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Study Comparing Platform Wound Dressing, a Negative-Pressure Device without a Filler, with Three Conventional Negative-Pressure Wound Therapy Systems in the Treatment of Excisional and Incisional Wounds

Nuutila, Kristo M.Sc., Ph.D.; Broomhead, Michael M.B.A.; Proppe, Karl M.D.; Eriksson, Elof M.D., Ph.D.

Author Information
Plastic and Reconstructive Surgery: January 2021 - Volume 147 - Issue 1 - p 76-86
doi: 10.1097/PRS.0000000000007450
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Abstract

All commercially available negative-pressure wound therapy systems consist of a filler material (most commonly foam or gauze) that is placed on the wound. A thin, clear occlusive dressing is then used to seal the wound, and tubing connects the space under the membrane to an exudate-collecting canister and further to a precisely set negative pressure pump.1–4 In conventional clinical practice, a negative pressure of −80 to −125 mmHg is used, either continuous or intermittent, and the negative-pressure wound therapy dressing is changed every 48 to 72 hours.5,6

Negative-pressure wound therapy has proven to be an efficient and useful treatment modality, especially in the management of complex wounds.7,8 However, there are some challenges that should be addressed when using negative-pressure devices. The most common clinical problems are usually associated with the filler material of the dressings. During negative-pressure wound therapy, new tissue may grow into the filler material and cause pain when the dressing is removed.9–11 It has been shown that particularly foam can adhere to the wound bed firmly, and force is often required to remove it, causing not only pain but bleeding and disruption of the granulation tissue.12,13 Furthermore, tissue ingrowth into the filler material may lead to fragmentation of the foam being incorporated in the wound bed, possibly initiating a foreign body reaction that might impact the healing process.11 Another concern is that the filler material may become colonized with bacteria and increase the number of pathogens in the wound.14–16 Also, from a wound monitoring point of view, an opaque foam or gauze prevents inspection of the wound without a dressing change.

Recently, we introduced the Platform Wound Dressing (Applied Tissue Technologies LLC, Hingham, Mass.) with negative pressure, a negative-pressure wound therapy system without foam or gauze. The Platform Wound Dressing is a transparent, single-component dressing that consists of an impermeable polyurethane membrane. It has a permeable adhesive base that is attached to the perimeter of the wound, enabling fast adhesive bandage–like application. The suction pump is connected to the underside of the membrane with tubing. The inner surface of the Platform Wound Dressing contains pyramid-like structures protruding toward the wound. Once the suction pump is turned on and the desired negative pressure is achieved, the embossed membrane is pulled into contact with the entire surface area of the wound and the space between the pyramids provides channels for even distribution of negative pressure and for exudate removal (Fig. 1). Folds in the membrane provide secondary channels for negative pressure and fluid removal. As the Platform Wound Dressing system does not contain a filler material and is impermeable, it can operate efficiently at a lower negative pressure than the conventional negative-pressure wound therapy systems with a foam or gauze.17,18 In our recent publication, we validated the Platform Wound Dressing’s safety and efficacy in the treatment of porcine full-thickness wounds. The results showed that the Platform Wound Dressing promoted wound healing better compared to wounds that did not receive negative-pressure wound therapy and that the Platform Wound Dressing effectively reduced the number of bacteria in the wound bed. The study also demonstrated that the Platform Wound Dressing could promote wound healing with a negative pressure of −50 mmHg and with a negative pressure of −80 mmHg.17 The same Platform Wound Dressing can be also used as a delivery platform for topical treatments and tissue engineering approaches, as has been described in our previous communications.19–21 The purpose of the present study was to compare the Platform Wound Dressing to the most common commercially available negative-pressure wound therapy systems in the treatment of porcine full-thickness open excisions, open incisions, and closed incisions.

