Axial Skeleton Flashcards
Why do different areas of the spine favor different motions?
the orientation of the facets allow for different motions in each area of the body (cervical, thoracic, etc)
What 4 things does the axial skeleton do?
1) transmission of forces to the lower extremity during walking
2) supports body weight
3) protects
4) shock absorption from disks
Why are the curves in our spine so important?
they help us absorb the compressive forces we endure; we’re 25% less effective at absorbing those forces without them
Why are the transitional areas in the spine (ex: C to T, T to L) likely to break down easier for pts?
- those areas are more subject to sheer forces and can develop bone spurs more quickly
- these areas are more likely for patients to have pain
T/F: Cervical and lumbar curves are primary curves.
false, secondary
- primary are thoracic and sacral
What creates the lumbar lordosis in a developing child?
the psoas tilts pelvis forward during walking, creating the lumbar lordosis
How are the curves physiologically able to form in a growing baby?
- their vertebral bodies are half bone and half cartilage, they haven’t ossified yet
- to get them to ossify, the babies need to weight bear
At what age is the spine at adult proportions?
10 y/o
Describe the line of gravity throughout the head to feet.
1) head: through mastoid/ext. acoustic meatus
2) thoracic: anterior to thoracic curve
3) hip: slightly posterior to hip, causing extension moment
4) knee: slightly anterior to knee: extension moment
5) ankle: anterior to ankle, dorsiflexion moment
How does the spine change when we age?
- decreased lumbar lordosis
- increased thoracic kyphosis
- increased cervical lordosis
How can osteoporosis change the curves of the spine for women?
can cause an increased thoracic kyphosis, which can be compensated by a lumbar lordosis
T/F: The long SPs on thoracic vertebrae limit flexion.
false, extension
How are the thoracic vertebrae limited in motion? (by what bony anatomy?)
1) costal facets limit motion due to the articulation with the ribs
2) long SPs limit extension
What spinous ligament resists excessive side bend on the contralateral side?
intertransverse ligament
What ligaments resist excessive trunk flexion?
- ligamentum flavum
- interspinous ligaments
- supraspinous ligaments
- PLL
What motion does the ALL resist?
hyperextension
Describe the two parts of the IVD and their purpose.
- nucleus pulposa = gel-like inner portion of disk, filled with H20, proteoglycans, and type II collagen
- annulus fibrosis = rings of fibrous cartilage that contain the nucleus pulposa, helps distribute compressive forces
At what time of the day is the disk most hydrated?
Right in the morning, since it regains water overnight and swells up
What happens to the disk as we age? What is the “vicious cycle” that occurs?
- nucleus pulposa dehydrates
- this causes the disk to breakdown and vertebral bodies begin to touch, resulting in degeneration of the vertebral end plate
- b/c the vertebral end plate is broken down, now the disk won’t get its nutrients, so it breaks down even more - vicious cycle
How do we prevent the degeneration of our disks as we age?
- stay active
- get lots of calcium
- don’t smoke (prolongs healing time for disks, bad)
T/F: Creams can help prevent disk degeneration.
false, but certain injections can
How do intervertebral disks get nutrients?
- end plates get peripheral blood flow, and then diffuse these nutrients into the disk
- diffusion occurs from annulus fibrosis to nucleus pulposa
What are the two nutrient sources for the disk?
1) blood vessels in the superficial annulus
2) blood in adjacent vertebral bodies
What does a spinal motion segment consist of?
adjacent halves of two vertebrae, the disk in between, the related spinal canal and foramen
Which is stronger, ALL or PLL?
ALL
What motion occurs in the frontal plane, and about what axis?
side bend, about the AP axis
What motion occurs about the ML axis?
flexion/extension, in the sagittal plane
What plane and axis does rotation occur in?
plane = horizontal axis = vertical
T/F: Facets are smaller in the cervical region and larger in the lumbar region.
true
If the facet orientation is parallel to the horizontal plane, what motion is favored?
rotation (like the C-spine orientation)
The cervical facets are at what angle with the horizontal plane?
45 degrees
What plane are the cervical facets parallel to, and what motion does this make them good for?
frontal, so really good for side bend
T/F: Cervical facets are equally as good at flexion/extension as they are at side bending.
false
- best at side bend, then equally good at rotation and flex/extend (since 45 deg from both horizontal and vertical axes)
In what direction do the cervical IAPs and SAPs lie?
IAP = inferior and anterior direction SAP = superior and posterior direction
What motion do thoracic vertebrae favor?
side bend, b/c they’re so close (20 deg) to the frontal plane
Which way do the IAPs and SAPs face in the thoracic region?
