7. Lumbar Spine Flashcards
(76 cards)
1
Q
What proportion of the length of the vertebral column is due to the intervertebral discs?
A
~ 1/4
2
Q
How many of each type of vertebrae are present?
A
33 vertebrae:
7 cervical, 12 thoracic, 5 lumbar, 5 sacral,
4 coccygeal
3
Q
How are intervertebral discs named?
A
Relative to the vertebrae on each side of the disc
E.g. the disc between L3 and L4 is the L3/L4 intervertebral disc
4
Q
Which part(s) of the vertebral column is mobile and which are immobile?
A
- 24 separable vertebrae
- All capable of individual movement
- Mobile: Cervical and Lumbar (and coccyx)
- Relatively Immobile: Thoracic (and sacrum)
5
Q
Which vertebrae are fused?
A
- Sacrum (fusion of 5 vertebrae)
- Coccyx (fusion of 4 vertebrae)
6
Q
Why are the thoracic vertebrae relatively immobile?
A
they are joined by the ribs to the sternum
7
Q
What are the functions of the vertebral column?
A
- Support - of the the skull, pelvis, upper limbs and the thoracic cage.
- Protection - of the spinal cord and the cauda equina
- Movement - Highly flexible structure of bones, intervertebral discs and ligaments -important role in posture
- Haemopoiesis - Within red marrow
8
Q
What are the primary kyphotic curvatures?
A
Thoracic and sacral - develop during fetal period and concave anteriorly
9
Q
What are the secondary lordotic curvatures?
A
Cervical and lumbar - develop during childhood when head is lifted and through sitting, concave posteriorly
10
Q
Why are the vertebral bodies lower down in body bigger?
A
The compression forces to which they are subjected to increase with increasing weight
- larger surface area → less force going through
11
Q
What are adaptations of sacral vertebrae and where do they transmit the weight they carry?
A
They are fused, widened and concave anteriorly.
Transmit the weight of the body through the pelvis to the legs.
12
Q
What are the general features of lumbar vertebrae?
A
- Kidney-shaped vertebral body
- Vertebral arch posteriorly
- Vertebral foramen
13
Q
Which structures form the vertebral arch?
A
- 2 pedicles: connect transverse processes to the vertebral body
- 2 lamina: connect transverse processes to the spinous process
14
Q
What structures are contained within lumbar vertebral foramen?
A
Contains the conus medullaris, cauda equina
and meninges
15
Q
What processes arise from the vertebral arch?
A
- 1 Spinous process
- 2 Transverse processes
- 2 Superior articular processes
- 2 Inferior articular processes
16
Q
What is the bone composition of the vertebral body?
A
- 10% Cortical bone
* 90% Cancellous bone
17
Q
Why do vertebral bodies have high proportion of cancellous bone?
A
- reduces the weight of the vertebrae
- permits haematopoiesis to take place
- resists gravitational forces
18
Q
What are the superior and inferior surfaces of the vertebral body called and what are they covered with?
A
Vertebral end plates
- covered in hyaline cartilage
19
Q
What links adjacent vertebral bodies?
A
intervertebral discs
20
Q
What forms the facet (zygapophyseal) joint?
A
Articulation of superior articular processes with inferior articular processes of adjacent vertebrae.
21
Q
What are the posterior elements?
A
Structures posterior to the vertebral body
1/3 of the load is carried through these elements (the rest is carried through the vertebral body itself)
22
Q
What do the transverse and spinous processes provide?
A
Provide attachment points for muscles and ligaments to control the positions of the vertebral bodies
Their shape provides a lever arm to provide the system with mechanical advantage
23
Q
What is a vertebral notch?
A
Concavity created by concave articular processed
Each vertebra has two superior and inferior vertebral notches
The inferior notch of one vertebra comes together with the superior notch of another to form the intervertebral foramen -space created on each side
24
Q
What type of joint is a facet joint?
A
Synovial joint lined with hyaline cartilage
25
What opening is created by facet joint and what travels through it/
Intervertebral foramen
| - allows passage of spinal nerves
26
What does the interlocking design of the facet joints prevent?
antero-posterior (forward-backward) displacement of the vertebrae.
27
What plane are articulating surfaces in cervical vertebrae in and what movements do they allow?
- in the coronal plane
- 45° to axial (transverse) plane
Allows rotation, flexion, extension, lateral flexion
28
What plane are articulating surfaces in thoracic vertebrae in and what movements do they allow?
- 60° to axial plane
- 20° to coronal plane - superior articulating process facing laterally by 20° from the coronal plane
Allows rotation and lateral flexion
29
What plane are articulating surfaces in lumbar vertebrae in and what movements do they allow?
