Lumbar Spine Biomechanics Flashcards
What is the main role of the throacolumbar fascia (TLF)
Stabilize the spine
Characteristics of the lumbar spine
Large
Transverse diameter greater than A-P and height
True or False:
The lumbar vertebral bodies progressively wedge shaped from L1-L5
True
What does wedge shaped mean
The anterior body is larger than posterior body
How do the spinous processes of the lumbar vertebrae look from a lateral view
Broad and thick
How do the spinous processes of the lumbar vertebrae look from a superior view
Thin
What does the vertebrae being progressively wedge shaped contribute to
Lumbar lordosis
What is the lateral gutter
The septum between iliocostalis and longissumus where the transverse processes lay
True or False:
The transverse processes of the lumbar vertebrae are large and at the same level of the spinous process
True
How are the facets oriented
They are progressing toward the sagittal plane
How close to the sagittal plane is L5
90%
How are the superior facets oriented
Concave facing medially and slightly posterior
How are the inferior facets oriented
Convex facing laterally and slightly anterior
Are the lumbar facets weight bearing structures
Yes but not too much
How does the amount of WB change from L1-L5 facets
The amount of WB decreases
True or False:
The inferior facets of lumbar vertebrae are more medial than the superior facets
True
What is sacraliztion of L5
L5 has fused to the sacrum
Is sacralization acquired or congenital
Congenital
What occurs because of sacralization of L5
L1-L4 have increased mobility to make up for the mobility lost at L5
What is lumbarization of the sacrum
S1 is not fused to the sacrum
Is lumbarization acquired or congenital
Congenital
What occurs because of lumbarization of the sacrum
You have 6 free floating lumbar vertebrae so each segment has decreased mobility
True or False:
The PLL is almost non existence in the lumbar spine
True
True or False:
The ligamentum flavum has a higher concentration of elastin which provides preload to motion segments
True
What are the iliolumbar ligaments
5 bands extending from L4 and L5 transverse processes to the iliac crest just above the PSIS
What do the iliolumbar ligaments prevent
Anterior displacement of L4 and L5
True or False:
It is more important to stabilize L5 than L4
True
How do nutrients get to the disc
The vertebral end plate
What are the 3 layers of the thoracolumbar fascia
Anterior, middle, and posterior
Where does the thoracolumbar fascia attach to
Spinous and transverse process
Which 2 layers of the TLF are derivatives of the quadratus lumborum
Anterior and middle
What does the posterior layer of the TLF fuse with (3)
- Transversus abdominis
- Gluteus maximus
- Latissimus dorsi
What fibers of the posterior layer of the TLF attach to the gluteus maximus
Vertical fibers
What fibers of the posterior layer of the TLF attach to the abdominal obliques
Horizonatl fibers
What fibers of the posterior layer of the TLF attach to the latissimus dorsi
Oblique fibers
What layers of the TLF attach to the transverse processes
Anterior and Middle
What layer of the TLF attach to the spinous processes
Posterior
What is the origin to insertion of the erector spinae considered
Diverge
What does a diverging origin to insertion mean
Attach central to lateral
Are the erector spinae shunt or spurt muscles
Spurt muscles
Are spurt muscles stabilizers or movers
Movers
Which way do the erector spinae rotate and side bend
Ipsilaterally
What is the origin to insertion considered for the multifidi and rotatores
Converge
What does a converging origin to insertion mean
Attach lateral to central
Are the multifidi or rotatores shunt or spurt muscles
Shunt muscles
Are shunt muscles stabilizers or movers
Stabilizers
Which way do the multifidi and rotatores side bend and rotate
Side bend ipsilaterally
Rotate contralaterally
True or False:
People with chronic back pain have atrophy of the multifidi and rotatores
True
What type of motion does the rectus abdominis create with top down motion
Trunk flexion
What type of motion does the rectus abdominis create with bottom up motion
Posterior pelvic rotation
What is the agonist to trunk flexion
Gravity
How do the internal obliques rotate the trunk
Ipsilaterally
What does contraction of both the trunk flexors and extensors simultaneously cause
Co-contraction and stability
What does co-contraction cause
Increased compressive forces and decreased shear forces
How do the external obliques rotate the trunk
Contralaterally
What does co-contraction increase (3)
- Intrathecal pressure
- Intra-abdominal pressure
- Intradiskal pressure
What happens when the erector spinae contract
They become shortened and thickened which pushes into the TLF
What does the erector spinae pushing into the TLF do
Increases passive stabilization
What does neutral spine refer to
Point at which normal lumbar lordosis is maintained
What does the compressive force via superincumbent body weight and muscle contraction do to the disc
Increases hydrostatic pressure in the disc
What does increased hydrostatic pressure in the disc result in
Increased tension in the annulus fibrosis
What does the increased annular tension causes
Inhibits radial expansion of the nucleus
What does inhibiting the radial expansion of the nucleus result in
Rise in nuclear pressure that is exerted on the endplates
What does the rise in nuclear pressure that is exerted on the enplates cause
Hoop stress
What is hoop stress
Annulus fibrosis pushing back providing stability
What does hoop stress do
Reinforces the peripheral annulus fibrosis
What does reinforcing the peripheral annulus fibrosis do
Converts the disc into a stable WB structure
Where is the pressure in the disc transmitted ultimately
To the endplates to the next bertebrae
What is imbibation
Absorbing water in disc while lying at night