IAP = anterior SAP = posterior
T/F: Thoracic vertebrae are better at rotation than flexion/extension.
true?
What areas of the spine are good for rotation?
cervical -> thoracic -> lumbar
Why is thoracic extension limited?
by the thoracic SPs and ribs
What directions do the IAPs and SAPs of the lumbar spine point to?
IAP = anteriolateral SAP = posteriolateral
What motion does the lumbar spine favor?
flexion/extension due to being nearly parallel to the sagittal plane
T/F: Lumbar facets are oriented 90 degrees from the horizontal plane.
true, making them not good for rotation at all
What kind of forces cause herniated disks?
shear and torque forces
What is spondylothesis?
when two vertebral bodies shear off
What structure helps control the compressive forces that the disk endures?
the annulus fibrosis evenly distributes the force about the disk so as to not have it
Where does a common spondylysis occur?
at L5 and S1, lots of shear forces here due to angle of lumbosacral joint
Do the facets gap or approximate in trunk flexion?
gap; they approximate in extension
What’s the normal angle for the lumbosacral joint? How much body weight does this joint hold?
- 40 deg
- takes 64% of body weight; will do more if angle is increased
What structures are taut in flexion?
ligamentum flavum, interspinous lig, supraspinous lig, ligamentum nuchae at neck, PLL, posterior disk
What happens at the facets and joint capsules on both sides for L side bend?
L side: facet closes down, capsule compressed
R side: facet gaps, capsule stretched
T/F: When side-bending, the disk protrudes contralaterally towards the convex side.
true
Pressure loss in the nucleus of a disk can cause what?
disk collapse: delaminating stressing can pull annulus apart
- commonly found in older spines
What does the transverse ligament do?
holds down the dens
What ligament in the neck is the big ligament preventing excessive rotation?
alar ligament
What does the cruciate ligament do?
limit side bend and flex/extend, stabilize AA joint
What does the tectorial membrane do?
limits rotation and flexion (extension of PLL), stabilizes low C-spine
T/F: There is radial bulging both outwards and inwards during disc collapse.
true
What arthrokinematics are occuring at the AO joint during flexion? AA joint?
- AO = anterior roll and posterior slide of occipital condyles on their facets
- AA = tilts forward
What arthrokinematics occur at the C2-C7 level during flexion?
IAPs slide superior and anterior on the SAPs
Which joint in the neck doesn’t move much during motion?
AA joint
What arthrokinematic motions occur at each neck joint during side bend?
- AO = condyles roll toward side of bend and away on contralateral side
- AA = minimal motion
- C2-7 = ipsilateral IAPs slide inferior and some posterior, while contralateral IAPs slide superior and a little anterior
In what movement does the AO not do much?
rotation
What c-spine arthrokinematics occur with rotation?
- AO = not much
- AA = ipsilateral IAPs slide posterior, contralateral slide anterior
- C2-7 = ipsilateral IAPs slide mostly posterior, some inferior; contralateral IAPs slide mostly anterior, some superior
What happens with craniocervical spinal coupling?
- when low c-spine rotates R, it will also R side bend
- upper c-spine will also R side bend, but rotate L
Where does the AA joint have the most motion?
during rotation
T/F: The C-spine is naturally slightly protracted
true (flexed lower c-spine, extended upper c-spine)
What bony structures in the c-spine facilitate flexion and extension, but limit side bend?
uncinate processes
What motion opens up the IVFs?
flexion
The patient doesn’t want to turn their head to the right because it’s painful. What bony issue could be causing this?
stenosis on the right side: ipsilateral IVFs close down during rotation, so if it’s painful to rotate to the right, it may be because of those IVFs
T/F: T-spine and L-spine move the same.
true THANK GOD
What arthrokinematics occur during extension at the t-spine?
same as C-spine: IAPs slide posterior and inferior to SAPs
What arthrokinematics occur during t-spine side bending?
ipsilateral IAP slides inferior, contralateral slides superior
What do the facets do in the t-spine during right rotation?
both right and left IAPs slide left (contralateral slide)
When rotating left, which facet gaps and which approximates in the L-spine?
ipsilateral side gaps, so L gap, R approximate
In rotation, what is the difference in arthrokinematics between L-spine and T-spine?
T-spine slides inferiorly and superiorly, while L-spine just gaps and approximates
In what motion does the coccyx tilt posteriorly?
nutation
How are the sacroiliac joints stabilized?
1) form closure = good bony articulation btwn joint, occurs with age (increased integrity of ligaments, bones have grown together)
2) force closure = comes from the erector spinae, multifidus, thoracolumbar fascia
