Vertebral Column Flashcards
requirements of vertebrae
protection, weight bearing/ force transmission, mobility
vertebrae vs intervertebral discs
24 mobile vertebrae
23 intervertebral discs - C! has no intervertebral disc
How do requirements vary in different regions?
Lordosis in cervical & lumbar regions = more mobility, less stability
Kyphosis in thoracic & sacral = less mobility, more stability
vertebral column motion segment consists of
3 joints, 2 vertebrae, 1 intervertebral disc, ligaments, muscles & nerves
movements of vertebral column motion segment
flexion, extension, lateral flexion, axial flexion
usually involve a combination of rotation and translation components
ring apophysis
secondary ossification centre that incorporates/fuses in the outer the annular fibrosis fibres into bone for secure attachment. Filled in is hyaline cartilage that is end plate
bone of vertebral body consists of
outer shell cortical bone, inner trabecular bone & red bone marrow (gives ability to slightly compress)
organisation of trabeculae in vertebral body
vertical trabeculae are stronger and thicker than the horizontal trabeculae (withstands more compression with the support of horizontal struts)
what is the vertebral body able to resist
compressive forces (not translation or rotational forces)
what does the nucleus pulposus consist of
- 90% water (incompressible)
- proteoglycans (thickness & viscosity)
- collagen (thickness & viscosity)
what do the vertebral endplates consists of
- hyaline cartilage / fibrocartilage due to annular fibres
what does the annulus fibrosis consist of
- collagen type 1 (largest, strongest, resist lengthening)
- 10-20 concentric fibres
annulus fibrosis weakness
posterolateral corners concentric rings are incomplete
orientation of annular fibres
65° angle to vertical
when does disfunction in weight-bearing occur?
NP has dried out
stretching or tearing of AF fibres (leads to translation/ instability)
which region has the lowest disc to vertebral body height? consequence?
thoracic region
less mobility
what is the role of the intervertebral disc in resisting movement?
collagen fibres in annulus fibrosus resist tension
- distraction - all AF fibres resist
- translation - 50% AF fibres resist
what movements can the intervertebral discs resist?
flexion, extension, lateral flexion
- compression of the AF will resist further movement, and tension on the opposite side, pressure deforms NP & creates further compression
- axial rotation - 50% of fibres limit excessive rotation
4 posterior elements of vertebrae & function
- lamina
- articular process
- spinous process
- transverse process
- muscle & ligament attachment
- provide stability
- guide movement
how does the zygoaphyseal joint resist movement?
inferior articular processes hook onto the superior articular processes of the vertebra below
- depending on the ORIENTATION of the articular facets
- or the HEIGHT of the superior articular processes
vertebral movements for spinal flexion
anterior rotation and anterior translation of the superior vertebrae on inferior vertebrae
how does vertebral structure limit translation, extension & axial rotation
- translation is blocked due to processes and limits rotation due to the height of the process
- extension limited due to spinous process, ribs and disc height to body ratio
- axial rotation of the superior vertebra is limited by the superior articular facets alighted in the sagittal plane
angle of zygapophysial joint in the cervical vertebra
almost coronal orientation
45° to transverse
allow all movements
angle of zygapophysial joint in the thoracic vertebra
almost coronal orientation
60-80° to transverse
allow axial rotation & lateral flexion
angle of zygapophysial joint in the lumbar vertebra
sagittal plane orientation vertical
allow flexion-extension
how does pars interarticularis fracture occur
posterior weight bearing - under compression & extension, weight can be transferred through inferior articular processes to the lamina below
transfers weight bearing from inf art to lamina - pars interarticularis
when does posterior weight bearing occur
occurs in extension & rotation/lateral flexion
why is a pars interarticularis fracture bad?
separates anterior & posterior and limits support to translation/rotation
lumbar lordosis - L4/5
spinal ligaments/structures that limit extension 3
- anterior longitudinal ligament
- anterior annular fibres
- compression posteriorly
spinal ligaments/structures that limit flexion 5
- interspinous ligament
- posterior longitudinal ligament
- ligamentum flavum (not much)
- supraspinous ligament
- fascia and muscles
interspinous ligaments - orientation, purpose
oblique fibre orientation
anterior/inferior
resists posterior translation
keeps the Z joints in place to maintain stability
during flexion - combine anterior rotation with anterior translation, keeps z joints in contact, resist posterior shear of superior vertebra
