Harrison Fryette was a DO that studied the
relationship of the thoracic spine and the lumbar spine
and he came up with several principles relating
to the, based on the anatomy of the spine,
the motions that is associated with it.
And so a lot of his principles are utilized when
we're diagnosing somatic dysfunctions of the spine.
So, Dr. Fryette's 1st principle is that when
we have side-bending introduced to the spine,
in a neutral spine, meaning that there
is no flexion or extension component,
you're gonna have the bodies of the vertebrae
rotate to the side of the convexity.
So side-bending and rotation
occur in opposite directions.
So If I'm sidebending my body to the right,
my vertebra will rotate to the left
due to anatomical connections between
the muscles and the ligaments.
This applies again to group curves,
a group curve is defined by having
three or more vertebral bodies.
And also neutral curves, meaning that there
is not a flexion or extension component.
So this is, like I said before,
considered type I somatic dysfunctions.
Fryette's 2nd principle applies
to a non-neutral spine.
What a non-neutral spine means is
that it is usually a single segment
that has associated freedom
with flexion or extension.
So, what happens in a type II dysfunction is that
you have rotation to the side of the concavity.
That means that rotation and sidebending
are coupled to the same direction.
Again, it applies to a single unit and so this
is what we call a type II somatic dysfunction
when you have side-bending
rotation to the same direction.
Another observation that he made is that
in his 3rd principle, he talks about
if you initiate a motion of the vertebra in one
plane of motion, you will modify or usually limit
the motion of the segment in the other
So here, we're reviewing the principle of
side-bending and rotation being coupled.
So if I have a type I dysfunction,
the neutral spine will display sidebending
rotation in opposite directions.
In a type II dysfunction, side-bending
rotation will be coupled to the same side.
This is because a lot of times that dysfunction
is due to a restriction of a facet on one side.
Fryette's 3rd principle discusses motion of vertebra
in one plane will influence motion in the other.
So if you think about it, if I try to just side bend
to the side, I have a certain freedom in motion.
If I add rotation and then try
to side-bend to the side,
now I'm more limited with how much
I could rotate and side-bend.
So, anytime you have more than one movement,
it will influence motion in the others.
So, how does this play into
diagnosing somatic dysfunctions?
So, taking a closer look at Fryette's first
principle, if we have a neutral spine,
side-bending rotation are gonna
So in a type I group curve, this is
what occurs when you have tight muscles
on one side of the spine or sometimes there
may be a sort of asymmetry in the pelvis,
a leg length which cause a
curve to occur in the spine.
So let's take a look at type I dysfunctions.
Here's an example, we have a T5 to T9 neutral side
bend right, rotated left somatic dysfunction.
So here, we know that it's neutral,
side bent right, rotated left.
It's a neutral curve and so it
has to be a group dysfunction.
Again, a type I dysfunction has
to be at least three or more segments.
So here, we have T5 to T9
which meets that criteria.
And what we usually find on palpation
is that from T5 to 9 here,
we have the transverse process
on the left, more posterior.
So we have asymmetry here,
there's a freedom of motion.
Those transverse processes like to rotate
left, so as we palpate from T5 to T9,
we have transverse processes
If I check in flexion and extension,
the segment does not change much.
That's what defines a neutral curve.
And so, we have T5 to (9) neutral, rotated
left and following Fryette's principle no. 1,
we now assume that it's gonna be
side bend right
because that's the only way
the spine moves anatomically
So, these type of neutral dysfunctions
may be adaption such as in scoliosis.
We have tight muscles and that could pull the
curve and cause it to side bend to a certain side
thus causing a rotation to the
And usually, what happens is, it doesn't really
exaggerate when I check in flexion or extension.
So, here is another example for
a type I somatic dysfunction.
As I'm palpating the segments from T3 to T6,
They're more posterior now on the right side.
and when I motion test in flexion and
extension, it doesn't really have a change.
So now you have T3 to T6, you know it's a neutral
curve and you know it's posterior on the right.
And following Fryette's principle no. 1,
you assume that the side-bending is left.
Taking a closer look at Fryette's 2nd principle, again,
this is usually a single unit in a non neutral spine.
meaning, there is a flexion
or extension component,
you're gonna have the bodies of the vertebrae
rotate and side-bend the same direction.
So with a type II dysfunction, usually this
is due to some sort of trauma.
The intertransverse ligament, the
interspinous ligaments, the facet is stuck.
And so, there is a problem here of one
single segment as it moves on the one below.
Again, it's maintained by the
those deep muscles in the thoracic
spinem, in between the thoracic spine.
And usually when you're treating, you should
treat these before type I dysfunctions.
Sometimes you might even find a type
II dysfunction mixed in a type I
at the apex or at the top or
bottom of a type I curve.
Let's take a closer look at
type II dysfunctions.
So type II dysfunctions occur in a
meaning that there is a flexion or
extension, freedom or component.
Remember that we name somatic
dysfunctions for the freedom of motion.
And so with extension dysfunction, what we usually find
typically is that there is a posterior transverse process,
a segment that resist anterior springing on the
right or left that gives us a rotational freedom.
What happens in extension, is that
rotational freedoms seems to even out,
it becomes more symmetric because
that is the freedom of motion.
