How we can use tension relief techniques to aid primary closure?

Introduction and background

The overall goal in the management of any equine wound is to attain an excellent functional and cosmetic result. To achieve this, primary closure, delayed primary closure (before the appearance of granulation tissue) and secondary closure (after the appearance of granulation tissue) are preferred techniques over healing by second intention. Second-intention healing, of distal limb wounds in particular, is at high risk of complications such as chronic inflammation, the development of exuberant granulation tissue, poor wound contraction and slow epithelialization [1]. In addition, the surface of epithelialized wounds are only a few cell layers thick; making it far more susceptible to trauma compared to normal skin, particularly in areas of high mobility [2]. Primary intention healing can be challenging however, as the result of skin loss, excessive tension, or mobility at the wound site. There appears to be a significant risk of partial or complete dehiscence. In a large retrospective study, complete primary healing after closure of traumatic wounds was successful in only 26% of horses and 41% of ponies [3].

Physiology of skin stretching

Excessive tension during wound closure can result in circulatory compromise, impaired wound healing, and skin necrosis. Skin is a non- homogenous viscoelastic tissue with the combined characteristics of a viscous fluid and elastic solid. These inherent properties can be harnessed to promote wound closure. The skin is capable of further extension beyond its initial elasticity with the application of a stretching or tension force over time. This is called mechanical creep and is complemented by stress relaxation; the progressive reduction in the force required to maintain the stretched dermal collagen fibers at a given length. During this process, tissue fluid is displaced from around the randomly arranged dermal collagen fibers, as they progressively align and compact longitudinally in the direction of the stretching force[4]. [...]