Assessing alignment of the lateral cervical spine (neck) X-ray Video Lecture

SAL KHAN: This is
Sal here again.
And I'm still here with my
good friend Dr. Mahadevan
from Stanford University.
And in the last video, we had
looked at adequacy of x-rays,
for the neck, which is,
is the x-ray good enough.
But now let's assume
we have good x-rays.
Now, what do we look at?
DR. MAHADEVAN: The next step
is to look at the alignment.
So we talk about the ABCs of
reading a cervical spine film.
And A starts with adequacy,
that we went over.
And the second part
of A is alignment.
SAL KHAN: OK.
So we're still in A.
So now it's alignment.
I was expecting something with
a B. All right, alignment.
All right.
So this looks like this
is about alignment.
DR. MAHADEVAN: This
is about alignment.
And there's four
lines that we look at.
The first is the anterior
vertebral body line.
SAL KHAN: OK, AVBL,
right over there.
DR. MAHADEVAN: Exactly.
And basically, what
you're doing is,
you're trying to draw a smooth
line that connects the anterior
aspect, the front of all
the vertebral bodies.
It should be nice and smooth.
It's usually curved.
And all the points should
sort of fit on that line.
Nothing should be
off of that line.
That would suggest that
there was a problem there.
SAL KHAN: I see.
And anterior, as you
just said, means front.
DR. MAHADEVAN: Exactly.
SAL KHAN: Right, OK.
DR. MAHADEVAN: The
next line is going
to the back of the
vertebral body.
It's the posterior
vertebral body.
SAL KHAN: So not the back
of the entire vertebrae,
the vertebral body, which is
this boxy part right in front.
DR. MAHADEVAN: Exactly.
And so same thing,
connecting a line up and down
should be nice and smooth,
as you've drawn it.
And nothing should
fall off that line.
No piece of that vertebral
body should fall off
of the line you've draw.
SAL KHAN: All
right, sounds good.
And then?
DR. MAHADEVAN: The next is, we
connect all the spinolaminar
junctions.
So this is the
spinolaminar line.
And it's where the
lamina connects
to the spinous process.
SAL KHAN: Spinous
process, it sounds
like we could make a
whole video about that.
DR. MAHADEVAN: Spinous
process, if you
look at the back
of somebody's neck,
are those little bumps
that you can see.
And that's the very back end.
SAL KHAN: And that's these
triangular things right here.
DR. MAHADEVAN: Exactly.
SAL KHAN: OK.
So you're just
connecting that line.
Kind of the front
of these triangles,
the base of these
triangles, so to speak.
DR. MAHADEVAN: Exactly.
SAL KHAN: And then the last one?
DR. MAHADEVAN: And the last line
is the spinous process tips.
And again, we're just
connecting the top,
the tip of all these
spinous processes,
the little bony
projections you can
see if you look at the
back of somebody's neck.
And these two should generally
fall in a nice, smooth curve.
SAL KHAN: And so the general
rule-- if any of these
aren't aligned the way
that we've drawn here,
it's a problem.
DR. MAHADEVAN: Exactly, exactly.
We call it subluxation or
malalignment or misalignment.
And these all suggest that
there is a problem there.
SAL KHAN: Which is a big
deal, because your spinal cord
is running through there.
DR. MAHADEVAN: Absolutely.
If you look between the two,
the green and the blue line,
that's actually where your
actual spinal cord runs.
SAL KHAN: Right.
Right down there.
DR. MAHADEVAN: Exactly.
SAL KHAN: I see.
So you don't want
that to get messed up.
All right.
So let's look at a
few of these x-rays
and see if, one,
anything's wrong.
Or if there's something,
if we can spot it.
DR. MAHADEVAN:
Actually, Sal, now
that you know how to read
cervical spine x-rays.
I'm going to have you
look at the first x-ray.
SAL KHAN: OK, let's see.
I'm going to get
sued for malpractice.
Let's see.
All right.
So this one over here.
So let me just do the first one.
Let me just go with
what you told me to do.
So I'm going to do the anterior
side of this vertebral body.
DR. MAHADEVAN: Exactly.
SAL KHAN: Look, I'm
learning the words too,
talking like a doctor.
So I'm going to
draw a line here.
That looks pretty good.
That looks decent.
What is it?
I'm kind of-- let me see.
