What is the water content of the Nucleus pulposus at: 1. birth 2. age 20 3. old age

1. birth = 90% 2. age 20 = 80% 3. old age = 70%

(1) Biomechanics-- IVD Flashcards by Michelle Farrow

How many adult IVD are there? What is their numeric name based on?

23 discs; name based on segment ABOVE

How well did you know this?

Not at all

Perfectly

What does the unique and resilient structure of the disc allow for?

function in weight-bearing and motion

How well did you know this?

Not at all

Perfectly

What percentage do the discs contribute to of the entire height of the vertebral column?

20-33%

How well did you know this?

Not at all

Perfectly

What are the three parts of the IVD?

Nucleus pulposus
Annulus fibrosus
Cartilaginous end plates

How well did you know this?

Not at all

Perfectly

What are we comparing in the Disc to VB Ratio? What does a greater ratio mean?

height of IVD compared to height of VB

greater ratio means greater spinal segmental mobility

How well did you know this?

Not at all

Perfectly

Describe the IVD and VB ratio in the cervicals, thoracics, and lumbars.

Greatest in C spine (2:5)
Least in T spine (1:5)
in b/w in L spine (1:3)

How well did you know this?

Not at all

Perfectly

List from most mobile to least mobile of the regions of the spine.

Most mobile = cervicals
in b/w = lumbars
least mobile = thoracic

How well did you know this?

Not at all

Perfectly

What is the water content of the Nucleus Pulposus?

70-90% water content

How well did you know this?

Not at all

Perfectly

What is the water content of the Nucleus pulposus at:

birth
age 20
old age

birth = 90%
age 20 = 80%
old age = 70%

How well did you know this?

Not at all

Perfectly

Do larger or smaller size discs have more capacity to change size? aka creep

bigger discs have more capacity to change size (creep)

How well did you know this?

Not at all

Perfectly

What do the IVD disc cells make?

the “solutes”–> matrix (proteins, proteoglycans, GAGs)

How well did you know this?

Not at all

Perfectly

How much of the total disc area in cross-section do the Lumbar nuclei fill? What direction are they more located?

fill 30-50% of total disc cross-section

located more POSTERIOR than central

How well did you know this?

Not at all

Perfectly

Where is the annulus more minimal in the cervicals? Why?

on the lateral borders; and only a thin strip in back

due to uncinate processes reinforcing at lateral border

How well did you know this?

Not at all

Perfectly

Describe the make up of the Annulus Fibrosus.

Fibrous tissue in concentric laminated bands

How well did you know this?

Not at all

Perfectly

What is the orientation of the concentric laminated bands w/in a band and in adjacent bands?

SAME direction w/in a band

OPPOSITE directions in any two adjacent bands

How well did you know this?

Not at all

Perfectly

At what orientation do the concentric laminated bands appear to cross another? What degree angle does this form to the VB?

appear to cross one another obliquely

form angle of ~30 degrees to VB

How well did you know this?

Not at all

Perfectly

What do the Annular fibers firmly attach to?

the cartilaginous endplates in the inner zone

How well did you know this?

Not at all

Perfectly

How do the inner zone annular fibers attach to the endplates? How do the peripheral zone fibers attach to the VB?

inner zone–> firmly attached to endplates

peripheral zone –> attach to VB via “Sharpey’s Fibers”-> STRONGER than other attachments

How well did you know this?

Not at all

Perfectly

What two ligaments of the spine reinforce the annular fibers?

ALL and PLL

How well did you know this?

Not at all

Perfectly

Describe the PLL along the spine as it goes from Cervicals to Lumbars.

narrows from C –> L, until it covers only ~50% of central portion of lower lumbar discs

How well did you know this?

Not at all

Perfectly

What percentage of the lower lumbar discs are covered by the PLL?

~50%

How well did you know this?

Not at all

Perfectly

What is the WEAKEST area of the annulus? What does this increase the risk of?

