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Biomechanics Exam I > Intervertebral Discs > Flashcards

Intervertebral Discs Flashcards

1
Q

How many intervertebral discs are in the human body?

A

23

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2
Q

Each intervertebral disc is given a numeric name relative to which segment?

A

The segment above

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3
Q

Intervertebral discs constitute what percentage of the entire height of the vertebral column?

A

20-33%

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4
Q

What are the three parts of the intervertebral disc?

A

Nucleus pulposus
Annulus fibrosus
Cartilaginous end plates

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5
Q

What makes up the disc to vertebral body ratio?

A

Height of the IVD compared to the height of the vertebral body

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6
Q

What amount of a disc to vertebral body ratio means there is greater spinal segmental mobility?

A

Greater ratio

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7
Q

In what area of the spine is the disc to vertebral body ratio greatest? Least? In between?

A

Greatest = Cervical spine (2:5)
Least = Thoracic spine (1:5)
In Between = Lumbar spine (1:3)

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8
Q

Based on disc to vertebral body ratios, where in the spine do we see the most mobility? Least?

A

Cervical spine = most

Thoracic spine = least

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9
Q

Where is the nucleus pulposus located in the IVD?

A

Centrally

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10
Q

What makes up the nucleus pulposus?

A

Mucoprotein gel with fine fibrous strands

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11
Q

What makes up 70-90% of the nucleus pulposus?

A

Water

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12
Q

When do we see the most water composition of the nucleus pulposus?

A

At birth (90%)

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13
Q

When do we see 80% water content of the nucleus pulposus? 70%?

A 
80% = age 20
70% = at old age
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14
Q

Do larger or smaller discs have more capacity to change size? By what mechanism do they accomplish this change?

A

Bigger discs; creep

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15
Q

What are the differences between cervical and lumbar nuclei of the IVD?

A

Lumbar - fill 30-50% of the total disc area in cross-section, more posterior than central
Cervical - less defined discs

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16
Q

At what locations is the cervical annulus minimal?

A

Minimal on lateral borders with thin strip in back

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17
Q

What makes up the annulus fibrosus?

A

Fibrous tissue in concentric laminated bands

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18
Q

What is the arrangement style of the annulus fibrosis?

A

Same direction within a band, opposite directions in any two adjacent bands

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19
Q

What angle measurement is formed by the concentric, laminated bands that cross each other obliquely in the annulus fibrosus?

A

30 degrees to the vertebral body

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20
Q

To where are annular fibers firmly attached?

A

Cartilaginous endplates in the inner zone

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21
Q

How do peripheral zone annular fibers attach to the vertebral body?

A

Sharpey’s fibers

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22
Q

What is unique about the attachment involving Sharpey’s fibers?

A

Stronger than other forms of attachment

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23
Q

What two ligaments reinforce the annular attachments of the IVD?

A

Anterior and posterior longitudinal ligaments

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24
Q

In which direction does the posterior longitudinal ligament narrow along its path?

A

Narrows from cervicals to lumbars (descending)

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25
Q

About how much of the central portion of the lower lumbar discs are covered by the posterior longitudinal ligament?

A

About 50%

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26
Q

What is the weakest area of the annulus and therefore the area most prone to injury? **

A

Posterolateral aspect

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27
Q

Where in the spine is the most common location for a disc herniation?

A

Lumbar spine

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28
Q

What are the three functions of the cartilaginous end plate?

A

Anchor for fibers of the nucleus and annulus
Prevent vertebral bodies from pressure atrophy
Maintain nuclear and annular borders

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29
Q

What part of the cartilaginous end plate is fairly impermeable?

A

Outer portion

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30
Q

Where does diffusion of nutrients occur in the cartilaginous end plate?

A

Central portion

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31
Q

What supplies the nucleus pulposus with most or all of its nutrition?

A

Cartilaginous end plate

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32
Q

Are there any blood vessels that go directly to the IVD?

A

NO

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33
Q

How do the annular fibers achieve their blood supply?

A

From adjacent soft tissues

34
Q

How does the nucleus pulposus achieve its blood supply?

A

From vertebral bodies

35
Q

From where can nutrients diffuse into the IVD?

A

Cartilaginous end plate

36
Q

When is an IVD considered avascular and aneural?

A

When healthy

37
Q

After damage, is the IVD able to self repair easily after the rapid degeneration that occurs?

A

No - limited self repair

38
Q

When do IVDs become increasingly vascularized and innervated by sensory nerve fibers?

A

During disc degeneration and osteoarthritis

39
Q

What changes occur to the IVD overnight?

A 
Decreased hydrostatic pressure
Increased osmotic pressure
Increased fluid volume in disc
Disc expansion
** INCREASED RESISTANCE TO FORCES = RESULT **
40
Q

What changes occur to the IVD during the daytime?

