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KIN 316 - Biomechanics of Tissue > Module 10 - Lumbar Spine > Flashcards

Module 10 - Lumbar Spine Flashcards

1
Q

What are major structural components of the vertebral column?

A
  • Vertebral bodies
  • Intervertebral disks
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2
Q

What is the spinal cord important for?

A
  • Relaying neural information
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3
Q

How do the vertebral bodies of the lumbar spine compare to the thoracic and cervical spine?

A
  • Thicker
  • Wider
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4
Q

Why are lumbar vertebral bodies thicker and wider than the thoracic and cervical ones?

A
  • Designed mainly to bare compressive loads
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5
Q

What percentage of body load is on the lumbar vertebra?

A
  • 50%
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6
Q

What percentage of body load is on the thoracic vertebra?

A
  • 20-30%
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7
Q

What happens when the vertebra is under compression?

A
  • Walls of vertebra remain rigid
  • End plates bulge inwards: when the intervertebral disk pressurizes
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8
Q

What fails first under compression?

A
  • Cancellous bone
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9
Q

What is the determinant factor of tolerance to compression?

A
  • Cancellous bone
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10
Q

What plays a dominant role in shock absorption?

A
  • Vertebral Body
  • Not the disks
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11
Q

What is the deformation of cancellous bone due to?

A

architecture
- vertical and transverse trabeculae

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12
Q

What do the vertical and transverse trabeculae offer?

A

Balance between
- Elasticity
- Rigidity

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13
Q

What happens upon axial compression?

A
  • End plate bulge into the vertebral body
  • Vertical trabeculae experience compression and bend
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14
Q

What is the microfracture of trabeculae called?

A
  • subfailure
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15
Q

When can a micro-fracture of trabeculae occur?

A
  • Following repeated loading
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16
Q

Will there be damage to the trabeculae if the loading is less than 10% of ultimate compressive load?

A
  • No
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17
Q

How many cycles of a load of 20-30% will lead to damage to the trabeculae?

A
  • 20000
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18
Q

What does damage of the trabeculae lead to?

A
  • Decreased stiffness
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19
Q

What does an osteoporotic bone lead to?

A
  • Decrease in number and size of transverse trabeculae
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20
Q

What does an osteoporotic vertebra have?

A
  • Decreased compressive strength
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21
Q

What are the posterior elements of the vertebrae?

A
  • Pedicles
  • Laminae
  • Spinous Process
  • Transverse processes
  • Facet joints
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22
Q

Describe the posterior vertebrae structure.

A
  • Shell of cortical bone
  • Contains cancellous bony core in thick section
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23
Q

Describe the neural arch of the vertebrae

A
  • Pedicles
  • Laminae
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24
Q

What is spondylolysis?

A
  • Anterior displacement of vertebral body with respect to the segment below
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25
Q

How does spondylolysis occur?

A
  • Failure of posterior elements
  • Shear forces acting on posterior elements
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26
Q

What type of athlete often experiences spondylolysis?

A
  • Gymnasts
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27
Q

Why might spondylolisthesis be asymptomatic in fit people?

A
  • Spine stability
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28
Q

What can happen for someone who has asymptomatic Spondylolisthesis?

A
  • May experience symptoms later in life
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29
Q

What is the intervention method for treating spondylolisthesis?

A
  • Surgery
  • Stability exercises
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30
Q

At what level does spondylolisthesis usually occur?

A
  • L5 to S1
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31
Q

Is spondylolisthesis congenital?

A
  • No: detected as early as 4 months
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32
Q

What might predispose an individual to develop spondylolisthesis?

A
  • Genetic factors
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33
Q

Can Spondylolisthesis occur at multiple levels?

A
  • Yes
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34
Q

What level is degenerative spondylolisthesis most frequent?

A
  • L4
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35
Q

What level is the most common for spondylolisthesis?

A
  • L5
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36
Q

What do Intervertebral disks do?

A
  • Bear and distribute loads
  • Restrain motion
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37
Q

Why are intervertebral disks well suited to bear and distribute loads and restrain motion?

A
  • Located between vertebrae
  • Composition of inner and outer structures (hard to distinguish)
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38
Q

What is the inner portion of the intervertebral disks comprised of?

A
  • Gelatinous mass (nucleus pulposus)
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39
Q

What does the inner portion of the intervertebral disk do?

A
  • Cushion between vertebrae
  • Store energy
  • distribute loads
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40
Q

What is the outer portion of the intervertebral disk made of?

