Module 10 - Lumbar Spine Flashcards
What are major structural components of the vertebral column?
- Vertebral bodies
- Intervertebral disks
What is the spinal cord important for?
- Relaying neural information
How do the vertebral bodies of the lumbar spine compare to the thoracic and cervical spine?
- Thicker
- Wider
Why are lumbar vertebral bodies thicker and wider than the thoracic and cervical ones?
- Designed mainly to bare compressive loads
What percentage of body load is on the lumbar vertebra?
- 50%
What percentage of body load is on the thoracic vertebra?
- 20-30%
What happens when the vertebra is under compression?
- Walls of vertebra remain rigid
- End plates bulge inwards: when the intervertebral disk pressurizes
What fails first under compression?
- Cancellous bone
What is the determinant factor of tolerance to compression?
- Cancellous bone
What plays a dominant role in shock absorption?
- Vertebral Body
- Not the disks
What is the deformation of cancellous bone due to?
architecture
- vertical and transverse trabeculae
What do the vertical and transverse trabeculae offer?
Balance between
- Elasticity
- Rigidity
What happens upon axial compression?
- End plate bulge into the vertebral body
- Vertical trabeculae experience compression and bend
What is the microfracture of trabeculae called?
- subfailure
When can a micro-fracture of trabeculae occur?
- Following repeated loading
Will there be damage to the trabeculae if the loading is less than 10% of ultimate compressive load?
- No
How many cycles of a load of 20-30% will lead to damage to the trabeculae?
- 20000
What does damage of the trabeculae lead to?
- Decreased stiffness
What does an osteoporotic bone lead to?
- Decrease in number and size of transverse trabeculae
What does an osteoporotic vertebra have?
- Decreased compressive strength
What are the posterior elements of the vertebrae?
- Pedicles
- Laminae
- Spinous Process
- Transverse processes
- Facet joints
Describe the posterior vertebrae structure.
- Shell of cortical bone
- Contains cancellous bony core in thick section
Describe the neural arch of the vertebrae
- Pedicles
- Laminae
What is spondylolysis?
- Anterior displacement of vertebral body with respect to the segment below
How does spondylolysis occur?
- Failure of posterior elements
- Shear forces acting on posterior elements
What type of athlete often experiences spondylolysis?
- Gymnasts
Why might spondylolisthesis be asymptomatic in fit people?
- Spine stability
What can happen for someone who has asymptomatic Spondylolisthesis?
- May experience symptoms later in life
What is the intervention method for treating spondylolisthesis?
- Surgery
- Stability exercises
At what level does spondylolisthesis usually occur?
- L5 to S1
Is spondylolisthesis congenital?
- No: detected as early as 4 months
What might predispose an individual to develop spondylolisthesis?
- Genetic factors
Can Spondylolisthesis occur at multiple levels?
- Yes
What level is degenerative spondylolisthesis most frequent?
- L4
What level is the most common for spondylolisthesis?
- L5
What do Intervertebral disks do?
- Bear and distribute loads
- Restrain motion
Why are intervertebral disks well suited to bear and distribute loads and restrain motion?
- Located between vertebrae
- Composition of inner and outer structures (hard to distinguish)
What is the inner portion of the intervertebral disks comprised of?
- Gelatinous mass (nucleus pulposus)
What does the inner portion of the intervertebral disk do?
- Cushion between vertebrae
- Store energy
- distribute loads
What is the outer portion of the intervertebral disk made of?
- Tough covering of fibrocartilage (annulus fibrosus)
What does the outer portion of the intervertebral disk do?
- Withstand large bending
- Withstand torsional loads
What happens to the annulus fibrosus during axial rotation (twisting)?
- Half resists load
- Half relaxes
What happens as a result of axial rotations effect on annulus fibrosus?
- Decreases its ability to bear the load
What happens to the intervertebral disk during compression or bending?
- Annulus and nucleus work together
What happens to the nucleus and annulus of the intervertebral disk during compression?
Nucleus
- Pressurizes
- Applies vertical forces to end plates
- lateral forces to inner annulus
Annulus
- Minimal deformation
What happens to the nucleus and annulus of the intervertebral disk during bending?
Annulus
- Compression (outward bulging)
- Traction
Nucleus
- Moves in direction of traction
What happens to intervertebral discs in healthy joints under compressive load?
- Minimal deformation
What must occur for an intervertebral disc to herniate?
- Must be bent to full end range
What is the easiest way to elicit a disc herniation?
- Repeated Flexion
What is disc herniation associated with?
- Extreme deviated postures
- Repeated loading
What does herniation depend on?
- Compressive load during full flexion cycle
What are risk factors for herniation?
- Sedentary occupations
- Sitting postures
What type of spines does herniation tend to occur in?
Younger spines
- with high water content
What should you do for a patient with a herniation?
Identify daily motion exacerbating it
- eliminate it
- Change motion
Where does the herniation process occur?
- Innermost annulus rings
What happens when herniation process progresses?
- Moves radially outwards
What is the McKenzie protocol?
- Extension exercises to drive the nucleus forward within the disk
What happens when a healthy disk under compressive loads, develops internal disk pressure that is so high that no blood vessels or nerve can survive?
- End plate damage
- Disc no longer develops high pressures
- Degenerated discs vascularize and generate pain
What do the ligaments of the lumbar spine do?
- Contribute to intrinsic stability
- Depends on anatomical location
- Depends on type of motion
What does the Ligamentum Flavum contain?
