Lumbar Biomechanics Flashcards
What is Type I mechanics?
Sidebending and rotation are coupled to opposite sides. Also known as neutral mechanics.
Does the lumbar region follow Fryette mechanics?
Yes
What is Type II mechanics?
Sidebending and rotation are coupled to the same side. Also known as non-neutral mechanics.
What vertebrae are exceptions to Fryette’s rule?
L5/S1
Explain the exceptions to Fryette’s rules.
L5/S1 has more connections, thus is less predictable. This segment is the site of more spinal anomalies than anywhere else in the spinal column. Anomalous facings of the facet joints negates Fryette mechanics. Trauma is common here, with loss of stability due to ligamentous or disc injury, again negating Fryette mechanics.
Describe lumbar kinesiology.
Motion is permitted by bones & joints, restrained by ligaments, and produced & stabilized by muscles.
What vertebrae make up the anatomical lumbar spine?
L1-L5
What vertebrae make up the functional lumbar spine?
T11-L5
What kind of curve and design does the lumbar spine have?
Lordotic curve; weight-bearing design.
Describe the sagittal plane orientation of the facets.
Superior articular facet - faces posteromedially
Inferior articular facet - faces anterolaterally
Allows for good forward & backward bending
Discourages rotation & sidebending
How much does each lumbar vertebra move in total flexion & extension?
L1 on L2: 9-16 degrees L2 on L3: 11-18 degrees L3 on L4: 12-18 degrees L4 on L5: 14-21 degrees L5 on S1: 18-22 degrees
How much does each lumbar vertebra move in sidebending?
Approximately 10 degrees in each direction per segment.
How much does each lumbar vertebra move in rotation?
L1-L3: about 2 degrees in each direction
L4-L5: about 3-4 degrees in each direction
Intervertebral discs are thicker where, and what does this contribute to?
They are thicker anteriorly. This contributes to the shape of lumbar lordosis.
To what and where do the discs attach?
They attach to hyaline cartilage at the vertebral end plates (which are parallel).
What is the blood supply like for IV discs?
They are avascular (except at the periphery); receive nutrients by diffusion from vertebrae.
What does motion loss impair and thus lead to?
It impairs nutrition, leading to premature disc degeneration.
What is needed for normal disc development?
Motion
IV discs make up how much of the length of the spinal column?
1/5
What checks rotary motion and “screws” down the disc?
The fiber arrangement of annulus fibrosus.
Where is the nucleus pulposus?
Near the posterior surface of the disc.
If the IV discs are healthy and compressive forces are applied to the spine, what will happen?
The vertebrae will fractures before the discs give away.
When does disc degeneration happen for men and women?
Men: begins 11-20 years of age
Women: begins 21-30 years of age
By age 50, what percentage of lumbar discs show degenerative changes?
97%
Which disc sees the most common herniation?
L5-S1
What reinforces the strength of the disc posteriorly in the mid-line?
Posterior longitudinal ligament - becomes narrower and weaker as you descend the spine (goes postero-laterally), predisposing the lower discs to herniation.
What does ligamentous function do?
Allows adequate physiologic motion and fixed postural attitudes between vertebrae with a minimum expenditure of muscular energy. Example - relax while standing (minimal muscle energy used). Also provides stability to the spine within physiologic ranges of motion (shared task with musculature).
What do ligaments protect, and how do they do so?
They protect the spinal cord and cauda equina by restricting the motions within well-defined limits. Go to far - spinal cord damage. Must protect spinal cord in traumatic situations in which high loads are applied at fast speeds. All of this requires the absorption and dissipation of large amounts of energy.
What movements are check ligaments responsible for?
Forward bending
Backward bending
Lateral bending
Rotation
What movements are kinetic ligaments responsible for?
Absorbtion and re-dispersement of energy
What are the 8 ligaments to the lumbar spine?
Anterior longitudinal ligament Posterior longitudinal ligament Intertransverse ligaments Capsular ligaments Ligamenta flava Interspinous ligaments Supraspinous ligaments Iliolumbar ligaments
Which ligaments are forward bending check ligaments?
Supraspinous
Interspinous
Posterior longitudinal
Capsular ligaments
Which ligament is the first to tear when in violent flexion?
Supraspinous ligament
How do you know if you have a torn supraspinous ligament?
If you can put your finger in between 2 spinous processes
If area of injury is tender, swollen, and painful, what kind of tear is it?
Acute, non-palpable
Describe the capsular ligaments, as well as what they do.
Fibers are oriented at right angles to the facet joint surface. The ligaments provide increasing stability with increasing flexion of the spine.
What is the kinetic ligament?
Ligamentum flavum
Describe ligamentum flavum.
Yellow
Packed with elastic fibers
Purest form of elastic tissue in human body
In forward bending, it stores kinetic energy to assist the musculature in returning the spine to the upright posture.
What are the sidebending check ligaments?
Intertransverse check ligaments
Describe the intertransverse check ligaments.
They form from the thickening of the anterior layer of the lumbodorsal fascia, enclosing the intertransverse musculature in the lumbar region (think muscle sandwich). One subset is the lumbosacral ligaments (L5-S1).
What are the rotational check ligaments?
Iliolumbar ligaments