True or False:
Every other layer of the annulus fibrosis runs in the same direction
True
What is the angle at which the annulus fibers run
65-80
What happens to the disc with rotation
The disc is wound up increasing tension
What is the most common place for lumbar problems
L4/L5 followed by L5/S1
What direction do the facet joints allow the most motion in
Flexion and extension
What is more limited flexion or extension
Flexion
What does flexion require
Synergistic activity by the pelvis
Where does the greatest flexion occur in the lumbar spine
L4/L5 and lumbosacral junction
What percent of the flexion occurs at L4/L5 and L1-L4
L4/L5: 80-90%
L1-L4: 10-20%
How does side bending and rotation change as you go down the lumbar spine segments
They decrease
How much side bending occurs in the lumbar spine
Left and right: 20
Total: 40
How much rotation occurs in the lumbar spine
1 degree per segment so total of 5 degrees left and right
What do facets dictate
The direction of motion
What does disc size dictate
Amount of motion
How much flexion occurs because of the lumbar spine
60
What is fryette’s law 1
Rotation and side bending occur to opposite sides in a neutral spine
What is fryette’s law 2
Rotation and side bending occur to opposite sides in a non-neutral spine
Fryette’s Laws refer to which plane of motion
Sagittal plane
What is fryette’s law 3
If you introduce motion in 1 plane or direction adding another motion will result in that motion being limited
What happens to the facets during right rotation
Left facet is compressed
Right facet is decompressed
What happens to the facets during right side bending
Left facet is decompressed
Right facet is compressed
What is the angle of the sacrum
The angle between the base of the sacrum and the horizontal plane
What is the normal angle of the sacrum
30
What does increasing the angle of the sacrum do to the lordosis and shear
Increases lumbar lordosis and anterior shear
Does the sacrum move the same direction as the pelvis or in a different direction as the pelvis
The same direction
What happens to the angle of the sacrum during anterior pelvic tilting
Sacral angle increases which increases the lumbar lordosis
What is the lumbosacral angle
Measured of the obtuse angle formed by the middle axes of L5 and S1
Which way does the lumbosacral angle open
Posterior
What is the normal lumbosacral angle
140
What does the lumbosacral angle and wedged shape of the L5/S1 disc initiate
Lumbar lordosis
How does flexion effect the lumbosacral angle
Increases the lumbosacral angle
How does anterior pelvic tilt effect the sacral angle and lumbosacral angle
Increases sacral angle, increases lordosis, and decreases lumbosacral angle
What happens to the amount of shear force if you increase the lumbar lordosis
The amount of shear force increase
What prevents L4 and L5 vertebrae from slipping forward
Iliolumbar ligaments
What are the 3 structures that keeps the anterior shear forces in check
- Iliolumbar ligaments
- Disc
- ALL
True or False:
The surface of the disc is able to counteract shear forces because the superior fibers are horizontal
True
Do you want the disc to combat the shear forces
Not really because it leads to DDD
Is there more or less load on the disc while sitting with erect posture when compared to standing
More
Is there more or less load on the disc while sitting with a slumped posture when compared to standing
More
Is there more or less load on the disc while sitting with erect posture or slumped posture
Slumped posture
Is there more or less load on the disc while sacral sitting when compared to standing
Less
Why does the amount of load increase when sitting with a slumped posture
The MA of gravity increases increasing the torque of gravity
True or False:
The lumbar spine allows for the first 60 of flexion
True
How do we achieve terminal flexion
Synergistic pelvic tilting
What is lumbo-pelvic rhythm
Inter connection of movement between the lumbar spine, sacrum and pelvis
What is normal lumbo-pelvic rhythm discussed in
Top down motion
What are the tissues that move in the lumbar spine with flexion in order
1st segment moves then posterior ligaments tighten then next segment moves so on so forth
What is nutation a term for
Sacral flexion
What is nutation
Sacral base moves anterior/inferior and coccyx moves posterior/superior
What is counternutation a term for
Sacral extension
What is counternutation
Sacral base moves posterior/inferior and coccyx moves anterior/superior
What are the motions that occur due to lumbo-pelvic rhythm following lumbar flexion (4)
- Sacral nutation (flexion)
- Anterior pelvic tilt
- Sacral counternutation
- Posterior pelvic translation
What is the anterior pelvic tilt controlled by
Hamstring tension
How does hamstring tension control the anterior pelvic tilt
Part of the biceps femoris long head attaches to the sacrotuberous ligament that tethers the sacrum which when tensioned pulls on the sacrotuberous ligament
True or False:
The sacral counternutation is relative to the pelvis because the anterior rotation makes it appear that the sacrum has counternutated (extended)
True
What does the posterior pelvic translation do
Pushes the COM posteriorly
Why do we need the posterior pelvic translation
To prevent us from falling flat on our face
What is non-lumbo-pelvic rhythm
Bottom up motion
What occurs with supine flexion of the hips
Posterior pelvic rotation and sacral nutation
True or False:
For the relative sacral nutation to occur during supine flexion you need to be lying on a relatively stiff surface
True
What occurs with supine extension of the hips
Anterior pelvic tilt and sacral counternutation
True or False:
For the relative sacral counter nutation to occur during supine extension you need to be lying on a relatively stiff surface
True
Motivation
Keep pushing through only a few more days!