Fig. 1.
Fig. 1.:
The Platform Wound Dressing (PWD) is a single-component, impermeable, polyurethane dressing for negative-pressure wound therapy. In the Platform Wound Dressing, no filler material is needed and it can be designed to enclose any size and type of a wound. When the negative-pressure pump is activated, the embossed membrane of the Platform Wound Dressing is pulled into direct contact with all geometries of the wound. The space created between the embossments provides primary channels for air and fluid, and folds in the membrane to create secondary channels that provide an even distribution of negative pressure across the wound. This allows wound care professionals to administer negative pressure to the wound without a foam or gauze. It also allows direct inspection of the wound without removing the dressing. The Platform Wound Dressing does not need to fit the wound borders precisely. If it covers normal periwound skin, it has no negative effect and probably a positive effect. Periwound dermatitis will heal during treatment.

Materials and Methods

Negative-Pressure Wound Therapy Systems

Four different negative-pressure wound therapy systems were used in the study: (1) Platform Wound Dressing with Invia Motion Negative-Pressure Wound Therapy pump (Medela, Baar, Switzerland), (2) PREVENA Incision Management System (Acelity, San Antonio, Texas), (3) V.A.C.VIA Therapy System (Acelity), and (4) PICO Negative Pressure Wound Therapy Kit (Smith & Nephew, London, United Kingdom) (Table 1). The negative-pressure wound therapy systems were used exactly as recommended by the manufacturer; therefore, the same negative pressure was not used in all the devices.

Table 1. - Wound Types, Devices, Pressure Settings, and Number of Wounds
Wound Type and Treatment System Pressure Setting (mmHg) No. of Wounds
Excisional wound (2.5 × 2.5 cm)
 PWD with Invia Motion NPWT  pump Continuous, −80 8
 PICO NPWT Kit Continuous, −80 8
 V.A.C.VIA Therapy System Continuous, −125 8
Open incision (5 cm)
 PWD with Invia Motion  NPWT pump Continuous, −80 8
 PICO NPWT Kit Continuous, −80 8
 PREVENA Incision  Management System Continuous, −125 8
Closed incision (5 cm)
 PWD with Invia Motion  NPWT pump Continuous, −80 8
 PICO NPWT Kit Continuous, −80 8
 PREVENA Incision  Management System Continuous, −125 8
PWD, Platform Wound Dressing; NPWT, Negative Pressure Wound Therapy.

Animals, Anesthesia, and Analgesia

All animal procedures were performed under good laboratory practice, with the presence of an independent observer at Toxikon Corp. (Bedford, Mass.). The study protocol was approved by Toxikon’s Institutional Animal Care and Use Committee, and conformed to federal animal laws and regulations. Eight Yorkshire pigs (Animal Biotech Industries, Danboro, Pa.) weighing between 70 and 80 kg were used in the study. Anesthesia was induced with intramuscular administration of 3.3 mg/kg ketamine, 1.1 mg/kg acepromazine, 2.2 mg/kg xylazine, and 0.02 mg/kg atropine. General anesthesia was maintained with 0 to 5% isoflurane and oxygen. After the procedure, a transdermal patch releasing 2 to 3 μg/kg fentanyl per hour for 72 hours (Duralgesic; Janssen Pharmaceuticals, Beerse, Belgium) was given for pain management during surgical recovery, and buprenorphine 0.01 to 0.03 mg/kg was administered intramuscularly immediately at the end of the procedure.

Porcine Wound Model

Up to 12 wounds (2.5 × 2.5-cm full-thickness excisions or 5-cm-long full-thickness incisions) were created using a scalpel on the dorsum of each pig. Half of the incisions had an excision of a 1-cm-wide strip of skin (to keep them consistently open along the incision) and left open and half of them were closed by suturing. After wound creation, the pigs with excisional wounds were assigned randomly to receive continuous negative pressure for 9 days with the Platform Wound Dressing plus Invia Motion pump at −80 mmHg, with the V.A.C.VIA at −125 mmHg, or with the PICO at −80 mmHg. Open and closed incisions were assigned to receive negative pressure for 9 days with the Platform Wound Dressing plus Invia Motion pump at −80 mmHg, with the PREVENA at −125 mmHg, or with the PICO at −80 mmHg (Table 1). Next, custom-made jackets (Lomir Biomedical, Inc., Malone, N.Y.) were placed on each pig to protect the wounds with negative-pressure dressings and to carry the negative-pressure pumps, allowing continuous administration of negative-pressure wound therapy. The devices and the wounds were observed daily and dressing changes were performed on days 3 and 6 postoperatively. On postoperative day 9, the animals were euthanized and the wounds were excised for histologic evaluation (Fig. 2 and Table 1).

