In medicine, a fracture is a break in a bone. In normal bones, fracture results from injury or from violent stress. In bones weakened by disease, fractures can occur spontaneously under ordinary stresses, a condition called pathological fracture. The susceptibility of a bone to fracture under stress depends on its brittleness, which in turn is determined by its degree of calcification. The bones of infants and young children have low calcification and are therefore softer and more flexible than those of older persons, whose bones are highly calcified. Fractures in infants and young children are commonly incomplete fractures, called greenstick fractures, because the bone cracks on one side and bends on the other. In contrast, brittle bones of older persons can shatter.
When bone fragments protrude through skin, the fracture is called open, or compound; if the skin is not broken, it is called a closed, or simple, fracture. Although fractures of the extremities are painful and partially disabling, they are not as dangerous as fractures of the skull or spinal column, which can result in permanent damage if bone fragments penetrate nerve tissue. Only a trained professional should move an individual who might have a broken neck or back.
Signs of a limb fracture may include pain and swelling in the overlying tissues, skin discoloration, distortion, impaired or complete loss of function, and a grinding sensation in the limb during movement. The injured person should not be moved unless the limb has been immobilized with splints.
Fractures are treated by aligning the ends of broken bones by traction or surgery and holding them in place for several weeks in plaster casts or splints; metal wires or screws may be needed for smaller bone fragments. Healing begins with formation of special tissue called callus. This grows in excess of need, so that a bone is permanently thicker in the vicinity of a healed fracture. A polymer has also been developed that is absorbed by the body as it holds bones in place without metal fixtures, and specially treated coral is being used in the same manner. Other methods to speed bone healing are also being researched. Treatment of a fracture is usually followed by physical therapy.