Intervertebral Disc Flashcards
Nucleus Pulposus is composed of?
70-90% water which allows deformation under pressure
15-20% type II collagen
65% dry weight is proteoglycans
Annulus fibrosis is composed of?
60-70% water
50-60% of dry weight collage is type I which is found in ligaments and tendons to withstand tensile forces
20% dry weight is proteoglycans
What do the lamellae of the annulus function for?
sheets of rings that resist distraction, shear, torsional stress, posterior fibers are thinner but put together tightly to allow flexion
How does the nucleus move?
the nucleus and annulus move together as a unit like gel surrounded by spaghetti
Annulus fibrosis is innervated by?
the recurrent sinuvertebral nerve which supplies the disc at its level and the level above
Sinuvertebral nerve supplies what 3 structures?
the outer 1/3 of the disc, PLL, and dura mater
Free nerve endings serve to what
pain and proprioceptive function
Vertebral end-plates serve to?
hold the disc in place; the nucleus is well contained by inner annulus and vertebral endplate
Sharpy’s fibers are what?
annulus fibers that insert on vertebral bodies
What are pain generators in the disc?
The end plate and outer annulus are highly innervated which can cause pain with injury
3 functions of Intervertebral Disc?
- transmit loads form one vertebral body to the next
- allow movement between the vertebral bodies
- other function; proprioception
Proprioceptive function of disc and injury theory….
distortion of the disc gives rise to a measurable electrical discharge and electrical stimulation of the outer annulus led to discreet contraction of the multifidus….. so deteriorated discs can lead to segmental instability from motor control loss and wasting of multifidus
Normal disc nuclear movement and tensile forces
compression and distraction
pathological nuclear movement and tensile forces
rotation and shear
Events of disc during compression (7)
- vertebral bodies approximate
- nucleus deforms
- pressure on annulus and endplates (pressure equilibrium between nucleus and endplate prevents too much bulging)
- radial bulging and end plate bulging
- resistance from annulus and trabecular bone of vertebral bodies
- equilibrium and load transfer from body to body
- people with osteoporosis cannot accept WB activity as well from compromised vertebral bodies
The inter body joint is the?
principle WB component of the LS
Distraction of disc and pain indicates?
all fibers of annulus are stressed so pain can indicate tear of annulus, facet jt problem, or ligament tear
Movement that is most detrimental to the disc?
Lateral shearing from rotation of the spine with lifting and twisting
People with posterior herniations will what movement?
Rock forward or be partially flexed to remove some pressure off of posterior nucleus
disc is what kind of a structure
avascular
How does disc get nutrients?
the end plate, outer 1/3 of annulus receive blood and nutrition from bone marrow and spinal arteries, most of the disc is avascular though and starts to degenerate by age 30
What is the best way to regenerate the annulus?
rotation thru modified tension in line of stress without load
Best way to regenerate nucleus?
intermittent compression and decompression
3 things that happen with disc degeneration
- disc integrity decreases with age
- decreased ability to retain water “dry out”
- ability to distribute load across disc changes