Spine Anatomy Flashcards
when is the body of C1 visible radiographically?
1 year old
when do the posterior spinous process synchondroses fuse?
3 years
when do the synchondrosis of the ondontoid and C2 fuse?
3-6 years
when does anterior wedging of the vertebral bodies resolve?
age 3-6 years
when doe the cervical spine assume lordosis
8 years
when does pseudosubluxation and widening of predental space resolve?
8 years old
when do secondary ossification centres appear at the tips of the spinous processes?
puberty
when to the secondary ossification centres at the tips of the SPs fuse?
25 years
when do the superior and inferior epiphyseal rings fuse to the main vertebral body?
25 years old
where does the spinal column end?
L1
where do you do a lumbar puncture?
L4/5 space
central grey matter
dorsal columns:
gracile and cuneate respectively
lateral corticospinal tract
spinothalamic tract
ventral white commissure
describe central cord syndrome
a disruption in trauma of the central cord resulting in disproportionally greater motor impairment in upper compared to lower extremities with variable degree of sensory loss below the level of injury.
usually combined with bladder/bowel dysfunction and urinary retention
caused by acute hyperextension, mostly in elderly with cervical spondylosis
describe anterior cord syndrome
due to ischemia from the anterior spinal artery supply disruption
loss of motor function below injury
loss of pain and temperature
*preservation of touch, vibration and proprioception
*the most common type of spinal cord infarction
urinary retention and flaccid anus
autonomic dysreflexia above T6
describe brown-sequard syndrome
damage to 1/2 of the spinal cord
paralysis and loss of touch/proprioception ipsilaterally
loss of pain/temperature opposite
what does the corticospinal tract do?
descending motor function
crosses in lower medulla
therefore ipsilateral with respect to spinal injury and deficit
*the exception is the 10% of fibres in the anterior bundle that do not cross until they reach their destination to innervate truncal muscles
what does the posterior column of the spinal cord do?
there are 2 bundles: gracile (legs) medial and cuneate (arms) lateral
they provide ascending fine touch and proprioception
cross at the upper medulla - therefore causes ipsilateral deficits with respect to spinal injuries
what does the spinal thalamic tract do?
lateral and anterior bundles that transmit ascending pain and temperature (lateral) and crude touch (anterior) to the brain
cross at the level of their innervation - therefore the cause contralateral deficits with respect to spinal injuries
what is the bulbocavernous reflex?
compression of the glans should elicit anal sphincter contraction
dervied from S2-4
the abscence of reflex in acute traumatic paralysis is actually good - it means that there is spinal shock. A spinal cord transection with have maintained reflex.
what is autonomic dysreflexia?
presents as uncontrolled hypertension and bradycardia
lesion above T6
triggered by sympathetic stimulation below the lesion that cannot be counteracted by descending parasympathetic flow when barorecptors notice a problem. Essentially, your circulation CAN go across the lesion, but your neuro CANNOT.
often triggered by urinary bladder distention
explain ASIA grading
A = no response below lesion
B = sensation preserved below lesion
C = >50% of muscles are < 3/5
D = > 50% of muscles are >/= 3/5
E = full function
what do we mean when we say ‘motor level’ in a spinal cord injury?
the most caudal level where power is not 5/5
what do we mean by ‘sensory level’ in spinal cord injury?
most caudal level with normal pinprick and light touch
what is the highest level of spinal cord injury that can be ventilator independent initially? how about after time?
C5
eventually C3 and C4 can become independent
where do the majority of stenoses occur?
at the level of the disc anteriorly with facet joint posteriorly
where is the foramen in relation to the pedicle?
the pedicles arise from the superior portion of the vertebrae, the nerves exit below them and superior to the disc
what are the boundaries of the foramen?
the pedicle superiorly
the superior facet inferiorly
the pars posteriorly
the vertebral body anteriorly
where is the lateral recess?
the space between the medial pedicle and medial superior facet
notice that this means the vertebral body/disc is anterior and the superior facet of the vertebra below is posterior
which nerve will an L4/5 foraminal (far lateral) bulge impinge?
