Chapter 11. Disorders Due to Physical Agents

Management of trauma (eg, from motor-vehicle or other accidents, penetrating gunshot wounds) makes up a large part of modern medical practice. Specialized trauma centers have been established in most large city hospitals, and they are often the busiest part of the hospital. In many industrialized societies, trauma is the leading cause of death in children and young adults.

The type of tissue injury incurred varies with the type and severity of trauma (eg, blunt trauma, crush injury, gunshot wound) and the structures involved. Several broad categories of tissue injury are recognized.

Abrasion (Scrape)

(Figure 11-1)

Abrasions are the most minor type of injury and occur in the skin; the superficial layers of the epidermis are scraped away. Healing is rapidly achieved by regeneration of epidermal cells from the remaining deeper basal epidermal layers, and there is no scarring.

Contusion (Bruise)

Contusions usually result from blunt trauma. Vascular damage occurs, with extravasation of blood into the tissue. The bleeding is usually rapidly controlled by hemostatic mechanisms. The red blood cells present in the injured tissue are then slowly degraded. The various pigments derived from the breakdown of hemoglobin are responsible for the change in color from red through purple, black, green, and brown. The presence of hemosiderin-laden macrophages on microscopic examination of the region signifies that hemorrhage has occurred there. In more severe injuries, sufficient blood may collect in the tissues to produce a distinct lump (hematoma).

Contusions are most commonly seen in the skin, but they may also occur in internal organs, where they can cause significant malfunction. Myocardial contusion may lead to cardiac arrhythmias and acute cardiac failure. In the brain, contusions are common in the inferior frontal lobe because of movement of the brain against protuberances of the base of the skull in the anterior cranial fossa (Figure 11-2). Cerebral lesions represent foci for possible development of epileptic seizures.

Contusions are dangerous in patients with bleeding disorders such as hemophilia. In these patients, bleeding is not controlled by hemostatic mechanisms, and minor vascular injury often leads to massive bleeding (hematoma) in soft tissue, muscle, and joints with devastating results.

Laceration & Incision (Tearing & Cutting)

(Figure 11-1)

Lacerations and incisions are characterized ...