- 90° to axial plane
- 45° to coronal plane
Superior facets face posteromedially (posteriorly and 45° medially) and the inferior facets face anterolaterally (anteriorly and 45° laterally)
major movements permitted in the lumbar spine are flexion and extension.
- some lateral flexion and rotation
30
How does the orientation of the facets change at the lumbosacral junction?
- the inferior facet on L5 faces anteriorly
| - the change in orientation prevents the vertebral column from sliding anteriorly on the sacrum
31
What are the different types of joints in the spine?
* Fibrous: Non-mobile e.g. sacroiliac joint
* Secondary cartilaginous (symphyses): Partially mobile e.g. intervertebral discs
* Synovial Joints: Highly mobile e.g. facet joints
32
What is the composition of the intervertebral discs?
70% water, 20% collagen, 10% proteoglycans
33
What are the 2 regions of the intervertebral discs?
- nucleus pulposus which is central
| - annulus fibrosus which is peripheral
34
What is the function of the anulus fibrosus?
Major shock absorber
| - highly resilient under axial (top-to-bottom) compression and is stronger than the vertebral body
35
Describe the structure of the anulus fibrosus.
- lamellae of annular bands of collagen in varying orientations
- outer lamellae are type 1 collagen
- inner lamellae are fibrocartilaginous
- is avascular and aneural
36
What is the nucleus pulposus the remnant of?
Notochord.
37
Describe the structure of nucleus pulposus.
Gelatinous and consists of type 2 collagen.
38
When does the intervertebral body decrease in height and why?
During the day and as we age
| - due do mechanical pressure which squeezes water out
39
Where is the nucleus pulposus located within the intervertebral disc relatively in the child and in an adult?
Centrally in a child and posteriorly in the adult
40
What are the ligaments the vertebral column?
- Anterior and posterior longitudinal ligaments
- Ligamentum flavum
- interspinous ligament
- supraspinous ligament
41
Why is it important to keep your spine straight whilst lifting heavy loads?
Intevertebral discs are strong in axial compression but less so under tangential loading (load applied at an angle)
42
What do the ligaments of the vertebral column do?
- provide stability by preventing excessive movement between the vertebrae
- good at supporting loads applied in the same direction in which their fibres run
- store energy and provide resistance - under enough compression the fibres can buckle
43
Describe the anterior longitudinal ligament.
- runs anterior to the vertebral bodies
- runs continuously from the anterior tubercle of the atlas (C1 vertebra) to the sacrum
- united with the periosteum of the vertebral bodies.
- Over the intervertebral discs, it is loosely attached and mobile
44
What is the function of the anterior longitudinal ligament?
Prevent hyperextension of the vertebral column
45
Describe the posterior longitudinal ligament.
- runs posterior to the vertebral bodies
- from the body of the axis (C2 vertebra) to the sacral canal.
- weaker than anterior ligament
- superior to the axis, it continues as the tectorial membrane of the atlanto-axial joint
46
What is the function of the posterior longitudinal ligament?
Prevent hyperflexion of the vertebral column
47
What is the main clinical relevance of the posterior longitudinal ligament?
Reinforces the annulus fibrosus centrally so that intervertebral disc prolapse tends to occur lateral to the posterior longitudinal ligament.
- This type of prolapse is called a paracentral disc prolapse
48
Why is the ligamentum flavum called that?
It has a high elastin content and appears yellow to the naked eye (Flava = yellow in Latin).
49
Where is the ligamentum flavum located and what is its function?
- situated between the laminae of adjacent vertebrae
| - becomes stretched during flexion of the spine.
50
Describe the interspinous ligaments.
- Relatively weak sheets of fibrous tissue
- unite the spinous processes along their adjacent borders.
- fuse posteriorly with the supraspinous ligament
51
Where is the interspinous ligaments most developed and what is its function there?
Lumbar region
| - increase the stability of the vertebral column by resisting excessive flexion.
52
Describe the supraspinous ligament.
- runs along the tips of the adjacent spinous processes
- is a strong band of fibrous tissue
- lax in extension and taught in flexion,
- further increasing the stability of the vertebral column.
53
How does force transmission through the vertebrae change with age?
- young: 80% of our body weight is transmitted through the vertebral bodies and 20% through the facet joints
- age: the nucleus pulposus dehydrates and decreases in size. A greater proportion of the load is therefore borne through the facet joints e.g. 65% vertebral bodies, 35% facet joints
increased stress on the facet joints leads to osteoarthritic changes, similar to those seen in the knees and hips.
54
What happens as we flex the spine?
As we flex the spine, the posterior longitudinal ligament, ligamentum flavum, interspinous ligament and supraspinous ligament are all under tension. The
vertebral bodies, intervertebral discs and anterior longitudinal ligament are under compression
55
What is the conus medullaris and where is it located?
