Structure and Function of Spine

thoracic, sacral

What are the 2 primary curves of the spine?

HINT: kyphotic (posterior convexity)

cervical, lumbar

What are the 2 secondary curves of the spine?

HINT: lordotic (posterior concavity)

mobility

A flattened spine leads to decreased what?

HINT: protective mechanism

flexibility

An increased curvature of spine leads to increased what?

pars interarticularis

the area between the superior and inferior articulations of the vertebrae

*common site of fractures due to spondylolysis

bifid

Cervical vertebrae have a __________ spinous process.

transverse foramen

only found in the cervical vertebrae and allow passage of the vertebral artery

cartilaginous joints (interbody joints)

between the vertebral bodies and discs

diarthrodial joints (facet joints)

plane synovial joints with joint capsule present

*formed by superior articulating surface of the lower segment and the inferior articulating surface of the upper segment

intervertebral disc

mass of fibrocartilage between adjacent vertebrae that acts as a shock absorber and spacer beginning at C2

*makes up 20-30% of the height of the column

**thickness varies and increases as you go down the spine

nucleus pulposus, annulus fibrosus

What are the 2 parts of the intervertebral disc?

disc thickness, body height

The ratio between what 2 things determines the available motion at a particular spine segment?

cervical

Which spine segment has the most motion?

thoracic

Which spine segment has the least motion?

hyaline cartilage

What is located between each vertebral body and intervertebral disc?

nucleus pulposus

inner gelatinous mass that gives the disc its elasticity and compressibility

*70-90% water

**compression throughout the day forces the water out (shorter at night than in morning)

compressive

Hydration of the vertebral disc will decrease with ___________________ loading.

mechanical function

The loss of hydration of the IV disc during compressive loading decreases its __________________ ________________.

HINT: less mobility

annulus fibrosus

outer ring of fibrocartilage that surrounds nucleus pulposus

*mostly avascular and aneural (except very outermost layers)

anteriorly

The annulus fibrosus is thickest in which direction?

Sharpey's fibers

connect periosteum to compact bone

*outermost 1/3 annulus fibrosus connects to vertebral body via these

endplates

deformate cartilage plate at the top and bottom of vertebrae

*thin in adults, thick at birth and function as growth plates for the vertebrae in children

collagen fibers

Annulus fibrosus consists of 15-25 concentric rings of ________________ ___________.

tensile

The annulus fibrosus is designed to resist _____________ forces.

compressive, tensile

____________________ stresses on the disc (hydrostatic pressure) translate into ______________ stresses in the annulus fibrosis.

stability

The translation of compressive to tensile stress makes the disc stiffer which adds ________________ and supports the spine.

endplate

Because the disc is avascular, nutrition diffusion occurs through what?

HINT: via compressive forces

facet orientation

1. determines amount of motion (gliding and rotation)

2. protects the disc from shear forces

occipito-atlantal joint

convex occiput with concave C1

atlantoaxial joint

pivot joint (C1-C2)

*facet orientation parallel to the transverse plane

**primary motion is rotation

C2-C7 facet orientation

45 degree angle to the transverse plane

*parallel to frontal plane

inferior facet of upper--> faces inferior, anterior, slightly lateral

superior facet of lower--> faces superior, posterior, and slightly medial

inferior, anterior, lateral

In CERVICAL SPINE, the inferior facet of upper segment faces _____________, ____________, slightly ___________.

superior, posterior, medial

In CERVICAL SPINE, the superior facet of lower segment faces ______________, ______________, and slightly ___________.

thoracic spine facet orientation

60 degrees to transverse plane, 20 degrees to frontal plane

*primarily lateral flexion

lumbar spine facet orientation

90 degrees to transverse plane, 45 degrees to frontal plane

inferior facet--> faces lateral, slightly anterior

superior facet--> faces medial, slightly posterior

medial, posterior

In LUMBAR SPINE, the superior facet of lower segment faces _____________ and slightly ______________.

