21. The cervical and thoracic spine

Question 1

How many cervical vertebrae are there?

Answer 1

7 (C1-C7)

Question 2

Which cervical vertebrae are typical and which are atypical?

Answer 2

C1, C2, C7 —> atypical cervical vertebrae

C3 - C6 —> fairly uniform, typical cervical vertebrae

Question 3

What is the structure of typical cervical vertebrae?

Answer 3

• Body that is small and broad from side to side.
• Large triangular vertebral (neural) foramen
• Bifid spinous process (except C7)
• Transverse foramen in the transverse process; a
conduit for the vertebral artery, vein and sympathetic plexus (except C7)
• Articular facets orientated in the coronal plane and at 45° to the axial plane.

Question 4

How are the articular facets orientated in typical cervical vertebrae?

Answer 4

• superior articular facet faces upward and backward

- inferior articular facet faces downward and forward

Question 5

What is the structure of the C1 vertebra?

Answer 5

• the atlas
• a bony ring with anterior and posterior arches connected by two strong lateral masses
• widest cervical vertebra
• does not have a vertebral body or spinous process
• anterior arch occupies 20% of the circumference of the ring
• posterior arch occupies 40% of the circumference of the ring
• vertebral arches are thick and strong and form a powerful lateral mass

Question 6

which vertebrae are the smallest?

Answer 6

Cervical

Question 7

what is the difference between cervical and thoracic in terms of mobility?

Answer 7

• Cervical Spine – Mobile

* Thoracic Spine - Immobile

Question 8

what is the difference between typical cervical vertebrae and the lumbar spine?

Answer 8

• Majority of features of cervical is the the same as Lumbar Spine
Except, cervical has:
• Bifid Spinous Process
• Transverse Foramen

Question 9

Where are the articular facets found on the atlas?

Answer 9

• positioned on the lateral mass
• the superior articular facets are cup-shaped and articulate with the occipital condyles of the skull
• the inferior articular facets articulate with the superior articular facets of the C2 vertebra

Question 10

What attaches as the anterior and posterior arches of the atlas?

Answer 10

• The anterior arch is the site of attachment of the anterior longitudinal ligament
• The posterior arch contains the posterior tubercle which is a site of attachment of the ligamentum nuchae

Question 11

which is the widest cervical vertebra and why?

Answer 11

C1 - bears the weight of the skull and tries to transmit it to the rest of the vertebrae

Question 12

Where is the atlanto-occipital joint and what is its function?

Answer 12

• Between the occiput of the skull and the atlas vertebra

- permits nodding of the head and contributes to half of the total range of flexion and extension of the head and neck

Question 13

Where is the atlanto-axial joint and what is its function?

Answer 13

• between the atlas and the axis (C2)

- responsible for 50% of the total rotation of the head and neck

Question 14

What is the axis, its structure and its function?

Answer 14

• C2 - provides a pivot on which the atlas rotates

- strongest cervical vertebra and has a rugged lateral mass and a large spinous process

Question 15

What is the odontoid process, its structure?

Answer 15

• aka the dens or odontoid peg
• projects vertically upwards from the axis body and attaches to its articular facet for the dens on the atlas
• vestigial remnant of the atlas body
• held in place by the transverse ligament of the atlas and acts as a pivot joint
• the atypical ligament attaches between the odontoid process and the base of the skull superiorly

Question 16

What is the function of the odontoid process?

Answer 16

the odontoid process and transverse ligament together prevent horizontal displacement of the atlas on the axis below

Question 17

Why is it difficult to see the odontoid process on an x-ray?

Answer 17

Sometimes covered by the skull

Question 18

What is atlantoaxial instability?

Answer 18

• Excessive movement between the C1 and C2 vertebrae
• can be congenital but mostly results from acute trauma or degenerative changes in RA
• can cause the spinal cord/ adjacent nerve roots to be compressed which can cause neurological symptoms

Question 19

What is the vertebra prominens?

Answer 19

C7

Question 20

What is the structure of the vertebra prominens?

Answer 20

• has the longest spinous process of the cervical vertebrae
• only cervical vertebra that does not have a bifid spinous process
• large transverse process with a small transverse foramen which only transmits the accessory vertebral veins

Question 21

How do spinal nerves pass through the cervical region?

