Acute traumatic wounds are caused either by shear, compressive, or tensile forces, which vertically separate the epithelium and dermis. 7 Shear forces are produced by sharp objects that cut through the skin. The amount of energy required to cut through the skin with a sharp object is relatively low and directed to a very small area. Thus, little energy is deposited into the surrounding tissue and there is minimal cell damage. Typically, the resultant wound has straight edges, little contamination, and heals with a good result. Compressive and tensile forces are produced when a blunt object impacts the skin at right and oblique angles, respectively. In contrast to shear forces, the amount of energy deposited from compressive and tensile injuries is larger, with significant amounts applied to the area around the wound causing disruption of the microvasculature. The amount of force required to produce a cutaneous laceration is in the range of 2.5 J/cm 2 The devitalized tissue creates an anaerobic environment, which impairs the ability of leukocytes to function and supports bacterial proliferation. Experimentally, wound infections have been produced in compressive injuries with inoculums of about 100,000 organisms per gram of tissue compared with the requirement for about 10,000,000 organisms per gram in shear injuries. Compressive wounds tend to be stellate or complex, with ragged or shredded edges. Tensile wounds tend to be triangular or produce a flap. In cross section, tensile wounds tend to be "skived," that is, cut oblique through the skin with a thin edge on one side and a thick edge on the other.
The body responds to the injury by initiating a series of restorative stages to recover tissue continuity and strength. In general, tensile strength of the wounded area recovers approximately 50 percent by 40 days and nearly 100 percent by 150 days after injury. These stages of wound healing are described as hemostasis, inflammation, epithelialization, angiogenesis, fibroplasia, contraction, and scar maturation. All these stages are stimulated by various tissue growth factors ( Table
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