Spine Lecture

8/13/2019 Spine Lecture

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The

Trunk/Spine

largest segment of body

most significant functional

unit for general movement

integral role in upper and

lower extremity function

relatively little movement

between 2 vertebrae


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The Vertebral

Column7 cervical vertebrae

develop as an infant begins to lift its head

12 thoracic vertebrae

present at birth

Sacrum - 5 fused vertebrae

Coccyx - 4-5 fused vertebrae

Cervicothoracic junction

Thoracolumbar junction

Lumbosacral junction

5 lumbar vertebrae

develop in response to weight bearing


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Vertebral

Articulation

Inferior articular process

Superior articular process

each articulation

is a fully

encapsulatedsynovial joint

these are often

called

apophyseal joints

Note: the processes are bony outcroppings.


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Costal (Rib)

Articulation

Note: the facets are

the articular surfaces.

Inferiorcostal

facet

Transverse

costal

facet

Superior

costal

facet


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Spinous process

Transverse processBody

Vertebral foraman

Intervertebral foraman


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Muscular Attachments

muscular attachments on spinous andtransverse processes


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Vertebral shape

changes to reflect

movements possible

within a given region


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Further

depiction

of vertebralshapes


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Motion Segment: Functional unit of the vertebral column

Two bodies of vertebrae

common vertebral disc

ant & post longitudinal ligaments

Neural arches

intervertebral joints

transverse & spinous processes

ligaments


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Intervertebral Disks

shock absorbers of the spine

capable of withstanding compressive

torsional and bending loads

role is to bear and distribute loads invertebral column and restrain

excessive motion in vertebral segment


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Shock Absorbers

Bending Loads


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2 regions of vertebral diskNP-- nucleus pulposus

gel-like mass in center of disk under

pressure such that it preloads disk80-90% water, 15-20% collagen

AF-- annulus fibrosus

fibrocartilaginous material

50-60% collagen

Disc is avascular & aneural

so healing of a damaged disc is

unpredictable & not promising

Disc rarely fails under compression

vertebral body will usually fracture

before damage to disc occurs


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Ant. Longitudinal ligament

very dense & powerful

attaches to ant disc & vert body

limits hyperextension and fwd mvmtof vertebrae relative to each other

Post. Longitudinal Ligament

travels inside the spinal canalconnects to rim of vertebral bodies &

center of disc

posterolateral aspect of segment not

covered - this is a common site for

disc protrusion

offers resistance to flexion

Anterior Motion Segment


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Posterior Motion Segment

Bone tissue in the

pedicles and laminae

is very hard providinggood protection

for spinal cord

Muscle attachments at spinous &

transverse processes

articulation between vertebrae occursat superior and inferior facets

these facets are oriented at different

angles related to spinal section

accounting for functional differences


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Posterior Motion Segment

Ligamentum flavumspans laminae

connecting adjacent vertebral archesvery elastic thus aids in extension

following flexion of the trunk

under constant tension to maintain

tension on disc

Supraspinousand interspinous

ligaments span spinous processes

resist shear and forward bendingof spine


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Spinal

Movement collectively -- LARGE ROM flex/ext

L-R rotation

L-R lateral flexion


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MOVEMENTS OF THE SPINE

ACCOMPANIED BY PELVIC TILTING

1st 50-60 in

lumbar vertebraeFlexion beyond 50

due to anterior

pelvic tilting


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Regional ROM in Spine

Atlas (C1) & axis (C2)

account for 50% of

rotation in the cervical

region.

Thoracic region is

restricted, mainly due

to connection to ribs.


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p ne -Posterior Muscular

Support

primarily produce extension

and medial/lateral flexion

Superficial to deep

erector spinae semispinalis

deep posterior


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Spine -Posterior Muscular Supportprimarily produce extension and

medial/lateral flexion

Posteriorly

erector spinaeiliocostalis

longissumus

thoracis

spinalis


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spinalislongissimus

iliocostalis

Erector spinaeVersatile muscles that can generate

rapid force yet are fatigue resistant

thoracis lumborumcervicis


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Semispinalis

thoraciscerviciscapitis


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Deep posterior

interspinalesintertransversarius

IT

IS


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rectus abdominis

external obliqueinternal oblique

transverse abdominus

Abdominals

I t Abd i l P


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Intra-Abdominal Pressureacts like a balloon to expand

the spine thus reducing compressive

load, this in turn reduces the activity

in the erector spinae

Internal & external oblique

muscles & transverse abdominis

attached to the thoracolumbar

fasciacovering the posterior

region of the trunk

when these abdominals contract - added

support for the low back is created


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Additional muscles contributing to trunk flexion

Collectively known as the iliopsoas

Powerful flexor

whose action is

mediated by the

abdominals

Quadratus lumborum

forms lateral wall of abdomen

also maintains pelvic position

during swing phase of gait

Mo ement into f ll fle ed position


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Movement into fully flexed position

1) initiated by abdominals (1/3 of flexor moment) and iliopsoas

2) once it has begun gravity becomes a contributing factor

such that the erector spinae act eccentrically to control

the movement (thru ~50-60)

