0:01

We just saw a case of grade one spondylolisthesis that was

0:06

secondary to degenerative facet joint disease

0:09

leading to foraminal stenosis.

0:11

I mentioned that with spondylolisthesis, one can also have

0:15

an etiology that is secondary to pars interarticularis

0:20

defects or fractures.

0:22

This is an example of a patient who at L5-S1,

0:25

really shows pretty nice normal alignment and we

0:30

probably wouldn't say anything about malalignment

0:33

or spondylolisthesis.

0:34

However, as we scroll through the sagittal images,

0:38

we notice that there is a defect in the pars interarticularis at the L5 level,

0:44

which is the most common level,

0:46

and it is a bilateral process.

0:49

By virtue true of the sclerosis,

0:51

we would know that this is a chronic process as opposed

0:54

to something secondary to acute injury, which we might

1:00

worry about in the trauma setting of a motor vehicle

1:03

collision. When you look at the same finding on the CT scan,

1:08

I'm just going to show the

1:10

localizer here. As we come through the L5 vertebra,

1:16

you'll notice the defect here bilaterally

1:19

in the pars interarticularis,

1:21

and

1:23

it is a bilateral process.

1:26

And here we see the facet joint.

1:28

Sometimes, you have a difficulty in separating the facet

1:34

joint disease and the pars interarticularis

1:37

defect and the facet joint below.

1:39

But in this case, I think it's pretty clear.

1:41

And certainly, if you do sagittal reconstructions,

1:44

you will notice the so-called neck of this scotty

1:48

dog defect with the pars interarticularis defects.

1:54

So this is the point to be made here,

1:57

is that the presence of spondylolysis,

2:00

while it predisposes you to spondylolisthesis,

2:04

it need not be absolutely present in each case of

2:09

spondylolysis. This patient also had an MRI scan,

2:13

and I just want to point out that the defect in the

2:17

pars interarticularis is clearly not as well

2:21

identified on the MRI scan as on a CT scan.

2:28

One thing that I will note is that

2:32

in, again, the trauma setting,

2:34

it's useful to look for high signal intensity on your

2:37

STIR sequences, at the pars interarticularis, to determine

2:42

whether there's bone edema suggesting

2:44

either an acute injury or

2:48

an exacerbation of the irritation

2:51

or inflammation around the pars.