POSTEROLATERAL ASPECT

area most likely to be injured– like disc herniation

How well did you know this?

Not at all

Perfectly

Where is the most likely spot for a DISC HERNIATION in the lumbar spine?

posterolateral aspect (b/c that is where annulus is weakest

How well did you know this?

Not at all

Perfectly

What is responsible for being an anchor for fibers of the nucleus and annulus, preventing VBs from pressure atrophy, and maintaining nuclear and annular borders?

Cartilaginous End plates

How well did you know this?

Not at all

Perfectly

Where part of the cartilaginous end plate is fairly impermeable? Where does it get its nutrient from?

outer portion is fairly impermeable gets nutrients from diffusion in central portion

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

cartilaginous end plates

T/F. The disc has blood vessels that go directly to it.

FALSE--- NO blood vessels go directly to the disc

Where do annular fibers of the disc get blood supply?

from adjacent soft tissues

Where does the nucleus pulposus get blood supply from?

vertebral bodies

Where does the IVD get its nutrients from?

annular fibers--> from adjacent soft tissues nucleus pulposus--> from VBs also diffuse into disc from end plate

What type of vascularity and neural tissue does the IVD have?

avascular and aneural tissue!!!!

Describe the repair ability of a IVD when it undergoes rapid degeneration.

limited self repair

What happens to disc during disc degeneration and osteoarthritis?

they become increasingly vascularized and innervated by sensory nerve fibers

What happens to the disc overnight: 1. Hydrostatic pressure 2. osmotic pressure 3. fluid volume in disc What overall effect does this have on the disc?*

1. decreases 2. increases 3. increases disc EXPANDS = increased resistance to forces*

What happens to the disc during daytime: 1. fluid of disc 2. ligment tension 3. ROM

1. CREEP--> fluid exits the disc and disc space NARROWS 2. decreases 3. ROM increases

What is the loss in seated height during the daytime due to the disc space narrowing?

~20mm

What is the percentage that the lumbar flexion ROM increases?*

up to 50% | hence why right in the morning if one bends over right away, may hear a "snap"

T/F. The IVD is viscoelastic

True

What makes it difficult to study the disc?

due to variation in loading in different sections of the disc

What does compression of the nucleus pulposus result in?

tension of the annular fibers

Where does flexion put compression and tension on the disc?

compression on ANTERIOR disc tension on POSTERIOR disc

Where is compression and tension put on the IVD during extension?

compression at POSTERIOR disc tension on ANTERIOR disc

Out of compression and tension, which are we more concerned about when it comes to the IVD?

more concerned about where tension is placed, b/c the disc can handle compression

What happens to the disc as we age in relation to elasticity?

with age-- exposure to biomechanical stresses, disc becomes more fibrous and flexibility diminishes

Will a healthy disc or a disc that has been injured deform more?

an injured disc deforms more than a healthy one

T/F. All viscoelastic structures exhibit hysteresis.

True | hysteresis = the absorption or dissipation of energy by a distorted structure

What three things will Hysteresis vary with associated to the IVD?

1. age of disc 2. Level of disc 3. Repetitive load on disc

Where along the spine do the IVD has less hysteresis? Why does this mean for that area?

lower thoracic and upper lumbar region--> therefore cannot load and unload well

How will a repetitive load have an impact on Hysteresis for IVDs?

hysteresis decreases when successively loaded

Compare the impact on a rapidly loaded disc vs one that is slowly loaded.

loaded more rapidly--> disc behaves more STIFFLY (deforms less) than when loaded slowly with rapid loading the IVD is less effective at absorbing shock

When loading occurs on the IVD, what type of forces does the nucleus pulposus resists? What about the Annular fibrosus?

nucleus pulposus resists COMPRESSIVE forces annular fibers resists TENSILE forces (resists being "stretched")

What are the three loads imposed on IVDs?