Fig. 2.
Fig. 2.:
Animal study design.

Computerized Morphometric Wound Analysis

To measure wound area reduction and wound depth on day 9, wound images were taken on days 3 and 6 and on day 9 before the animals were euthanized using a specialized Silhouette Star camera (Aranz Medical Ltd., Christchurch, New Zealand), and numeric measurements were derived from Silhouette Connect software (Aranz Medical) according to the manufacturer’s instructions.

Histopathologic Evaluation

After the animals were euthanized, the wounds were excised and processed for histologic evaluation. The hematoxylin and eosin– and Masson trichrome–stained slides were analyzed for dimensions of viable granulation tissue, inflammatory infiltrate, hemorrhage, and amount of early and mature collagen using the following scale: 1 = marked, 2 = moderate, 3 = minimal, and 4 = absent. In addition, the slides were analyzed for binding pattern of collagen fibrils (1 = reticular, 2 = mixed, and 3 = fascicle) and collagen fiber orientation (1 = vertical, 2 = mixed, and 3 = horizontal) in the granulation tissue. All of the analyses were performed by an independent veterinary pathologist (Mass Histology Service, Worcester, Mass.) in a blinded manner. In addition, the amount of granulation tissue and the reepithelialization percentage were measured using the hematoxylin and eosin– and the Masson trichrome–stained slides.

Immunohistologic Evaluation

The excisional wound sections were further immunostained for von Willebrand factor, Ki67, α-smooth muscle actin (Agilent Technologies, Santa Clara, Calif.), and CD3 (Ventana Medical Systems, Oro Valley, Ariz.), and the amount of positive staining was quantified in a blinded manner using a light microscope. Morphometric analyses were carried out using ImageJ (National Institutes of Health, Bethesda, Md.).

Statistical Analyses

Statistical comparisons were performed using GraphPad Prism 6.0 (Graph Pad Software, Inc., La Jolla, Calif.). Data are presented as mean ± SEM. Comparison of treatments was performed using the t test, and values of p < 0.05 were considered statistically significant. The number in each treatment group was eight.

RESULTS

Computerized Morphometric Wound Analysis

Excisions

Reduction of the wound area from the original wound area at day 0 was measured at day 9. All of the wounds demonstrated good healing and had decreased in size by day 9 after wounding. Figure 3, left, displays representative macroscopic images of the wounds at day 9. The wound area reduction in the Platform Wound Dressing–, PICO-, and V.A.C.VIA-treated wounds was 41.4 ± 5.3, 25.1 ± 8.1, and 18.4 ± 7.0 percent, respectively. The difference between the Platform Wound Dressing– and V.A.C.VIA-treated wounds was statistically significant (p = 0.0207) (Fig. 3, left). The measurements also showed that, in the excisional wounds, the maximum wound depth at day 9 after wounding in the Platform Wound Dressing–, PICO-, and V.A.C.VIA-treated wounds was 0.4 ± 0.2, 1.5 ± 0.4, and 1.8 ± 0.5 mm, respectively. The difference between the Platform Wound Dressing and PICO (p = 0.0403) and the difference between the Platform Wound Dressing and V.A.C.VIA (p = 0.014) were statistically significant (Fig. 3, above, center).

Fig. 3.
Fig. 3.:
(Left) Representative macroscopic images of the wounds on day 9 after wounding. (Above, center) The wound area reduction from the original wound area in the Platform Wound Dressing (PWD)–, PICO-, and V.A.C.VIA -treated wounds was 41.4 ± 5.3, 25.1 ± 8.1, and 18.4 ± 7.0 percent, respectively. The difference between the Platform Wound Dressing and V.A.C.VIA was statistically significant (p = 0.0207). (Above, right) The maximum wound depth on day 9 after wounding in the Platform Wound Dressing–, PICO-, and V.A.C.VIA-treated wounds was 0.4 ± 0.2, 1.5 ± 0.4, and 1.8 ± 0.5 mm, respectively. The difference between the Platform Wound Dressing and PICO (p = 0.0403) and the difference between the Platform Wound Dressing and V.A.C.VIA (p = 0.014) were statistically significant. (Below, center) The wound area reduction from the original wound area in the Platform Wound Dressing–, PICO-, and PREVENA-treated wounds was 30.4 ± 7.6, 53.2 ± 11.1, and 24.4 ± 8.6 percent, respectively. (Below, right) The maximum wound depth in the Platform Wound Dressing–, PICO-, and PREVENA-treated wounds was 0.6 ± 0.5, 1.0 ± 0.8, and 1.1 ± 0.5 mm, respectively. No statistically significant differences between the groups were observed. NPWT, Negative Pressure Wound Therapy; IHC, immunohistochemistry.