Tapered end of spinal cord
| - around L2
56
Why should you lift a weight close to the body?
If you lift a weight at a distance from the body, the force is multiplied many-fold through the spine leading to a greater risk of intervertebral disc prolapse
57
Where does the central canal of the vertebral column end and what does it contain?
Continues along the core of the sacrum and ends at the fourth sacral vertebra - sacral hiatus
Contains the cauda equina
58
What is the cauda equina?
Bundle of spinal nerve rootlets fibres, consisting of:
- L2- L5 (exit vertebral canal in lumbar region)
- S1 - S4 (exit sacral canal via posterior sacral foramen)
- S5 and Coccygeal nerve (exit via sacral hiatus)
Proximal parts of these nerves are contained within the dural sac which terminates at S2
59
What do the nerves that compase the cauda equina innervate?
innervate the pelvic organs (e.g. bladder) and the lower limbs.
60
What is the filum terminale?
Continuation of the pia mater from the conus medullaris of the spinal cord to the first segment of the coccyx.
It is approximately 20cm in length and gives longitudinal support to the spinal cord.
61
What is the continuation of the vertebral column in the sacrum called and where does it end?
vertebral column continues along the core of the sacrum as the sacral canal and ends at the fourth sacral vertebra.
62
What is the end of the sacral canal called?
Sacral hiatus
63
How do the sacral nerves enter and leave the central canal?
The transverse processes of the five sacral vertebrae are incompletely fused and the sacral nerves enter and leave the central canal by way of four pairs of posterior sacral foramina
64
Why do humans have a cauda equina?
In embryo, spinal cord grows slower than rest of the body —> starts off level but the rate of growths become imbalanced so when born the spinal cord only reaches L2
65
What is the shape of the vertebral column in the fetus?
C shaped, concave anteriorly
| - primary curvature - and is retained throughout life in the thoracic, sacral and coccygeal regions.
66
Define kyphosis.
Anterior flexion of the spine (anteriorly concave)
67
Define lordosis.
Posterior flexion of the spine (posterior concave)
68
What are the secondary curvatures of the spine?
the lordotic curvatures: cervical and lumbar
69
How do the secondary curves form?
When the young child begins to lift its head the cervical spine develops a posterior concavity.
During crawling, the lumbar spine loses its primary kyphosis and straightens out. When the child begins to stand up and walk, a lumbar lordosis develops
Primarily develop due to intervertebral discs becoming more wedge shaped.
70
Why is a spine sinusoidal in shape?
- flexibility
| - resilience
71
What can lead to exaggeration of the lumbar lordosis and why?
- pregnancy
- obesity
Restore centre of gravity
72
What is senile kyphosis?
Secondary curvatures start to disappear, and a continuous primary curvature is reestablished in old age.
73
Why does senile kyphosis occur?
With increasing age:
- annulus fibrosis degeneration
- nucleus pulposus loses its turgor and becomes thinner because of dehydration and degeneration.
- account for some loss of height.
- patients commonly experience osteoporotic vertebral compression fractures
- resulting in wedge-shaped vertebrae
- Disc atrophy, with or without accompanying osteoporotic fractures, means that the secondary curvatures start to disappear, and a continuous primary curvature is reestablished
74
How does the sacrum aid transmission of weight?
The sacral vertebrae are fused, widened and concave anteriorly to transmit the weight of the
body through the pelvis to the lower limbs.
75
At which sites does centre of gravity pass through the vertebral column and what do these sites represent?
Between C1-C2, C7-T1, T12-L1, L5-S1
These sites represent weak points of the vertebral column at which pathology tends to develop.
The centre of gravity of the body is projected into the lower limbs through a line that passes centrally through the natural curvatures of the vertebral column.
76
What is lumbar puncture? How is it carried out?
- withdrawal of fluid from the subarachnoid space of the lumbar cistern
- important to diagnose CNS disorders like meningitis and MS
- patient lies on the side with the back and hips flexed to help insertion of the needle as this spreads part the vertebral laminae and spinous processes, stretching the ligamentum flavum
- the skin covering the lower lumbar vertebrae is anaesthetised and a lumbar puncture needle is inserted in the midline between the spinous processes of the L3 and L4 (or L4 and L5) vertebrae: at these levels there's no danger of damaging the spinal cord
- this can be located by finding the plane transecting the highest points of the iliac crests - the supracristal plane- which passes through the L4 spinous process
- 4-6cm (or more in obese people) in, the needle pops through the ligamentum flavum then punctures the dura and arachnoid, to enter the lumbar cistern to collect CSF