lateral, anterior

In LUMBAR SPINE, the inferior facet of upper segment faces _____________ and slightly ______________.

upper

Spinal rotation is named based upon the movement of the _____________ segment.

right

Which transverse process moves posterior with right rotation?

left

What way does the spinous process move with right rotation?

intervertebral foramen

opening located between adjacent vertebrae for exit of a spinal nerve

posteriorly

During FLEXION, the nuclear material is pushed _________________.

anteriorly

During EXTENSION, the nuclear material is pushed _________________.

tensile, compressive

During FLEXION, _____________ forces are created posteriorly, while __________________ forces are created anteriorly.

compressive, tensile

During EXTENSION, ___________________ forces are created posteriorly, while ____________ forces are created anteriorly.

open, tensile

During FLEXION, the IV foramen and facets ____________ which puts ______________ forces on the capsule.

close, compressive

During EXTENSION, the IV foramen and facets ____________ which puts ______________ forces on the capsule.

anterior longitudinal ligament

broad, connects anterior surfaces of adjacent vertebral bodies

*taut in extension, on slack w/ flexion

posterior longitudinal ligament

connects all the posterior surfaces of the vertebral bodies

*wider at disc, narrow at body

**only attaches at discs

***taut in flexion, slack extension

ligamentum flavum

connects the laminae of adjacent vertebrae

*thickest in lumbar spine

**always keeps tension and brings the lamina together (increase stability of disc)

supraspinous ligament

connects tips of spinous processes

*1st ligament to fail in hyperflexion

**taut in flexion

interspinous ligament

connects the spinous processes of adjacent vertebrae

*taut in flexion, slack extension

intertransverse ligament

connects adjacent transverse processes

iliolumbar ligament

connects the transverse process of L5 with ilium

*originally a muscle

apical ligament

connects the apex of the dens to the anterior margin of the foramen magnum

alar ligament

extends from sides of the dens to lateral margins of foramen magnum

transverse ligament

attaches to the lateral masses of C1 to hold the dens in place

thoracic, lumbar

The facet joint capsule is strongest in which 2 regions?

after

Will the facet joint capsule fail before or after ligaments?

flexion

The facet joint capsule is vulnerable to excessive _______________.

neutral zone

area where no elastic deformation occurs

*nothing is stretched

instability

A large neutral zone means greater ___________________.

HINT: no tension is generated

axial compression, bending, torsion, shear

What are the 4 types of segmental loading?

axial compression

TYPE OF SEGMENTAL LOADING

CAUSED BY:

1. gravity

2. ground reaction forces

3. muscle contraction

4. ligaments reaction to tensile forces

*intradiscal loads can range depending on position

**compression at the disc causes tension at the annulus, changing the angle of the fibers and increasing the stability

intradiscal pressure

pressure present between vertebral discs

flexion of upper body while standing

What position results in the highest intradiscal pressures?

lying down (prone, supine)

What position(s) relieve intradiscal pressure?

bending

TYPE OF SEGMENTAL LOADING

combination of compression, shear and tensile forces on the segment from translation

bending into flexion

resisted by posterior annulus, posterior longitudinal ligament, facet capsule (tensile) and anterior compressive forces on anterior structures

*causes disc displacement posteriorly

bending into extension

resisted by anterior portion of annulus, anterior longitudinal ligament (tensile), compressive load on facet and posterior compressive forces on posterior segment

*causing disc displacement anteriorly

torsion

TYPE OF SEGMENTAL LOADING

caused by axial rotation and coupled motions

*annulus fibrosus resists (1/2 CW, other 1/2 CCW) depending upon facet orientation

**resists in TENSILE manner

***flexion + rotation = injury (decrease force required for tissue failure)

shear

TYPE OF SEGMENTAL LOADING

facet joint resists ____________ especially in the lumbar area (lordosis)

*annulus will experience some of these forces depending upon direction and the fiber orientation or angle

spinal flexion

superior vertebra will anterior tilt and forward glide

*intervertebral foramina widens

**compressive forces on anterior aspect of disc, tensile forces posterior

***central canal widened

flexion exercises

What type of exercises should a patient with a nerve root injury be performing?

