Motion Segments Flashcards
What is a motion segment?
The functional unit of the vertebral column since it allows movement
What does a vertebral motion segment consist of?
Two adjacent vertebrae
Soft tissues between them
What is the reference for definition of motion Segments?
Hall, 2014
What is the function of the vertebral bodies in the motion segment?
Allow body to support its weight
Stable attachment for IVDs, ligaments and muscles
(Duran et al., 2017)
What movements of the vertebral column do the annulus fibres of the IVDs resist? (Reference?)
Flexion
Extension
Torsion
(McNah and McCulloch, 1990)
What percentage of the nucleus pulposus is water?
90%
What are the other components of the nucleus pulposus apart from water? (Reference?)
Proteoglycans
Collagen
Glycosaminoglycans
(Palastanga et al., 2012)
What are the five steps involved in the development of the IV discs?
- Paraxial somites gather around notochord
- Pericordial condensation of sclerotome
- Metameric patterning of disc and vertebral bodies
- Involution of notochord
- Establishment of annulus fibrosus lamellar structure
How does the notochord form? (Reference?)
Epiblast cells invaginating at Hensen’s node and filling the mesoblastic space
(Colombier et al., 2014)
What does the nucleus pulposus derive from? (Reference?)
Notochord
Martinez et al., 2017
What does the annulus fibrosus derive from? (Reference?)
Sclerotome
Colombier et al., 2014
When does the notochord tend to be completely degraded and where can it remain up to 10 years of age? (Reference?)
Usually gone by 4-5 years of age
Can remain in IV disc up to 10 years
(Ashley et al., 2016)
What applies tension to IV discs?
Ligaments
What applies external loads to the IV discs?
Things we carry
Body weight and its compression on the vertebral column and IV discs is a risk factor for what?
(Reference?)
Lower back pain
Shiraz et al., 2015
What does a study by Yar (2008) show between body weight and IV discs?
Spinal shrinkage is associated with obesity
What is torque?
The force that tends to cause rotation
What is the equation for torque?
Torque (Nm) = Force (N) x Distance (m)
Force is the contraction of the muscles
Distance is the perpendicular lengths
Why are annulus fibres always under stress? (Reference?)
Weight of IV disc
Palastanga
How does the nucleus pulposus resist compression? (Reference?)
High fluid content
Hall, 2014
What effect does the nucleus pulposus have on movement of the vertebral column? (Reference?)
Allows vertebrae to move efficiently and smoothly in all planes
(McNab and McCulloch, 1990)
What did Duran et al., (2017) show in regards to IV disc degeneration?
Association between disc degeneration and morphology of vertebral body endplates:
- Increased endplate sagittal concave angle in herniated disc
- Decreased endplate sagittal concave depth in herniated disc
What did Colombier et al., (2014) show in regards to IV disc degeneration?
There is a singular nucleus pulposus phenotype associated with it
What is IV disc prolapse?
Nucleus pulposus pushes against a weakened area of annulus fibres
How can annulus fibres weaken?
Over time: - Age - Working with heavily vibrating machinery Suddenly: - Lifting heavy object with poor form
What vertebral region is IV disc prolapse most common?
Lumbar
What are the symptoms of IV disc prolapse?
Back/Neck pain/tingling/numbness Issues with back movements Cord compression if: - Large prolapse - Posterior prolapse
What are the conservative options for treatment of IV disc prolapse?
Analgesia
Physiotherapy
Muscle relaxants
Steroid injections
What are the surgical managements of IV disc prolapse?
Laminotomy to relieve pressure on nerve roots
Discectomy
Self-closing U-clips for Duran repair
What is IV disc sequestration? (Reference?)
Nucleus pulposus separates from IV disc by seeping out through annulus fibres
(Harder et al., 2015)
What is the most common cause of IV disc sequestration?
Weakness due to ageing
What are the symptoms of IV disc sequestration?
More severe:
- Back pain
- Numbness and tingling
- Muscle weakness
