In wound healing, a wound closure takes place through the formation of a scar as a result of accumulation of substrates that have properties similar to those of the dermis at the damaged skin, which contributes to recovering the continuity of the skin. In this process, wound contraction by the surrounding dermis and fat tissues plays an important role [7
]. It is known that wound contraction results from the pulling of dermis and fat tissues as collagen fibrils are concentrated with cells such as fibroblasts, become collagen fibers, and again become granuloma tissue, which reduces the volume [7
]. Unlike the human wound healing process, experimental animals such as rats experience less tension of the skin pulling around the wound due to looser skin. Thus, active wound contraction, as in this experiment, plays an important role in healing [9
]. In this experiment, it turned out that the progress of wound healing was slow in the groups in which adhesive polyvinyl chloride film or Duoderm CGF was used to fix the loose skin and to stabilize the skin tension.
It has been demonstrated in a number of studies that as above, the fixation of skin around a wound could affect the wound healing rate because of the decreased influence of contraction in the process of wound healing. Green et al. [10
] and Ehrlich and Needle [2
] reported difference in the duration of wound healing in mice with a tight-skin mutation compared with normal rats.
Engin et al. [11
] found that removing nerves around the wound reduces the wound contraction and thus slows down the wound healing. In a rat wound healing experiment, therefore, fixing the skin around the wound could be of great importance, and thus various skin fixation methods have been designed to this effect. Korula et al. [3
], for example, attempted to prevent wound contraction by means of adherent splints, while Callaghan et al. [4
] and Lin et al. [5
] sutured wounds with nylon on a silicone splint. Lindenblatt et al. [6
] used a titanium splint to reduce errors due to wound contraction. However, most such methods did not show a reduction in wound contraction relative to a control group. Further, these methods were designed with materials that are not readily available to other researchers. Thus, the authors designed a new method for reducing the effect of wound contraction simply and economically, and conducted an experiment to compare this method with a control group to demonstrate that of the method could reduce wound contraction.
In this experiment, the authors attached Duoderm CGF (15×15 mm) over the 10×10 mm wound in group B in order to stabilize the tension of the area around the wounded skin. In group C, 15×15 mm Duoderm CGF was also attached to the wound, but then an adhesive polyvinyl chloride film was applied over it in order to provide stronger force than that applied to group B to further reduce any error arising from wound contraction. The 2.5 mm wide gap between the borders of the wound and Duoderm CGF served to fix the skin around the wound and minimize the effect of the Duoderm CGF at the same time. Further, Peha-Haft and Ioban were also used to prevent the dressing materials from being damaged or lost. Also, when the authors took photographs or handled the rats, inhalation anesthesia by means of isoflurane was used. Furthermore, the initially attached dressing material was kept unchanged in order to minimize the effect of unexpected factors that might take place while handling the rats, and also to maintain the humidity [12
]. Thus the number of variables that could affect the results of the experiment was reduced as much as possible and wound healing could proceed undeterred.
Among the dressing materials used in this experiment, Tegaderm is made of polyurethane, which protects the wound from external conditions and prevents microorganisms from penetrating. In addition, its adhesive makes it easy to apply to the skin. Duoderm CGF is a dressing material that contains hydrocolloid. It is known that this material can absorb wound exudate; maintain the humidity, which helps the wounded skin recover; and remove foreign substances and necrotic tissue. In addition, as Duoderm CGF adheres well to the skin around a wound, the wounded area could be completely isolated from the external environment, and no dead space exists between the wound and dressing, which limits the reproduction of microorganisms. Thus, in this experiment, the authors used this material because it is a more rigid material with adherence than Tegaderm.
As for the adhesive polyvinyl chloride film, laminating films that are available in regular office supply stores were used. Although this film is not a dressing material, it was used in this experiment to fix the skin with sufficient force. Polyvinyl chloride, which is a component of adhesive polyvinyl chloride film, softens at 65
or higher and is stable in the solid state at room temperature, and the flexibility may change depending on the plasticizer. This material is utilized for various products such as film, toys, food containers, and so forth. In this experiment, the authors used this material because it is the most rigid among these three kinds of materials.
In this experiment, it can be said that the skin-fixing strength is in the order of group A, group B, and group C. As a result of the experiment, it turned out that the skin-fixing force affects the area of the wounded skin and wound area reduction rate, which indicates that preventing wound contraction could result in a significant decrease in the wound healing speed. Meanwhile, between B and C, a difference in the area of the wounded skin was observed, which shows that the group C approach better prevented wound contraction in the wound healing process than that of group B. Hence, it would be most desirable to fix the skin with a material that is durable enough to prevent deformation during the period of experimentation, as in the case of group C. This experiment shows that the results of rat wound healing experiemnts might not be reliable unless the back skin of the rats is properly fixed during wound healing using an adequate skin fixation method to prevent wound contraction from influencing wound size.
However, the effect of the dressing materials, that is, the Tegaderm, Duoderm CGF, and adhesive polyvinyl chloride film, on the wound was not taken into consideration. Nor was the effect of the pressure by the Peha-Haft and Ioban considered in this study, which could be important variables as well. It is thought, therefore, that additional studies on these factors should be performed. In addition, the method that the authors designed basically fixes the dressing materials on the back skin of rats by using suturing fibers, which cannot be applied to experiments where the wound should be regularly opened and sterilized.
For the wound healing experiment, the authors used materials that are commonly available in one of two proposed methods of fixing the skin around the wound in order to reduce the effect of wound contraction. The wound healing experiment was conducted by means of experimental rats, and it turned out that the two skin fixation methods reduced the effect of wound contraction compared to the control group in which only Tegaderm was used to cover the wound. In addition, of the two methods, the group with Duoderm CGF and an adhesive polyvinyl chloride film reduced the effect of wound contraction better than in the group with Duoderm CGF and Tegaderm. It is expected, therefore, that the skin fixation method that the authors presented could be applied to other researchers' wound healing experiments as a skin fixation method: for example, experiments on wound healing regulators, growth factors, and inflammatory mediators, and those comparing products that support the wound healing process.
The present study could also function as a reference in the design of future studies evaluating skin fixation methods by means of other materials.