Lumbar Biomechanics and Pathology

what is the function of lumbar spine bodies?

wide bodies that support the weight of the trunk and UE

is the spinal cord present at the level of the lumbar vertebrae? what does this mean?

no, means that problems coming fro m this level will have LMN presentation

how do lumbar vertebra change as the level descends (L1-L5)

greater area for greater loading, shape of the vertebral canal becomes more triangular

connects transverse processes of adjacent vertebrae and limits side bending

Intertransverse ligament

in what plane of motion is there the greatest amount of motion in the spine

sagittal

in what plane of motion is there the leas amount of motion in the lumbar spine

rotation

what level is the greatest amount of pathology in the lumbar spine seen? why?

L4-S1, there is the greatest amount of sagittal plane motion available there

what 3 parts make up the intervertebral junction?

transverse and spinous processes, facet joints, interbody joint

what is the function of interbody jooints?

connect disc with vertebral bodies, absorb and distribute load

how much of vertebral column height is made up of disc space?

25%

what is the function of facet (apophyseal) joints

guide motion (railroad tracks)

can you isolate just the lumbar spine during flexion?

no

what part of the spine is compressed during flexion?

anterior disc

what kinematics are happening at the intervertebral junction during flexion?

each vertebra is sliding up the adjacent one

what part of the spine is on tension during flexion?

ligaments behind the center of rotation (interspinous, superspinous)

what kinematics are happening at the intervertebral junction during extension?

each vertebra slides down the adjacent one

what is compressed during spinal extension?

intervertebral foramen (narrows), posterior ligamants

do vertebral discs have good healing capacity?

no, there are only bvs in the outer rings

where are sensory fibers located in the vertebral discs?

only the outermost layers

what makes up vertebral discs?

collagen fibers arranged in multiple concentric layers oriented about 65 degrees from vertical, fibers in every other layer run in identical directions

what types of collegen make up vertebral discs?

outer part is type 1 and inner is type 2

cartilage caps of connective tissue that bind to the collagen of the annulus fibrous

endplates

what is the first part of the endplate that fractures due to repetitive loading and why?

the top portion that faces the vertebral body which is made of calcified cartilage

what is the function of intervertebral discs?

load transfer (compressive to tensile, bearing, stabilizer, spacer

what changes occur in the intervertebral discs with aging?

less water and GAGs, nucleus is less distinct, less stiff, increased creep response (deforms faster and further)→ causes greater loading to other structures including facet joints

what positions put the highest amount of pressure on the discs?

flexion w/ a load in front of body, slouched postures

what positions put low pressures on the discs?

supine, sidling, sitting reclined

why are pressure changes critical to disc health?

Intermittent is needed for pressure gradients to get nutrients

what causes a gain of 1-2 cm of height at night?

discs go through diurnal cycle and is at low pressure at night during rest so fluid is re-imbibed

what is DDD?

degenerative disc disease, not a disease→ degeneration of the vertebral body

what are the phases of degeneration?

dysfunction, instability, restabilization

where can we help to reduce pain?

Responding to the inflammatory cell infiltrate

what direction do discs typically tend to herniate?

posteriolaterally

a bulge where the disc material pushes out, but the outer layer (annulus fibrosus) remains mostly intact

protrusion

more severe herniation where the disc material breaks through the annulus, and the material may or may not be connected to the original disc

extrusion

2 possible causes of facet arthrosis

capsular swelling or osteophytes

IV disc degeneration is associated with fibrosis in the _______ muscle

multifidus

how does physical activity impact fibrosis?

reduces it

the expression of ECM components are ______ following disc degeneration

dysregualted

a narrow section of bone located in the vertebral arch, connecting the superior and inferior articular processes (dog collar), the area that is affected by spondylolysis

pars interarticularis

how is the pars interarticularis stressed?

strong, forceful extension

forward slippage of one vertebral body compared to the other

spondylolisthesis

treatment for spondylolysis and spondylolisthesis

stabilization training, may consider bracing

what should be avoided for spondylolysis and spondylolisthesis

end ranges- especially extension, high loads

narrowing of the spinal canal, nerve root canal, or IV foramina

spinal stenosis

how is spinal stenosis classified?

by anatomic location (central or lateral)

what is the dynamic component of spinal stenosis?

with lumbar extension, the degrnerated IV discs and thickened ligamenta flava protrude posteriorly into the lumbar canal causing transient compression of the cauda equina

what happens to the lumbar canal in flexion?

widens

what causes exercise induced ishemia in people with stenosis?

narrowing of small intraneural arterial branches and venous congestion (associated w/ walking)

signs/symptoms of neurogenic claudication

middle aged/elderly men, back or bilateral leg pain in buttock/thick/calf/feet, pain, paresthesia, weakness, leg fatigue, difficulty walking but able to ride a bike (flexion), stoped posture

what is the basis of PT treatment for spinal stenosis?

flexion based exercise and postural strategies