Vertebral Column Flashcards
how many vertebrae does the typical adult vertebral column have?
33:
- 7 cervical (C1 – C7)
- 12 thoracic (T1 – T12) articulate with ribs
- 5 lumbar (L1 – L5)
- 5 sacral (S1 – S5) fused into = sacrum – transfers weight to pelvis and lower limbs
- 4 coccygeal (Co) fused into one = coccyx
In adults, where does the spinal cord typically end?
L1-L2
What are vertebrae held together by?
- Facet joints
- Intervertebral discs
- Ligaments
What are facet joints? What do they connect?
- (also called zygapophyseal joints)
- connect the superior and inferior articular processes of adjacent vertebrae
- interlocking maintains stability
What passes through intervertebral foramen?
Spinal nerves
What are intervertebral discs? Function?
- Between all non-fused vertebrae
- Provide flexibility and act as shock absorbers
What is the function of the ligaments of the spinal cord?
Bind the vertebrae together and stabilise the vertebral column
function of vertebral canal?
- Protects spinal cord
- Supports body weight
- Semi-rigid axis axis for the body
- Allows pivoting of the head
- Attachment for supporting ligaments and muscles of the back that stabilise and move the vertebral column - supports posture and locomotion
Curvatures are present along the spinal cord. What are these important for?
Allow flexibility and shock absorption
Describe 1ary and 2ary curvatures of the spine
Foetus:
- Thoracic and sacral kyphoses –> 1ary curvatures seen in foetus
Adult:
- Cervical and lumbar lordoses –> 2ary curvatures that develop later
What type of curvature is:
- cervical
- thoracic
- lumbar
- sacral
- 2ary
- 1ary
- 2ary
- 1ary
What is kyphosis?
Kyphosis is a spinal disorder in which an excessive outward curve of the spine (near neck) results in an abnormal rounding of the upper back.
What is lordosis?
An excessive inward curve of the lumbar spine (closer to low back)
What is scoliosis?
A sideways curvature of the spine
General plan of a vertebra:
- Anterior vertebral body
- Posterior section:
- Pedicles
- Laminae
- Superior and inferior articular processes
- Transverse processes
- Spinous process
- Project directly posteriorly
- These are little bones you can feel in your back
What is the function of the pedicles?
Attaches the transverse process to the body of the vertebra
What is the function of the lamina?
Attaches transverse process to spinous process
What is the function of the superior and inferior articular processes and facets?
Joints between adjacent vertebrae; alignment determines movement
Which vertebral segment is the smallest?
Cervical spine C1-C7
Which cervical vertebrae are considered ‘atypical’? Why?
- C1 and C2 –> these are highly modified
- C1 articulates with occiput –> allows us to nod our head up and down
- C1 and C2 articulate with each other and form a pivot joint –> allows us to turn our head from side to side
- C7 is considered typical BUT:
- Has a long spinous process (vertebra prominens) which may not be bifid
- Used as a landmark to count the vertebrae from
- The transverse foramina of C7 might be small, or even absent
- Has a long spinous process (vertebra prominens) which may not be bifid
Why are injuries to the C-spine common?
- the C-spine is flexible
- the head is heavy
What do injuries to the C-spine risk?
Damage to the cervical spinal cord or brainstem:
- Fractures and dislocations: traumatic, crush / compression
- Dislocations can cause fractures because of the interlocking joints in the VC
- Rupture of ligaments > can compromise stability
- Cord / spinal nerve injuries occur if fracture fragments or dislocations compress or sever the cord
- Hence C-spine injuries are the most catastrophic – can lead to death or tetraplegia
What feature distinguish the cervical vertebrae?
The cervical vertebrae have three main features which distinguish them from other vertebrae:
- Triangular vertebral foramen.
- Bifid spinous process – this is where the spinous process splits into two distally.
- Transverse foramina – holes in the transverse processes. They give passage to the vertebral artery, vein and sympathetic nerves.
