Axial Skeleton: Thoracolumbar spine/SIJ – Osteology and Arthrology Flashcards
What do the vertebra and ribs do?
- Provide vertebral stability
- protects spinal cord
- protects ventral and dorsal nerve roots and exiting spinal nerve
What is a vertebral body?
Anterior, primary weight-bearing component of the vertebra
What are the posterior elements of a vertebrae?
- transverse/spinous processes, laminae, articular processes
What are the pedicles?
bridge that connects body - posterior elements; thick and strong
What do pedicles do?
Transfers muscle forces applied to posterior elements for dispersion across body/disc
What are the 3 divisions of a vertebrae?
- vertebral body
- posterior elements
- pedicles
How many body segments are there?
33
- 7 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 4 coccygeal, last 2 fused as an adult
Where are there reciprocal curves in the sagittal plane?
- Cervical spine and lumber spine lordosis and kyphosis in thoracic spine and sacrum
What do spinal curves provide?
Strength and resilience
What do the spinal curves make the spine vulnerable to?
Shear forces at transitions
What can impact the LOG?
Limb position, fat deposition, muscle strength and endurance, connective tissue extensibility, the loads supported by the body, shape of facets and vertebral bodies and discs
What do spinal ligaments do?
- limit motions
- help maintain natural curves
- protect the spinal cord/nerve roots by stabilizing the spine
What is the ligamentum flavum?
anterior lamina to posterior lamina, end ROM flexion, 80% elastin, posterior to spinal cord
What are the interspinous ligaments?
between adjacent spinous processes; blends with LF, more elastin, more superficial, more collagen and blend with SS lig, fiber direction varies - Lumbar spine
What is the supraspinous ligament?
Between tips of spinous processes; resist separation - flexion; less developed in the lumbar spine
What are intertransverse ligaments?
Thin, taut in contralateral flexion
What is the anterior longitudinal ligament (ALL)?
Long, strong strap, occiput to sacrum, fibers into and reinforce anterior disc
What is the posterior longitudinal ligament (PLL)?
posterior surfaces of vertebral bodies C2- sacrum (in canal)
- blends with and reinforces posterior discs
What are the capsular ligaments (facets)?
Entire rim of facets, connect and stabilize, reinforced by adjacent muscles (multifidus)
What should we consider when looking at ligaments in a biomechanical perspective?
- collagen/elastin ratio
- fiber direction
- it’s location relative to the axis of rotation of a joint
- usually lose in anatomic position
What happens to at least some fibers near end ROM?
Become taut ( largest joint surface motions - largest passive tension)
What are some clinical questions to ask regarding ligaments?
1.) what might have been injured
2.) chronically overstretched?
3.) is it capable of stabilizing?
4.) its impact
What is spinal instability?
Loss of intervertebral stiffness that can lead to abnormal and increased intervertebral motion
What is the neutral zone?
The amount of intervertebral movement that occurs with the least passive resistance from the surrounding tissues
What increases the neutral zone?
Injury or weakness of surrounding tissues
What can cause further injury regarding the neutral zone?
marked or chronic instability of the ligs/facets/discs/neural
What happens if the neutral zone is larger than normal?
the spinal segments become usntable
What decreases the neutral zone?
muscle force
What increases the neutral zone?
Injury and degeneration
What does injury do to the vertebral motion pattern?
Changes and influences the motion of the whole spine potentially causing pain and hypermobility
What does marked or chronic spinal instability cause?
Further injury to local ligaments, injury to facets (apophyseal joints), discs, and possibly neural structures, can result in loss of pain-free spinal ROM
What are Panjabi’s 3 subsystems of control?
- Passive system
- Active system
- neural subsystem
What is the passive system?
consists of the bony structures, ligaments joint capsules, discs, and passive portion of the musculotendinous units. Sends feedback to the neural subsystem about joint positions
What does the passive system challenge?
stability at the passive level
What is the active system composed of?
muscles and tendons
What is the neural subsystem?
Recieves and transmits information from and to the other two systems to manage spinal stability
What kind of patient can have compromised neuromuscular control?
Patients with LBP
What are the osteologic features of the thoracic vertebrae 2-9?
- downward pointing spinous process
- superior/inferior facets oritented vertically - sup facing posterior/inferior anterior; aligned close to the frontal plane
- pair of costal facets
Why are T1 and T10-12 atypical?
T1 full costal attachment and demi; T10-T12 full coastal attachment
What are the features of the lumbar region vertebra for?
