Shape memory alloy as an internal splint in a rat model of excisional wound healing

The purpose of an animal wound model is to replicate the wound healing process of humans as accurately as possible. Although rodents are attractive candidates for animal wound models, the drawback is that their major wound healing occurs by contraction, which is fundamentally different from that seen in humans, where healing is achieved mainly by re-epithelialization and granulation tissue growth. There has been an attempt to overcome such drawbacks by applying an external splint on wounded mice. This model, however, has a few problems concerning the assimilating ability of external splints with the dynamic soft tissue movements and robustness issues. The authors hereby describe a new animal wound model using an internal splint made of nitinol, one of the shape memory alloys (SMAs). SMA wire was inserted intradermally around the full-thickness excisional wound to act as the internal splint, and its ability to impede wound contraction was analyzed. In experiment 1, three different sizes of SMAs (0.18 mm, 0.24 mm, and 0.30 mm diameters of thickness) were inserted as the internal splint and their ability to impede the wound contraction was compared. The most effective size of SMA as the internal splint was selected among them. In experiment 2, contraction of the wound with the selected size of SMA inserted as the internal splint was compared with that of the unsplinted wound. SMA as an internal splint effectively impeded wound contraction without affecting the re-epithelialization rate, thereby successfully mimicking the human wound healing mechanism. In this study, the authors introduce a novel animal wound model that replicates the human wound healing mechanism. This model is robust, reliable, and easily reproducible.