Describe the articular facets of the cervical vertebrae
- The articulating facets in the cervical vertebrae face 45 degrees to the transverse plane and lie parallel to the frontal plane
- The superior articulating process facing posterior and up
- The inferior articulating processes facing anteriorly and down
What runs through the transverse foramina?
- Vertebral arteries
- Vertebral veins
- Sympathetic nerves
What is important to note about the size of the cervical vertebral foramen?
Is large relative to the size of the spinal cord –> therefore, injuries to the cervical vertebrae don’t always result in spinal cord damage due to wiggle room
Which transverse process of the cervical vertebrae does the vertebral artery not pass through?
The vertebral artery doesn’t travel through the transverse foramina of C7
What is C1 also referred to as?
The atlas
How is C1 highly atypical?
- Is a ring structure with 2 lateral masses
- No vertebral body or spinous process
- Has 2 lateral masses which are connected by an anterior and posterior arch
- Anterior arch has facet for articulation with the dens of C2
- Posterior arch has groove for vertebral artery and C1 spinal nerve
- Each lateral mass contains a superior articular facet (for articulation with occipital condyles) and an inferior articular facet (for articulation with C2).
What does C1 articulate with superiorly? What action does this allow?
The occiput of the head - allows us to nod our head up and down
The posterior arch of the atlas (C1) contains a groove for what?
Vertebral artery and C1 spinal nerve
What is C2 also referred to as?
‘axis’
How is C2 highly atypical?
- No vertebral body
- This is highly modified to form the odontoid process / dens/ peg
- Hens dens is an anterior structure
- Dens articulates with the inner aspect of the anterior arch of C1 to form a pivot joint
- Allows us to turn head from side to side
- This is highly modified to form the odontoid process / dens/ peg
View of C2
What does the dens of C2 articulate with? What joint does this create? What movement does this allow?
- the inner aspect of the anterior arch of C1
- creates the medial atlanto-axial joint
- allows for rotation of the head independently of the torso
What are the atlantoaxial joints? Where are they located?
- Between C1 and C2
- 2 lateral and 1 median
- 2 lateral: between the lateral masses of C1 and superior facets of C2
- 1 median: pivot joint between dens and atlas
The median atlantoaxial joint (between the dens and atlas) is synovial. What disease can it therefore be affected by?
Rheumatoid arthritis
What is the median atlantoaxial joint (between the dens and atlas) reinforced by?
Ligaments which hold the dens in place –> key ligament is the transverse ligament of the atlas
What is the dens of the axis secured by?
The transverse ligament of the atlas - which attaches to the lateral masses
What happens if the dens is displaced?
The spinal cord can be damaged
Normal C-spine x-rays
- look for normal alignment
- trace around all the vertebrae looking for signs of fracture
- Look for uniformity in the thickness of the spaces between vertebral bodies
What type of injury is ‘axial loading’?
Most cervical spinal cord injuries are the result of axial loading (force directed through the top of the head and through the spine) forcing the head into hyperflexion and/or rotation –> e.g. diving into swimming pool and hitting bottom
What can happen during ‘axial loading’?
- Can cause a burst fracture of the C1 ring - a Jefferson fracture
- The occipital condyles impact into the lateral masses of C1 and cause it to break in at least 2 places (anterior and posterior)
- Surprisingly, this doesn’t necessarily cause spinal cord injury
- However, if fracture fragments impact on the spinal cord, it can be a catastrophic injury
What is a ‘Jefferson fracture’?
a bone fracture of the vertebra C1
Why does ‘axial loading’ not always result in spinal cord injury?
- Impact can widen the vertebral foramen which the spinal cord sits in
- Spinlal cord is then not compressed
- N.B. there may be damage further down the vertebral column.
Which part of C2 is most likely to be fractured?
The dens/odontoid process
What are fractures of the dens often caused by?
