Atypical Thoracic Vertebrae: Th1 & Th9

Front view of the lower cervical and upper thoracic vertebraw

The 1^st thoracic vertebra is considered an "atypical" because of the complete costal facet for the head of the 1^st rib. However, being the transitional form between the cervical vertebra and typical thoracic, it shares some standard features with cervicals – like the high of the vertebral body and the spinous process's shape.

Latin terminology for the side view of the cervical-thoracic transition zone of the spine

Side view of the cervical-thoracic transition zone of the spine

Unlike typical thoracic, having half of the costal facet on the upper & half – on the lower edge of the body of the vertebra, the 1^st thoracic vertebra has one complete costal facet articulating with the head of the 1^st rib + the 1/2 of costal facet (fovea costalis inferior) for the head of 2^nd rib.

The list of terms:

Fovea costalis 1 – Complete costal facet for the 1^st rib
Fovea costalis superior & inferior (caput costae 2) – Superior & inferior costal facet (for the head of the 2^nd rib)
Fovea costalis superior & inferior (caput costae 3) – Superior & inferior costal facet (for the head of the 3^rd rib)
Fovea costalis superior & inferior (caput costae 4) – Superior & inferior costal facet (for the head of the 4^th rib)

Latin terminology for the oblique view on the spine from C6 to Th6

Oblique view on the spine from C6 to Th6

Oblique inferior view of the lower cervical and upper thoracic parts of spine.

The list of terms:

Fovea costalis 1 – Complete costal facet for the 1^st rib
Fovea costalis superior & inferior (caput costae 2) – Superior & inferior costal facet (for the head of the 2^nd rib)
Fovea costalis superior & inferior (caput costae 3) – Superior & inferior costal facet (for the head of the 3^rd rib)
Fovea costalis superior & inferior (caput costae 4) – Superior & inferior costal facet (for the head of the 4^th rib)

Side view of the thoracolumbar spine with the anatomical terminology markup

The side view of the thoracolumbar spine from Th8 to L1

Instead of two 1/2 of costal facets present on typical vertebrae, the 9^th thoracic vertebra has only one fovea costalis superior at the vertebral body's upper edge. In its turn, the Th10, Th11, and Th12 has one complete costal facet each.

The list of terms:

Fovea costalis 12 – Complete costal facet for the 12^th rib
Fovea costalis 11 – Complete costal facet for the 11^th rib
Fovea costalis 10 – Complete costal facet for the 10^th rib
Fovea costalis superior & inferior (caput costae 9) – Superior & inferior costal facet (for the head of the 9^th rib)
Fovea costalis superior & inferior (caput costae 8) – Superior & inferior costal facet (for the head of the 8^th rib)

Oblique view of the thoracolumbar spine with the anatomical terminology markup

The thoracolumbar spine. Oblique anterior aspect

Note the absence of the fovea costalis processus transversi for the last two thoracic vertebrae. The shape of the body of these vertebrae also resembles those of the lumbar.

The list of terms:

Fovea costalis 12 – Complete costal facet for the 12^th rib
Fovea costalis 11 – Complete costal facet for the 11^th rib
Fovea costalis 10 – Complete costal facet for the 10^th rib
Fovea costalis superior & inferior (caput costae 9) – Superior & inferior costal facet (for the head of the 9^th rib)
Fovea costalis processus transversi – Costal facet of transverse process

Atypical thoracic vertebrae