III. Biomechanics of the Lumbar Spine Flashcards
What are common sources for low back pain?
disc facet joints soft tissue
What are the major functions of the lumbar spine?
support for trunk and upper extremities resist compression provide mobility muscular attachment protect the spinal cord/cauda equina
How does the width of the lumbar vertebrae change from above down?
width increases
what kind of curve does the lumbar spine form?
lordotic
What is the normal lumbar lordosis angle?
40-60 degrees
What is the normal lumbosacral angle?
26-57 degrees
What is the shape of a lumbar vertebral body?
kidney
Are lumbar vertebral bodies wider side to side or A to P?
side to side
What is the approximate height of an IVD in the lumbar region?
9mm
What percentage of spinal height is attributed to IVD height?
25%
What is the ration of IVD to vertebral body height in cervical region?
2 : 5
What is the ration of IVD to vertebral body height in thoracic region?
1:5
What is the ration of IVD to vertebral body height in lumbar region?
1:3
The large disc to vertebral body height ratio seen in the lumbar region attributes to what?
increased lumbar flexibility
increased shock absorption
Nucleus puplosus is located where in the disc?
posterior 1/3
What causes the nucleus pulposus to become mobile?
annular tearing
How much possible height variation may occur in a person throughout the day due to IVD hydration/dehydration?
3/4”
How much possible height loss may occur in a person due to normal IVD aging?
1 inch
What plane are the articular fects of the lumbar spine in?
mostly sagittal but becoming more coronal at L5
Which articular facet surface in the lumbar region is convex, superior or inferior?
inferior
Which articular facet surface in the lumbar region is concave, superior or inferior?
superior
Which articular facets face inferiorly, laterally and anteriorly in the lumbar region, superior or inferior?
inferior
Which articular facets face superiorly, medially and posteriorly in the lumbar region, superior or inferior?
superior
Where is the most common site for facet asymmetry (facetal tropism)?
lumbar region
What kind of motion do the lumbar facets facilitate and what motion do the lumbar facets resist?
facilitate flexion and extension
resist rotation and lateral flexion
Asymmetrical facets (facetal tropism) can cause what?
increased cartilage wear, increased disc stress
Facets carry what percentage of the spine’s axial load?
3-25%, depending on anatomy and posture
Facets carry what percentage of the spine’s axial load when in extended posture?
up to 33%
Facets and their articular cpasules provide what percentage of the torsional strength of the lumbar spine?
up to 45%
Describe the TPs of the lumbar region?
small and run posterolaterally
site of muscle and ligament attachment
Describe the SPs of the lumbar region?
fewer anomalies than in the thoracics
run horizontal (no sloping as in thoracics)
large and hatchet shaped
Describe the SP of L5?
shorter and rounder than the rest of the lumbar vertebrae
Where would you palpate for mamillary processes?
in the lumbar region, lateral to the interspinous space above the corresponding SP
Describe the vertebral end plates in the thoracic and lumbar spine?
made of thin cortical bone
lined with hyaline cartilage
outer rim is ossified around age 14-15
The possibility of permanent correction of scoliosis dereases after what event?
ossification of the rim of the vertebral end plates at age 14-15
What is Wolff’s law?
ossification in mature bone is in proportion to the stress on the bone
more stress/pressure = more bone growth
What is Heuter Volkman’s law?
increased pressure across an epiphyseal growth plate of immature bone, inhibits growth
more pressure/stress = less growth
How does Heuter Volkman’s law explain idiopathic scoliosis?
Increased pressure causes decreased bone growth which decreased pressure causes increased bone growth which makes vertebrae develop wedge shape. This causes concavity on the high pressure side and covexity on the low pressure side as pictured