Spine & Disc Flashcards
How does thickness vary in outer & inner layers of IVD
Inner layers: Thicker (0.4mm)
Outer layers: Thinner (0.1mm)
How are fibres orientated in outer & inner layers of IVD
Inner layers: 60 degrees to spinal axis
Outer layers: 45 degrees
What type of collagen is found in outer & inner layers of IVD
Outer: Type 1
Inner: Type 2
Make-up of nucleus pulposus
75-90% Water
Proteoglycans
Type 2 collagen
How is collagen arranged in nucleus pulposus
Randomly arranged
Is the annulus isotropic or anisotropic
Anisotropic
How does age change the composition of IVD
Increased fibrous content in Nucleus
Decreased water in AF & NP
Endplates become irregularly thick/sclerotic leading to osteophytes
Alteration in types of collagen
How do mechanical properties vary with age
Shear modulus of NP increases
Compressive & Shear moduli of AF increases
These increase lower back pain and injury risk
Is the Nucleus Pulposus isotropic or anisotropic
Isotropic
What happens in Annular fibrosis injury
The AF becomes overstretched and weak
Nucleus can break through weak annular rings in one of 2 ways (Extrusion vs Prolapse)
Extrusion vs Prolapse of NP
Prolapse: NP dissects its way through weakened annular rings but still confined within rings
Extrusion: Nucleus breaches entire stretch of annular rings into perineural space
How do back-rests and lumbar support help?
Reduce moment arm of the trunk weight
Make up of cartilaginous endplates
Hyaline cartilage so similar to articular cartilage
70-80% Water
Type 2 collagen
Proteoglycans
Function of cartilage endplate (2)
Selectively allows for diffusion of nutrients into the NP
Maintaining uniform stress distribution at endplate (via fluid pressurisation)
Differences between articular cartilage and endplate
Endplate does not have the zonal arrangement