Answer 21

• there is a groove that runs across the superior aspect of the vertebral pedicle and then between the anterior and posterior tubercles of the transverse process
• the spinal nerve passes posterior to the vertebral artery which ascends through the foramina transversaria in C1-C6, together with the vertebral vein and sympathetic plexus

Question 22

Where do cervical spinal nerves exit?

Answer 22

• above their corresponding vertebrae until the C7/T1 junction, where the C8 nerve root is the ‘exiting nerve root’
• the neural segments are much more in line with their respective vertebrae (than in the lumbar spine), so the spinal nerve roots leave the cord more horizontally to pass through the intervertebral formamina

Question 23

What type of nerve root tends to be compressed by disc herniation in the cervical spine

Answer 23

when comparing the effect of intervertebral disc prolapse in the cervical spine with that in the lumbar spine, as there is no traversing nerve root in the cervical spine and it is the exiting nerve root that tends to be compressed by the disc

Question 24

What is the ligamentum nuchae?

Answer 24

• A thickening of the supraspinous ligament:
• extends from the external occipital protuberance of the skull and the median nuchae line to the spinous process of C7
• from its anterior border, a fibrous lamina attaches to the posterior tubercle of the atlas and to the spinous processes of all seven vertebrae
• continour inferiorly with the supraspinous ligament

Question 25

What are the roles of the ligamentum nuchae?

Answer 25

• to maintain the secondary curvature of the cervical spine
• to assist the cervical spine in supporting the weight of the head
• in continuity with the supraspinous ligament of the thoracic and lumbar spine, to be a major site of attachment of the muscles in the neck and trunk e.g. trapezius, rhomboids

Question 26

Where is the anterior longitudinal ligament and what is its function?

Answer 26

• stronger than the posterior longitudinal ligament
• runs continuously from the tubercle of the atlas to the sacrum and is united with the periosteum of the vertebral bodies
• loosely attached and mobile over the intervertebral discs
• function is to prevent hyperextension of the vertebral column

Question 27

Where is the posterior longitudinal ligament and what is its function?

Answer 27

• runs posterior to the vertebral bodies from the body of the axis to the sacral canal
• superior to the axis it continues as the tectorial membrane of the atlanto-axial joint (a strong band that covers the dens of the axis)
• main role is that it prevents hyperflexion of the vertebral column

Question 28

What is the main clinical relevance of the posterior longitudinal ligament?

Answer 28

Intervertebral disc prolapse tends to occur lateral to it i.e. paracentral disc herniation

Question 29

Where does the movement of nodding the head take place?

Answer 29

• 50% takes place through flexion and extension of the atlanto-occipital joint
• the remainder of the flexion-extension of the cervical spine occurs in the facet joints between the cervical vertebrae

Question 30

Where does the movement of shaking the head from side to side take place?

Answer 30

• 50% of this rotation takes place between the atlas and axis at the atlanto-axial joint
• remainder occurs at the facet joints

Question 31

What allows lateral flexion of the head?

Answer 31

• the cervical spine permits about 45% of lateral flexion (moving ear towards tip of shoulder) —> occurs at facet joints
• this is why articulating facets in the cervical vertebrae are orientated in the coronal plane at 45 degrees to the axial (transverse) plane

Question 32

How many thoracic vertebrae are there?

Answer 32

12 (T1-T12)

Question 33

What are the characteristics of the thoracic vertebrae?

Answer 33

• medium sized, heart shaped vertebral bodies
• small circular vertebral foramen
• prominent transverse processes with transverse costal facets to allow for articulation with tubercles of the ribs (present on only T1-T10)
• Either demi-facets (T2-T8) or whole facets (T9-T10) on the sides of the vertebral bodies for articulation with the heads of the ribs. [T11-12 have whole facets on the pedicles instead.]
• long spinous processes angulated inferiorly
• articular facets orientated at 20 degrees to the coronal plane and at 60 degrees to the axial plane (superior articular processes face posterolaterally and inferior articular processes face anteromedially)

Question 34

What does the orientation of the articular facets in the thoracic spine allow for?