Incisions

In the open incisions, the wound area reduction in the Platform Wound Dressing–, PICO-, and PREVENA-treated wounds was 30.4 ± 7.6, 53.2 ± 11.1, and 24.4 ± 8.6 percent, respectively (Fig. 3, left, and above, right). The maximum wound depth in the Platform Wound Dressing–, PICO-, and PREVENA-treated wounds was 0.6 ± 0.5, 1.00 ± 0.8, and 1.1 ± 0.5 mm, respectively. No statistically significant differences between the groups were observed (Fig. 3, below, right).

Histopathologic Evaluation

Excisions

The hematoxylin and eosin–stained slides demonstrated that the Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds were 16.9 ± 2.7, 14.9 ± 2.8, and 16.6 ± 2.9 percent reepithelialized, respectively (Fig. 4, above, and center, left). Bleeding was almost absent in all wounds, and the Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds were scored 3.4 ± 0.2, 3.5 ± 0.3, and 3.5 ± 0.3 for hemorrhage. No statistically significant differences were observed.

Fig. 4.
Fig. 4.:
(Above) Representative histologic images of the wounds on day 9 after wounding. (Center, left) By day 9, the Platform Wound Dressing (PWD)–, V.A.C.VIA-, and PICO-treated excisional wounds were 17.0 ± 2.7, 14.9 ± 2.8, and 16.6 ± 2.9 percent reepithelialized, respectively. (Center, right) The Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wound beds contained 92.3 ± 1.8, 91.6 ± 2.1, and 95.1 ± 0.6 percent granulation tissue, respectively. (Below, left) The Platform Wound Dressing–, PREVENA-, and PICO-treated wounds were 24.7 ± 4.0, 50.4 ± 10.0, and 35.5 ± 4.2 percent reepithelialized, respectively. The difference between the Platform Wound Dressing– and PREVENA-treated wounds was statistically significant (p = 0.0320). (Below, right) The Platform Wound Dressing–, PREVENA-, and PICO-treated wounds had 83.4 ± 3.7, 87.3 ± 2.4, and 88.9 ± 2.4 percent granulation tissue, respectively.

The amount of granulation tissue in the wound bed was quantified and the results showed that in the Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds, the amount of granulation tissue from the wound bed was 92.3 ± 1.8, 91.6 ± 2.1, and 95.1 ± 0.6 percent, respectively (Fig. 4, center, right). Furthermore, collagen content of the granulation tissue was analyzed. The analyses showed that pattern of collagen, collagen fiber orientation, and amount of both early and mature collagen were consistent in all the excisions regardless of the treatment. In all of the wounds, the pattern of collagen fibrils was mixed, with reticular and fascicle. The orientation of collagen fibers was mixed, with horizontal and vertical. In addition, on a scale from absent to marked, the amount of both early and mature collagen was moderate in all wounds (Table 2). Histologic examination also revealed that inflammation was present in all of the wounds. No differences between different treatments were observed (Table 2).

