Spine Biomechanics and Lumbar Pathology Flashcards
load distribution
80% load through vertebrae and interbody joint
20% through posterior elements
Annulus fibrosis
concentric rings to contain the nucleus pulposus
Opposite directed collagen, fibers, 65° from vertical
Peripheral strength, flexibility protection from distraction, shear, torsion
nucleus pulposus
70 to 90% water in younger individuals
shock absorber
Dehydrated discs can increase load to facet joints
diurnal variation
Lose about 25% of fluid in disc during the day then you rehydrate it at night
Zygapophyseal joint
Facet joint
synovial plane joint
Allows flexion, but also a restraint to excessive flexion to protect the IVD
Zygapophyseal joint blocks excessive
anterior translation
Protects spinal cord
Contains fat plugs - may be a source of symptoms
How do you name the movement?
superior vertebrae on the inferior vertebrae
Direction of anterior surface of the vertebral body
OK- flexion and extension
Sagittal plane
Medial lateral axis
Forward and backward bending
OK- lateral flexion to the right or left
Frontal plane
Anterior posterior axis
Side bending to the right or left
OK- axial rotation to the right or left
Horizontal plane
Vertical axis
Rotation or torsion
Fryettes laws
Coupled motions
Type one mechanics
neutral
Coupled motions in opposite directions
lateral flexion to one side is accompanied by rotation to the opposite side
(left lateral flexion and right rotation)
type 2 mechanics
non-neutral
Coupled motion in the same direction
Lateral flexion to one side is accompanied by rotation to the same side
(left lateral flexion and left rotation)
type three mechanics
Motion in one plane reduces availability of motion in all remaining planes
Most relevant to lumbar mechanics
lumbar flexion
Anterior rotation, transverse axis
Translate anteriorly, Sagittal axis
45-55 degrees of lumbar flexion
lumbar flexion; anteriorly
compresses anterior disc
anterior longitudinal ligament laxity
lumbar flexion… facet joint and spinous processes do what
Inferior articular process of superior vertebra moves superiorly on superior articular process of the inferior vertebra
Opening of facet joints
Separation of a spinous processes
Posterior ligaments, facet capsule tightens
increases the diameter of NF, spinal canal
lumbar extension
Superior vertebra-
Rotates posteriorly , transverse axis
Translate posteriorly , sagittal axis
15 to 25° of lumbar extension
Lumbar extension puts tension on…
Tension in the anterior disc, the ALL, and anterior musculature
lumbar extension causes the facets to… and where is the laxity
Closing of facets. narrowing NF
Posterior ligaments and facet capsule lax
Inferior articular process of superior vertebra moves inferior on the superior process of the inferior vertebra
Lumbo pelvic rhythm
coordinated movements between the lumbar spine and pelvis, during flexion extension
flexion - lumbar flexion, followed by anterior pelvic tilt
Extension - posterior pelvic tilt, followed by lumbar extension
Clinical implications of Lumbopelvic rhythm
tight hamstrings
Weak hip extensors
Predisposing, anterior or posterior pelvic tilt
Limited hip or lumbar range of motion
lumbar axial rotation
rotates around vertical axis
Translation dependent on level of involved segment
range of motion
5 to 7°
Limited by sagittal plane alignment, facet joints, facet separation
Anulus tension
lumbar lateral flexion
rotates around anterior posterior axis
Translate laterally along horizontal axis
Side of convexity contralateral
Side of concavity ipsilateral
ROM is about 20° lumbar
intrinsic muscles stabilizers
deep short, muscles, precision control
high degree of muscle spindles
Semispinalis
Multifidis
rotatores
interspinalis
intertransversarius muscles
extrinsic muscles stabilizers
More superficial
Spans multiple segments
Important for course control of stabilization
Important role in torque production
Abdominals
Erector spinae
Quadratus lumborum
Psoas major
Hip muscles
what has an important role to maintain intra-abdominal pressure for stability?
Diaphragm and pelvic floor muscles
neural control system
Receive input from passive and active subsystems to determine requirement for maintaining stability
Effectiveness may be impaired with injury
retraining system in order
Localized stabilization
General stabilization
Functional stabilization
At each level, you need to demonstrate mobility sufficient for movement
Stability. Balance, and proprioception.
