Review of Spinal Biomechanics Flashcards
Which way do the superior and inferior facet joints of the lumbar spine face? And which joints do they articulate with?
Superior Facet Joints = medial facing and Inferior Facet Joints = lateral facing
The Superior Facet Joints articulate with the Inferior Facet Joints
Describe the facet joint orientation of L1-L4 and what movements they permit and limit.
L1-L4 are orientated in the sagittal plane
They permit flexion and extension, and limit axial rotation
Describe the facet joint orientation of L5-S1 and what movements it prevents and allows.
L5-S1 are orientated more in the frontal plane
They prevent anterior shear of L5 on S1, also affecting how much flexion/extension is available
What are the kinematics during lumbar spinal flexion?
Anterior roll and glide of superior vertebra
During lumbar flexion of the spine, what has tension and compression placed on it?
Tension = interspinous ligaments, supraspinous ligaments, facet capsules, posterior disc
Compression = anterior disc
During lumbar spine extension, what are the kinematics?
A posterior roll and glide of superior vertebra
During lumbar spinal extension, what has tension and compression on it?
Tension = anterior longitudinal ligament and anterior disc
Compression = facet joints
What kinematics occur during lumbar lateral flexion?
A lateral roll and glide of superior vertebral body
During lumbar spinal lateral flexion, what is placed on tension and compression?
Tension = contralateral intertransverse ligament and facet capsule
Compression = ipsilateral facet
What motion occurs during lumbar spinal rotation?
Very little motion, but (1) facet joint gapping at ipsilateral facet (2) facet joint compression at contralateral facet
What are Fryette’s Laws of Physiologic Spinal Motions for the lumbar spine coupled motions?
- When the lumbar spine is in a neutral position, sidebending of a vertebral segment will be opposite to the direction of rotation
- When the lumbar spine is flexed or extended (non-neutral), sidebending of a vertebral segment will be in the same direction of rotation
- If motion is introduced at a segment in any plane of motion, motion in the other planes will be reduced
Describe how the thoracic superior and inferior facets are orientated and in what plane.
The superior facet joint is in the posterior direction and the inferior facet joint is in the anterior direction. They are in the frontal plane.
How are the upper thoracic spinal facet joints orientated and what motions does it limit and promote?
They are orientated in the frontal plane.
They limit flexion and extension and promote axial rotation and lateral flexion.
How are the lower thoracic spinal facet joints orientated and what motions does it limit and promote?
They are more sagittally orientated.
They permit somewhat more flexion and extension.
What are the kinematics in the thoracic spine during flexion?
Anterior roll and glide of the superior vertebra
What is placed on tension and compression in the thoracic spine during flexion?
Tension = interspinous ligaments, supraspinous ligaments, facet capsule, posterior disc
Compression = anterior disc
What are the kinematics in the thoracic spine during extension?
Posterior roll and glide of superior vertebra
What is placed on tension and compression in the thoracic spine during extension?
Tension = anterior longitudinal ligament and anterior disc
Compression = facet joints
What are the kinematics in the thoracic spine during lateral flexion?
lateral roll and glide of superior vertebral body
What is placed on tension and compression in the thoracic spine during lateral flexion?
Tension = contralateral intertransverse ligament and facet capsule
Compression = ipsilateral facet
What are the kinematics in the thoracic spine during rotation?
Inferior articular facet of superior vertebra slides on superior articular facet of inferior vertebra
How is axial rotation affected in the thoracic spine?
Freedom of this motion decreases in a cranial-to-caudal direction
What are the thoracic spine coupled motions?
Coupled motion patterns are variable in the thoracic spine
- Lower thoracic spine motion takes on qualities of the lumbar spine
- Upper thoracic spine motion takes on qualities of the cervical spine
How are the facet joints orientated in the cervical spine and what does this provide for motion?
They are orientated approximately 45 degrees between frontal and transverse planes. Which provides freedom of motion in all three planes.
What are the kinematics of the cervical spine during flexion for the AO, AA, and C2-C7 joints?
AO = anterior roll and posterior glide of O on A
AA = anterior tilt of atlas on axis
C2-C7 = anterior roll and glide of superior on inferior body and antero-superior glide at facet joints
What are the kinematics of the cervical spine during extension for the AO, AA, and C2-C7 joints?
AO = posterior roll and anterior glide of O on A
AA = posterior tilt of atlas on axis
C2-C7 = posterior roll and glide of superior on inferior body and posterior inferior glide at facet joints
What does flexion do to the diameter of the intervertebral foramen?
It decreases the diameter (which could lead to spinal stenosis)
What is the coupled motion in the cervical spine during rotation? During rotation, what occurs at the AA and C2-C7 joints?
Rotation occurs with side-bending to the same side.