Table 2. - Analysis of Slides for Dimensions of Viable Granulation Tissue, Inflammatory Infiltrate, Hemorrhage, and Amount of Early and Mature Collagen*
Granulation Tissue Hemorrhage Inflammation Collagen Orientation Collagen Pattern Early Collagen Mature Collagen
Excisions
 PWD with Invia Motion pump 1.0 ± 0.0 3.4 ± 0.2 1.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 V.A.C.VIA Therapy System 1.0 ± 0.0 3.5 ± 0.3 1.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 PICO NPWT Kit 1.0 ± 0.0 3.5 ± 0.3 1.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
Open incisions
 PWD with Invia Motion pump 1.0 ± 0.0 3.3 ± 0.3 1.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 PREVENA Incision Management  System 1.3 ± 0.2 4.0 ± 0.0 2.4 ± 0.2 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 PICO NPWT Kit 1.0 ± 0.0 3.6 ± 0.4 1.3 ± 0.2 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
Closed incisions
 PWD with Invia Motion pump 3.0 ± 0.0 4.0 ± 0.0 3.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 PREVENA Incision Management  System 3.0 ± 0.0 4.0 ± 0.0 3.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0
 PICO NPWT Kit 3.0 ± 0.0 3.8 ± 0.3 3.0 ± 0.0 2.0 ± 0.0 2.0 ± 0.0 2.8 ± 0.2 1.3 ± 0.2
PWD, Platform Wound Dressing; NPWT, Negative Pressure Wound Therapy.
*Slides were analyzed using the following scale: 1 = marked, 2 = moderate, 3 = minimal, and 4 = absent. In addition, the slides were analyzed for binding pattern of collagen fibrils (1 = reticular, 2 = mixed, and 3 = fascicle) and collagen fiber orientation (1 = vertical, 2 = mixed, and 3 = horizontal) in the granulation tissue. All analyses were performed by an independent veterinary pathologist in a blinded manner.

Open Incisions

Hematoxylin and eosin–stained slides exhibited that the Platform Wound Dressing–, PREVENA-, and PICO-treated wounds were 24.7 ± 3.9, 50.4 ± 10.0, and 35.5 ± 4.2 percent reepithelialized, respectively (Fig. 4, above, and center, right). The difference between the Platform Wound Dressing– and PREVENA-treated wounds was statistically significant (p = 0.0320). Hemorrhage was minimal to absent in the wounds treated with Platform Wound Dressing (3.3 ± 0.3), PREVENA (4 ± 0.00), and PICO (3.6 ± 0.4) (Table 2). No statistically significant differences between the treatment groups were observed.

The amount of granulation tissue in the open incisions was measured and the results showed that the wounds in the Platform Wound Dressing–, PREVENA-, and PICO-treated wounds had 83.4 ± 3.7, 87.3 ± 2.4, and 88.9 ± 2.4 percent granulation tissue, respectively (Fig. 4, below, right). No statistically significant differences were seen between the treatment groups. As in excisional wounds, the results showed that the pattern of collagen and the collagen fiber orientation was mixed in all wounds and that the amount of both early and mature collagen was moderate regardless of the treatment (Table 2). Inflammation was present in all wounds. However, there was statistically significantly less inflammation in the PREVENA-treated open incisions in comparison to the wounds treated with the Platform Wound Dressing (p < 0.0001) and PICO (p < 0.0172) (Table 2).

Closed Incisions

All of the closed incisions were fully reepithelialized and demonstrated absent hemorrhage at day 9 after wounding (Fig. 3, left, and Fig. 4, above). Also, the amount of granulation tissue and inflammation was minimal, and no statistically significant differences were observed between the treatment groups. The pattern of collagen was a mix of reticular and fascicle fibrils, and the collagen fiber orientation was a mix of vertical and horizontal fibers in all treatment groups. The amount of early and mature collagen was moderate in the Platform Wound Dressing and PREVENA groups, whereas the results demonstrated that the PICO-treated wounds contained more early collagen (2.8 ± 0.2) than mature collagen (1.3 ± 0.2) (Table 2).

