Introduction to Fryette's Spinal Mechanics

What is the major purpose of learning Fryette’s spinal mechanics

to understand the predictable relationships between

• flexion/extension

• sidebending

• rotation

of vertebral segments so you can describe and diagnose spinal somatic dysfunction

What is a vertebral unit?

Two adjacent vertebrae together with their associated:

• Intervertebral disc

• Intervertebral joints

• Ligaments

• Muscular structures

• Neural components

When describing vertebral motion, the motion of one vertebrae is described relative to what

the vertebra immediately inferior to it

ex: when describing T3, you’re describing the position/motion of T3 relative to T4

What are the major load-bearing structures in the anterior column of a vertebral unit?

Vertebral bodies

Intervertebral disc

What are the paired posterior synovial joints between adjacent vertebrae called?

Facet joints, also called:

Zygapophyseal joints

Which processes form the facet/zygapophyseal joints?

Superior articular process

Inferior articular process

What determines the position or motion of a vertebral segment?

The position of the most anterior and superior aspect of the vertebral body.

If the anterior-superior portion of a vertebral body moves to the right, what direction has the vertebra rotated?

Right rotation.

Rotation is named according to the vertebral body, not the spinous process.

During right rotation of a vertebral body, which direction does the spinous process move?

Generally toward the left.

Body right → spinous process left.

What happens anatomically during sidebending to the left?

The vertebral column bends toward the left

The left side becomes relatively concave

The right side becomes relatively convex

During left side bending, what happens to the facet joints

left side; facets approximate/close

right side: facets separate/ open

What is the neutral position of the spine?

The range of motion in which the majority of the weight lies on the vertebral bodies and intervertebral discs, without significant engagement of the facets.

Is the neutral spine necessarily perfectly straight?

No.

Neutral refers to a range of motion, not one exact anatomical position.

What makes a spinal position non-neutral?

The spine has moved sufficiently into flexion or extension so that the facet joints become engaged and strongly influence subsequent motion

What happens to the facet joints during flexion?

The facets OPEN.

What happens to the facet joints during extension?

The facets CLOSE.

What does it mean when a facet is open

the adjacent articular surfaces have moved away from one another

What does it mean when a facet is “closed”

The adjacent articular surfaces have moved toward/approximated one another.

What does Fryette's First Principle describe?

Motion occurring when the spine is in a: NEUTRAL position

This is commonly called: Type I mechanics.

In neutral mechanics, what is the relationship between sidebending and rotation

sidebending and rotation occur in OPPOSITE directions

N

If a neutral spinal region sidebends LEFT, which way does it rotate according to Fryette’s first principle

RIGHT

NSlRr

If a neutral spinal region sidebends RIGHT, which way does it rotate?

LEFT

NSrRl

Does Fryette's First Principle usually involve one vertebra or a group of vertebrae

A group of vertebrae

T5–T9 are neutral, sidebent right and rotated left. What type of mechanics is present

Type I.

It could be written: T5–T9 NSrRl

because: Neutral + opposite sidebending/rotation + group dysfunction = Type I

What does Fryette's Second Principle describe?

Motion occurring when the spine is significantly flexed or extended

this is non-neutral / type II mechanics

In Type II mechanics, what is the relationship between sidebending and rotation?

Sidebending and rotation occur in the SAME direction.

E

If a flexed vertebra sidebends LEFT according to Type II mechanics, which way does it rotate?

LEFT.

FSℓRℓ

If an extended vertebra rotates RIGHT according to Type II mechanics, which way should it sidebend?

RIGHT.

ERrSr

Does Type II dysfunction usually involve a group of vertebrae or a single vertebral segment?

Usually a SINGLE vertebral segment

. Type I Type II

Position

Rotation/sidebending

Segments

. Type I Type II

Position Neutral flexed/extended

Rotation/Sidebending Opposite Same

Segments Group Single

I = Neutral + opposite + group

II = flex/extend + same + single

Why does flexion or extension change spinal mechanics

because flexion or extension engages the facet joints, causing the facets to exert a greater influence over sidebending and rotation

What is Fryette's Third Principle?