- Can be caused by hyperflexion or hyperextension injuries
- Bimodal age distribution of peak incidence: (i.e. peak in two age groups)
- Elderly (over 70 years) = low-energy trauma (e.g. falls from standing height) +/- osteoporosis
- Young (20-30 years) = high-energy trauma (e.g. RTA, diving injuries, falls from height, blunt trauma to the head)
Why is associated spinal cord injury infrequent in dens fractures? (2 reasons)
- Due to relatively larger size of spinal canal in upper C-spine compared to the size of the cord
- As the dens is held in place by the transverse ligament of the atlas
Why are fractures of the dens often unstable and at high risk of avascular necrosis?
due to the isolation of the distal fragment from any blood supply
If the dens fractures and the transverse ligament ruptures, what can happen?
- The dens may be driven into the brainstem
- In non-fatal cases, dens fracture often requires surgery as non-union is a problem
What is C-spine immobilisation?
Involves the fitting of a cervical collar as a means of minimising the risk of cervical spinal cord compromise.
C-spine injuries are more likely to dislocate than other vertebrae. Why is this important during imaging?
Beware: can subluxate and then move back into place by the time images are taken – careful neuro exam required.
What ar the basic features of the thoracic vertebrae?
- Vertebral body
- Heart-shaped
-
Superior and inferior costal demi-facets for articulation with the head of the rib
- Least flexible part of vertebral column
- Spinous process
- Long and extend postero-inferiorly
- Transverse process
- Has a costal facet for articulation with tubercle of a rib
- Articular facets
- superior faces posteriorly, inferior faces anterior
At what points do the thoracic vertebrae and ribs articulate (costovertebral joints)?
- The head of rib articulates with the superior demifacet of the corresponding (same number) vertebra and the inferior demifacet of the vertebra above
- The tubercle of the rib articulates with the costal facet on the transverse process
Which thoracic vertebrae are most commonly fractured?
T11 and T12 (more flexible segment of column)
What vertebrae does osteoporosis typically affect?
Thoracic
How does osteoporosis affect thoracic vertebrae?
- Vertebral bodies become weaker due to osteoporosis and start to buckle and crack and become compressed
- End up with compression of anterior part of vertebral body –> compression (‘wedge’) fracture
- Very common – leads to excessive thoracic kyphosis, height loss, pain and reduced mobility
Who is osteoporosis most common in?
Postmenopausal women
Difference between osteoporosis and osteoarthritis?
While OA is a degeneration of a joint, osteoporosis is the loss of BONE mass which causes risk of fractures, even spontaneously.
What features are seen in osteoarthritis?
- Osteophytes
- Sclerotic changes
- Joint space narrowing
Features of lumbar vertebrae?
- Large vertebral body
- For increased weight bearing
- Significant traumatic forces usually required to fracture lumbar vertebrae
- Articular facets:
- Superior face medially
- Inferior face laterally
- Spinous process short and sturdy
- Relatively narrow vertebral foramen
How is the sacrum formed?
By fusion of the five sacral vertebrae –> no intervertebral discs
What is the ‘ala’/’wing’ of the sacrum?
upper part of the lateral part of sacrum, lateral to the first sacral vertebra.
What does the apex of the sacrum articulate with?
The coccyx
Lateral view and articulations of sacrum
Superior articular process and facet for articulation with L5
What movements of the verteral column are possible?
- Flexion
- Extension
- Lateral flexion
- Rotation
These movements are possible to different degrees at different parts of the vertebral column
What factors influence the range of movement of different parts of the vertebral column?
- the orientation of facet joints
- the thickness of the intervertebral discs
Which part of the vertebral column are most flexible?
Cervical and lumbar spine
Which movements are limited at the T-spine?
flexion limited, but rotation possible
What movements are the intrinsic muscles of the back responsible for?
associated with movements of the vertebral column.
What are the intrinsic muscles of the back innervated by?
