Use of Bacteria- and Fungus-Binding Mesh in Negative Pressure Wound Therapy Provides Significant Granulation Tissue Without Tissue Ingrowth

Malin Malmsjö, MD, PhD; Sandra Lindstedt, MD, PhD; Richard Ingemansson, MD, PhD; Lotta Gustafsson, MD, PhD

Disclosures

ePlasty. 2014;14 

In This Article

Abstract and Introduction

Abstract

Objective: Bacteria- and fungus-binding mesh traps and inactivates bacteria and fungus, which makes it interesting, alternative, and wound filler for negative pressure wound therapy (NPWT). The aim of this study was to compare pathogen-binding mesh, black foam, and gauze in NPWT with regard to granulation tissue formation and ingrowth of wound bed tissue in the wound filler.

Methods: Wounds on the backs of 8 pigs underwent 72 hours of NPWT using pathogen-binding mesh, foam, or gauze. Microdeformation of the wound bed and granulation tissue formation and the force required to remove the wound fillers was studied.

Results: Pathogen-binding mesh produced more granulation tissue, leukocyte infiltration, and tissue disorganization in the wound bed than gauze, but less than foam. All 3 wound fillers caused microdeformation of the wound bed surface. Little force was required to remove pathogen-binding mesh and gauze, while considerable force was needed to remove foam. This is the result of tissue growth into the foam, but not into pathogen-binding mesh or gauze, as shown by examination of biopsy sections from the wound bed.

Conclusions: This study shows that using pathogen-binding mesh as a wound filler for NPWT leads to a significant amount of granulation tissue in the wound bed, more than that with gauze, but eliminates the problems of ingrowth of the wound bed into the wound filler. Pathogen-binding mesh is thus an interesting wound filler in NPWT.

Introduction

Negative pressure wound therapy (NPWT) employs a closed drainage system to apply controlled suction to a wound bed. NPWT has revolutionized the treatment of patients with both chronic and acute wounds,[1,2] including orthopedic trauma,[3] soft tissue trauma,[4] skin grafts,[5] pressure ulcers,[6] venous leg ulcers,[7] vascular surgery wounds, diabetic foot ulcers,[8] burns,[9] surgical infections,[10] and the management of open wounds following abdominal surgery[11] and thoracic surgery.[12,13] We are beginning to understand the mechanisms by which negative pressure promotes wound healing. NPWT creates a moist environment,[14] drains exudate,[15–17] reduces tissue edema,[18] contracts the wound edges,[15–17] mechanically stimulates the wound bed,[19–21] alters blood flow in the wound edges,[16,22–24] and stimulates angiogenesis[25,26] and the formation of granulation tissue.[16] The biological effects of NPWT on the wound bed depend on the type of wound filler used and the negative pressure setting.

There is a common misconception that NPWT controls or reduces the bacterial burden in the wound. In an initial study on pig wounds inoculated with human Staphylococcus aureus and Staphylococcus epidermidis a reduction in bacterial counts during the course of NPWT was reported.[16] However, no clinical studies since then have been able to confirm the early in vivo findings of Morykwas et al,[27–30] and some have even reported an increase in bacterial numbers during NPWT.[27,31,32] NPWT has been shown to cause a shift in the bacterial species toward biofilm-producing organisms such as S. aureus and S. epidermidis.[27,28,30] It has been hypothesized that occlusion and negative pressure create relative hypoxia, thus promoting anaerobes and a shift in microorganism populations.[30] Furthermore, the gauze used in NPWT has been a particular type of cotton gauze (Kerlix AMD), which may provide pathogen-binding control because it is impregnated with polyhexamethylene biguanide.[33] However, the current recommendation is that NPWT should not be used in isolation to control wound infections (http://www.npwtexperts.com).

Studies are now emerging showing that the amount and character of granulation tissue formed differ depending on the type of wound filler used for NPWT. Foam and gauze are the most common wound filler materials used in NPWT. The use of foam produces thick granulation tissue,[19,34,35] while gauze produces thinner but denser granulation tissue.[19,34] The choice of wound filler for NPWT may therefore be tailored to the individual wound.[36] Pathogen-binding mesh may provide an interesting alternative wound filler for NPWT. Mesh of this kind makes use of the hydrophobic interaction to remove pathogenic wound bacteria. The hydrophobic interaction is a basic physical phenomenon causing hydrophobic (water-repellent) particles to accumulate in an aqueous environment, held together by the forces of the surrounding water molecules. Bacteria have hydrophobic cell surface structures that allow them to adhere to wound tissue in the initial phase of infection. Pathogen-binding mesh is coated with a fatty acid derivative, which gives the dressing strongly hydrophobic properties. Wound bacteria are thus irreversibly bound to the dressing when they come into contact with the hydrophobic dressing fibers in the moist wound environment.[37] Pathogen-binding mesh can thus adsorb and inactivate a wide range of bacteria, for example, Staphylococcus aureus and Pseudomonas aeruginosa, and fungi. It has been shown to reduce the microbial load in wounds[38,39] and offers a nonallergic, nontoxic alternative for reducing the microbial load in open wounds. The mesh binds and inactivates bacteria and fungus without the development of resistance among microorganisms.

The aim of this study was to compare the effects of hydrophobic pathogen-binding mesh with foam and gauze during NPWT with regard to wound bed appearance and granulation tissue formation using an in vivo porcine wound model.

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