It is used to define the term major trauma (polytrauma), recognized when the ISS is greater than 15. The AIS Committee of the Association for the Advancement of Automotive Medicine designed and updates the scale. Mechanisms
Trauma
Traumatic injury is caused by an external object making forceful contact with the body, resulting in a wound. Major trauma is a severe traumatic injury that has the potential to cause disability or death. Serious traumatic injury most often occurs as a result of traffic collisions. Traumatic injury is the leading cause of death in people under the age of 45.Blunt trauma injuries are caused by the forceful impact of an external object. Injuries from blunt trauma may cause internal bleeding and bruising from ruptured capillaries beneath the skin, abrasion from scraping against the superficial epidermis, lacerated tears on the skin or internal organs, or bone fractures. Crush injuries are a severe form of blunt trauma damage that apply large force to a large area over a longer period of time. Penetrating trauma injuries are caused by external objects entering the tissue of the body through the skin. Low-velocity penetration injuries are caused by sharp objects, such as stab wounds, while high-velocity penetration injuries are caused by ballistic projectiles, such as gunshot wounds or injuries caused by shell fragments. Perforated injuries result in an entry wound and an exit wound, while puncture wounds result only in an entry wound. Puncture injuries result in a cavity in the tissue. Burns
Burn injury is caused by contact with extreme temperature, chemicals, or radiation.
The LIN28 gene also plays a role in wound healing. It is dormant in most mammals. Also, the proteins MG53 and TGF beta 1 play important roles in wound healing. Wound healing
In response to an incision or wound, a wound healing cascade is unleashed. This cascade takes place in four phases: clot formation, inflammation, proliferation, and maturation. Clotting phase
Healing of a wound begins with clot formation to stop bleeding and to reduce infection by bacteria, viruses and fungi. Clotting is followed by neutrophil invasion three to 24 hours after the wound has been incurred, with mitoses beginning in epithelial cells after 24 to 48 hours. Inflammation phase
In the inflammatory phase, macrophages and other phagocytic cells kill bacteria, debride damaged tissue and release chemical factors such as growth hormones that encourage fibroblasts, epithelial cells and endothelial cells which make new capillaries to migrate to the area and divide. Proliferative phase
In the proliferative phase, immature granulation tissue containing plump, active fibroblasts forms. Fibroblasts quickly produce abundant type III collagen, which fills the defect left by an open wound. Granulation tissue moves, as a wave, from the border of the injury towards the center.As granulation tissue matures, the fibroblasts produce less collagen and become more spindly in appearance. They begin to produce the much stronger type I collagen. Some of the fibroblasts mature into myofibroblasts which contain the same type of actin found in smooth muscle, which enables them to contract and reduce the size of the wound.