L4
which nerve will a posterolateral (lateral recess) disc herniation of L4/5 impinge?
L5
which layer increases in width in lumbar spinal stenosis caused by hypertrophied ligamentum flavum?
the cartilage layer under the ligament
what are the signs of unstable spine?
pain with dynamic movement
dynamic shift on imaging
lack of osteoarthritic signs
facet joint effusions
evolving neurologic symptoms
where should occipital screws be placed?
+/- 2 cm at the nuchal line
+/- 1 cm 1 cm below nuchal line
+/- 0.5 cm 2 cm below nuchal line
*we are talking about the superior nuchal line, found in line with the EOP
why don’t you place transarticular C1-2 screws?
1) if there is a high-riding vertebral artery (present in 20%)
2) subluxation of C1-2
3) if there is cervicothoracic kyphosis
what is the relationship of the vertebral artery to C1?
emerge superiorly through the lateral foraminae then track medial on the superior aspect of the pedicles of C1 before continuing superiorly with the spinal cord to enter the cranium
where is the ICA in relation to C1?
abutting the anterolateral aspect of C1
where do you place a thoracic pedicle screw?
start at the junction of a lines:
1) vertically along midpoint of facet joint
2) along superior ridge of transverse process
where do you start a lumbar pedicle screw
intersection of lines:
1) vertically along the superior facet
2) horizontally along midpoint of transverse process
largest thoracic vertebra
T1
smallest thoracic vertebra
T4
smallest lumbar vertebra
L1
what screw size for lumbar spine?
L1 = 7.5
L2 = 8.0
L3 = 9.5
L4 = 12.5
L5 = 11.5
what is the toeing in trend for pedicle screws?
less as you go down T spine
to 5-10° at L1
then increase 5° per level from L1 down
where can you place S1 pedicle screws?
zone 1 = superior facet directed 10° from sagittal
zone 2 = notch lateral to facet directed 40° from sagittal
where are the safe zones for halo placement?
superolateral half of frontal bone above orbit
this avoids the temporalis muscle laterally, the supraorbital nerve over medial half of frontal bone above orbit, and the supratrochlear nerve arising from the superomedial aspect of the orbit
normal thoracic kyphosis
10-40°
what is the normal lumbar lordosis?
TK + 30°
what is normal sagittal alignment of the spine?
C7 should drop a vertical line through the posterior superior margin of the sacrum +/- 2.5 cm
normal sacral slope
41° +/- 16°
normal pelvic tilt
first, vertical line from center of acetabulum, second line from center of acetabulum and middle of sacrum
normal is 13° +/- 12°
what is pelvic incidence?
PT + SS
why is pelvic incidence important?
it dictates the lumbar lordosis, where
PI = LL + 10°
how can you increase lordosis?
spinous process + facet joint osteotomy
explain the arterial supply to the spinal cord
cervical and upper thoracic supplied by radicular branches or vertebral, ascending cervical and superior intercostal arteries
*watershed exists in mid-upper thoracic spine
mid/lower thoracic is supplied solely by the artery of adamkiewicz, which usually arises between 9th and 12th intercostal arteries, 70% of the time from the Left
lower thoracic-lumbar spine supplied by large vessel near diaphram
cauda supplied from lower lumbar, iliolumbar and lateral sacral arteries
what is ossification of PLL and how is it treated?
AS PER REVIEW BY CHOI 2011 - Asian Spine Journal
elderly, male, asians (2.4% of all asians)
type 2 diabetes also a risk
myelopathy is the indication for surgery, however this is less common as the disease is not usually rapidly progressive (Matsunaga - 450 patients)
(Chiba - 50% progression even with surgery - 131 patients - worse for posterior approach 70%, than anterior 50%)
