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Spine > Spine Anatomy > Flashcards

Spine Anatomy Flashcards

1
Q

% Of spinal column height due to intervertebral disc?

A

25% of spinal column height

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2
Q

What is the composition of intervertebral disc?

A

Annulus fibrosus and nucleus pulposus

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3
Q

Composition of annulus fibrosus?

A
  • type I collagen that is obliquely oriented + water + PG
  • high collagen / low proteoglycan ratio (low % dry weight of proteoglycans)
  • characterized by high tensile strength and its ability to prevent intervertebral distraction
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4
Q

Composition of nucleus pulposus?

A
  • type II collagen, water, and proteoglycans
  • low collagen / high proteoglycan ratio (high % dry weight of proteoglycans)
  • characterized by compressibility
  • 88% of water
  • Has no fibroblast like cells
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5
Q

What is the name of the PG responsible for maintaining water content of the disc?

A

Aggrecan

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6
Q

Where does the blood supply comes from?

A

◦ disk is avascular with capillaries terminating at the end plates

nutrition reaches nucleus pulposus through diffusion through pores in the endplates

annulus is not porous enough to allow diffusion

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7
Q

Innervation of the intervertebral disc?

A

sinuvertebral nerve which innervates the superficial fibers of annulus

neuropeptides thought to participate in sensory transmission include

substance P

calcitonin

VIP

CPON

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8
Q

How does the inter-vertebral pressure variates?

A
  • pressure is lowest when lying supine
  • pressure is intermediate when standing
  • pressure is highest when sitting and flexed forward with weights in the hands
  • when carrying weight, the closer the object is to the body the lower the pressure
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9
Q

What are the herniated disc associated with?

A
  • spontaneous increase in the production of
    • osteoprotegrin (OPG)
    • interleukin-1 beta
    • receptor activator of nuclear factor-kB ligand (RANKL)
    • parathyroid hormone (PTH)
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10
Q

Disc changes with age?

A

overall loss of water content and conversion to fibrocartilage. Specifically there is a decrease in

  • nutritional transport
  • water content
  • absolute number of viable cells
  • proteoglycans
  • pH

increase in

  • an increase keratin sulfate to chondroitin sulfate ratio
  • lactate
  • degradative enzyme activity
  • density of fibroblast-like cells
  • fibroblast-like cells reside in the annulus fibrosus only

no change in

  • absolute quantity of collagen
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11
Q

3 parts of the nervous system

A

CNS, PNS, ANS

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12
Q

What is the CNS composed of?

A

Brain and Spinal cord

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13
Q

What is the PNS composed of ?

A

Cranial nerves and peripheral nerves

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14
Q

What is the autonomic system composed of?

A

Sympathetic system

Parasympathetic system

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15
Q

What is the sympathetic system composed of?

A
  • 22 ganglia C3T11L4S4 (3 cervical, 11 thoracic, 4 lumbar, 4 sacral)
  • cervical ganglia
  • the three cervical include the stellate, middle, and superior
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16
Q

Which cervical ganglia is most at risk of injury? Consequence?

A
  • the middle ganglion is most at risk at the level of C6 where it lies close to the medial border of the longus colli muscles
  • injury to the middle ganglion/sympathetic chain will lead to Horner’s syndrome
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17
Q

What is the parasympathetic system composed of?

A

hypogastric plexus

S2, S3, S4 parasympathetic fibers and lumbar sympathetic fibers (splanchnic nerves)

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18
Q

Spinal cord extension?

A

Spinal cord extends from brainstem to inferior border of L1

conus medullaris: is termination of spinal cord

filum terminale: is residual fragment of spinal cord that extends from conus medullaris to sacrum.

thecal sac: the dural surrounded sac that extends from the spinal cord and contains CSF, nerve roots and the cauda equina

cauda equina: nerve roots and filum terminale surrounded by dura that extend from the spinal cord

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19
Q

Embryology of the spinal cord

A

Neural Tube—> spinal cord

  • failure of closure: anencephaly cranially
  • spinal bifida occulta, meningocele, myelomeningocele distally

Neural crest

forms dorsal to neural tube

becomes the peripheral nervous system

pia mater

spinal ganglia

sympathetic trunk

Notocord

forms ventral to neural tube

becomes

vertebral bodies

intervertebral discs

nucleus pulposus from cells of notocord

annulus from sclerotomal cells associated with resegmentation

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20
Q

Spinal cord functional Tracts

A

• Ascending Tracts (Sensory) dorsal columns (posterior funiculi)

deep touch, proprioception, vibratory

lateral spinothalamic tract

pain and temperature

site of chordotomy to alleviate intractable pain

ventral spinothalamic tract

light touch

Descending Tracts (Motor)lateral corticospinal tract

main voluntary motor

upper extremity motor pathways are more medial(central) which explains why a central cord injury affects the upper extremities more than the lower extremities

ventral corticospinal tract

voluntary motor

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21
Q

Spinal cord blood supply

A

◦ anterior spinal artery

primary blood supply of anterior 2/3 of spinal cord, including both the lateral corticospinal tract and ventral corticospinal tract

posterior spinal artery (right and left)

primary blood supply to the dorsal sensory columns

Artery of Adamkiewicz

largest anterior segmental artery

typically arises from left posterior intercostal artery, which branches from the aorta, and supplies the lower two thirds of the spinal cord via the anterior spinal artery

significant variation exists

in 75% it originates on the left side between the T8 and L1 vertebral segments

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22
Q

CSF Fluid

A

produced by the choroid plexus in the third, fourth, and lateral ventricles of the brain.