Immunohistologic Evaluation

The results showed that the Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds contained 68.8 ± 5.1, 52.5 ± 5.8, and 66.1 ± 2.9 percent α-smooth muscle actin–positive staining, respectively, demonstrating that the fibroblasts in the granulation tissue are differentiating into myofibroblasts. No statistically significant differences were seen (Fig. 5, left, and above, center). The presence of proliferating keratinocytes in the wounds was studied by immunostaining the slides with Ki67, and the results showed that the Platform Wound Dressing–,V.A.C.VIA-, and PICO-treated wounds contained 0.4 ± 0.1, 0.3 ± 0.1, and 0.2 ± 0.1 percent Ki67-positive staining, respectively. No statistically significant differences were seen between the treatment groups (Fig. 5, left, and above, right). The degree of active inflammation was studied by quantifying the amount of CD3+ T cells in the excisional wounds. The results showed that PICO-treated wounds had statistically significantly less CD3+ staining (0.1 ± 0.0 percent of the wound bed) in comparison with the wounds treated with the Platform Wound Dressing (0.4 ± 0.0 percent of the wound bed; p = 0.0230) and V.A.C.VIA (0.5 ± 0.2 percent of the wound bed; p = 0.0117) (Fig. 5, left, and below, center). Neovascularization of the dermis was studied by immunostaining the wounds with von Willebrand factor antibody. The results showed that at day 9 after wounding, the Platform Wound Dressing–, V.A.C.VIA-, and the PICO-treated wounds contained 8.1 ± 0.5, 5.5 ± 1.0, and 6.1 ± 1.4 percent von Willebrand factor–positive staining, respectively. The difference between the Platform Wound Dressing and the V.A.C.VIA was statistically significant (p = 0.0256) (Fig. 5, left, and below, right).

Fig. 5.
Fig. 5.:
(Left) Representative immunohistochemistry pictures of the wounds on day 9 after wounding. (Above, center) The results showed that showed that the Platform Wound Dressing (PWD)–, V.A.C.VIA-, and PICO-treated wounds contained 68.8 ± 5.1, 52.5 ± 5.8, and 66.1 ± 2.9 percent α-smooth muscle actin–positive staining, respectively. (Above, right) The Platform Wound Dressing–, the V.A.C.VIA-, and PICO-treated wounds contained 0.4 ± 0.1, 0.3 ± 0.1, and 0.2 ± 0.1 percent Ki67-positive staining, respectively. No statistically significant differences were seen between the treatment groups. (Below, center) The Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds contained 0.4 ± 0.1, 0.5 ± 0.2, and 0.1 ± 0.0 percent CD3+ staining, respectively. The PICO-treated wounds had statistically significantly less CD3+ staining than the wounds treated with the Platform Wound Dressing (p = 0.0230) and V.A.C.VIA (p = 0.0117). (Below, right) The Platform Wound Dressing–, V.A.C.VIA-, and PICO-treated wounds contained 8.1 ± 0.5, 5.5 ± 1.0, and 6.1 ± 1.4 percent von Willebrand factor–positive staining, respectively. The difference between the Platform Wound Dressing and the V.A.C.VIA was statistically significant (p = 0.0256). vwf, von Willebrand factor; α-SMA, α-smooth muscle actin.

DISCUSSION

The purpose of this study was to compare the Platform Wound Dressing, a negative-pressure wound therapy system without a filler material, to the most common foam- and gauze-based negative-pressure wound therapy systems in the treatment of porcine full-thickness excisions and incisions. We elected to use individual dressings, canisters, and pumps for each wound. This makes the experiment labor intensive and costly, but the results in these dorsal wounds in the pig are very consistent and reproducible. The effect of the different negative-pressure systems on wound healing was comprehensively evaluated using macroscopic and microscopic methods. Each negative-pressure wound therapy system was used precisely as recommended by the manufacturer. For this translational study, this approach appeared more relevant than using the same negative pressure for each device, which would have been scientifically more satisfying but would have reduced the ability to directly compare the devices. Morphometric analysis showed that all negative-pressure wound therapy systems used in the study reduced the wound size and depth efficiently. In the treatment of open incisions, no differences in the reduction of the wound size or in the maximum wound depth was seen between the Platform Wound Dressing and the foam- or gauze-based treatment systems. However, it was shown that the Platform Wound Dressing–treated excisional wounds promoted wound healing more efficiently than the foam-based V.A.C.VIA and the gauze-based PICO, in terms of reduction of wound area and depth (Fig. 3). This difference may be because the V.A.C.VIA’s foam and the PICO’s gauze will become hard when subjected to negative pressure, which may physically limit wound area reduction. The PREVENA had more reepithelialization in open incisions; however, in excisional wounds, there was no difference between the three negative-pressure wound therapy systems. In previous experiments, over a longer duration, with the Platform Wound Dressing but without negative pressure, we have seen evidence that the polyurethane membrane appears to serve as a guide for the advancing epithelium.22,23 No wounds that did not receive negative-pressure wound therapy were included in this study. However, in our two previous publications, we have compared the Platform Wound Dressing with negative-pressure–treated wounds to control wounds that did not receive negative-pressure wound therapy but instead were treated topically with a common antimicrobial cream. Our results showed that in comparison to control wounds, the Platform Wound Dressing treatment reduced wound area, depth, and volume statistically significantly. In addition, it was demonstrated that there was more granulation tissue and less necrotic tissue and inflammation in the wounds that received negative-pressure wound therapy. The same studies also showed that the Platform Wound Dressing with negative pressure is effective at reducing bacteria in the wounds.17,18

