Acute Disc Injuries

Question 1

Who is at highest risk of an acute disc injury?

Answer 1

Aged 30-50
Males more likely than females
Sustained periods of submaximal loading

Question 2

What kind of lifting increases risk of acute disc injuries?

Answer 2

Heavy lifting of combined Lx Flexion and Rotation - sustained over time

Question 3

What are the types of acute disc injury?

Answer 3

Torsional Injury

Internal disc degredation

Question 4

What is a torsional disc injury?

Answer 4

“Twisting” injury in flexion

Combination of rotation and lateral shearing resulting in circumferential tears of the AF

Question 5

Why does lifting in flexion increase the risk of torsional injury?

Answer 5

Posterior AF is stretched - usually have already some disc degeneration

Question 6

What is a internal disc disruption injury?

Answer 6

More common than torsion injury

Degredation of the nucleus and development of fissures inside the disc

Question 7

How are internal disc disruption injuries graded?

Answer 7

Based on how progressed the internal tear is:

• Grade I = radial fissure within the inner annulus
• Grade II = radial fissure in to the middle annulus
• Grade III = radial fissure in to the outer annulus
• Grade IV = circumferential tear throughout the whole annulus

Question 8

What causes an internal disc disruption injury?

Answer 8

Sudden compression of a degenerate disc causing the end plate to fail

E.g. due to heavy unaccustomed movement or a fall

Question 9

How does an end plate ‘fracture’ occur?

Answer 9

When there is internal disc disruption resulting in a tear which penetrates the cartilage end plate

Question 10

How does an end plate fracture result in disc degeneration?

Answer 10

Buckling of the disc into the end plate increases the volume of the NP = drop in hydrostatic pressure of NP = Inflammatory process occurs disrupting homeostasis = decreased proteoglycans and release of destructive enzymes

Question 11

What is the overall effect of end plate fractures?

Answer 11

Degeneration of the disc from the NP outwards - loss of water binding capacity and deterioration for nuclear fracture (less able to withstand compressive forces)

Question 12

What occurs when the degenerate NP extends into the annulus?

Answer 12

Forms fissures and the degraded NP follows the path of least resistance through the AF via fissures - NP ‘herniates’ through the AF

Question 13

When does internal disc disruption become painful?

Answer 13

When the NP has become degeraded and herniates through the outer 1/3rd of the annulus which is innervated

Question 14

What type of pain does a contained herniation cause and why?

Answer 14

Diffuse, non-deramatomal somatic and somatic referred pain

Because there is stretching of the outer 1/3rd of AF

Also stretching the PLL and surrounding soft tissues

Question 15

What type of pain does an uncontained herniation cause and why?

Answer 15

Somatic pain & Radicular pain with potential Radiculopathy

NP penetrates outer AF and PLL (causing somatic pain) and is in contact with spinal nerve root (causes inflammation of the nerve root)

Question 16

What happens when the NP completely herniates?

Answer 16

Inflammatory cytokines within the degenerate NP cause irritation and compression of the exiting nerve root - causing radicular pain in a dermatomal pattern

Question 17

What directions can herniation occur and what is the significance?

Answer 17

1. Posterolateral - more common due to incomplete lamellae of the AF here
2. Central - more serious as can cause cauda equina syndrome in Lx spine

Question 18

What is the healing potential for AF fissures?

Answer 18

Able to heal by granulation tissue - llamelae are lost so mechanically weaker than normal

Question 19

What is the healing potential for a herniated NP?

Answer 19

Able to resorb extruded disc material by inflammatory process

Question 20

Why are Cx spine discs less likely to herniate?

Answer 20

Because NP in cervical disc is fibrosed in mid-teens and so less fluid

Question 21

What is the effect of disc herniation on the nerve roots?

Answer 21

Compression and stretching of the nerve roots causing increased nerve root tension

Nerve become sensitised by inflammatory chemicals within the degenerate NP

Question 22

What is the effect of sustained compression of nerve roots on the blood vessels?

Answer 22

Compression of blood vessel surrounding a nerve = increased permeability of vessel = oedema = pain

Interneural oedema = decreased BF = ischemia

Question 23

What is the effect of sustained compression of nerve roots on their function?

Answer 23

Compression of BVs = oedema = fibroblast invasion = decreased fibre glide = tissue irritation = decreased conductivity and decreased axonal transport

Eventually leads to nerve degeneration and demyelination

Question 24

What causes radicular pain?

Answer 24

Interneural inflammation and ischemia of nerve roots due to prologued compression

Question 25

What is the likely cause of radicular pain in patients under 50?

Answer 25

IV disc herniation

Question 26

What is the likely cause of radicular pain in patients over 50?

Answer 26

Degenerate changes causing lateral spinal stenosis (impinging nerve root in the IV foramen)