Lumbar Biomechanics Flashcards
If the lumbar spine is in neutral position, it follows….
Type I mechanics – opposite side
What is the exception to Fryette mechanics in the lumbar spine?
L5/S1
Must test in neutral, flexion, and extension
Which segment is the site of more spinal anomalies than anywhere else in the spinal column?
L5/S1
Trauma is most common at which segment?
L5/S1
What permits motion?
Bones and joints
What restrains motion?
Ligaments
What stabilizes motion?
Muscles
Fascia
The lumbar spine is designed for ______
Weight bearing
Approximately ___% of body weight rests on the lumbosacral disc?
40
Total flexion and extension: L1 on L2
9-16 degrees
Total flexion and extension: L2 on L3
11-18 degrees
Total flexion and extension: L3 on L4
12-18 degrees
Total flexion and extension: L4 on L5
14-21 degrees
Total flexion and extension: L5 on S1
18-22 degrees
Which segments have the largest rotational component?
L4 and L5: 3-4 degrees
What leads to premature disc degeneration?
Motion loss–impairs nutrition
T/F: Intervertebral discs are avascular
True (except for the periphery)
What percentage of lumbar length is comprised of intervertebral discs?
20%
When does disc degeneration begin?
Second decade in men
Third decade in women
By age 50, ___% of lumbar discs show degeneration
97
Where is the most common disc herniation?
L5/S1
followed by L4/L5
Why are lower discs predisposed to herniation?
The posterior longitudinal ligament reinforces the strength of the disc in the midline. This ligament becomes narrower and weaker as you descend the spine.
What protects the spinal cord in traumatic situations in which high loads are applied at fast speeds?
Ligaments
What are the forward bending check ligaments?
Supraspinous
Posterior longitudinal
Interspinous
Capsular
What is the only kinetic ligament in the lumbar spine?
Ligamentum flavum
Yellow
Packed with elastic fibers
Purest form of elastic tissue in the human body
In forward bending, it stores kinetic energy to assist the musculature in returning the spine to the upright posture
Ligamentum flavum
What are the sidebending check ligaments?
Intertransverse check ligaments
What are the rotational check ligaments?
Iliolumbar ligaments
Which ligaments are injured in the classic lumbosacral sprain and strain?
Iliolumbar
Intertransverse
Discs are usually injured by ____ injury
Rotational (not compressed!)
What is the backbending check ligament?
Anterior longitudinal ligament
Broad and flat
Reinforces the disc anteriorly
Anterior longitudinal ligament
What is anatomically critical to the maintenance of lumbar stability?
Thoracolumbar fascia
What helps keep thoracolumbar fascia taut?
Positive pressure in the abdomen
What causes instability in thoracolumbar fascia?
Weakness
Hernias
Incisions
Pregnancy
T/F: The detailed patterns of lumbar muscles are virtually unknown.
True
What are the differences in short vs. long muscles of the lumbar spine?
Short:
Involuntary
Stabilize and balance the spine
Long:
Voluntary
Movers of the spine
Which muscles cause and maintain segmental somatic dysfunction?
Deep paraspinal muscles
These muscles respond to viscero-somatic and somato-somatic reflexes
What are the deep paraspinal muscles?
Intertransverse
Interspinalis
Rotatores brevis
Rotatores longus
Which deep paraspinal muscle stabilizes sidebending?
Intertransverse
Which deep paraspinal muscle stabilizes extension?
Interspinalis
Which deep paraspinal muscles stabilize rotation?
Rotatores brevis and longus
Deep paraspinal muscles function as …..
Guy wires (angle upward)
Rotatores muscles rotate segments to which side?
Opposite side
Flexion of trunk is initiated by which muscle?
Rectus abdominus
After initiation of flexion, which muscles take over control?
Erector spinae
In full flexion, which muscles and ligaments are in control?
Muscles are at rest–this is a passive posture maintained by check ligaments and resistance to disc deformation
Extenders of the spine from lateral to medial
Iliocostalis lumborum
Longissimus thoracis
Spinalis thoracis
Multifidus
When acting unilaterally, the extenders become _____
Sidebenders
When combined with the pull of the abdominal obliques, the extenders become _____
Rotators
Asthma and COPD tend to create flexed dysfunctions in which segments?
Upper lumbar segments L1-L3
Right to L1-3, Left to L1 and 2
Flexed dysfunction of upper lumbar segments will result in which symptom?
Shortness of breath
Which muscle is silent while standing and active while sitting?
Psoas major
Shortening of which muscle results in increased lumbar lordosis?
Psoas major
Acute psoas spasm will sidebend the trunk in which direction?
Toward the side of the spasm
What is typically the net effect of psoas spasm?
Type II dysfunction
Typically affecting L1, 2, or 3
Flexed
Rotated and sidebent to same side
T/F: Extended dysfunctions tend to CAUSE psoas spasm, while flexed dysfunctions tend to be a RESULT of psoas spasm.
True
Chronic shoulder problems may be caused by which muscle?
Latissimus dorsi
Accessory muscle for forced exhalation
Serratus posterior inferior
L1 nerve roots are ____ mm long
60
S1 nerve roots are _____ mm long
170
Axons from S1 to final destination may exceed _____ in length
100 cm
Blood flow is reduced when a nerve root is stretched to ___% of its length; completely ceases when stretched to ____%.
8 / 15
