Overview of Tissue Injury, Inflammation, and Healing

Question 1

Regions of Stress Strain Curve

Answer 1

1. Toe Region - fibers not under stress
2. Linear Physiological Range - Elastic Region
3. Primary Failure - permanent changes
4. Complete failure - tear or break

Question 2

List mechanisms of tissue injury

Answer 2

• Ischemia
• Infection: Bacterial or Viral
• Immune Reaction
• Mechanical
• Chemical
• Thermal

Question 3

List the methods for protection against stress in the body

Answer 3

• Crimp
• Viscoelasticity
• Creep & Stress Relaxation
• Stress Response
• Plastic Deformation (not really a protection)

Question 4

What are the external forces acting on the body

Answer 4

Ground Rxn Force
Gravity
Applied Force through contact

Question 5

Stress vs Strain

Answer 5

Stress is type of force applied to tissue vs strain is the elongation that occurs due to the stress

Question 6

T or F: Viscoelastic Tissue has a time dependent response to stress

Answer 6

True

Question 7

What is the first line of response to stress?

Answer 7

Crimp: takes up the slack in collagen tissues parallel to the direction of the force- approximately 5 degrees of motion

Question 8

What is the second line of response to stress?

Answer 8

Viscoelasticity - 4% stretch that will return to original state after load

Question 9

What is the third line of response to stress?

Answer 9

Creep and Stress Relaxation - 3-4% increase in length before failure

Question 10

What is creep

Answer 10

gradual rearrangement of collagen, proteoglycans, and water molecules in response to a CONSTANT PROLONGED stretch - microfailure is occuring

Question 11

What is an example of stress relaxation?

Answer 11

Serial Casting - allows for elongation and creep without injury over a time period of 6 weeks

Question 12

What is hysteresis?

Answer 12

The breaking of chemical bonds within tissue that is directly proportional with plastic deformation

Question 13

How can we use plastic deformation clinically?

Answer 13

To soften scar tissue via a prolonged stretch

Question 14

What is the stress response?

Answer 14

Wolff’s law - the body responds to repeated stress in attempt to make itself longer in the long term (collagen and bone)

Question 15

Why is Wolff’s law important?

Answer 15

WB early on helps the body respond to the demands placed on it - however, it is not always the better answer

Question 16

What is the most common form of MSK injury?

Answer 16

Mechanical Injury

Question 17

What can cause mechanical injury?

Answer 17

Tension, Compression, or Shearing forces from direct or indirect trauma

Question 18

Acute Injury

• what is it
• common symptoms
• time frame

Answer 18

• Sudden tissue disruption w/symptoms manifesting immediately or greater than 8 hours after the event
• mm spasm, deceased ROM, functional impairment
• lasts 7-10 days

Question 19

Subacute Injury

• what is it
• common symptoms
• time frame

Answer 19

• Now in healing phase
• edema and pain decreasing, function improving
• Lasts 5-10 days

Question 20

Chronic Injury

• what is it
• time frame

Answer 20

• Remodeling is now occurring

- begins 26-34 days after injury and length of duration is highly variable

Question 21

What is Chronicity?

Answer 21

A persistent inflammatory stage that does not improve after a month

Question 22

What is an acute on chronic injury?

Answer 22

Acute exacerbation of a chronic injury

Question 23

List the Stages of Healing and their “percentages” along the timeline

Answer 23

1. Hemostasis (occurs w/inflammation stage)
2. Inflammation Phase (10%) … overlaps w/
3. Proliferation Phase (40%) … overlaps w/
4. Maturation Phase (70%)

Question 24

What are the two phases of hemostasis?

Answer 24

Vasoconstriction (5-10 minutes to create a clot)

Vasodilation (15-30 minutes: breaks down clot and plasma leaks proportional to the extent of injury)

Question 25

Goals of the Inflammatory Process

Answer 25

• Limit blood loss
• get rid of debris (phago and pinocytosis)
• Prevent infection
• Promotes tissue repair via capillary regrowth

Question 26

Cardinal s/s of inflammation

Answer 26

• Rubor: redness
• Tumor: swelling
• Calor: heat
• Dolor: pain
• LOF: loss of function

Question 27

When do fibroblasts being producing collagen?

Answer 27

In the inflammatory phase

Question 28

What is occurring in the proliferation phase?

Answer 28

Type III collagen being produced in a random fashion by fibroblasts that are gradually turned into type I collagen

Question 29

What are the two phases of the proliferation stage

Answer 29

Granulation - deliver nutrients, gas exchange, activate collagen production and deposition
Fibroplasia - fibroblasts turn to specific tissue type

Question 30

What occurs in the maturation phase?

Answer 30

• Collagen realignment and decrease in wound size

- lasts 3 weeks to 12-18 months

Question 31

Immobilization effects after 2 weeks

Answer 31

• Thickening of capsule and ligaments w/adhesion formation occurring to contribute to the adaptive mm shortening
• dec. [GAG] and in water content

Question 32

What should treatment focus on in 2 weeks of immobilization?

Answer 32

PROM to oppose adhesion formations

Question 33

Immobilization effects after 4 weeks

Answer 33

• decrease in nourishment in joint and structure

- decrease in ligament stiffness –> dec. strength and elasticity

Question 34

What should treatment focus on in 4 weeks of immobilization?

Answer 34

• regain accessory motion by stretching specific shortened structures

Question 35

Immobilization effects after 6 weeks

Answer 35

Joint mobility significantly limited, thickening continues –> loss of 50% of strength

Question 36

T or F: Immobilization can decrease number of sarcomeres and rate of protein synthesis

Answer 36

True