0:01

As we moved from the craniovertebral junction, the CVJ,

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into the atlantoaxial region, which is the C1-C2 region,

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we finally get to the subaxial cervical spine.

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So the axis being the C2 vertebra,

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the atlantis being the C1 vertebra.

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We're now into the C3 through C7

0:25

vertebra of the cervical spine.

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I want to introduce at this point the three column

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injury model that Denis, D-E-N-I-S, has

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the classification which actually originally

0:38

described in the thoracic spine.

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But it does make sense even in the cervical spine.

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And what we have are three different columns.

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The first column represents the anterior longitudinal ligament

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and the anterior half of the vertebrae as the first column.

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The second column represents the posterior vertebra,

0:59

including the posterior longitudinal ligament.

1:03

And then the third column are the posterior ligaments of the

1:07

interspinous ligaments and the ligamentum flavum, and the

1:10

spinal laminar line and these posterior

1:13

portion of the vertebral bodies.

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What the Denis classification says is that if you

1:18

have two out of three of the columns injured,

1:23

it's likely to represent an unstable spine.

1:26

So here we have the same anatomy on the axial scan,

1:30

the first column, the second column,

1:32

posterior vertebra and posterior longitudinal ligament,

1:35

and then the third column with the posterior elements,

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as well as the interspinous ligaments and ligamentum flavum.

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This is also demonstrated here on the diagram to the left.

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Now, if you have a fracture that goes all the way through

1:50

the intervertebral disc from anterior to posterior,

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you're actually incorporating two columns, right?

1:57

So this is the first column,

1:58

but if it crosses into the posterior vertebra segment,

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you'd have two column disease.

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So this is the spinal stability theory,

2:08

at least of the subaxial cervical spine in the Denis

2:13

classification. And we actually think about it in those terms

2:16

for stability or instability.

2:19

I'm going to move in the cervical spine to the

2:22

subaxial spine hyperflexion injuries.

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And here are some of the hyperflexion

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injury fracture types that can occur,

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which include your flexion teardrop injury,

2:35

your bilateral facet dislocation and your clay shovelers

2:39

fracture, which is in the spinous process.

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Here's a couple of examples.

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You notice that with these flexion injuries,

2:47

you often show anterior displacement of one vertebral

2:51

body versus the other, because these do represent not

2:55

just the bony injury, but often there is two column

3:00

injury leading to instability. In this case,

3:04

we have a perched facet.

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This is one tip touching the other tip.

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But as we go off midline,

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we also see that this facet is now anteriorly

3:15

located versus the facet below.

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Normally,

3:18

the top of the superior facet is anterior to the inferior facet.

3:24

This superior facet is posterior to the inferior facet.

3:28

And we also have flexion teardrop fracture of the

3:32

vertebra. So angulation, offset, dislocation, perched facet.

3:39

This is a bilateral process,

3:41

in this case, of a flexion injury type,

3:44

leading to the fractures and the unstable spine.

3:49

Here is the MRI scan of that exact same patient.

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And not only do we see the continued offset,

3:57

but we see the injury to the posterior longitudinal ligament,

4:01

we see the injury to the ligamentum flavum,

4:04

we see the high signal intensity in the interspinous ligaments,

4:08

we see the high signal intensity in the intervertebral disc,

4:11

and we see the injury also to the anterior longitudinal

4:15

ligament. This is three column disease,

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and let's not forget to look at the spinal cord.

4:22

Whereas you can see there has been injury to

4:24

the spinal cord with bright signal intensity.

4:27

So this was a bilateral facet dislocation and a flexion

4:31

teardrop fracture with ligamentous injury to anterior

4:35

longitudinal ligament, posterior longitudinal ligament,

4:38

as well as ligamentum flavum and interspinous ligament.

4:42

Unstable spine. Another example.

4:45

Here you can see the compression deformity

4:47

and the flexion teardrop pattern.

4:51

Little bit of posterior displacement of this vertebral

4:54

body, compromising the spinal canal.

4:57

And this is this triangular fracture,

4:59

which is fairly typical of a flexion teardrop fracture.

5:04

Here is the last of the flexion injury,

5:07

the clay shoveler's fracture. This clay shoveler fracture,

5:11

as you see,

5:12

represents a fracture of the spinous process, that if you can

5:17

imagine the individual taking the shovel and pushing

5:22

it into the clay and then yanking the neck back,

5:25

that's what causes the fracture of that spinous process,

5:30

as they're trying to, you know, pull that clay out of the ground.

5:35

Notice that in this instance,

5:37

you do not have any offset of the anterior margin of the

5:41

vertebral body, the posterior margin of the vertebral body,

5:44

nor the spinal lamina ligament,

5:47

but the spinous process is offset.