- massive wide bodies for support
- TPs project laterally 1-4 thin, 5 strong and thick
- SP broad, rectangular off lamina
- mammillary processes off sup articular surfaces (posterior side)
What is facet orientation of the vertebrae in the superior lumbar region?
concave, face medial to medial-posterior
When are the lumbar region vertebrae closest to the sagittal plane?
in the upper lumbar spine
what is the orientation of the articular facets in the lumbar region?
Vertical
What is the orientation of the inferior articular processes?
Convex- lateral to anterior-lateral
What is the inferior articular process of L5 also?
The superior articular process of the sacrum
What do the L5-S1 apophyseal joints provide to the lumbosacral junction?
A-P stability
What is unique about the L5-S1 apophyseal joints?
Much closer to the frontal plane
What is the orientation of the sacrum base and apex?
Base faces superiorly, apex inferiorly
What is the anterior edge of the sacrum known as?
Sacral promontory
What are the Ala of the sacrum?
Wings
What direction do the superior articular surfaces face?
Posterior-medially
What do the facets do in the sacrum?
Transmits weight off vertebral column to pelvis
What is unique about the sacrum from childhood to adulthood?
Each of 5 segments are joined by cartilaginous membrane in childhood, fuses by adulthood
What articulates to form the SI joint?
Auricular surface of sacrum and the ilium
What is the coccyx composed of?
- 4 fused vertebrae
- sacrococcygeal joint
- fibrocartilaginous disc
- small ligaments
What comes out of the 4 ventral foramina of the sacrum?
Ventral rami of sacral plexus
Why is the dorsal surface of the sacrum rough and convex?
Attachments of musculature
What are the spinal and lateral tubercles remnants of?
The SP/TP
What do the dorsal sacral foramina transmit?
Dorsi rami sacral spinal nerve roots
What should we know about the caudal equina at birth?
at birth Spinal cord = vertebral column but vertebral column grows faster
What grows faster? Spinal cord or vertebral column?
Vertebral column
Where does the adult spinal cord end?
At L1/2
Where do the roots travel out of the cauda equina?
caudally to reach their corresponding foramina
What are the 3 functional components of the typical intervetebral joints?
- transverse/spinous processes
- apophyseal joints
- interbody joint
What are transverse/spinous processes for?
Mechanical levers that increase mechanical leverage of muscles and ligaments
What are the apophyseal joints for?
Guiding intervertebral motion
What are inter body joints for?
Absorbing and distributing load, greatest adhesion between vertebrae, houses axis of rotation, is a spacer, provides passage for nerves
What is the axis for each intervertebral junction?
near/at interbody joint
Where is the rotation reference point for the more cranial vertebra?
anterior
How many pairs of apophyseal joints are there?
24 pairs
What kind of joint are apophyseal joint?
Plane joints
What encloses the apophyseal joints?
Synovial well-innervated capsule
What do apophyseal joints do?
Acts as a mechanical barricade
What do the horizontal facet surfaces favor?
Axial rotation
What do vertical facet surfaces do?
Block axial rotation in either sagittal or frontal planes
Where are intervertebral/interbody joints found?
C2-3 through L5-S1
- disc, endplates, adjacent vertebral bodies
What makes up the disc?
- Nucleus pulposus -pulplike gel mid to posterior aspect of disc, 70-90% water in youth
- annulus fibrosis
What do the disc and NP do?
Shock absorption, dissipates and transfers loads across consecutive vertebra
What is the annulus fibrosis?
15-25 concentric rings of collagen fibers, 65 degrees from vertical
What does the annulus fibrosis do?
Prevents distraction/shear/torsion, entraps and encases the liquid based nucleus
What are vertebral endplates?
Relatively thin cartilaginous caps the cover most of the superior/inferior surface of vertebral bodies
What is the difference between the surface of the vertebral endplate facing the disc and the surface facing the bone?
- Surface facing disc is fibrocartilage and binds directly and strongly to collagen in AF
- Surface facing bone calcified cartilage, weakly affixed to bone
Why is there limited healing at the disc?
Outer rings of AF with vascular supply diffuse O2 and glucose
Why can reduced permeability be so impactful?
Reduced permeability inhibits syntheses of proteoglygcans, leading to less water, leading to less ability to absorb and transfer loads
Where is 80% of the load carried in standing?
Intervertebral joint at lumbar spine, only 20% in posterior elements
What are discs designed to handle the force of?
BW AND muscle activation
Where do compressive loads push the endplates?
Inward toward the NP
How do the collagen rings resist/balance force?
Stretched rings of collagen and elastin create tension to resist/balance force - uniformly transferred to vertebral bodies then return when load is off
What does viscoelastic mean?
Resists a fast/strongly applied load; less resistance to slow or light compression
-flexible low loads/ rigid at higher loads
What can allow water to be reabsorbed into the disc?
sustained and full lumbar extension - reduces pressure in discs
What happens with diurnal fluctuations?