3) beyond 50-60 flexion continues by anterior tilt of pelvis

this mvmt is controlled by an eccentric action of hamstrings and gluteus

maximus while erector spinae contribution diminishes to zero

4) in this fully flexed position the posterior spinal ligaments and the passive

resistance in the erector spinae resist further flexion5) this places the ligaments at or near the failure strength placing a greater

importance on the load sustained by the thoracolumbar fascia loads

supported thru the lumbar articulations

6) return to standing posture initiated by posterior hip muscles

7) erector spinae (1/2 of extensor moment) muscle active initially but peakactivity during the final 45-50 of movement


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Strength of Trunk Movements

Extension

Flexion (70% of extension)

Lateral Flexion (69% of extension)

Rotation (43% of extension)


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Postural

Alignment 2 naturally occurring curves

LORDOTIC (in lumbar

region) KYPHOTIC (in upper

thoracic lower cervical

regions)

Abnormalities -- accentuated

vertebral curves


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Lumbar

Lordosis exaggeration of the lumbar

curve

associated w/weakenedabdominals (relative toextensors)

characterized by low back

pain prevalent in gymnasts,figure skaters, swimmers(flyers)


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Thoracic

Kyphosis exaggerated thoracic curve

occurs more frequently than

lordosis mechanism -- vertebra

becomes wedge shaped

causes a person to hunch

over


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Kyphosis

aka Swimmers Back

develops in children

swimmers who train withan excessive amount of

butterfly

also seen in elderly women

suffering from osteoporosis


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Scoliosis

lateral deviation of the

spinal column

can be a C or S shape involves the thoracic and/or

lumbar regions

associated w/disease, leg

length abnormalities,

muscular imbalances


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Scoliosis

more prevalent in females

cases range from mild to

severe small deviations may

result from repeated

unilateral loading (e.g.

carrying books on oneshoulder)

Consequences of


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Consequences of

Pelvic Tilt in normal standing the line of gravity

passes ventral (anterior) to the center

of the 4th lumbar vertebral body TWTm

This creates a forward bending

torquewhich must be counter-

balanced by ligaments and

muscles in the back

any movement or displacement

of this line of gravity affects the

magnitude of the bending

moment (or torque)

slouched posture support comes

from ligamentsthis is bad for

extended periods of time


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Pelvic Tilt and

Lumbar

Loading

relaxed standing:

the angle of

inclination of the

sacrum (sacral

angle) is 30 to the

transverse plane


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Pelvic Tilt and

LumbarLoading posterior pelvic tilt

reduces the sacral angle

or flattens the lumbarspine (reduces lordosis)

causes the thoracic

spine to extend which

adjusts line of gravitysuch that muscle

expenditure is minimized

BUT load is now passed

on to ligaments


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Pelvic Tilt and

Lumbar

Loading anterior pelvic tilt

increases sacral angle

accentuate lumbarlordosis and thoracic

kyphosis

this adjusts line of gravity

to increase muscleenergy expenditure


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Pelvic Tilt and

Sitting

Sitting (relative to standing) pelvis posteriorly tilted

lumbar curvature isflattened

line of gravity (alreadyventral to lumbar spine)shifts further ventrally

increases the momentcreated by body weight

about the lumbar spine increased muscular

support increases theload on the spine

vs.


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erect sitting

pelvis tilts anteriorly

increases lumbarcurvature

reduces the momentarm of body weight

reduces need formuscular support

reduces load on lumbarspine

however, pelvis stillmuch more tilted thanduring normal erectstanding

vs.

Pelvic Tilt and

Sitting


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L3 Load

lowest when lying

supine

normal when

standing upright

140% when

sitting with no

back support

150% when

hunched over

180% when sitting

hunched over with no

back support


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apparent that lumbar load is strongly related to support needed

to maintain lumbar lordosis

in erect, supported sitting the addition of a back rest reduces

lumbar load reclining seated position reduces disc pressure even further


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Spinal Injuries


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Progression

of DiscDegeneration


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Degenerative Disksdisk integrity

decreases with

age

lose ability to retainwater in disk so

disks dry out

ability to distribute

load across disk

changes


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Herniated Disks

NP protrudes out

from between the

vertebrae nerves are

impinged by the

bulging NP lead to numbness

and/or pain


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Disk Herniation

Tearing of Annulus


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Whiplash

Rapid flexion/extension injuries in cervical region

strain posterior ligaments

dislocate posterior apophyseal joints

7th cervical vertebra is likely site for fracture in this injury


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Low Back Pain

1) Muscle strain from

lifting may create musclespasms

2) distorted posture for long

periods of time

3) avoid crossing legs at the

knee4) tight hamstrings or

inflexible iliotibial band

5) weak abdominals

Verteb

ralinstability


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Lift With Your Legs

What does this mean? the idea is to keep the weight (W) as close

to the axis of rotation as possible

Waxis

muscular

torque

W

smaller

muscular

torque

axis

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Spine Lecture