Physiology of wound healing.

Wound healing is a complicated process that recruits at least 4 distinct cell types. Though the process is continuous, it is commonly referred to as occurring in "phases." The main phases of wound healing include coagulation, which begins immediately after injury; inflammation, which initiates shortly thereafter; a migratory and proliferative process, which begins within days and includes the major processes of healing; and a remodeling process, which may last for up to a year and is responsible for scar tissue formation and development of new skin. Wound healing is affected by several factors. These include local factors (growth factors, edema and ischemia, low oxygen tension, and infection), regional factors (arterial insufficiency, venous insufficiency, and neuropathy), systemic factors (inadequate perfusion and metabolic disease), and other miscellaneous factors, such as nutritional state, preexisting illnesses, exposure to radiation therapy, and smoking. In general, chronic wounds may be managed by preventing or medically treating infections through debridement and occlusive dressings. For wounds that are unresponsive to such interventions, the use of skin replacements is becoming a viable option. In this regard, a product such as Graftskin (APLIGRAF, Organogenesis Inc, Canton, MA, and Novartis Pharmaceuticals Corporation, East Hanover, NJ), a bilayered living skin construct with allogeneic dermis and epidermis, is a positive development.