Motion segments

Question 1

What is a motion segment?

Answer 1

Two adjacent vertebral bodies and the soft tissue between them.

Essentially the functional unit of the vertebral column

Question 2

List the functions of the vertebral bodies

Answer 2

• Allows the body to support its weight
  
  • Increased size of vertebral bodies for extra weight
• Stable attachment sites for intervertebral discs, ligaments and muscles

Question 3

What 2 structures comprise the intervertebral disc?

Answer 3

• Nucleus pulposus
• Annulus fibrosis

Question 4

Describe the annulus fibrosus

Answer 4

• Collagen fibres orientated at different angles
• Help to hold the vertebrae together and resist flexion, extension and torsion

Question 5

Describe the nucleus pulposus

Answer 5

• Mostly water (90%)
• Consists of proteoglycans, collagen and glycosaminoglycans to help retain fluid
• Responsible for resisting compression
• Allows vertebrae to glide smoothly in all planes
• Gets pushed to opposite side of compression

Question 6

Where is the nucleus pulposus derived from?

Answer 6

Notochord

Question 7

Where is the annulus fibrosus derived from?

Answer 7

Sclerotome

Question 8

How does the notochord form?

Answer 8

Epiblast cells invaginating at Hensen’s node and filling the mesoblastic space.

Question 9

What happens to the remnants of the notochord in the intervertebral disc?

Answer 9

They remain in the intervertebral disc until the child is up to 10 years.

Question 10

Illustrate the formation of the intervertebral disc

Answer 10

Question 11

Which forces can be applied to intervertebral discs?

Answer 11

• Tension - caused by ligaments
• External loads
• Body weight - fat = back pain.
  
  • Spinal shrinkage associated with obseity
  • Yar (2008)

Question 12

How to calculate torque of the lumbar region

Answer 12

Torque (Nm) = Force (N) x Distance (m)

Calculate torque of the lumbar region:

Contraction force of muscles x L1-L5 length

Question 13

Degeneration of intervertebral discs

Answer 13

• Duran et al. (2014) evaluated the link between disc degeneration and morphology of vertebral body endplates.
• Examined endplate sagittal concave depth (ECD) and endplate sagittal concave angle (ECA).
• Conclusion: increased ECA and decreased ECD commonly found in patients with herniated intervertebral discs.

Question 14

Intervertebral disc prolapse

(slipped disc)

Answer 14

• Nucleus pulopsus pushes against a weakened area of annulus fibrosus.
• Most often in lumbar spine.
• Occurs when annulus fibres have been weakened, either over a long time or suddenly.

Question 15

List the symptoms of intervertebral disc prolapse

Answer 15

• Back and/or neck pain
• Tingling
• Numbness
• Issues with bending/straightening back

Question 16

How is a prolapsed intervertebral disc treated?

Answer 16

• Painkillers
• Physiotherapy
• Muscle relaxant
• Steroid injection
• Last option - surgical intervention

Question 17

What happens when prolapse of intervertebral disc occurs posteriorly?

Answer 17

It is very large and often presses against the spinal cord and other nerves in the spinal column, causing extreme pain.

Question 18

What is sequestration of an intervertebral disc?

Answer 18

• Nucleus pulposus is separated from the disc by seeping out through the annulus fibres.
• Most often occurs due to ageing
• Causes back pain, numbness, tingling and muscle weakness

Question 19

What are the treatments for a herniated disc?

Answer 19

• Laminotomy - opening or removal of part of the lamina to relieve the pressure on the nerve roots.
• Discectomy - portion of the intervertebral disc is removed