A

Fluid exits the disc
Disc space narrows
Decreased ligament tension
Increased range of motion

41
Q

How much of the IVD space is lost in seated height?

A

20 mm

42
Q

During the day, lumbar flexion can increase by what pecentage?

A

Up to 50%

43
Q

Is the IVD viscous or elastic?

A

Trick question: it’s viscoelastic :)

44
Q

Compression of what area of the IVD results in tension of the annular fibers?

A

Nucleus pulposus

45
Q

What is the result of flexion of the nucleus pulposus?

A

Compression of the anterior disc and tension on the posterior disc

46
Q

What chemical change and appearance is seen of the IVD due to age and exposure to biomechanical stresses?

A

Becomes more fibrous

47
Q

When flexibility is diminished due to the IVD becoming more fibrous overtime, where is the pressure on the IVD then exerted?

A

On the annulus and peripheral areas of the end plate

48
Q

Do all viscoelastic structures exhibit hysteresis?

A

Yes

49
Q

What three things make the level of hysteresis vary within a tissue?

A

Age of the disc
Spinal level involved
Repetitive load

50
Q

What is the difference of hysteresis in young people vs old people?

A

Large with very young people and smallest in middle-aged people

51
Q

At what level of the spine do we see less hysteresis?

A

Lower thoracic and upper lumbar region

52
Q

How does hysteresis changes due to repetitive load?

A

Decreases when successively loaded

53
Q

What kind of forces are resisted by the nucleus pulposus?

A

Compressive

54
Q

How are compressive forces resisted by the nucleus pulposus?

A

Pushing out against annular fibers

55
Q

What kind of forces are resisted by annular fibers?

A

Tensile forces

56
Q

Gravity and muscle co-contraction are examples of what kind of loads imposed onto the IVD?

A

Compressive

57
Q

Flexion, extension, and lateral bending are examples of what kinds of stresses imposed onto the IVD?

A

Both compressive loads and tensile stresses

58
Q

What kind of stress occurs on the IVD during axial rotation of the torso with respect to the pelvis?

A

Shear stress

59
Q

Is the IVD more susceptible to failure in the area of the forces of tension or compression?

A

Tension

60
Q

In what area of the IVD does mechanical failure following compression occur first?

A

Cartilaginous end plate (nuclear migration occurs)

61
Q

What physical change is the result of the failure of the cartilaginous end plate and nuclear migration of the IVD?

A

Schmorl’s node

62
Q

What is the damaged result from compressive loads in flexion of the IVD?

A

Anterior collapse of the end plate or vertebral body

63
Q

Compressive loads in extension are transmitted through what areas?

A

Facets

64
Q

Compressive loads in extension result in what type of injury?

A

Capsular injuries

65
Q

What is the damaged result from compressive loads applied with torque around the long axis?

A

Circumferential tears in the annular fibers of the IVD

66
Q

What provides 90% of the resistance to torque of a motion segment?

A

Intervertebral discs

67
Q

What provides the MAJORITY of the torsional resistance?

A

Annulus

68
Q

What protects the annulus from being strained by axial rotation in torsion?

A

Zygapophyseal joints

69
Q

By what age are 97% of all lumbar discs degenerated?

A

Age 50

70
Q

What segments are known to be the most degenerated segments?

A

L3-L4, L4-L5, and L5-S1

71
Q

What are the four stages/types of disc herniation?

A

1 Nuclear herniation
2 Bulge/Prolapse
3 Extrusion
4 Sequestration

72
Q

In what stage of disc herniation does the nucleus pulposus begin to migrate outward through the defects of the inner annulus but stays within the confines of the IVD?

A

Nuclear herniation

73
Q

In what stage of disc herniation does the nucleus pulposus continue to migrate outside the confines of the IVD but NO rupture of the outermost annular fibers occurs?

A

Bulge/Prolapse

74
Q

In what stage of disc herniation do the outer annular fibers tear and the contents of the nucleus pulposus move into the epidural space?

A

Extrusion

75
Q

In what stage of disc herniation do the discal fragments break loose from the IVD and float freely in the cerebrospinal fluid?

A

Sequestration

76
Q

Disc herniation is associated with repeated loading but also what forms of extreme deviated posture?

A

Full flexion or lateral bending

77
Q

Is a disc herniation a contraindication to adjust?

A

NO NO NO NO

78
Q

What is an example of an additional form of treatment that could help with a disc herniation?

A

Axial traction

79
Q

What is the name of the stretching exercising used for treatment of herniated discs?

A

McKenzie Extension

80
Q

Can intervertebral discs heal?

A

YES (takes time)

81
Q

What kinds of physical activity can we recommend to a patient suffering from a disc herniation?

A

Low-impact activities like walking/hiking, swimming, elliptical trainer, core muscle strengthening

Biomechanics Exam I (5 decks)

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