Introducing motion in one plane reduces motion in the other planes.

What does Fryette's Third Principle mean in plain English?

The more you move a spinal segment toward its limit in one direction, the less freedom it has to move in other directions.

Why is Fryette's Third Principle important for OMT?

It helps explain localization.

By introducing motion in several planes, you progressively restrict unwanted motion and localize forces to the desired vertebral segment.

What is spinal somatic dysfunction in the context of Fryette mechanics?

A vertebral segment or group has an abnormal/restricted positional or motion relationship that can be described using:

Flexion/extension/neutral

Rotation

Sidebending

Are somatic dysfunctions named for the direction of restriction or the direction of ease?

The position/direction of EASE.

If T5 rotates easily RIGHT but is restricted in LEFT rotation, how is the rotational component named

Rr

because T5 prefers/eases into the right rotation

If a vertebra prefers flexion and becomes more asymmetric during extension, is it flexed or extended?

Flexed dysfunction

It prefers flexion and has difficulty moving fully into extension.

T5 is rotated right and sidebent right, and its asymmetry becomes worse during extension but improves during flexion. What is the diagnosis?

T5 FRrSr

Better in flexion → prefers flexion

Rotation right

Sidebending right

Same direction → Type II

T7 is rotated left and sidebent left. Its asymmetry becomes worse with flexion and improves with extension. Diagnosis?

T7 ERlSl

Prefers extension

Rotated left

Sidebent left

Same direction → Type II

During a Type II diagnosis, what does improvement of asymmetry during flexion suggest?

The segment prefers flexion.

Therefore: F dysfunction

A group of thoracic vertebrae displays neutral mechanics, sidebends left and rotates right. How is it described

NSlRr

T3–T7 are neutral, rotated right, and sidebent left. What type of dysfunction is this?

Type I: T3–T7 NSlRr

Group dysfunction

Neutral

Rotation and sidebending opposite

T6 alone is flexed, rotated right, and sidebent right. Type I or II?

Type II

T6 FRrSr

Neutral + rotation opposite sidebending = ?

type I

Flexed/extended + rotation same direction as sidebending = ?

Type II

Group dysfunction = think what first?

Type I

Single-segment dysfunction = think what first?

type II

T4–T8 are neutral and rotate left. Based on Fryette Principle I, which way should they sidebend

Right, because Type I rotation and sidebending are opposite.

Diagnosis: T4–T8 NSrRl

T6 is flexed and rotated left. Assuming Type II mechanics, which direction is sidebending?

Left

Diagnosis: T6 FRlSl

T8 is extended and sidebent right. Assuming Type II mechanics, which direction is rotation?

Right

Diagnosis: T8 ERrSr

A physician identifies T4–T9 as NSlRr. Is this consistent with Fryette mechanics?

Yes.

Neutral

Group dysfunction

Sidebending left

Rotation right

→ Type I

A physician documents T5 FRrSl. Is that the expected relationship for classic Type II Fryette mechanics?

No.

For Type II: Rotation and sidebending should occur to the SAME side.

FRr would therefore classically pair with Sr.

A physician documents T3–T8 NSrRr. Does this follow classic Fryette Principle I?

No.

In Type I neutral mechanics:

Sidebending and rotation should be opposite.

NSr should classically pair with Rl.

If a vertebral segment flexes, what happens to both facets?

Both facets open.

If a vertebral segment extends, what happens to both facets?

Both facets close

Type I = NOG

Neutral

Opposite

Group

Type II = FESS

FE = flexed or extended

S = same direction

s = single segment

What is a common mistake when describing vertebral rotation?

Naming rotation according to the spinous process rather than the vertebral body.

Rotation is named according to the VERTEBRAL BODY.

Body rotates right → spinous process moves left.