One of the most important effects of negative-pressure wound therapy is the promotion of granulation tissue formation, which is an essential part of the wound healing process.24 We studied and compared the formation and the characteristics of the newly formed granulation tissue after administration of negative-pressure wound therapy. We chose day 9 as an endpoint because, at that point, the granulation tissue had reached the level of the surface in the excisional wounds, which were approximately 9 mm deep at the start of the study. In a clinical situation, at this point, a granulating wound would be covered with a skin graft or flap. It has been shown that by stimulating the wound bed, negative pressure promotes neovascularization and accelerates granulation tissue formation.25 In the present study, neovascularization was studied by immunostaining the excisional wounds with von Willebrand factor, which is a common marker for endothelial cells.26 The results showed that the Platform Wound Dressing–treated excisions contained more von Willebrand factor–positive staining than the foam-based V.A.C.VIA system (Fig. 5, below, right). The amount of granulation tissue in the wounds was also measured and, in general, no differences were seen between the different treatment groups, demonstrating that the negative-pressure wound therapy had promoted the formation of granulation tissue regardless of the filler material or the lack of it (Fig. 4). Granulation tissue consists of a three-dimensional extracellular matrix that provides a structural network for cells to proliferate, migrate, and differentiate. A variety of cell types can be found in the granulation tissue, with fibroblasts being the most dominant.27,28 During wound healing, fibroblasts differentiate into myofibroblasts that help close the injured area by contraction.29,30 Our results showed that all of the excisions, regardless of the negative-pressure wound therapy device, contained abundantly α-smooth muscle actin–positive staining indicating that, in all wounds, fibroblasts are proficiently differentiating from fibroblasts into myofibroblasts (Fig. 5, above, center).

Besides accelerating tissue regeneration, negative-pressure wound therapy also promotes wound healing by removing microbes and infiltrating leukocytes containing fluid from the wound.31,32 The inflammatory reaction in the wound after negative-pressure wound therapy with the different systems was studied using both histology and immunohistochemistry. Histopathologic evaluations showed no differences between the treatment systems in the excisions and closed incisions, whereas in the open incisions, the foam-based PREVENA-treated wounds demonstrated less inflammation than the Platform Wound Dressing– and the PICO-treated wounds. The inflammation was further studied by immunostaining the excisional wounds with CD3 antibody, which is a marker for T cells.33 The results showed no difference between the Platform Wound Dressing and the foam-based V.A.C.VIA, whereas the wounds treated with the gauze-based PICO contained less CD3+ staining (Fig. 5, below, center).

CONCLUSIONS

The Platform Wound Dressing is a negative-pressure wound therapy system without a foam or gauze. Currently, the Platform Wound Dressing has been cleared through the U.S. Food and Drug Administration 510k pathway as a class II device and is indicated in patients who would benefit from negative-pressure wound therapy. The results demonstrated that the devices—with foam, with gauze, or without either—and just an embossed membrane performed equally in general. There were a few statistically significant differences in some parameters, but these may not amount to a difference in clinical effectiveness. Therefore, the results suggest that the current devices including foam or gauze can be replaced with a device without a filler, containing an embossed membrane to achieve similar clinical results.

DISCLAIMER

The views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the Army position, policy, or decision unless so designated by other documentation.

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