–12 months postsurgery (paired rows). Note the significant scar elevation, widening, discoloration, and irregularity in unshielded control incisions (i, iii, v, vii, ix, xi, xiii, xv, xvii) compared with device stress-shielded treatment incisions (ii, iv, vi, viii, x, xii, xiv, xvi, xviii). (C) Quantification of expert and lay panel analyses using a visual analog scale (VAS), with lower scores indicating improved scar appearance. Data are means±standard errors of the mean. Scale bar is 1 cm. *p<0.01. Figure reprinted with permission from Gurtner et al. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound

Figure 6.

Development of current stress-shielding polymer device. (A) Blueprint schematic and (B) photograph of the polymer device loaded into the book-style strain applicator. (C) The polymer device has been developed in several sizes to accommodate various size wounds in different body regions. (D) Photograph of the polymer device after application to the lower abdomen. Images courtesy of Neodyne Biosciences, Inc. To see this illustration in color, the reader is referred to the web version of this article at www.liebertpub.com/wound