The cervical vertebrae are divided into two groups:
The typical cervical vertebrae span from the 3rd to the 6th cervical vertebrae. The characteristic feature of the cervical vertebrae is that each transverse process has its own foramen of transverse process (foramen processus transversi) through which the vertebral artery ascends (except C7). The spinous process is small and bifid (except C1 and C7). The body of the typical cervical vertebrae is rectangular and has uncus of vertebral body. The intervertebral foramen is triangular. In addition, the anterior and posterior surfaces of the small vertebral body are flattened (except C1 and C2).
The typical cervical vertebrae have the:
Vertebral body is elongated transversely (rectangle). It is smaller than the thoracic and lumbar vertebral body. It contains the uncus of the body (uncus corporis) or uncinate process which forms the posterolateral lip on the superior vertebral surface.
Vertebral arch consists of the:
- pedicle of vertebral arch (pedunculus arcus vertebrae) which is one of the paired narrow parts of the vertebral arch that connects the lamina of the vertebral arch. It is marked by the:
- superior vertebral notch (incisura vertebralis superior) above the pedicle
- inferior vertebral notch (incisura vertebralis inferior) under the pedicle
- lamina of vertebral arch (lamina arcus vertebrae) which is one of the paired broad flat plates located between the transverse, articular and the spinous process.
Vertebral foramen which is triangular in shape.
Transverse process (procesus transversus) is for the attachment of muscles and ligaments. It has the following parts:
- foramen of transverse process (foramen processus transversi) or foramen of vertebral artery is in each cervical vertebrae to transmit and protect vertebral vessels.
- anterior tubercle (tuberculum anterius) usually smaller but the anterior tubercle of the 6th cervical vertebra is large and known as the carotid tubercle (tuberculum caroticum); the common carotid artery runs anterior to it.
- posterior tubercle (tuberculum posterius) which is usually larger than anterior and is located lateral and slightly lower to the anterior tubercle.
- groove for spinal nerve (sulcus nervi spinalis) which is a shallow furrow located on superior surface of transverse prosess between anterior and posterior tubercles and it leads the ventral primary branches of the spinal cervical nerves.
Spinous process, which is split (bifid) for all vertebrae except the C1 and C7, C3-C6 have bifid spinous processes
for the attachment of the ligamentum nuchae.
Superior articular process with its superior articular facet for vertebra above faces backwards and upwards.
Inferior articular process with its inferior articular facet for vertebra below faces forwards and downwards.
Each atypical cervical vertebrae have distinguishing characteristic features. The atypical cervical vertebrae are the following:
First cervical vertebra (C1) is called the atlas (atlas). The atlas consists of the anterior and posterior arch; it also has lateral mass on either side where the articular surfaces are located. The atlas is modified to support the skull, which articulates with the occipital condyles.
The atlas lacks:
- Vertebral body because embryologically it becomes the odontoid process of the axis.
- Spinous process.
- Superior and inferior articulate process.
The atlas has:
Anterior arch (arcus anterior) which is shorter than the posterior one with:
- anterior tubercle (tuberculum anterius) which is the tiny conical eminence located at the midline on the external surface of arch.
- facet for dens of axis (fovea dentis) which is the small indentation located at the midline on the internal surface of arch.
Posterior arch (arcus posterior) with the:
- posterior tubercle (tuberculum posterius) which is a variable prominence located at the midline of the posterior arch on its posterior surface it represents a spinous process and gives attachment to the rectus capitis posterior minor muscle.
- groove for vertebral artery (sulcus arteriae vertebralis) on its superior surface where the vertebral artery passes along with the first cervical spinal nerve (suboccipital nerve).
Lateral mass (massa lateralis); it is a big part of the atlas located between anterior and posterior arch:
- superior articular facet (facies articularis superior) – kidney-shaped and concave
- inferior articular facet (facies articularis inferior) – round and flat (see mnemonic)
Transverse process with foramen of transverse process, located posterior to the angle of the mandible and mastoid process of the temporal bone.
Differences between the superior and inferior articular facet of the atlas:
Remember that the:
- Superior articular facet is concave and it has a kidney shape surface.
- Inferior articular facet is flat and it has a round shape.
Second cervical vertebra (C2) is called the axis (axis). The axis is modified vertebra to support the atlas and the skull and to control their movements. It has the:
Dens (dens) or odontoid process which represents the transposed body of the atlas which projects superiorly and it permits the atlas to rotate on its axis. On the dens of axis is distinguishable the:
- Apex of dens (apex dentis) which is attachment place for the apical ligament of dens (ligamentum apices dentis)
- Anterior articular surface (facies articularis anterior) which forms with the facet for dens of the anterior arch of the atlas synovial articulation called the anterior median atlantoaxial joint.
- Posterior articular surface (facies articularis posterior) forms the posterior median atlantoaxial joint which connects with the articular surface of transverse ligament of atlas (ligamentum transversum atlantis).
Fracture of dens or fracture of the arch of axis is called hangman’s fracture. When this fracture occurs, the axis breaks symmetrically across its pedicles or lateral masses and the fracture may extend across the posterior part of the body. This fracture is seen in victims of falls and traf fic collisions but the term hangman’s fracture was first used to describe the characteristic lesion seen in judicial hanging.
Superior articular surface but it lacks a superior articular process.
Inferior articular surface which is located on the inferior articular process.
Inferior vertebral notch but it lacks a superior one.
Spinous process which is bifid and long.
Transverse process with foramen of transverse process, it lacks a groove for the spinal nerve and anterior and posterior tubercles.
Seventh cervical vertebra (C7), is called the prominens (vertebra prominens). The vertebra prominens has modified spinous and transverse processes (Fig. 2-11). Characteristics for vertebra prominens are:
- Non-bifid, long spinous processes (distinctly palpable) for attachment of the ligamentum nuchae.
- Transverse processes have a small anterior tubercle and the bigger posterior tubercle.
- They may have costal facets on the vertebral body.
Uncovertebral joints or Luschka joints are an articulation in the five lower cervical vertebral bodies (C3-C7). They are formed by the space between the inferior portion of vertebral body and the uncinate processes (uncus) that project superiorly from the vertebral body immediately below it. These joints are not true synovial joint but it is a clinical definition of this connection. They have features of both cartilaginous and synovial joints.
Uncovertebral joints limits lateral motion between vertebrae to protect the vertebral arteries from lateral translation, assist in the prevention of intervertebral disc protrusion, and aid in weight bearing with degenerative changes. Here occurs the first sign of degeneration in the cervical spine using radiography. Clinically the uncovertebral joints may undergo degeneration and produce radiculopathy. Plain radiographs and CT scans are useful in diagnosing the abnormal relationships resulting from disc degeneration, which often lead to hyperostosis of the uncinate process and adjacent vertebral body.