This still looks decent.
And that doesn't look great.
Would this count?
I mean, this looks like it
got shifted over a little bit.
DR. MAHADEVAN: Absolutely.
SAL KHAN: It's not
a huge shifting.
But it's enough that it's
not easy to draw a line.
So I was right?
DR. MAHADEVAN: You're
absolutely right.
And in fact, sometimes
it's very subtle.
And you picked up a
very subtle abnormality.
But again, even though
it's subtle on the x-ray,
it could be serious
for the patient.
So you potentially saved their
spinal cord and their lives,
by picking up an
injury like this.
SAL KHAN: OK, good.
You're making me
feel-- very good.
So that's-- it's literally
something as subtle as that is
what you're looking for.
DR. MAHADEVAN: Exactly.
Again, it should be
a nice, smooth line
or a nice, smooth curve.
And as you can see,
at that junction,
it's no longer smooth.
SAL KHAN: And you
don't even have
to look at the other lines.
Any one of these that you don't
align, that's enough to say,
hey, do something else.
DR. MAHADEVAN: Exactly.
And that's a great,
important teaching
point, which is, if you see
any abnormality on a plane film
on an x-ray like this, you stop.
And you protect
their cervical spine.
And then you get a
more important study
or a better quality
study, like a CT scan.
SAL KHAN: Fascinating.
Although if I do
look here, it does
look like we could
have done the PVBL.
And it looks like that
also is a little off too.
DR. MAHADEVAN: Absolutely.
SAL KHAN: That one and-- OK,
well, let's get a few more.
DR. MAHADEVAN: Great.
SAL KHAN: I don't want to focus
too much on my first victory.
All right.
So it's clear this person
is facing this way.
I can see their teeth.
So let's see what
we can do here.
Can I give it a shot again?
DR. MAHADEVAN: Please, please.
SAL KHAN: So let's-- the
AVBL, it looks pretty good.
This is-- well,
that looks close.
DR. MAHADEVAN: It
looks close, I agree.
And potentially, again,
you've got a very keen eye
and might have picked it up.
But most people might--
SAL KHAN: A gift, you might say.
DR. MAHADEVAN: --might
have overlooked that.
SAL KHAN: So let's try
the other lines here.
OK.
So this one is more obvious.
This one is more
obvious that there's
kind of that disconnection
right over there.
DR. MAHADEVAN: Exactly.
And this is the PVBL, or the
posterior vertebral body line.
You can see clearly,
that line is not smooth.
It doesn't connect, and
so there is a problem
right there at that junction.
SAL KHAN: OK.
All right, and so now we have
this last one right over here.
Let me see what I can do.
Let me see, don't want
to lose my streak.
All right.
So interior side-- this actually
looks pretty perfect actually.
DR. MAHADEVAN: And in
fact, it is a perfect.
SAL KHAN: OK.
Let me try the next lines here.
This is the posterior
vertebral body.
Let me do that in a color
that's easier to see.
I already used orange.
I'll do magenta.
All right.
So this is looking OK.
It looks OK.
I mean, nothing
obvious on that line.
DR. MAHADEVAN: I would say,
again, you've got the keen eye.
But in this particular
case, I'd say, it's fine.
It's within the normal
range, as we say.
SAL KHAN: And so let me do
the base of those triangles.
Let me do-- so this is a
triangle right over here.
DR. MAHADEVAN: Again, you want
it to be a nice, smooth curve.
Everything should
fall on that curve.
SAL KHAN: So this-- I would
have to be a little bit generous
with my curve to make it
go to these guys down here.
DR. MAHADEVAN: Exactly.
And this is the
spinal laminar line.
This is the third
line of alignment.
As you can see, to try to
get those to work, you could.
But they're not smooth
like the other lines.
And this is, again,
another subtle finding.
But missing this finding because
the first two lines are normal
could again be devastating
for the patient.
SAL KHAN: Right.
You always want to err
on the side of caution.
I mean, if anything looks
even a little bit suspicious,
maybe another x-ray.
DR. MAHADEVAN: Yeah, another
x-ray, another view, like we
talked about before.
Or the definitive study is a CT
scan, or Computed Tomography.
SAL KHAN: I see, very cool.
Well, thanks for this.
This is useful.
DR. MAHADEVAN: My pleasure.