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
What are Schmorl’s nodes?
herniations of the nucleus pulposus through the vertebral end plates
What is Scheuermann’s disease?
idiopathic process of unknown etiology that effects ossification of the outer rim of the end plate resulting in:
- vertebral wedging (decreased anterior vertebral height)
- rough end plates
- schmorl’s nodes
increased kyphosis
What muscles are relevant in the biomechanics of the lumbar spine?
- transversospinales (multifidus, rotatores)
- quadratus lumborum
- psoas major
- iliocostalis lumborum
- abdominal muscles
- intertransversarii
- interspinous
What ligaments are relevant in the biomechanics of the lumbar spine?
- ALL
- PLL
- ligamentum flavum
- capsular ligaments
- iliolumbar ligaments
- interspinours ligaments
- supraspinous ligaments
intertransverse ligaments
-transforaminal ligaments
What is the normal global ROM for flexion in the lumbar spine?
40-60 degrees (excluding hip flexion)
What is the normal global ROM for extension in the lumbar spine?
20-35 degrees
What is the normal global ROM for rotation in the lumbar spine?
5-18 degrees
Approximately what percentage of overall trunk flexion occurs in the lumbar spine?
75%
Flexion increases in what part of the lumbar spine?
increases superior to inferior
i.e. less flexion at L1 and more at L5
Where is the IAR of flexion in the lumbar spine?
anterior disc
What is the pattern of motion around the IAR in flexion of the lumbar spine?
forward tilting with anterior translation
i.e. +z and +θx
orthogonal description of lumbar flexion?
+θx
positive rotation about the X axis
orthogonal description of lumbar extension?
-θx
negative rotation about the X-axis
Extension increases in what part of the lumbar spine?
increases superior to inferior
i.e. less extension at L1, more at L5
Where is the IAR of extension in the lumbar spine?
posterior disc
What is the pattern of motion around the IAR in extension of the lumbar spine?
backward tilting with posterior translation
NOTE: posterior translation accentuated with DJD
What is the segmental motion for rotation of L5 in the lumbar spine?
5 degrees (compared to 1-2 degrees in L1-L4)
What is the segmental motion for rotation of L1-L4 in the lumbar spine?
1-2 degrees (compared to 5 degrees of L5)
What allows for more segemental rotation but less lateral flexion at L5 than L1-L4 ?
Facets are sagittal L1-L4
Facets are more coronal L5
Where is the IAR of rotation in the lumbar region?
posterior annulus on the contralateral side
What is the pattern of motion around the IAR in rotation of the lumbar spine?
rotation around the y-axis
+θy for right lateral flexion
-θy for left lateral flexion
What is the normal global ROM for lateral flexion in the lumbar spine?
15-25 degrees
What is the segmental motion for lateral flexion of L1-L4 in the lumbar spine?
5-8 degrees per segment (compared to 2-3 degrees for L5)
What is the segmental motion for rotation of L5 in the lumbar spine?
2-3 degrees per segment (compared to 5-8 degrees for L1-4)
Where is the IAR of lateral flexion in the lumbar region?
contralateral disc
i.e. right lateral flexion will have IAR on the left side of disc
What is the pattern of motion around the IAR in lateral flexion of the lumbar spine?
There is some controversy/lack of consensus over this but:
- if lumbar spine starts neutral or extended and then lateral flexes, there is contralateral coupled rotation.
- if the lubar spine starts flexed and then lateral flexes, there is ipsilateral couple rotation
What kind of contraction is occuring when a muscle shortens and muscle tension overcomes resistance?
concentric muslce contraction
What kind of contraction is occuring when a muscle elongates and resistance overcomes muscle tension?
eccentric contraction
What does lumbopelvic rhythm describe?
the expected sequence of events in the lumbar spine, pelvis and hips as a person flexes and returns to normal
What initiates lumbopelvic flexion and what controls motion once gravity takes over?
- concentric contraction of psoas and abdominals initiates
- eccentric contraction of erector spinae muscles control motion once gravity takes over
In the first 60 degrees of lumbopelvic flexion, where is the motion?
only the lumbar spine because pelvis is locked in place by gluteus maximus and hamstrings
After the first 60 degrees of lumbopelvic flexion, where is the motion?
the pelvis because the stabilizing forces of glut max and hamstrings has been overcome and the pelvis rotatates another 25-30 degrees
When returning to neutral from a flexed lumbopalvis, where does the motion start?
the pelvis moves first under control of the hip extensors, followed by extension of the lumbar spine controlled by erector spinae muscles
What ligaments limit lumbopelvic flexion?
ligamentum flavum
PLL
capsular ligaments
interspinal ligaments
What initiates lumbopelvic extension and what controls motion once gravity takes over?
- concentric contraction of the sacrospinalis (erector spinae) initiates
- eccentric contraction of abdominal muscles control motion once gravity takes over
What ligaments limit lumbopelvic extension?
ALL
anterior annulus
Other than ligaments, what is the most significant limiter of lumbopelvic extension?
spinous processes
What initiates lumbopelvic lateral flexion and what controls motion once gravity takes over?
concentric contraction of ipsilateral quadratus lumborum initiates lateral flexion
eccentric contraction of contralateral quadratus lumborum controls motion once gravity takes over
What ligaments limit lumbopelvic lateral flexion?
capsular ligmants
ligamentum flavum
intertransverse ligaments
deep lumbar fascia on contralateral side
Approximation of the ipsilateral articular facets limits what lumbopelvic motion?
lateral flexion
What initiates lumbopelvic rotation and what controls motion?
- concentric contraction of ipsilateral internal obliques and contralateral external obliques (some contribution from rotatores and multifidus on contralateral side)
- Eccentric contractions of the ipsilateral rotatores and multifidus control motion
What ligaments limit lumbopelvic rotation?
capsular ligaments
interspinous ligaments
ligamentum flavum
Other than ligaments, lumbopelvic rotation is mainly limited by what?
facetal design
What is the normal global ROM for lumbopelvic flexion?
90 degrees
What is the normal global ROM for lumbopelvic extension?
25-30 degrees
What is the normal global ROM for lumbopelvic lateral flexion?
15-25 degrees
What is the normal global ROM for lumbopelvic rotation?
45 degrees
examination of the lumbar spine could include:
postural exam
global ROM evaluation
static palpation
motion palpation
X-ray evaluation
orthopedic testing
neurologic testing
What is Type I lumbar motion?
normal, SP rotation into concavity with lateral flexion
What is type II lumbar motion?
abnormal, early dysfunction in which SP rotates into convexity with lateral flexion
What is type III lumbar motion?
abnormal, loss of lateral flexion
What is type IV lumbar motion?
abnormal, loss of flexion and rotation
What is facet syndrome?
mechanical, degenerative or traumatic derangement of posterior joints?
What is the affect of facet tropism?
increased stress to the joints and more prone to facet syndrome
What is IVD syndrome?
annular tearing, fissuring that causes pain, derangements, joint locking and/or joint restrictions
What is interdiscal block?
nuclear material migrating into the fissures causing pain, derangements, joint locking and/or joint restrictions
What is a disc herniation?
disc bulge or protrusion caused by extrusion of the nucleus into the canal (usually still contained in annulus)