CSF is an ultra-filtrate of blood plasma through the permeable capillaries of the choroid plexus

volume

total CSF volume between brain, spinal cord, and thecal sac is ~150 mL

CSF formation occurs at rate of ~500mL per day

thus the total amount of CSF is turned over 3-4 times per day

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23
Q

Nerve Root Anatomy

A

• Cervical spinenerve roots exit above corresponding pedicle

C5 nerve root exits above the C5 pedicle

nerve root travel horizontally to exit

there is an extra C8 nerve root

Thoracic spine

nerve root travel below corresponding pedicle

Lumbar spine

nerve roots descend vertically before exiting

nerve root travel below corresponding pedicle

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24
Q

key difference between cervical and lumbar spine is

A

▪ pedicle/nerve root mismatch

cervical spine C6 nerve root travels under C5 pedicle (mismatch)

lumbar spine L5 nerve root travels under L5 pedicle (match)

extra C8 nerve root (no C8 pedicle) allows transition

horizontal (cervical) vs. vertical (lumbar) anatomy of nerve root

  • because of vertical anatomy of lumbar nerve root a paracentral and foraminal disc will affect different nerve roots
  • because of horizontal anatomy of cervical nerve root a central and foraminal disc will affect the same nerve root
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25
Q

Trans-psoas approach: How do lumbar plexus move in the spine?

A

lumbar plexus moves dorsal to ventral moving down the lumbar spine *

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26
Q

Trans-psoas approach

A

L4-L5 is lowest accessible disc space, highest risk of iatrogenic nerve injury

27
Q

nerves that may be injured during retroperitoneal approach

A

Ilio-inguinal and ilio-hypogastric: resulting in groin paresthesias and abdominal paresis

28
Q

Anterior approach to the spine:

  • Level of aorta bifurcation
  • superior hypogastric plexus: consequence of injury?
A
  • Aorta: At level of L4/L5
  • on L5 body: retrograde ejaculation
29
Q

What is the pelvic incidence?

A

pelvic incidence = pelvic tilt + sacral slope

a line is drawn from the center of the S1 endplate to the center of the femoral head

30
Q

vertebral artery travels through which transverse foramen

A

C1 to C6

31
Q

Particularity of C2 to C6

A

have bifid spinous process

32
Q

Spinal Canal Normal dialmeter

A

normal diameter is 17mm

<13mm indicates possible cord compression

33
Q

What is C2 sub-dental synchondrosis?

A

Sub-dental (basilar) synchondrosis is an initial cartilagenous junction between the dens and vertebral body that does not fuse until ~6 years of age

the secondary ossification center appears at ~ age 3 and fuses to the dens at ~ age 12

34
Q

Orientation of articular facets of subaxial cervical spine?

A

subaxial cervical spine (C3-C7) are oriented in a postero-medial direction at C3 and posterolateral direction at C7, with a variable transition between these levels

35
Q
A
  1. genitofemoral
  2. ilioinguinal and iliohypogastric nerves
  3. Femoral Nerve
  4. LFCN
  5. Obturator Nerve
36
Q

Which parameter does not vary with the position of the pelvis?

A

Pelvic Incidence

37
Q

What area of the spinal anatomy has the highest ratio of cortical to cancellous bone?

A

Pedicles of the thoracic spine

38
Q

Level of the smallest pedicle diameter?

A

L1

39
Q

L1 ad S4 Sensory, motor table

A
40
Q

Nerve Responsible for hip Abduction?

A

L5

41
Q

Muscle Grading System (ASIA)

A
42
Q

straight leg raise

A

compression of lower lumbar nerve roots (L4-S1)

important to distinguish from hamstring tightness

considered positive if symptoms produced with leg raised to 40°

43
Q

crossed straight leg raise

A

performing straight leg raise in uninvolved leg produces symptoms in involved leg

44
Q

Babinski’s test

A

positive findings suggests upper motor neuron lesion

45
Q

ankle clonus test

A

Clonus at the ankle is tested by rapidly flexing the foot into dorsiflexion (upward), inducing a stretch to the gastrocnemius muscle. Subsequent beating of the foot will result, however only a sustained clonus (5 beats or more) is considered abnormal.

46
Q

bulbocavernous reflex

A

tests for the presence of spinal shock

positive reflex with anal sphincter contraction with squeezing of glans penis or clitorus

can alternatively tug on foley catheter to stimulate reflex

47
Q

Best method to detect injury to the spinal cord during operative procedures.

A

MEP (motor evoked potentials)

100% sensitive, 100% specific

48
Q

Sensitivity and specifity of somatosensory evoked potentials

A

25% sensitive, 100% specific

49
Q

Function of SEP

A

monitor integrity of dorsal column sensory pathways of the spinal cord

50
Q

Intraoperative considerations of SEP?

