A fracture—a break in bone or cartilage—usually results from injury or an underlying bone disease, such as osteoporosis. Fractures are categorized as either simple (closed)
in which the broken bone does not break the skin, or compound (open), in which the broken bone punctures the skin. When the two ends of a fractured bone have not separated, it is called a nondisplaced fracture. When the two ends have separated, it is a displaced fracture. Within the categories of simple and compound are other types of fractures, including transverse fracture, spiral fracture, comminuted fracture, and greenstick fracture. The type of fracture determines the choice of treatment.