And when I try to flex,
it becomes more pronounced.
You'll see that rotation become stiffer
and harder to spring in the barrier.
So, what happens is when I extend
the spine, the facets will close.
And when I flex the spine, the facets
In extension dysfunction, what happens
is one of those facets is not opening.
And because that facet stays closed, it causes that
vertebra to rotate and side bend to that side.
The opposite occurs in a
So if I find asymmetry in the spine
and I have someone flex forward,
then the dysfunction seems to disappear
or become more symmetric.
But then when I have them extend, that
asymmetry now becomes more pronounced.
So what happens in extension is the
and what happens in a flexion dysfunction
is one of the facets is not closing
and that causes the vertebrae to pivot and cause
rotation and side-bending to the opposite side.
So, here's an example describing
a type II somatic dysfunction.
If we have one single segment, let's say T3, and you
find a motion restriction of that transverse process
to be more posterior, here
let's say on the right side.
So I have a posterior transverse process on the right
when I try to push anteriorly, it resist springing,
there might be some tenderness, some
other tissue texture changes at that location.
And now if I motion test that segment, it's gonna
actually improve in flexion or improve in extension.
So there is a non-neutral,
there is a position of ease.
So following Fryette's principle, we would
assume that rotation, right here
is gonna be coupled with side
bending to the same side.
So here our somatic dysfunction will be T3 flexed, the
freedoms in flexion, and is side bent, rotated to the right.
We name the motion of T3 as it
moves on T4.
So in type II non neutral somatic dysfunctions,
there's always a flexion or extension component.
The side-bending rotation are
coupled to the same side.
The restricted facet pretty much acts like a pivot
which rotation occurs causing that asymmetry.
And the segment will appear more symmetric at
some point in the sagittal range of motion.
The lesion becomes more prominent as
you move in the opposite direction.
Here are a couple of charts for
you to look over and review.
This helps to summarize the differences between a
flexion or extension type II somatic dysfunction.
This is additional chart.
What we're looking at here is what happens
in each specific somatic dysfunction,
especially when the facet is restricted.
So what I would recommend if you could get your
hands on anatomical models of the thoracic spine
and look at what happens when you try to flex and open
the facets but don't allow one of the facets to open,
you'll see that that transverse
process then becomes more posterior
and side bent and rotated
in the same direction.
The opposite occurs when we're
looking at a flexion dysfunction.
If I am able to open both but I'm
not able to close one of the facets,
you'll notice that the side-bending rotation
is gonna occur to the opposite side.
So the best way to really understand this a
little better is to get model thoracic segments
and really practice looking at what occurs
when you have a facet that doesn't open,
when you flex and doesn't close
when you try to extend the segment.
When we write out somatic dysfunctions, there is a
specific way that we have to write somatic dysfunctions.
For type II dysfunctions, we always write
the rotation before the side-bending
because the rotation is the more important
component in a type II dysfunction.
Whereas in a type I dysfunction, side
bending is written before rotation.
This is because the side-bending is the more
important component in a type I dysfunctions
due to the muscles pulling on the side,
causing the side-bending.
Some key review points,
take home points.
In type II somatic dysfunctions,
they are non neutral dysfunctions,
meaning there is a flexion or
In that instance, rotation and side
bending are coupled to the same side.
When we notate it, we always write the
rotation first in a type II dysfunction.
Flexion dysfunctions in a type II dysfunction
become more prominent in extension and vice versa.
Extension dysfunctions become
more prominent in flexion.
In an extension dysfunction,
the facet on the same side is restricted.
In flexion dysfunctions,
the facet on the opposite side is restricted.
In a type I dysfunction,
this occur in a neutral spine and remember that
it is usually a group curve,
so it has to be at least 3 segments.
Rotation and side-bending are
coupled to opposite sides.
When we notate it, we usually put the side-bending
component first and in a type I dysfunction,
there's really little change in flexion
Let's do a practice question together.
So in your patient, you find a right posterior
transverse process to the level of T7
and it improves with flexion
and is worse with extension.
What is the somatic dysfunction diagnosis and
which Fryette's principle does it follow?
So here, we have a single segment
and it has a freedom in flexion.
So you know that it's going to follow Fryette's principle
type II because this is a non neutral dysfunction.
So this is T7 and it's flexed.
Because we felt that it is more posterior on the right
side, that tells you that the segment is rotated right.
So knowing that it's flexed and rotated right,
we can then follow the principle and assume
that the side-bending is occuring in the
same direction so it's also side-bent right.
So we here have a T7 flexed,
rotated right and side bent right dysfunction.
So in this practice item, we find that your patient has
posterior transverse processes from T1 to T5 on the left
And they do not change with
flexion or extension.
What is your somatic dysfunction diagnosis and
which Fryette's principle does it follow?
So here, we note that this is a group curve from T1
to T5 and they are all posterior on the left side
which means that they're rotated left.
Since they do not change with flexion or
extension, you know that this is a neutral curve.
So neutral curves usually follow's
Fryette's principle no 1.
So because it's T1 to T5, neutral
curve and we know it's rotated left,
since we follow Fryette's principle no 1, we know
that rotation and side-bending are opposite.
That brings us to the diagnosis of T1 to T5 neutral,
side bent right and rotated left.