- supine causes low pressure which attracts water, swells slightly when sleeping
- WB forces push water out of the disc
- height change
- related to age, as proteoglycan reduces, water retaining reduces
- less hydrostatic pressure
What is spine coupling?
- Any movement of the spine in a plane is combined with an automatic and often imperceptible movement in another plane
Is there a consensus as to which coupling pattern is normal for a specific region?
NO
Where is spine coupling consistent?
Middle and lower cervical spine: lateral flexion and ipsilateral rotation
What does the thoracic region provide?
Stable base for musculature, protective for organs, breathing
What are the joints in the thoracic region?
- costocorpeal/costovertebral joints
- costotransverse joints
How many apophyseal joints in the thoracic region?
24
What is the orientation of the facets in the thoracic region?
- in frontal plane and 15-25 degrees from vertical
What is the movement in the thoracic region limited by?
Costovertebral and costotransverse joints - links all to sternum
How many degrees of flexion are there in the thoracic region? what is it limited by?
30-40
limited by connective tissues located posterior to vertebral bodies
How many degrees of extension are there in the thoracic region? what is it limited by?
15-20
Limited by tension in ALL and lamina of adjacent vertebrae
Why is there more flx/ext in the lower thoracic spine?
Free floating ribs and facets more sagittal
How many degrees of rotation in the thoracic region?
25-35 horizontal plane
How many degrees of lateral flexion to each side in the thoracic region?
25-30 degrees (ribs prohibit more)
Bucket handle is used to represent?
Inspiration - shaft of rib elevates upward and outward
What are the ranges for the thoracic spine?
Flexion: 30-40
Extension: 15-20
Rotation: 25-35
Lateral Flexion: 25-30
What are the ranges for the thoracolumbar spine?
Flexion: 35 (T) + 50 (L) = 85
Extension: 20 (T) + 15 (L) = 35
Rotation: 25-35
Lateral Flexion: 25-30
What are the ranges for the lumbar spine?
Flexion: 45-55 (60)
Extension: 15-25
Rotation: 5-7
Lateral Flexion: 20 (25-30)
What is the lumbosacral angle?
Angle between the horizontal plane and the superior surface of the sacrum
How is the base of the sacrum inclined?
Base of sacrum inclined anteriorly and inferiorly at 40 degrees
What happens for anterior tilt of the pelvis?
Contration of hip flexors/back extensors // or hip flexion contracture
What happens for posterior tilt of the pelvis?
Contraction of the hip extensors/abs
What structures resist shear at L5/S1?
- disc
- capsule
- ALL
- wide and sturdy facets
- iliolumbar ligaments
create a resistance force of compression at L5/S1 facets
Why is flexion dominant in the lumbar spine?
Due to sagittal plan orientation of facets
What is flexion a reversal of?
Lordosis
Where do compression forces shift in the lumbar spine?
Away from facets, on anterior aspects of discs and bodies
What happens during flexion of the lumbar spine regarding the disc?
Can change, NP into posterior direction. Normal disc AF can withstand this - but weakened / cracked cannot. Variations of a HNP can occur.
What happens during extension of the lumbar spine to the load?
Increased contact and load in facets, causes tips of inferior articular facets to slide inferior beyond the joint surface
What can hyperextension cause regarding the tips of the inferior articular processes?
Hyperextension can cause the tips of the inferior articular process to contact the adjacent lamina, can cause damage and compress posterior ligaments
What happens to the size of the intervertebral foramina when the lumbar spine extends?
Size of the foramina is reduced and the nucleus presses anterior
What has full lumbar extension been shown to reduce?
Pressure within the disc and reduced contact pressure between disc materials and neural tissues
What is lumbopelvic rhythym?
The kinematic relationship between the spine and hips during sagittal plane motions
What is the early phase of return from full flexion?
Trunk extension occurs to a greater extent through extension of the hips under relatively strong activation of hip extensor muscles (glut max and hamstrings)
What happens in the middle phase of return from full flexion?
Trunk extension occurs through a shared activation of the hip and lumbar extensors
What happens at completion of return from full flexion?
muscle activity typically ceases once the line of force from body weight falls posterior to the hips
Where is the axis of rotation for trunk extension for all three phases of returning from full flexion?
through the body of L3
What would happen if there was more than 3 degrees of axial rotation at any lumbar segment?
would damage facet surface and tear AF
How much axial rotation is there of the lumbar spine?
5-7 degrees each side
How much lateral flexion is there of the lumbar spine?
20 degrees to each side
What happens to the disc during lumbar spine lateral flexion?
slight deformation in disc