Posterior rami of spinal nerves
The muscles of the back can be divided into three groups. What are they and what is their function?
- Superficial: associated with movements of the shoulder and upper limb
- Intermediate: associated with movements of the thoracic cage
- Intrinsic: associated with movements of the vertebral column
What is the chief intrinsic muscle of the back?
-
Erector spinae –> this is the chief extensor of the vertebral column
- Composed of 3 separate muscles:
- Longissimus muscle
- Iliocostalis muscle
- Spinalis muscle
- Large muscle that runs longitudinally either side of VC (You don’t need to know their attachments)
- Composed of 3 separate muscles:
Deep to erector spinae (intrinsic muscle of back) is another, much smaller, group of intrinsic back muscles.
(You don’t need to know the names or attachments of these muscles but know they exist.)
What do these muscles connect?
Connect the transverse processes of the vertebrae to the spinous processes of more superior vertebrae
Where do the intervertebral discs lie?
Between the vertebral bodies
There are 2 parts to each intervertebral discs. What are these?
- Outer annulus fibrosus
- Fibrocartilage ring attached to the rim of vertebral body
- Inner nucleus pulposus
- gelatinous ‘shock absorber’
Function: flexibility, shock absorption and stability
What does the thickeness of the intervertebral discs determine?
The flexibility of the vertebral column: relatively thicker in C and L spine, hence why these regions are most flexible
The intervertebral discs have a high water content. How does this change with age?
they dehydrate with age – become thinner and stiffer
What is a slipped disc/herniated disc?
A herniated disc occurs when the intervertebral disc’s outer fibers (the annulus) are damaged and the soft inner material of the nucleus pulposus ruptures out of its normal space.
Where does IV disc herniation typically occur?
At L4/5 or L5/S1, followed by the C-spine
What can IV disc herniation lead to?
- Nucleus pulposus bulging out of disc can compress the spinal nerve roots or the spinal cord itself (surgical emergency)
- Causes pain / paraesthesia in the distribution of that nerve, e.g. lower back pain or leg pain (‘sciatica’)
- Can also compress the cauda equina
- Causes cauda equina syndrome which is a surgical emergency
What is cauda equina? Symptoms?
Compression of cauda equina (all of the nerves in the lower back suddenly become severely compressed). Symptoms:
- sciatica on both sides
- weakness or numbness in both legs that is severe or getting worse
- numbness around or under your genitals, or around your anus.
- incontinence
What are the key ligaments of the vertebral column?
- Posterior longitudinal ligament
- Anterior longitudinal ligament
- Ligamentum flavum
Location and function of anterior longitudinal ligament?
- Location: runs anterior to vertebral bodies from occiptal bone and C1 and passes all the way to sacrum
- Function: only ligament to resist hyperextension of vertebral column (all the rest resist hyperflexion)
Location and function of posterior longitudinal ligament?
- Location: posterior to vertebral bodies (inside canal) and runs from C2 to sacrum
- Function:
- Resists hyperflexion
- Prevents posterior herniation of IV discs
Location and function of ligamentum flavum?
- Location: binds lamina of adjacent vertebrae, (traversed in lumbar puncture)
- Gives ‘pop’
Other ligaments to be aware of: series of ligaments that bind the spinous processes together.
- Interspinous ligament: between adjacent spinous processes
- Supraspinous ligament: joins tips of spinous processes together
These must both be traversed in a lumbar puncture
Lumbar puncture view of ligaments
What is whiplash?
- Rapid, forceful hyperextension then hyperflexion e.g. RTA
- Injuries range from mild muscular sprain to catastrophic injuries depending on force > ligaments can be ruptured and / or bones of the C-spine fractured
- Severe forces – think high-speed impact RTA, rapid deceleration on impact
N.B. Anterior longitudinal ligament is torn in hyperextension injuries - part of a vertebral body may be avulsed and posterior part of the vertebral body dislocated > compression of spinal cord
