Biomechanics, Mvmts, Diagnostic Imaging of Lumbar Spine Flashcards by Emily Harrell

what motion occurs when every point on the bone moves in the same direction

translation

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translation is caused by what force?

shear

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what is the difference b/w stress and strain

stress = the applied or elongated force
strain = the extent to which the CNT is elongated

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when do micro tears occur in collagen?

after > 4% of elongation

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what is the resistance to deformation and the slope of the stress-strain curve

stiffness

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if a constant force is applied to a collagenous structure for a more prolonged period, further mvmt is detectable

creep

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why does creep occur

due to a gradual realignment of collagen fibers and proteoglycans

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how do we apply the creep phenomenon

stretch

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restoration of initial length of CNT occurs at a less rate and to a lesser extent than the deformation

hysteresis

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what does hysteresis indicate?

that energy was lost during deformation

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after several frequent repetitions of a stress, the structure becomes weaker

fatigue failure

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in fatigue failure, material may fail under ______

normal stress

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when is fatigue failure seen most often

overuse syndrome

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during slow loading of the axial spine with compression, what happens to the:
- VB
- NP
- AF
- end plate

VB - approximates
NP - increase in pressure
AF - bulges radially
end plate - bows towards vertebrae

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during slow axial compression of L spine, where is there a greater amt of bulging?

greater anteriorly vs posterolaterally

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describe the creep phenomenon in relation to slow axial compression of the L spine

rapid creep of 1.5 mm in the first 2-10 min
then slower rate 1mm/hr - plateau is at 90 min

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what is the weakest component of the disc

end plate

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what is the intradiscal pressure of the lumbar spine in standing

100%

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when do you have the least amt of intradiscal pressure

supine with knees up posture

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what is the intradiscal pressure of the lumbar spine in sidelying

75% of standing (or decreases by 25% from standing)

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what is the intradiscal pressure of the lumbar spine in supine

25 % of what standing pressure is

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what is the intradiscal pressure of the lumbar spine in slight lean forward

increases by 50-100% (150% -200% of what it is in standing)

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what is the intradiscal pressure of the lumbar spine in sitting

increases by 50%

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what positions aggravate the disc or increase the intradiscal pressure?
what factors relieve it?

aggravating - sitting, leaning forward, lifting objects, jumping, twisting
relieving - SL, supine, supine with knees up

with a normal disc, the facets take how much pressure?

abt 8%

with a diseased disc, how much load does the facet take?

40-70%

during axial distraction, what happens to the: - disc - capsules of facets

disc = less stiff capsule = strong when subject to traction

____ % of lengthening of the L spine during traction occurs due to ______ of lumbar Lordosis. the remaining ______ % occur due to _____ of the VB

40% - flattening 60% - separating

how much creep occurs immediately during axial distraction of L spine

1-2mm

how does traction affect young vs old

lengthening is greater in young than old

describe what is happening to the curve of the lumbar spine during flexion

straightening in the upper L spine - does not occur at L5-S1

describe the kinematics of flexion if the L spine

anterior sagittal rotation (rocking forward of VB) and anterior sagittal translation

what happens to the facets in flexion

slide superior and anterior

describe the pressure on the facets, anterior and posterior disc during flexion

facet and post disc = decrease in compression anterior disc = compression increase

what structure resists sagittal rotation (rocking of VB) in flexion

tension of capsule

what structures resist segmental flexion (4, list in order of greatest to least)

1. joint capsule (39% 2. IV disc (29%) 3. supraspinous lig and interspin lig 4. lig flavum

what are the top 2 structures that resist segmental flexion

1. joint capsule 2. IV disc

what 4 things resist anterior sagittal translation of top VB on bottom VB during flexion at end range

- direct impact on facet joint (C and J curves) - superior/anterior orientation of lateral fibers of annulus - iliolumbar and supraspinous lig - MF and ES

about how much segmental flexion occurs at each segment? L1-2 L2-3 L3-4 L4-5 L5-S1

L1-2 = 8 deg L2-3 = 10 L3-4 = 12 L4-5 = 13 L5-S1 = 9

what effect does bending alone have on the disc? what about when you have bending + compression

alone = little effect + compression = causes failure in disc or pars interarticularis

describe the kinematics of extension of VB in L spine

posterior sagittal rotation (rock backward) + posterior sagittal translation

what happens to the facets during extension

approximation of inferior facet on superior facet - slide inferior and posterior

what happens to the WB status of the facet during extension

it becomes WB, whole IV joint becomes compressed

what end feel should you feel with extension

bony from SP on SP

what happens to the interspinous ligament during extension

buckles

what 4 things restrict segmental extension of L spine

- SP on SP - inferior articular process on the laminae below - ability of disc to allow compression - ability of ant structures to allow elongation

about how much segmental extension occurs at each segment? L1-2 L2-3 L3-4 L4-5 L5-S1

L1-2 = 5 L2-3 = 3 L3-4 = 1 L4-5 = 2 L5-S1 = 5

most of the segmental extension occurs at what segments?

L1-2 and L5-S1

describe what happens to the disc, I/L and C/L facets during axial rotation

disc = torsion I/L facet = gapping C/L = compression/approximation

maximal segmental rotation is limited to ______ because collagen can only be elongated to ______

3 degrees 4%

how much rotation does it take to increase tension in interspinous and supraspinous ligaments

< 1 degree

what has the greatest resistance to rotation

65% - facet joint, ligaments, capsule 35% - from disc

rotation + flexion increases the chances of injury to what structure? Why?

annulus fibrosus b/c minimal contact of facet joints

describe what happens to the facets during lateral flexion/side bending

I/L glides inferior C/L glides superiorly

if the segments in the thoracic or lumbar spine are in neutral, ROTATION is in the _____ direction of SIDE BENDING which law is this?

Law 1 - rotation and SB in OPPOSITE directions

if segments in the cervical, thoracic or lumbar spine are in full flexion or extension with the z-joints engaged (locked), ROTATION and SB occur _______ what law is this

Law 2 - occur to the same side

if motion is introduced into a segment in any plane _______ what law is this?

motion in the other is reduced law 3

what is the standard view for radiographic views of the L spine

AP view

what are the 4 basic projections of the L spine for radiograph

AP lateral R and L oblique Lateral L5-S1