Spinal Column Stability and Mobility

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Questions and Answers

What is the Delmas index of a spinal column with normal curvatures?

Between 94-96%

Greater than 96%

Exactly 95% (correct)

Less than 94%

What is the main component of the nucleus pulposus?

Sharpey's fibers

Water and proteoglycans (correct)

Collagen type I

Collagen type II

What is the function of the lamellae in the intervertebral disk?

To keep the nucleus under constant pressure (correct)

To provide flexibility

To absorb shock

To connect the vertebral bodies

What is the difference between the collagen fibers in adjacent rings of the annulus?

They are in opposite directions Signup and view all the answers

What is the Delmas index of a spinal column with exaggerated curvatures?

Less than 94% Signup and view all the answers

What is the purpose of Sharpey's fibers?

To attach the annulus to the cartilaginous end plates Signup and view all the answers

What type of collagen is highest in the nucleus pulposus?

Neither type I nor II Signup and view all the answers

What is the relationship between the flexibility of the spinal column and its Delmas index?

A more flexible spine has a lower Delmas index Signup and view all the answers

What is the main function of the intervertebral disk structure in terms of stability?

To resist intervertebral distraction, shear, and torsion Signup and view all the answers

What is the direction of the collagen fibers that resist distraction forces?

Perpendicular to the endplate Signup and view all the answers

What type of forces are produced during horizontal plane movements?

Shear and torsion forces Signup and view all the answers

Why are torsional forces pertinent in the intervertebral disk?

Because only the fibers oriented in the direction of the slide or twist become taut Signup and view all the answers

What determines the mobility of a particular segment?

The ratio of disk thickness to vertebral body height Signup and view all the answers

Which segment has the greatest mobility?

Lumbar segment (L 1/3) Signup and view all the answers

What is the role of the nucleus position in the intervertebral disk as a shock absorber?

To provide better shock absorption when closer to the center Signup and view all the answers

What is the result of increased hydrostatic pressure in the nucleus pulposus?

Increased tension in the annular fibrosus Signup and view all the answers

What is the primary function of the pressure within the nucleus in the spinal disc?

To convert the annulus fibrosus into a stable weight-bearing structure Signup and view all the answers

What happens to the pressure in the Nucleus Pulposus when lifting a load with the knees straight?

It increases significantly Signup and view all the answers

How many pairs of apophyseal joints are present in the vertebral column?

24 pairs Signup and view all the answers

What type of joints are the apophyseal joints classified as?

Plain joints Signup and view all the answers

What is the primary factor that influences the kinematics at different regions of the vertebral column?

The orientation of the facet surfaces Signup and view all the answers

What type of motion is favored by horizontal facet surfaces?

Axial rotation Signup and view all the answers

What type of motion is blocked by vertical facet surfaces?

Axial rotation Signup and view all the answers

What is the ratio between the vertebral body and the intervertebral discs that influences the predominant motion at each spinal region?

Variable ratio Signup and view all the answers

What is the effect of sitting in a forward-slouched position on the lumbar disc?

It increases the pressure on the lumbar disc Signup and view all the answers

What is the role of the apophyseal joints in the vertebral column?

To facilitate movement Signup and view all the answers

Study Notes

Stability and Mobility

A reference straight column with N=0 and R=1 contrasts with a flexible column like the spine, which has curvatures leading to a resistance of R=10.
Normal spinal curvatures show an index of 95% (normal limits: 94-96).
Exaggerated spinal curvatures yield a Delmas index below 94%, while attenuated curvatures result in an index above 96%.

Intervertebral Disk Structure

Composed of two parts:
- Nucleus pulposus (central portion)
- Annulus fibrosus (peripheral portion)
High concentrations of water and proteoglycans in the nucleus; collagen (Type I and II) is predominant in the annulus.
Annulus fibers organized in concentric lamellae, enclosing the nucleus and maintaining constant pressure.

Intervertebral Disk Functions - Stability

Disk structure provides resistance against:
- Intervertebral distraction (vertical separation)
- Shear (sliding)
- Torsion (twisting)
Collagen fibers oriented vertically resist distraction but less effective against sliding and torsion movements.
Parallel fibers to the endplate effectively resist shear and torsion but not distraction.

Intervertebral Disk Functions - Mobility

The ratio of disk thickness to vertebral body height influences mobility; larger ratios lead to greater mobility.
Mobility ranks (decreasing order):
- Cervical (C) 2/5
- Lumbar (L) 1/3
- Thoracic (T) 1/5

Intervertebral Disc as a Shock Absorber

Nucleus center position is optimal for function; increased hydrostatic pressure is generated from body weight and muscle contraction.
Increased nuclear pressure elevates tension in the annulus fibrosus, counteracting radial expansion and stabilizing the structure.
Pressure transmitted through endplates to adjacent vertebrae; key during loading activities.

Nucleus Pulposus Pressure Dynamics

High disc pressures occur during forward bends or weight-bearing;
Lifting while squatting minimizes lumbar disc pressure compared to lifting with straight knees.
Slouched sitting increases disc pressure versus an erect position.

Apophyseal Joints

Comprises 24 pairs formed by opposing facet surfaces, classified as plain joints.
The orientation of facet surfaces influences spinal kinematics:
- Horizontal facets favor axial rotation.
- Vertical facets promote flexion-extension.
- Frontal facets facilitate lateral flexion but restrict axial rotation.

Influencing Factors on Joint Motion

Joint motion affected by:
- Ratio of vertebral body to intervertebral discs.
- Shape of vertebrae.
- Local muscle actions.
- Attachment of ribs and ligaments.

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Description

Assess your knowledge of spinal column stability and mobility, including the Delmas index and its relation to functional types of spinal columns. Learn about the effects of curvatures on resistance and more. Test your understanding of this crucial anatomy concept!