The common vertebra consists of the body and the arch, which enclose the vertebral foramen. The body consists of a loose trabecular bone, the spongiosa, which contains the bone marrow and is encased by the corticalis. The vertebral bodies increase in width from C2 to L3 and then decrease again in the lower lumbar spine towards the coccyx. The superior and inferior surfaces of the vertebral body are called endplates and consist of a ringlike cortical bone that surrounds the hyaline cartilage plates, which are remnants of the epiphysis of the vertebral body.

The epiphysis of the vertebral body undergoes a ring-like ossification at the age of 8 years and fuses with the vertebral body by the age of 18–21 years.

Imaging: The non-ossified epiphysis and the adjacent intervertebral disc account for the wide intervertebral distance between the ossified centres in children on CT and plain films (Fig. 2.2).

At the posterior surface, an irregular-shaped aperture can be found for the exit of the basivertebral veins from the body of the vertebra. The perivenous fat leads to a bright signal in MRI on T1w. Typically, a strong enhancement can be detected after administration of intravenous contrast agent.

During the first months of life, the appearance of the vertebral bodies on MRI occurs through three subsequent stages:

First month (Fig. 2.3):

The enchondral ossification centres of the vertebral bodies show a lower signal in T1w compared to muscles (Fig. 2.3a). The basivertebral veins appear as a horizontal band of high signal intensity in the centre of the osseous part. The adjacent cartilaginous endplates are markedly hyperintense on T1w compared to the osseous portion and are each about half the size of the central vertebral component (Fig. 2.3b). In T2w imaging, the osseous part of the vertebral body appears hypointense, while the endplates appear mildly hyperintense compared to muscles (Fig. 2.3c). The administration of contrast agent enhances the cartilaginous endplates and the central osseous portion.

One to six months (Fig. 2.4): The osseous portion of the vertebral body increases in signal intensity on T1w, starting at the superior and inferior portions of the body until the entire vertebral body is involved. Increasing signal intensity can also be detected on T2w until the body becomes isointense with the endplates at the age of 3 months.

From the age of about 7 months (Fig. 2.5): The vertebral bodies become hyperintense on T1w imaging compared to the cartilaginous endplates and surrounding muscles, while the cartilaginous endplates undergo ossification and therefore decrease in signal and incorporate into the vertebral body. On T2w imaging, the whole vertebral body now shows a homogenous and mildly hyperintense signal compared to muscles.

In children and adults the signal intensity of the vertebral body depends on its marrow contents.

Imaging: For children, haematopoietic marrow is dominant resulting in a relatively low signal intensity on T1w in MRI (Figs. 2.3, 2.4 and 2.5). The red marrow contains intermixed fat so that its signal intensity in T1w is higher compared to muscles and also compared to the intervertebral disc. The haematopoietic marrow markedly enhances after administration of contrast agent.

Fatty conversion of the marrow starts at the age of 8–12 years around the central venous plexus, yielding increasing signal of the vertebral body on T1w. With increasing age, the replacement of the red marrow by fatty marrow continues.

The anterior part of the arch, which on both sides extends from the dorsolateral part of the body, is the pedicle. The dorsal part of the arch is formed by the paired lamina, which join at midline to the spinous process.

Ossification of the dorsal parts of the arch occurs at the age of 2–3 years, while fusion of the anterior part of the arch with the vertebral body takes place at the age of 3–6.

At each side, the transverse processes arise from the lateral parts of the arch. Moreover, a total of four articular processes can be found at the junction of pedicles and lamina which are called zygapophyses. Each side has a superior and inferior process, which articulates with zygapophyses of the adjacent vertebrae to the facet joint. The area between the superior and inferior articular processes is called the interarticular portion (Fig. 2.7).

Around the beginning of puberty, secondary apophyseal ossification centres can be seen at the edges of the spinous and the transverse processes. Synostosis occurs by completion of growth and can be mistakenly diagnosed as a traumatic bone fragment.