AA = atlas spins about dens of axis
C2-C7 = infero-medial glide at ipsilateral facets and supero-lateral glide at contralateral facets
What is the coupled motion in the cervical spine during lateral flexion? What occurs at the AO and C2-C7 joints?
Lateral flexion occurs with rotation to the same direction.
AO = ipsilateral roll and contralateral glide of O on A
C2-C7 = infero-medial glide at ipsilateral facets and supero-lateral glide at contralateral facets
What are the coupled motions in C2-C3 through C6-C7 and OA and AA?
C2/C3-C6/C7 = axial rotation coupled with side bending in the same direction
OA and AA = axial rotation coupled with side bending in opposite direction
What happens with lumbar flexion as it compresses the anterior annulus?
The nucleus is forced posteriorly…prolonged or repeated flexion can weaken the posterior annulus resulting in herniation
What are the 4 levels of severity of disc lesions? Describe them.
(1) Protrusion = may be without symptoms as nociceptors may not be present on the inner side of the disc
(2) Prolapse = will have radiculopathy symptoms
(3) Extrusion
(4) Sequestration = the nucleus pulposus has left the margins
What is increasing severity of disc lesions correlated with?
Reduced torsional stiffness
What two severities of disc lesions could respond to mechanical interventions?
Protrusion and Prolapse
What are the two consequences of a disc lesion?
(1) axis of rotation shifts from vertebral body to facet joint
(2) loss of disc stiffness can increase compression forces at facet joint surfaces
What can be the 3 different descriptions of spinal instability?
(1) mechanical structure becomes unstable when a “critical point” is reached
(2) abnormal joint motion patterns (typically too much motion)
(3) abnormal motor coordination patterns (typically not recruiting the muscles required for stability)
What occurs as a result of mechanical instability in the spine?
- decrease in Young’s modulus (stiffness)
- decrease in load to yield point
- decrease in ultimate strength
- decrease in load to rupture
- disruption to passive restraints
What can cause mechanical disruption to passive restraints to motion?
ligament disruption, loss of disc height, disc herniation, vertebral endplate fractures, laminectomy, reduced pars interarticularis integrity
Describe normal motor coordination vs. abnormal motor coordination in the spine.
Normal motor coordination = the transverse abdominus is contracted before the anterior deltoid
Abnormal motor coordination = the anterior deltoid is contracted before the transversus abdominus
Describe and name the short segmental muscles.
They are the deepest level of deep layer of back muscles, and include the interspinales and intertransversarii.
They have a small cross-sectional area, are rich in muscle spindles, and most likely act as position transducers
Describe and name the transversospinales.
They are intermediate level of deep layer of back muscles, and include semispinalis thoracis, multifidi, and rotatores.
They are extensors, position transducers, and vertical stabilizers
What are the actions of the quadratus lumborum?
unilateral contraction = lateral flexion of spine and unilateral pelvis elevation
bilateral contraction = lateral stabilizer of lumbar spine
Describe and name the erector spinae muscles.
They are the most superficial of the deep layer of back muscles, and include iliocostalis lumborum, longissimus thoracis, and spinalis thoracis.
They do spinal extension.
Describe the location and action of the latissimus dorsi muscle.
It is in the superficial layer and contributes to spinal extension (in addition to UE action).
What are the actions of the psoas major?
hip flexion, lateral flexion of lumbar spine, flexion of lumbar spine, and vertical stabilizer
What are the 2 roles of the transversus abdominis?
(1) compress the abdominal cavity
(2) increases tension in the thoracolumbar fascia
What are the actions of the internal oblique?
Unilateral = lateral flexion and ipsilateral rotation
Bilateral = trunk flexion, posterior pelvic tilt, and increases tension in thoracolumbar fascia
What are the actions of the external oblique?
Unilateral = lateral flexion and contralateral rotation
Bilateral = trunk flexion and posterior pelvic tilt
What is the action of the rectus abdominis?
Trunk flexion
What are the 2 things that the muscle contributes to spinal stability?
(1) increases intra-abdominal pressure which increases spine stiffness and reduces motion during sudden loads
(2) increases in all the “guy wire” muscle activity produces increases in intra-abdominal pressure
Can a single muscle be identified as most important for lumbar spine stability?
No! Spine stability is dependent on relative activation of all trunk muscles and other loading variables.
What are the “Big Three” stabilization exercises for the sipne?
(1) curl ups for rectus abdominis (anterior side)
(2) side bridge for obliques, transverus abdominis, quadratus lumborum (lateral side)
(3) progressions of “bird dog” for back extensors (posterior side)
Why is it recommended to begin stabilization exercises with ROM exercises such as Cat/Camel?
They are thought to reduce spine viscosity or viscous stress.