A
  • Tough covering of fibrocartilage (annulus fibrosus)
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41
Q

What does the outer portion of the intervertebral disk do?

A
  • Withstand large bending
  • Withstand torsional loads
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42
Q

What happens to the annulus fibrosus during axial rotation (twisting)?

A
  • Half resists load
  • Half relaxes
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43
Q

What happens as a result of axial rotations effect on annulus fibrosus?

A
  • Decreases its ability to bear the load
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44
Q

What happens to the intervertebral disk during compression or bending?

A
  • Annulus and nucleus work together
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45
Q

What happens to the nucleus and annulus of the intervertebral disk during compression?

A

Nucleus
- Pressurizes
- Applies vertical forces to end plates
- lateral forces to inner annulus
Annulus
- Minimal deformation

46
Q

What happens to the nucleus and annulus of the intervertebral disk during bending?

A

Annulus
- Compression (outward bulging)
- Traction
Nucleus
- Moves in direction of traction

47
Q

What happens to intervertebral discs in healthy joints under compressive load?

A
  • Minimal deformation
48
Q

What must occur for an intervertebral disc to herniate?

A
  • Must be bent to full end range
49
Q

What is the easiest way to elicit a disc herniation?

A
  • Repeated Flexion
50
Q

What is disc herniation associated with?

A
  • Extreme deviated postures
  • Repeated loading
51
Q

What does herniation depend on?

A
  • Compressive load during full flexion cycle
52
Q

What are risk factors for herniation?

A
  • Sedentary occupations
  • Sitting postures
53
Q

What type of spines does herniation tend to occur in?

A

Younger spines
- with high water content

54
Q

What should you do for a patient with a herniation?

A

Identify daily motion exacerbating it
- eliminate it
- Change motion

55
Q

Where does the herniation process occur?

A
  • Innermost annulus rings
56
Q

What happens when herniation process progresses?

A
  • Moves radially outwards
57
Q

What is the McKenzie protocol?

A
  • Extension exercises to drive the nucleus forward within the disk
58
Q

What happens when a healthy disk under compressive loads, develops internal disk pressure that is so high that no blood vessels or nerve can survive?

A
  • End plate damage
  • Disc no longer develops high pressures
  • Degenerated discs vascularize and generate pain
59
Q

What do the ligaments of the lumbar spine do?

A
  • Contribute to intrinsic stability
  • Depends on anatomical location
  • Depends on type of motion
60
Q

What does the Ligamentum Flavum contain?

A
  • Large percentage of elastin
61
Q

What does the Ligamentum Flavum do in a neutral position?

A
  • Is under tension
62
Q

Why is the Ligamentum Flavum under tension during neutral position?

A

Pre-stress the disk

63
Q

What does the pre-stressing of the disc in a neutral position by the tension of the Ligamentum Flavum do?

A
  • Provides spinal stability
64
Q

What roles do the interspinous ligaments have?

A
  • controls vertebral rotation during flexion
  • Protects against post-shear of sup. Vertebra
65
Q

What can the extensor muscles be divided into?

A

Three Groups
- Longissimus
- Iliocostalis
- Multifidus

66
Q

Where are the rotatores and intertransversarii located?

A
  • lumbar level
67
Q

What is the length of the Longissimus and Iliocostalis?

A
  • 20-30cm
68
Q

Where does the Pars lumborum attach?

A
  • lumbar spine
69
Q

What do the Longissimus and Iliocostalis have?

A

Pars thoracis and lumborum

70
Q

What percentage of muscle fibers are slow twitch in the pars lumborum?

A
  • 50%
71
Q

What percentage of muscle fibers are slow twitch in the pars thoracic?

A
  • 75%
72
Q

Where does the pars thoracis attach?

A

The thoracic spine

73
Q

What is the line of action of the pars lumborum?

A
  • Posterior and caudal
74
Q

Describe the pars lumborum line of action

A
  • Large moment arm: 50-100mm
75
Q

Are Iliocostalis and longissimus efficient lumbar extensors?

A
  • Yes
76
Q

Describe the iliocostalis and longissimus tendon

A
  • long
  • runs parallel to spine
  • large moment arm
77
Q

Why are the iliocostalis and longissimus efficient lumbar extensors?

A
  • Long moment arm
  • Large extensor moment of force
78
Q

What kind of exercise should be used to strengthen iliocostalis and longissimus pars thoracis muscles?

A
  • exercise that includes motion of the thoracic spine
79
Q

How many segments do the multifidus muscles span?

