Brought on by force, a compression fracture is a break in a vertebra that causes it to collapse. The vertebrae are the box-shaped bones that make up the spine. Typically, a compression fracture is wedge-shaped, with more collapse in the front, due to force on the spine from forward bending.
The spinal column of vertebrae, stacked one on top of another, supports the body in an upright position. When the force on the bone is greater than the strength of the bone, a compression fracture occurs. Fractures can also occur when the bones have been weakened. For example, in osteoporosis, fractures can occur spontaneously with no known injury. Compression fractures occur most often in the lower back or lumbar area. They also occur in the chest or thoracic area of the spine.
Most often, an injury is the cause. In young, healthy bone, a violent force such as a car accident or fall from a height is necessary to break the bone. In weak, thin bone, minor force such as sitting down hard or vigorous sneezing can cause the compression. Bone can be weak for various reasons, the most common being osteoporosis. Cancer can also weaken a vertebra.