Penetrating trauma

Penetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out the way it entered, or pass through the tissues and exit from another area. An injury in which an object enters the body or a structure and passes all the way through is called a perforating injury, while penetrating trauma implies that the object does not pass through. Perforating trauma is associated with an entrance wound and an often larger exit wound. Penetrating trauma is an injury that occurs when an object pierces the skin and enters a tissue of the body, creating an open wound. In blunt, or non-penetrating trauma, there may be an impact, but the skin is not necessarily broken. The penetrating object may remain in the tissues, come back out the way it entered, or pass through the tissues and exit from another area. An injury in which an object enters the body or a structure and passes all the way through is called a perforating injury, while penetrating trauma implies that the object does not pass through. Perforating trauma is associated with an entrance wound and an often larger exit wound. Penetrating trauma can be caused by a foreign object or by fragments of a broken bone. Usually occurring in violent crime or armed combat, penetrating injuries are commonly caused by gunshots and stabbings. Penetrating trauma can be serious because it can damage internal organs and presents a risk of shock and infection. The severity of the injury varies widely depending on the body parts involved, the characteristics of the penetrating object, and the amount of energy transmitted to the tissues. Assessment may involve X-rays or CT scans, and treatment may involve surgery, for example to repair damaged structures or to remove foreign objects. Following penetrating trauma, spinal motion restriction is associated with worse outcomes and therefore its should not be done routinely. As a missile passes through tissue, it decelerates, dissipating and transferring kinetic energy to the tissues; this is what causes the injury. The velocity of the projectile is a more important factor than its mass in determining how much damage is done; kinetic energy increases with the square of the velocity. In addition to injury caused directly by the object that enters the body, penetrating injuries may be associated with secondary injuries, due for example to a blast injury. The path of a projectile can be estimated by imagining a line from the entrance wound to the exit wound, but the actual trajectory may vary due to ricochet or differences in tissue density. In a cut, the discolouration and the swelling of the skin from a blow happens because of the ruptured blood vessels and escape of blood and fluid and other injury that interrupts the circulation. Low-velocity items, such as knives and swords, are usually propelled by a person's hand, and usually do damage only to the area that is directly contacted by the object. The space left by tissue that is destroyed by the penetrating object as it passes through forms a cavity; this is called permanent cavitation. High-velocity objects are usually projectiles such as bullets from high-powered rifles, such as assault rifles or sniper rifles. Bullets classed as medium-velocity projectiles include those from handguns, shotguns, and submachine guns. In addition to causing damage to the tissues they contact, medium- and high-velocity projectiles cause a secondary cavitation injury: as the object enters the body, it creates a pressure wave which forces tissue out of the way, creating a cavity can be much larger than the object itself; this is called temporary cavitation. The temporary cavity is the radial stretching of tissue around the bullet’s wound track, which momentarily leaves an empty space caused by high pressures surrounding the projectile that accelerate material away from its path. The characteristics of the tissue injured also help determine the severity of the injury; for example, the denser the tissue, the greater the amount of energy transmitted to it. Skin, muscles, and intestines absorb energy and so are resistant to the development of temporary cavitation, while organs such as the liver, spleen, kidney, and brain, which have relatively low tensile strength, are likely to split or shatter because of temporary cavitation. Flexible elastic soft tissues, such as muscle, intestine, skin, and blood vessels, are good energy absorbers and are resistant to tissue stretch. If enough energy is transferred, the liver may disintegrate. Temporary cavitation can be especially damaging when it affects delicate tissues such as the brain, as occurs in penetrating head trauma. While penetrating head trauma accounts for only a small percentage of all traumatic brain injuries (TBI), it is associated with a high mortality rate, and only a third of people with penetrating head trauma survive long enough to arrive at a hospital. Injuries from firearms are the leading cause of TBI-related deaths. Penetrating head trauma can cause cerebral contusions and lacerations, intracranial hematomas, pseudoaneurysms, and arteriovenous fistulas. The prognosis for penetrating head injuries varies widely.