1. Compressive loads 2. Tensile Stresses 3. Shear stresses

What causes the Compressive Loads on our IVDs?

- gravity and muscle co-contraction | - flexion, extension, and lateral bending

What causes Tensile Stresses on the IVDs?

- flexion, extension, and lateral bending | - traction

What causes Shear stresses on the IVDs?

- axial rotation of torso w/ respect to pelvis - Anterior posterior - Left right (translating in a linear direction)

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

more susceptible to failure in the area of the forces of TENSION

Where does Mechanical Failure occur first in the spine during compression forces?

in the cartilaginous endplates---> leads to nuclear herniation, called "Schmorl's node"

Where will compressive loads in flexion cause collapse of the endplate or VB?

anterior collapse

Besides Schmorl's nodes, what is an additional failure that occurs in the spine to withstand compressive forces?

compression fractures

Go through the steps of what occurs to the VB under compression.

disc compresses--> cartilaginous end plates bulge inward--> cortical bone (outside of barrel) is strong--> so cancellous bone compresses--> vertical struts buckle--> transverse bone may fracture (they can heal, maintaining the original structure)

Where are compression forces transmitted in the spine during extension? Why type of injuries does this lead to?

through the facets--> leading to capsular injuries

What can compressive loads on the spine, combined with torque around the long axis (aka ROTATION) produce in the IVD?

circumferential tears in the annular fibers of the IVD

What two forces will cause an Annular Tear?

compression and rotation

What percentage of the resistance to torque of a motion segment is provided by IVDs? Of this percentage, what part of the disc provides the majority of resistance?

90% annulus

How is our spine usually protected from torsion injuries?

due to the zygapophysis joints stopping body from rotating that far

What is Biomechanical behavior dependent on?

the state of degeneration--> which is dependent upon age of disc

By age 50, what percentage of lumbar discs are degenerated to some stage?

age 50

What are the most degenerated segments?

L3-L4 L4-L5 L5-S1 (lumbars)

What are the 4 Stages/Types of Disc Herniation?

1. Nuclear Herniation 2. Bulge/Prolapse 3. Extrusion 4. Segquestration

Describe how a Nuclear Herniation occurs.

nucleus pulposus begins migrating outward through defects of inner annulus it stays WITHIN confines of IVD

Describe a Bulged/Prolapsed disc.

additional migration of nucleus pulposus OUTSIDE confines of IVD, but NO rupture of outermost annular fibers

Describe an Extrusion of a disc. Why type of symptoms may one have?

outer annular fibers TEAR and contents of nucleus pulposus move into epidural space segment level symptoms--> like dermatome or muscle dysfunction

Describe a Sequestration of a disc. What type of symptoms may one have?

distal fragments break loose from IVD and float freely in CSF traveling of symptoms--~2 segments due to fragments floating around

What are two things disc herniation are associated with?

1. extreme deviated posture; full flexion or lateral bending | 2. repeated loading (hysteresis)--> 20-30 thousand times, fatigue

How can sudden disc prolapse occur?

sudden compressive loading and lateral bending

What are three common characteristics of those who had sudden disc prolapse with sudden compressive loading and lateral bending?

1. 40-49 years old 2. DDD 3. lumbar levels of L4/L5 or L5/S1

What are some postural habits that increase lumbar spine flexion?

1. crossing legs while sitting (53% flexion) 2. Squatting down on heels (70-75%) 3. Lifting light weights from ground (70-100%) 4. Rapid lunging (100-110%)

Can we and should we adjust a patient that has a herniated disc?

YES! - only a contraindication if patient can't tolerate it/ Cauda Equina Syndrome - safe if we are aware of position putting patient in

What are two other options for a patient that has a herniated disc, besides adjusting?

- Axial Traction (Traction = takes compressive forces off spine and allows disc to re-fill with water) - McKenzie Extension Exercises

(1) Biomechanics-- IVD Flashcards

(79 cards)