Vertebral Mechanics: The Fryette Model

Question 0

Define the 4 segmental motions.

Answer 0

1. Rotation - movement in a transverse plane about a vertical axis
2. Sidebending - movement in a coronal plane about an anterior-posterior axis
3. Flexion - anterior movement in a sagittal plane about a transverse axis
4. Extension - posterior movement in a sagittal plane about a transverse axis

Question 1

What are the 2 types of axial motion?

Answer 1

Rotational (motion ABOUT an axis) & translational (motion ALONG an axis)

Question 2

What are the 3 types of translated motion?

Answer 2

1. Lateral - movement in a transverse or coronal plane along a transverse axis
2. Vertical - movement in a sagittal or coronal plane along a vertical axis
3. Anterior-posterior translation - movement in a transverse or sagittal plane along an AP axis

Question 3

What is a helical axis?

Answer 3

An axis which is moving about another axis, even while motion is occurring about it.
Example - moon rotates on an axis while rotating around the Earth, which rotates around the sun, which also rotates around its own axis.

Question 4

What is a vertebral unit?

Answer 4

2 adjacent vertebrae with their associated IV discs; facet arthrodials; and ligamentous, muscular, vascular, lymphatic, and neural elements.

Question 5

When referring to motion of a single vertebra, we are actually referring to what?

Answer 5

That segment’s vertebral unit.

Question 6

Diagnosed somatic dysfunction may be referred to in terms of what?

Answer 6

Its position or directions of motion restriction relative to the vertebra below.

Question 7

What are the suffixes for positional diagnosis?

Answer 7

-ed/-ent

flexED, rotatED, extendED, sidebENT

Question 8

What are the suffixes for motion restriction diagnosis?

Answer 8

-ing/-ion

flexION, rotatION, extensION, sidebendING

Question 9

Which is used more often - positional or motion restriction language - when describing segmental dysfunction?

Answer 9

positional nomenclature

Question 10

How is somatic dysfunction named (in terms of direction)?

Answer 10

Direction of freedom and ease.

Question 11

In what year did Fryette do his work and what method did he use?

Answer 11

1918; he used palpation

Question 12

To what parts of the spine do Fryette Mechanics apply?

Answer 12

Lumbar & thoracic spine only.

Question 13

What does it mean to say that sidebending and rotation are coupled?

Answer 13

You can’t have one without the other.

Question 14

What are the 2 types of Fryette Mechanics?

Answer 14

Type I - neutral mechanics

Type II - non-neutral mechanics

Question 15

What are the physiologic laws of spinal motion?

Answer 15

I - in neutral range, sidebending & rotation are coupled in opposite directions
II - in sufficient flexion or extension, sidebending & rotation are coupled in the same direction
III - initiating motion of a vertebral segment in any plane of motion will modify the movement of that segment in other planes of motion

Question 16

Who described laws I & II of thoracic & lumbar motion? What year?

Answer 16

Harrison H. Fryette, D.O., 1918

Question 17

Who described law III of Fryette Mechanics? In what year?

Answer 17

C.R. Nelson, D.O., 1948

Question 18

Describe the neutral position and name the type of mechanics it is.

Answer 18

Neutral position is a range in which weight is predominantly born on the vertebral bodies and discs; the facets are idling. This is Type I Fryette Mechanics.

Question 19

Describe the non-neutral position and name the type of mechanics it is.

Answer 19

Non-neutral position is sufficiently flexed or extended beyond the neutral range so that non-neutral coupling occurs. This is Type II Fryette Mechanics.

Question 20

What are the abbreviations for Fryette Mechanics?

Answer 20

N (neutral), F (flexed), E (extended), R (rotated), S (sidebent), R (right; subscript), L (left; subscript)

Question 21

How would you write L5 Neutral, Rotated Left, Sidebent Right?

Answer 21

L5NRL(subscript)SR(subscript)
or
L5RL(subscript)SR(subscript)

Question 22

How would you write L5 Flexed, Rotated Right, Sidebent Right?

Answer 22

L5FRR(subscript)SR(subscript)
or
L5FRSR(subscript)

Question 23

Give 3 facts about Type I dysfunctions.

Answer 23

They tend to occur in groups, but can occur singly.
They often compensate for Type II dysfunctions.
They constitute typical scoliosis mechanics.

Question 24

Give 3 facts about Type II Dysfunctions.

Answer 24

They tend to occur singly, although you may have Type II dysfunctions adjacent to each other (more than that is rare).
They tend to occur at the ends, or at the apex of a Type I curve.
They tend to result from isolated segmental muscle contractions present in viscero-somatic reflexes.

Question 25

To which parts of the spine do Fryette Mechanics apply, and what is the motion pattern of the vertebrae controlled by?

Answer 25

Thoracic & lumbar; muscles, discs, and ligaments.

Question 26

What is motion of the cervical spine controlled by?

Answer 26

The shape of the bone, particularly the articular facets.
Occiput on C1 - Type I Fryette-like mechanics
C1 on C2 - considered to only rotate
C2 to C6 - Type II Fryette-like mechanics
C7 - tends to follow classical Fryette mechanics

Question 27

What are exceptions to the rule?

Answer 27

Single plane or compressive dysfunctions due to trauma, traumatic damage to ligamentous architecture (any direction of dysfunction is possible), advanced degenerative disc or facet joint disease can lead to segmental instability (any direction of dysfunction is possible; can lead to neural entrapment via dynamic lateral stenosis), congenital anomalies of vertebrae or facet joints alter motion characteristics, facet tropism, transitional segments