Spine Flashcards
What are the two types of curvatures and where are they located?
- Primary curvature - thoracic and sacral
2. Secondary - cervical and lumbar
What are the two main functions of the spine?
Mobility and stability
What is the shape of the primary curves?
Posteriorly convex (C)
What is the shape of the secondary curves?
Anteriorly convex (backwards C)
What is kyphosis and what area of the spine does it occur?
Flexed posture - primary curves
What is lordosis and what area of the spine does it occur?
Extended posture - secondary curves
What is the function of the curves?
Acts like a spring to resist higher compressive loads
What is the function of the vertebral body?
Weight bearing - resists compressive forces
What is the orientation of the lines in the vertebral body?
Vertical
What comprises the neural arch?
Pedicles and the posterior elements (everything except the vertebral body)
What are the posterior elements of the neural arch?
- Laminae
- Articular processes
- Spinous processes
- Transverse processes
What is the function of the laminae?
Protects the spinal cord and assists in bending forces
What is the roof of the neural arch?
Laminae
What is the pars interarticularis?
Part of the laminae - between the articular processes
How many articular processes does each vertebral body have?
2 superior and 2 inferior facets
What is the function of the spinous and transverse processes?
Increase the lever arm (regarding muscles)
What is the function of the pedicles?
Transmit tension and bending forces
How do the size of the pedicles change in the vertebrae?
Increase in size from the cervical to the lumbar regions
What is the function of the angle of the neural arch?
Transmits torsion forces
What is the function of the intervertebral (IV) disc?
Increases motion and transmits the load - compression, shock absorption, and movement
What are the three components of the IV disc?
- Nucleus pulposus
- Annulus fibrosus
- Vertebral end plate
What is the cartilaginous end plate attached to?
Annulus
Where is hyaline and fibrocartilage distributed with regards to the cartilaginous end plate?
Hyaline cartilage - closer to the end plate (vertebral body)
Fibrocartilage - closer to the disc
How does the cartilage change as we age?
When we are young, we have more cartilage in our end plate, but as we age, we get more fibrocartilage to counteract the weight of gravity and respond better to compression
What is the nucleus pulposus mostly comprised of?
Water (70-90%)
What type of collagen does the nucleus pulposus contain and what is the function?
Type II collagen - resists compression
When does the nucleus pulposus deform?
When it is compressed or when the walls stretch
How does the nucleus pulposus move with compression?
Compression on the front of the disc moves the nucleus pulposus back and vice versa
What happens during disc herniation with regards to pain?
When a disc is herniated, there is compression on the front of the disc pushing the nucleus pulposus to the back and impinging on the spinal cord
Annulus is being torn and pushed forward
How do people with herniated discs like to be?
Extended - they do not like to bend over
What type of collagen does the annulus have and what is the function?
Type I collagen - resists tensile forces
What does the annulus attach to?
End plate
What is the orientation of the annulus fibers?
Each layer is perpendicular but oriented diagonally in a criss-cross pattern
What is the purpose of the criss cross pattern of the annulus?
Provide more strength
What two directions stress the annulus the most?
Flexion and rotation
How thick are the cervical and lumbar discs?
Cervical - 3 mm
Lumbar - 9 mm
What are the discs larger in the lumbar region?
More compressive loads in the lumbar region
What is the relationship between disc thickness and vertebral body height?
Greater ratio yields greater movement
Where is the greatest motion and why?
Cervical region - little vertebral body with a fairly large disc
How does the IV disc receive nutrition?
Osmosis
Why can’t discs heal themselves very well?
No blood supply from the major arteries
What part of the IV disc is innervated?
Outer 1/3 to 1/2 of the annulus
How many DOF does the interbody joints have?
6
What are the DOF of the interbody joints?
- Gliding
- Distraction and compression
- AP translation
- Lateral tilting
- Rotation
- AP tilting
What joints contain the meniscus?
Facet joints
What is the function of the meniscoids?
Aid in cushion - exist because the meniscus does not cover the whole part of the bone
How are the facet joints oriented in each of the regions?
- Cervical - transverse plane
- Thoracic - frontal plane
- Lumbar - sagittal plane
What motions occur in the cervical region?
All motions - some limitation with rotation and side bending
What motions occur in the thoracic region?
Side bending and slight rotation - no flexion and extension
What motions occur in the lumbar region?
Extension and flexion - rotation and some flexion is limited
What is the strongest facet joint?
Thoracic region - due to joint stress
What is the importance of the kinematics coupling motion?
One motion about an axis occurs with another motion around a different axis - rotation and lateral flexion are coupled movements
Describe the coupling motion in the cervical region.
Right rotation occurs with a right side bend
Describe the coupling motion in the thoracic and lumbar region.
Right rotation occurs with a left side bend but with FLEXION, side bending and rotation occur to the SAME side
What occurs during flexion?
Anterior glide and tilt
During what movement do the foramen increase in size?
Flexion
During flexion, describe the compression on the annulus?
Anterior annulus compresses and the posterior annulus stretches (opposite during extension)
What occurs during extension?
Posterior glide and tilt
What occurs during lateral flexion?
Lateral tilt, rotation, and translation
During lateral flexion, describe the size of the foramen.
Right side bend would decrease the size of the foramen on the R side and increase the size of the foramen on the L side
During lateral flexion, describe the compression of the annulus.
Annulus compressed on concave side and stretched on convex side
What motion does the annulus limit?
Rotation
What percentage does the facet joints compress?
0-33%
How is the load transmitted through the vertebrae?
Superior end plate to inferior end plate
What can cause buckling of the annulus?
Sustained load
What does the nucleus pulposus try to do during compression?
Expand outward toward the annulus
How is the nucleus pulposus fluid changed with compression and distraction?
Compression - fluid is released
Distraction - fluid is absorbed