A

loss of signals during distraction mandates immediate removal of device and repeated assessment of monitoring signals

51
Q

Motor Evoked Potential (MEP) Function

A

monitor integrity of lateral and ventral corticospinal tract of the spinal cord

52
Q

What are the Disadvantages of MEP?

A

often unreliable due to effects of anesthesia

53
Q

Technique of MEP

A

signal initiation

transcranial stimulation of motor cortex

signal recording

muscle contraction in extremity (gastroc, soleus, EHL of lower extremity)

54
Q

3 methods for intraperative neuro monitoring

A

SEP, MEP, electromyography

three methods are used to monitor neurological function intraoperatively. Transcranial motor evoked potentials provide monitoring of the anterior corticospinal tracts by electrode stimulation of the pyramidal cells of the motor cortex and descend to the targeted muscle. Somatosensory evoked potentials provide monitoring to the dorsal ascending tracts and works by stimulating peripheral nerves and recording activity in the somatosensory cortex of the brain. Electromyography is useful for detecting nerve root injuries or cortical breaches during pedicle screw placement.

55
Q

technique of SEP

A

signal initiation

lower extremity usually involves stimulation of posterior tibial nerve behind ankle

upper extremity usually involve stimulation of ulnar nerve

signal recording

transcranial recording of somatosensory cortex

56
Q

2 types of EMG per-op

A
  1. Mechnical Electromyography (spontaneous)

monitor integrity of specific spinal nerve roots

Techniqueconcept

microtrauma to nerve root during surgery causes deplorization and a resulting action potential in the muscle that can be recorded

contact of a surgical instrument with nerve root will lead to “burst activity” and has no clinical significance

significant injury or traction to a nerve root will lead to “sustained train” activity, which may be clinically significance

signal initiation

mechanical stimulation (surgical manipulation) of nerve root

signal recording

muscle contraction in extremity

Advantages

allows monitoring of specific nerve roots

Disadvantages

may be overly sensitive (e.g., sustained train activity does not neccessary reflect nerve root injury)

  1. Electrical Electromyography (triggered)

allows detection of a breached pedicle screw

Techniqueconcept

bone conducts electricity poorly

an electrically stimulated pedicle screw that is confined to bone will not stimulate the nerve root

if there is a breach in a pedicle, stimulation of the screw will lead to activity of that specific nerve root

signal initiation

electrical stimulation of placed pedicle screw

signal recording

muscle contraction in extremity

Advantages

allows monitoring of specific nerve roots

Disadvantages

may be overly sensitive (e.g., sustained train activity does not neccessary reflect nerve root injury)

57
Q

What to do in the setting of neuro-monitoring and low MAP?

A

In the setting of low mean arterial pressure, the best course of action would be to restore MAP to >90 mm Hg and repeat testing.

58
Q

Dangerous Zone to avoid while dissecting C1?

A

Avoiding dissection more than 1.5 cm lateral to the midline and dissecting subperiosteally on the inferior aspect of the posterior arch of C1 can help avoid injury to the verterbral artery.

59
Q

Angulation of C1 lateral mass screw

A

C1 lateral mass screw should be placed in a 10 degrees medial and 22 degreees cephalad trajectory

60
Q

Symptoms of vertebro-basilar insuffisiency

A
  • dizziness
  • vertigo
  • nausea
  • diplopia
  • blindness
  • ataxia
  • bilateral weakness
  • oropharyngeal dysfunction
61
Q

Angio CT indications

A
  • Unexplained central or lateralizing neurologic deficit
  • Evidence of acute cerebral infarct on CT scan of head
  • GCS <9
  • Evidence of diffuse axonal injury
  • Facial fracture or Le Fort type-II or III fracture
  • Cervical spine fracture or subluxation
  • C1, 2, 3 fracture
  • Fracture extension into the transverse foramen
  • VAI demonstrated in 20%
  • Cervical spinal cord injury
  • Hanging injuries
  • Major thoracic injury or first-rib fracture
62
Q

Management of vertebral artery injury?

A

1- Local tamponade

2- consider direct repair of the artery

3- Angio to acess for collaterals:

  • If adequate collaterals –> endovascular embolization
  • If collateral circulation is inadequate, direct repair or stenting should be re-considered.
63
Q

Trajectory of vertebral artery

A

4 arterial segments

V1

  • extraosseous
  • origin at subclavian artery,
  • anterior to C7 transverse process, to the entry point of C6 transverse foramen

V2

  • within the transverse foramina of C6-C1
  • most traumatic injuries occur here
  • high risk during drilling, tapping, insertion of lateral mass or pedicle screws

V3

  • superior aspect of the arch of atlas to foramen magnum
  • VA is vulnerable during lateral exposure and laminectomy of C1
  • high risk of C1-2 transarticular screws are directed caudally and laterally

V4

  • intradural extension from foramen magnum to unite with contralateral vertebral artery
  • forms the basilar artery
  • most injuries from cervical trauma in V2 (foraminal segment)

Spine (6 decks)

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