Overview
The dog has thirteen thoracic vertebrae (T1–T13), one for each pair of ribs. Their bodies are short and their spinous processes are the tallest of the column, forming the skeleton of the withers. They are the least mobile segment of the vertebral column because the ribs brace them.
Key features
- Body: short, with costal foveae (foveae costales) at its cranial and caudal ends. The head of each rib articulates with the caudal fovea of the vertebra in front and the cranial fovea of its own vertebra; the last ribs articulate with a single vertebra.
- Transverse processes: short, each with a transverse costal fovea for the tubercle of the rib of the same number.
- Spinous processes: longest in the first thoracic vertebrae, then progressively shorter. Up to T10 they slope caudally; the anticlinal vertebra (usually T11) has an upright spinous process, and caudal to it the processes slope cranially, as in the lumbar region.
- Mammillary and accessory processes: appear on the caudal thoracic vertebrae and continue into the lumbar series.
- Intercapital ligaments: join the heads of each rib pair across the dorsal surface of the discs from T2 to T10.
Clinical relevance
- Intervertebral disc herniation is rare between T1 and T10, where the intercapital ligaments reinforce the dorsal annulus, and frequent at the thoracolumbar junction (T11–L2), especially in chondrodystrophic breeds such as the dachshund.
- Hemivertebrae (wedge-shaped malformed vertebrae) occur mostly in the mid-thoracic region of screw-tailed breeds (French bulldog, pug, English bulldog) and can cause kyphosis and spinal cord compression.
- The anticlinal vertebra is a radiographic landmark for counting the vertebrae.
In this model T1–T10 are reconstructed by deforming the scanned seventh cervical vertebra and T11–T13 by deforming the scanned first lumbar vertebra; their outline and proportions are approximate.