HINT: widens intervertebral foramen

spinal stenosis

narrowing of the spinal canal with compression of nerve roots

spinal extension

superior vertebrae will tilt and glide posteriorly

*intervertebral foramina narrows

**central canal narrows

***nucleus pulposus moves anteriorly (rationale for McKenzie Extension exercises)

McKenzie Extension exercises

help centralize a posterior bulging disc

*relieves disc pain by shifting nucleus pulposus anteriorly

spinal lateral flexion

superior vertebra will translate (tilt and rotate over inferior)

*concavity towards, convexity opposite

*tensile forces on convexity, compressive forces on concavity

coupling motion

relationship of lateral flexion and rotation

*varies depending upon the facet orientation

ex. C2-C7 = rotation and lateral flexion to SAME SIDE

opposite

In a neutral lumbar spine, rotation and sidebend are coupled in ________________ directions.

spinal rotation

rotary movement of spine in horizontal plane

*accessory motions are lateral flexion due to same coupling in cervical and upper thoracic spine

**exception with lower T & L in neutral coupling then opposite

***motion segment is flexed or extended spine the couple will be the same

7, 8

There are ___ cervical vertebrae and ___ cervical nerve roots.

dermatome

area of skin supplied by a single nerve root

*can be affected by compression at the spine

full extension

What is the closed pack position for the cervical spine?

HINT: increases stability to protect vertebral artery and spinal cord

flexion

What is the open pack position for the cervical spine?

HINT: large neutral zone (increases mobility b/c no tension)

O-A joint mobility

flexion/extension or nodding and minimal lateral flexion/rotation

(convex occiput on concave C1)

flexion--> roll anterior, glide posterior

extension--> roll posterior, glide anterior

*rotation and lateral flexion segmentally occurs to the OPPOSITE side

A-A joint mobility

primary motion is rotation

*transverse ligament helps control C1 on C2 anterior displacement

**allows nodding

can account for 50% of rotation in the neck and most of the initial ROM

(fully flex chin to chest, then rotate to assess this joint)

C3-C7 mobility

flexion--> glide anterior/superior

extension--> glide posterior/inferior

*side bending and rotation occurs to the SAME side

**facet orientation allows for motion in all planes and more rotation and lateral flexion than other regions

FRSL

R facet "stuck open"

LIMITED:

1. extension

2. R side bending

3. R rotation

FRSR

L facet "stuck open"

LIMITED:

1. extension

2. L side bending

3. L rotation

ERSL

L facet "stuck closed"

LIMITED:

1. flexion

2. R side bending

3. R rotation

ERSR

R facet "stuck closed"

LIMITED:

1. flexion

2. L side bending

3. L rotation

thoracic spine

STABILITY:

1. decreased movement due to length of spinous processes

2. ribcage provides stability

3. increasing load bearing

MOBILITY:

three degrees of freedom of motion

*lateral flexion the greatest

flexible

The thoracic spine is less ______________ due to rib articulation, smaller disc to body ratio, and longer SPs.

*flavum and ALL are thicker and facet capsule less flexible

Geelhoed's rule

the TPs of each thoracic vertebrae are generally at the level of the SP of the vertebra 1 level above throughout thoracic spine

costotransverse, costovertebral

What are the 2 articulations of the ribs?

costotransverse joint

tubercle of rib articulates with transverse process

costovertebral joint

head of rib articulates with demifacet on vertebral body

extension, contralateral lateral flexion

What 2 motions cause the ribs to separate?

flexion, ipsilateral lateral flexion

What 2 motions compress the ribs?

HINT: may affect ventilation