Overview of Tissue Injury, Inflammation, and Healing Flashcards
Regions of Stress Strain Curve
- Toe Region - fibers not under stress
- Linear Physiological Range - Elastic Region
- Primary Failure - permanent changes
- Complete failure - tear or break
List mechanisms of tissue injury
- Ischemia
- Infection: Bacterial or Viral
- Immune Reaction
- Mechanical
- Chemical
- Thermal
List the methods for protection against stress in the body
- Crimp
- Viscoelasticity
- Creep & Stress Relaxation
- Stress Response
- Plastic Deformation (not really a protection)
What are the external forces acting on the body
Ground Rxn Force
Gravity
Applied Force through contact
Stress vs Strain
Stress is type of force applied to tissue vs strain is the elongation that occurs due to the stress
T or F: Viscoelastic Tissue has a time dependent response to stress
True
What is the first line of response to stress?
Crimp: takes up the slack in collagen tissues parallel to the direction of the force- approximately 5 degrees of motion
What is the second line of response to stress?
Viscoelasticity - 4% stretch that will return to original state after load
What is the third line of response to stress?
Creep and Stress Relaxation - 3-4% increase in length before failure
What is creep
gradual rearrangement of collagen, proteoglycans, and water molecules in response to a CONSTANT PROLONGED stretch - microfailure is occuring
What is an example of stress relaxation?
Serial Casting - allows for elongation and creep without injury over a time period of 6 weeks
What is hysteresis?
The breaking of chemical bonds within tissue that is directly proportional with plastic deformation
How can we use plastic deformation clinically?
To soften scar tissue via a prolonged stretch
What is the stress response?
Wolff’s law - the body responds to repeated stress in attempt to make itself longer in the long term (collagen and bone)
Why is Wolff’s law important?
WB early on helps the body respond to the demands placed on it - however, it is not always the better answer
What is the most common form of MSK injury?
Mechanical Injury
What can cause mechanical injury?
Tension, Compression, or Shearing forces from direct or indirect trauma
Acute Injury
- what is it
- common symptoms
- time frame
- 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
Subacute Injury
- what is it
- common symptoms
- time frame
- Now in healing phase
- edema and pain decreasing, function improving
- Lasts 5-10 days
Chronic Injury
- what is it
- time frame
- Remodeling is now occurring
- begins 26-34 days after injury and length of duration is highly variable
What is Chronicity?
A persistent inflammatory stage that does not improve after a month
What is an acute on chronic injury?
Acute exacerbation of a chronic injury
List the Stages of Healing and their “percentages” along the timeline
- Hemostasis (occurs w/inflammation stage)
- Inflammation Phase (10%) … overlaps w/
- Proliferation Phase (40%) … overlaps w/
- Maturation Phase (70%)
What are the two phases of hemostasis?
Vasoconstriction (5-10 minutes to create a clot)
Vasodilation (15-30 minutes: breaks down clot and plasma leaks proportional to the extent of injury)
