repetitive stress injury or repetitive strain injury (RSI), injury caused by repeated movement of a particular part of the body. Often seen in workers whose physical routine is unvaried, RSI has become epidemic since computers have entered the workplace in large numbers. Many RSIs develop when the sheaths that cover muscle tendons swell and press on nerves. Constant typing can cause one form of RSI, carpal tunnel syndrome, a sometimes disabling pain and tingling in the thumb and first two fingers. It is caused by swelling and pressure on the median nerve passing through the wrist. Other common problems are rotator cuff injury, from overuse of the shoulder; tennis elbow, inflammation of a tendon in the elbow from overuse of the forearm; and back injuries from repeated heavy lifting. A 1998 report by the National Academy of Sciences in the United States called RSI a serious national problem, with financial costs ranging up to $20 billion annually.

Treatment of RSI usually begins with attempts to change the conditions that caused the injury. Often, exercises and anti-inflammatory drugs are prescribed; in some cases surgery is necessary. Many workers' compensation cases and lawsuits relating to RSI have been brought against employers and product manufacturers. To avoid the high costs of RSI, some businesses have introduced ergonomic workstations and enforced rest periods.

repetitive strain injury: see repetitive stress injury.

Tissue damage caused by exposure to ionizing radiation. Structures with rapid cell turnover (e.g., skin, stomach or intestinal lining, and bone marrow) are most susceptible. High-dose irradiation of the last two causes radiation sickness. Nausea and vomiting subside in a few hours. They are followed in intestinal cases by abdominal pain, fever, and diarrhea leading to dehydration and a fatal shocklike state, and in bone-marrow cases (two to three weeks later) by fever, weakness, hair loss, infection, and hemorrhage. In severe cases, death occurs from infection and uncontrollable bleeding. Lower radiation doses can cause cancer (notably leukemia and breast cancer), sometimes years later. Radiation exposure in early pregnancy can produce abnormalities in the embryo, whose cells are multiplying rapidly.

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or trauma

Break in any body tissue due to external action (including surgery). It may be closed (blunt trauma) or open (penetrating trauma). Blood vessels, nerves, muscles, bones, joints, and internal organs may be damaged. A closed wound can be caused by impact, twisting, bending, or deceleration (as in a car crash). It can range from a minor bruise or sprain to a skull fracture with brain damage or a spinal-cord injury with paralysis. In an open wound, foreign matter such as bacteria, dirt, and clothing fragments entering through broken skin or mucous membrane may result in infection. Other factors affecting severity include depth, surface area, degree of tearing, and structures damaged. Minor wounds need only first aid. For others, after examination and perhaps diagnostic imaging and exploratory surgery, treatment may include fluid replacement or drainage, sterilization and antibiotics, tetanus antitoxin, and repair of damaged structures. A closed wound may need to be opened or an open one sutured closed. Seealso burn, coagulation, crush injury, dislocation, scar.

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