The thoracic spinal vertebrae consist of 12 total vertebrae and are located between the cervical vertebrae (which begin at the base of the skull) and the lumbar spinal vertebrae.

The thoracic spine is attached to the ribs, rendering it less mobile than the cervical or lumbar spines. This is significant in its function of protecting important organs, including the heart and lungs.

The ninth thoracic vertebra (T9) communicates directly with the adrenal glands via nerves. Although rare, displacement of the T9 vertebra may cause severe symptoms in the kidney area, as the adrenal glands rest on the kidneys. The risk for displacement usually occurs in individuals over 40 years old, and is often associated with common, age-related degenerative changes. Although relatively uncommon in the thoracic spine, most displacement occurs between the ninth thoracic vertebra (T9) and the twelfth thoracic vertebra (T12). Treatment is usually nonsurgical, using a back brace or painkillers.