Week 1- Lumbar Biomechanics

Question 1

What subsystems are under consideration for lumbar biomechanics?

Answer 1

• Passive –> Spinal column
• Active –> Spinal muscles
• Control –> Neural

Question 2

Describe the load distribution present in the spinal column and IV discs

Answer 2

• 80% through vertebrae and interbody joint

- 20% posterior elements (i.e. the facet joints)

Question 3

What factors may impact the load distribution?

Answer 3

• Position
• Age
• Trauma

Question 4

Parts of the intervertebral disc

Answer 4

• Annulus fibrosis

- Nucleus pulposus

Question 5

Purpose of the annulus fibrosis

Answer 5

• Contain nucleus pulposus

- Provide strength, flexibility, and protection from external forces

Question 6

Describe the fiber orientation of the annulus fibrosis

Answer 6

Concentric rings, alternating in orientation (65 degrees)

Question 7

What is the water content of the nucleus pulposus?

Answer 7

70-90% in younger individuals

Question 8

Purpose of the nucleus pulposus

Answer 8

Shock absorption

Question 9

What happens as a result of disc dehydration?

Answer 9

Increase load to facet joints

Question 10

Describe the process of dehydration and rehydration of the nucleus pulposus throughout the day

Answer 10

• Lose ~25% during the day

- Rehydrate at night

Question 11

What process may lead to bulging in the disc?

Answer 11

Depressurization from age or trauma causes the disc to lose uniform cushioning

Question 12

What positions maximize intradiscal pressure?

Answer 12

Leaning over while holding a weighted object

Question 13

What positions minimize intradiscal pressure?

Answer 13

Laying down or sitting with the back supported

Question 14

What kind of joint is the zygapophyseal (facet) joint?

Answer 14

Synovial plane joint

Question 15

What movements do the facet joints allow in the lumbar spine?

Answer 15

• Mostly flexion, but also restrains excessive flexion to protect the IVD
• Limits rotation

Question 16

What do the facet joints do to block anterior translation of the vertebrae?

Answer 16

• The vertebrae are tilted such that they experience an anterior shear vector
• Facet joints work with the ALL to stabilize these joints and protect the spinal cord

Question 17

What is tropism?

Answer 17

Notable variation in facet plane

Question 18

What role does tropism play in lumbar vertebral stability?

Answer 18

May impair ability to resist forward displacement/rotation

Question 19

What role might fat plugs play in LBP?

Answer 19

• AKA fat pads and meniscoids

- Innervated, so they may be a source of symptoms

Question 20

What are the components of a motion segment in the spine?

Answer 20

• Superior vertebrae
• Intervertebral disc/interbody joint
• Inferior vertebrae

Question 21

How does a facet joint influence movement in the spine?

Answer 21

The orientation of the joint guides movement

Question 22

What is the role of the intervertebral disc in the motion segment?

Answer 22

Absorb/distribute load

Question 23

What is the convention for naming movement in the vertebral motion segment?

Answer 23

• Superior vertebrae on inferior

- Direction of anterior surface of vertebral body

Question 24

What motions are found in Fryette’s Laws?

Answer 24

• Type 1 (neutral)
• Type 2 (non-neutral)
• Type 3

Question 25

Type 1 Mechanics

Answer 25

- Coupled motions in opposite directions | - LF to one side is accompanied by rotation to opposite

Question 26

Type 2 Mechanics

Answer 26

- Coupled motion in same direction | - LF to one side is accompanied by rotation to same side

Question 27

Type 3 Mechanics

Answer 27

Motion in 1 plane reduces available ROM in all remaining planes

Question 28

What happens to the superior vertebra in a lumbar motion segment during lumbar flexion?

Answer 28

- Anterior rotation | - Translates anteriorly

Question 29

What happens anteriorly in a lumbar motion segment during lumbar flexion?

Answer 29

- Compresses anterior disc (annulus) | - Anterior longitudinal ligament laxity

Question 30

What happens posteriorly in a lumbar motion segment during lumbar flexion?

Answer 30

- Inf. articular process of superior vertebra moves superiorly on sup. articular process of inferior vertebra - Facet joints "open" - Separation of spinous processes, tightening posterior ligaments, facet capsules

Question 31

How much movement is allowed in lumbar flexion?

Answer 31

45-55 degrees

Question 32

What happens to the superior vertebra in a lumbar motion segment during lumbar extension?

Answer 32

- Posterior rotation | - Translates posteriorly

Question 33

What happens anteriorly in a lumbar motion segment during lumbar extension?

Answer 33

Tension in anterior disc, ALL, and anterior musculature

Question 34

What happens posteriorly in a lumbar motion segment during lumbar extension?

Answer 34

- Inf. articular process of superior vertebra moves inferior on sup. articular process of inferior vertebra - Facets "close" - Posterior ligaments and facet capsule lax

Question 35

How much movement is allowed in lumbar extension?

Answer 35

15-25 degrees

Question 36

What is the lumbopelvic rhythm?

Answer 36

Coordinated movements b/t lumbar spine and pelvis during flexion/extension

Question 37

What is the lumbopelvic rhythm during flexion?

Answer 37

Lumbar flexion followed by anterior pelvic tilt

Question 38

What is the lumbopelvic rhythm during extension?

Answer 38

Posterior pelvic tilt followed by lumbar extension

Question 39

What happens superiorly during lumbar axial rotation?

Answer 39

- Sup. vertebra rotates around vertical axis | - 5-7 degrees

Question 40

What limits lumbar axial rotation?

Answer 40

Sagittal plane alignment, facet joints, facet separation/approximation, and annulus tension

Question 41

What happens superiorly during lumbar lateral flexion?

Answer 41

- Rotates around AP axis | - Translates laterally along horizontal axis

Question 42

What happens on the side of convexity during lateral flexion?

Answer 42

- Contralateral side - Goes under tension - Inf. articular facet of superior vertebra translates superior to sup. articular facet of inferior vertebra

Question 43

What happens on the side of concavity during lateral flexion?

Answer 43

- Ipsilateeral - Becomes lax - Inf. articular facet of superior vertebra translates inferior to sup. articular facet of inferior vertebra

Question 44

Normal ROM for lumbar lateral flexion

Answer 44

~20 degrees

Question 45

What categories of muscles are found in the lumbar region?

Answer 45

- Intrinsic | - Extrinsic

Question 46

What is the function of the intrinsic muscles?

Answer 46

Precision control due to the high degree of muscle spindles

Question 47

What is the structure of the intrinsic muscles?

Answer 47

They are deep, short muscles

Question 48

List the intrinsic lumbar muscles

Answer 48

- Semispinalis - Multifidus - Rotatores - Interspinalis - Intertransversasrius muscles

Question 49

What is the function of the extrinsic muscles?

Answer 49

- Coarse control of stabilization | - Torque production

Question 50

What is the structure of the extrinsic muscles?

Answer 50

- Superficial | - Span multiple segments

Question 51

List the extrinsic lumbar muscles

Answer 51

- 4 abdominals - Erector spinae - QL - Psoas major - Hip muscles

Question 52

What is the role of the diaphragm and pelvic floor in the lumbar spine?

Answer 52

Maintain IAP for stability

Question 53

What is the role of the neural subsystem?

Answer 53

- Receive input from passive and active subsystems | - Determine requirement for maintaining stability

Question 54

What may impair the effectiveness of the neural subsystem?

Answer 54

- Injury | - Failure to regain control may lead to further injury