Answer 34

Permits rotation and lateral flexion but prevents flexion and extension

Question 35

Why does the thoracic spine have limited flexibility compared with the cervical and lumbar spine?

Answer 35

Because the rib cage is connected to each segment of the thoracic spine

Question 36

Where do the ribs attach from the thoracic spine?

Answer 36

• attach to the thoracic spine via the superior and inferior costal facets
• the ribs attached to T1-T10 curve around to meet at the front of the body and either attach to the sternum (ribs 1-7), to the costal cartilages of the rib superior to them (ribs 8-10) or do not have an anterior attachment so terminate in the abdominal musculature (ribs 11 and 12)

Question 37

What do the ribs connected to T11 and T12 provide protection for?

Answer 37

The kidneys in the retroperitoneum (posterior wall of the abdomen)

Question 38

What three things protect the heart, lungs, liver and other vital organs?

Answer 38

The thoracic spine, the sternum and the rib cage

Question 39

What do the costal facets of the thoracic vertebrae articulate with?

Answer 39

• In addition to the superior and inferior articular facets that are present on all
  vertebrae, in the thoracic region there are costal facets located on the sides of each
  vertebra
• cartilage lined depressions which articulate with the heads of the ribs
• T2-T8 (majority of thoracic vertebrae) have superior and inferior demi-facets on the sides of the vertebral body
• superior demi-facet on the transverse process articulates with the head (tubercle) of the adjacent rib
• inferior Demi- facet articulates with the head of the rib below

E.g. the T3 vertebra articulates with ribs 3 and 4

Question 40

Which atypical vertebrae possess whole facets?

Answer 40

T1: superior costal facet is whole as this is the only vertebra to articulate with the first rib. The inferior costal facet is a demifacet as per the typical thoracic vertebrae

T9 and T10: whole costal facets articulate with the 9th and 10th rib. These facets extend from the vertebral body to the pedicle

T11 and T12: whole costal facets are located on the pedicles

Question 41

How does the spinous process change from T1 down to T12?

Answer 41

Becomes shorter and less oblique so the T12 process more closely resembles that of a lumbar vertebra

Question 42

What are the key characteristics of lumbar vertebrae?

Answer 42

 Large, kidney-shaped vertebral body
 Triangular-shaped vertebral canal (contains the conus medullaris at L1-
2, and cauda equina inferior to this)
 Large, blunt transverse processes
 Short, blunt spinous processes
 Facet joints orientated at 90° to the axial (transverse) plane and 45° to the coronal plane. The superior articular processes face
posteromedially and inferior articular processes face anterolaterally;
these permit a large range of flexion and extension, plus a small amount of rotation and lateral flexion).

Question 43

What does the tubercle of the rib articlate with?

Answer 43

The tubercle of the rib articulates with the costal demi-facet on the transverse process of the similarly-numbered vertebra i.e. the tubercle of the fifth rib articulates with the costal demi-facet of the T5 vertebra

Question 44

what limits movement of the thoracic spine?

Answer 44

The attachment of the thoracic cage and the orientation of the facet joints limits the
movement of the thoracic spine.

Question 45

Which movements do the thoracic facet joints permit?

Answer 45

These facet joints permit lateral flexion and rotation but no flexion or extension

Question 46

which direction do the superior articular and inferior articular surfaces of the thoracic spine face?

Answer 46

The superior articular processes face posterolaterally and inferior articular processes face anteromedially.

Question 47

what are the actions of the upper limb myotomes?

Answer 47

C5: shoulder abduction and external rotation plus weak contribution to
elbow flexion
C6: elbow flexion/wrist extension/supination /internal rotation of
shoulder
C7: elbow extension/wrist flexion/pronation / weak contribution to finger
flexion and extension
C8: finger flexion / finger extension / thumb extension / wrist ulnar
deviation
T1: finger abduction and adduction

Question 48

what are the actions of the lower limb myotomes?

Answer 48

L2: hip flexion
L3: knee extension and hip adduction
L4: ankle dorsiflexion
L5: great toe extension /ankle inversion / hip abduction
S1: ankle plantar-flexion/ankle eversion/ hip extension (or L5)
S2: knee flexion (some sources say S1 for this) /great toe flexion