Intervertebral disc

Question 1

Anatomical difference of Annulus fibrosus and Nucleus pulposus

Answer 1

Annulus fibrosus

Consist of lamellae, predominantly type 1 collagen
High tensile strength and resists distractive and shear force
Function
To contain radial bulge of central nucleus pulposus
Enabling uniform distribution
Transfer of compressive loads between vertebral bodies
Distends and rotates, facilitation joint mobility

Nucleus pulposus
Contain water, type 2 collagen, proteoglycan matrix
Viscoelasticity, stiffness and resistance to compression
Function
Maintain vertebral height
Resist compression
Even force distribution

Question 2

Biomechanical properties
of intervertebral disc

Answer 2

Viscoelastic properties of the disc to ensure disc demonstrates creep (deformity over time) and hysteresis (energy absorption with repetitive axial compression)
Porous permeable collagen proteoglycan matrix
Annulus fibrosis has highest tensile stress
Nucleus pulposus has highest compressive stress
Biphasic phenomenon for discs: outer layers of generate hoop stresses, inner layers deform and act as shock absorbers

Question 3

Stages of disc herniation

Answer 3

Sequestration
Extrusion
Prolapse
Degeneration