- Large percentage of elastin
What does the Ligamentum Flavum do in a neutral position?
- Is under tension
Why is the Ligamentum Flavum under tension during neutral position?
Pre-stress the disk
What does the pre-stressing of the disc in a neutral position by the tension of the Ligamentum Flavum do?
- Provides spinal stability
What roles do the interspinous ligaments have?
- controls vertebral rotation during flexion
- Protects against post-shear of sup. Vertebra
What can the extensor muscles be divided into?
Three Groups
- Longissimus
- Iliocostalis
- Multifidus
Where are the rotatores and intertransversarii located?
- lumbar level
What is the length of the Longissimus and Iliocostalis?
- 20-30cm
Where does the Pars lumborum attach?
- lumbar spine
What do the Longissimus and Iliocostalis have?
Pars thoracis and lumborum
What percentage of muscle fibers are slow twitch in the pars lumborum?
- 50%
What percentage of muscle fibers are slow twitch in the pars thoracic?
- 75%
Where does the pars thoracis attach?
The thoracic spine
What is the line of action of the pars lumborum?
- Posterior and caudal
Describe the pars lumborum line of action
- Large moment arm: 50-100mm
Are Iliocostalis and longissimus efficient lumbar extensors?
- Yes
Describe the iliocostalis and longissimus tendon
- long
- runs parallel to spine
- large moment arm
Why are the iliocostalis and longissimus efficient lumbar extensors?
- Long moment arm
- Large extensor moment of force
What kind of exercise should be used to strengthen iliocostalis and longissimus pars thoracis muscles?
- exercise that includes motion of the thoracic spine
How many segments do the multifidus muscles span?
- 1-3 segments
How long are the multifidus muscles?
- 5-8cm
Where does the force generated from the multifidus muscles affect?
- Local areas of the spine
What is the line of action of the multifidus muscles?
- Parallel to the compressive axis or anterior and caudal
How long is the moment arm of multifidus muscles?
- 10-15mm
What do some authors describe as the role of multifidus muscles?
Could be:
- High muscle spindle density
- Spinal stability
What does the compressive forces at the intervertebral disc level depend on?
- Mass of trunk, head and arms
- Force developed by lumbar extensor muscles
- Angle of trunk
- orientation of intervertebral disk
What is the joint reaction force?
Counterbalance of:
- Extension moment
- Flexion moment
What is the relationship between the flexion-extension cycle and compressive load?
For herniation to occur:
- As compressive load increase
- Required flexion-extension cycle decreases
What are the three biomechanical concepts around lumbar?
- Orientation of facets determine types of motion possible
- Loading of lumbar intervertebral disc is influenced by posture
- Flexion-extension movement of the lumbar spine
What orientation are the facets in at a 90 degree angle?
- transverse plane
What orientation are the facets in at a 45 degree angle?
- Frontal plane
Describe the flexion-extension movement of the lumbar spine
- Motion between two vertebrae is small
- Combined motion of several segments
- Intersegmental kinematics
- strain on ligaments
What accounts for the amount of strain on each ligament?
- type of motion
What lumbar spine ligaments are strained during flexion?
- Supraspinous ligament
- Capsule and flavum ligament
What lumbar spine ligaments are strained during extension?
- Longitudinal anterior ligament
What lumbar spine ligaments are strained during rotation?
- Capsular ligament
- Lat. Flexion
- transverse ligament
What accounts for the first 50-60 degrees of spinal flexion?
- Lumbar spine
What accounts for the flexion of the spine beyond 60 degrees?
- Lumbar spine
- Pelvic tilting
What is the flexion-relaxation phenomenon?
- At full flexion, the lumbar ES are turned off
When the active muscular actions are turned off during the flexion-relaxation phenomenon, what takes over their role?
- The ligaments of the lumbar spine
- Passive properties of the muscles
How is the flexion-relaxation phenomenon possible?
- Force of passive structures increases when lengthened
What is the new equilibrium controlled by during the flexion-relaxation phenomenon?
- Flexor moment of gravity
- Extensor moment by the stretched passive structures
What is the elastic muscle force of the lumbar muscles developed through?
- Stretching of the muscle: PEC and SEC
What does the absence of electrical activity in the lumbar muscles during the flexion-relaxation phenomenon mean?
No action
- eccentric, isometric, or concentric
Why would the muscle turn off?
- The passive structures can bear the load
What is a low back disorder? (LBD)
- Injury and pain associated with the lumbar spine
How many people develop Lower back disorders at some point in their life?
- 80%
What can lead to lower back pain?
- Infections
- Fractures
- Dislocation
- Tumor
- Non-specific low back pain
What can lead to lower back pain?
- Infections
- Fractures
- Dislocation
- Tumor
- Non-specific low back painW
What causes of low back pain have adequate and precise diagnostic tools?
- Infections
- Fractures
- Dislocations
- Tumors
Are most types of back pain easily detected?
- No
What are the main risk factors for chronic lower back pain?
- History of low back pain
- Inadequate Rest Time
- Poor Social Interactions
- Catastrophizing
What is the working hypothesis on low back pain?
Single or Cumulative Microtrauma
- Subfailure injury
Ligaments and External layers of annulus fibrous
- Richly innervated with nociceptors and mechanoreceptors
Poor control of spinal musculature
- Higher stresses to spinal ligaments and discs