A
  • 1-3 segments
80
Q

How long are the multifidus muscles?

A
  • 5-8cm
81
Q

Where does the force generated from the multifidus muscles affect?

A
  • Local areas of the spine
82
Q

What is the line of action of the multifidus muscles?

A
  • Parallel to the compressive axis or anterior and caudal
83
Q

How long is the moment arm of multifidus muscles?

A
  • 10-15mm
84
Q

What do some authors describe as the role of multifidus muscles?

A

Could be:
- High muscle spindle density
- Spinal stability

85
Q

What does the compressive forces at the intervertebral disc level depend on?

A
  • Mass of trunk, head and arms
  • Force developed by lumbar extensor muscles
  • Angle of trunk
  • orientation of intervertebral disk
86
Q

What is the joint reaction force?

A

Counterbalance of:
- Extension moment
- Flexion moment

87
Q

What is the relationship between the flexion-extension cycle and compressive load?

A

For herniation to occur:
- As compressive load increase
- Required flexion-extension cycle decreases

88
Q

What are the three biomechanical concepts around lumbar?

A
  • Orientation of facets determine types of motion possible
  • Loading of lumbar intervertebral disc is influenced by posture
  • Flexion-extension movement of the lumbar spine
89
Q

What orientation are the facets in at a 90 degree angle?

A
  • transverse plane
90
Q

What orientation are the facets in at a 45 degree angle?

A
  • Frontal plane
91
Q

Describe the flexion-extension movement of the lumbar spine

A
  • Motion between two vertebrae is small
  • Combined motion of several segments
  • Intersegmental kinematics
  • strain on ligaments
92
Q

What accounts for the amount of strain on each ligament?

A
  • type of motion
93
Q

What lumbar spine ligaments are strained during flexion?

A
  • Supraspinous ligament
  • Capsule and flavum ligament
94
Q

What lumbar spine ligaments are strained during extension?

A
  • Longitudinal anterior ligament
95
Q

What lumbar spine ligaments are strained during rotation?

A
  • Capsular ligament
  • Lat. Flexion
  • transverse ligament
96
Q

What accounts for the first 50-60 degrees of spinal flexion?

A
  • Lumbar spine
97
Q

What accounts for the flexion of the spine beyond 60 degrees?

A
  • Lumbar spine
  • Pelvic tilting
98
Q

What is the flexion-relaxation phenomenon?

A
  • At full flexion, the lumbar ES are turned off
99
Q

When the active muscular actions are turned off during the flexion-relaxation phenomenon, what takes over their role?

A
  • The ligaments of the lumbar spine
  • Passive properties of the muscles
100
Q

How is the flexion-relaxation phenomenon possible?

A
  • Force of passive structures increases when lengthened
101
Q

What is the new equilibrium controlled by during the flexion-relaxation phenomenon?

A
  • Flexor moment of gravity
  • Extensor moment by the stretched passive structures
102
Q

What is the elastic muscle force of the lumbar muscles developed through?

A
  • Stretching of the muscle: PEC and SEC
103
Q

What does the absence of electrical activity in the lumbar muscles during the flexion-relaxation phenomenon mean?

A

No action
- eccentric, isometric, or concentric

104
Q

Why would the muscle turn off?

A
  • The passive structures can bear the load
105
Q

What is a low back disorder? (LBD)

A
  • Injury and pain associated with the lumbar spine
106
Q

How many people develop Lower back disorders at some point in their life?

A
  • 80%
107
Q

What can lead to lower back pain?

A
  • Infections
  • Fractures
  • Dislocation
  • Tumor
  • Non-specific low back pain
108
Q

What can lead to lower back pain?

A
  • Infections
  • Fractures
  • Dislocation
  • Tumor
  • Non-specific low back painW
109
Q

What causes of low back pain have adequate and precise diagnostic tools?

A
  • Infections
  • Fractures
  • Dislocations
  • Tumors
110
Q

Are most types of back pain easily detected?

A
  • No
111
Q

What are the main risk factors for chronic lower back pain?

A
  • History of low back pain
  • Inadequate Rest Time
  • Poor Social Interactions
  • Catastrophizing
112
Q

What is the working hypothesis on low back pain?

A

Single or Cumulative Microtrauma
- Subfailure injury
Ligaments and External layers of annulus fibrous
- Richly innervated with nociceptors and mechanoreceptors
Poor control of spinal musculature
- Higher stresses to spinal ligaments and discs

KIN 316 - Biomechanics of Tissue (11 decks)

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