BIOMED 10/21a CT Physiology and Response Flashcards
what is a tendon?
parallel collagen fibers that connects msucle to bone
what is a ligament
mostly parallel collagen fibers that connect bone to bone
what are the components of tendons and ligaments?
- cells
- collagen fibers
- type I = tensile stress
- type II = elasticity - fibroblasts to improve the healing process
- enzymatic cross links - help with sliding motion and give strength (tensile)
other important components of tendons and ligaments
- water
- elastin
- proteoglycans/GAGs
- Minor collagen
why is water important to tendons and ligaments?
it allows for tissue elongation
what are proteoglycans/GAGs?
- negatively charged
- attract water
- make tissue pliable
- helps with lubrication of tissues
- gives visco-elasticity
what are the aspects of the stress strain curve?
- slack range
- linear range
- primary failure loss of mechanical properties
- complete failure/ultimate failure point
what is the slack range of the stress/strain curve
ramen noodle, crimped pattern that is starting to stretch out
what is the linear range of the stress/strain curve?
elastic portion of stress strain, when you elongate it returns back to original length, slope defines stiffness/young’s modulus
what is the primary failure loss of mechanical properties?
stress is beyond yield point/elastic realm, tissue won’t go back to the original form
- cross links between collagen fibers, starting to break down
- micro failure between ligaments and tendons
with ____, the _____ changes
injury
threshold
What are the different aspects of viscoelasticity?
- creep
- stress/relaxation
- cyclic loading
what is creep?
constant load within elastic limit
-serial casting
how do you apply creep to clinical practices?
think about necessary total end range time necessary for the patient to see changes
-transient in nature, can help PT gauge and know how much change is possible
what is stress relaxation
constant deformation
-same amount of deformation over a period of time, the load is perceived as elastic
what is a clinical example of stress relaxation?
biceps contraction in a cast, load perceived over a period of time is going to decrease
what is cyclic loading?
loading and unloading tissues follows different patterns
-for repeated cycles, the graph is more reproducible
Clinical example of cyclic loading?
you will be able to reproduce a result after completing the task more vs just 1 time.
sprain vs strain
sprain - ligament
strain - muscle or tendon
grades of injury
Grade I
Grade II
Grade III
Grade I injury
repetitive microtrauma
- may have swelling
- will have pain
- ligamentous stretch
Grade II injury
repetitive microtrauma
- partial tear
- swelling, pain, redness
- lose parallel alignment > reduce ability to generate tensile stress
grade III injury
macro trauma
- injury that leads to break down of continuity of the tissue and the mechanical properties change
- swelling, pain, instability
what are the clinical implications for grade III injuries?
- utilize the physical stress theory to show the difference in tolerance of the issue
- after injury, need to apply lower thresholds
three phases of tissue healing
- acute inflammation (0-5 days)
- repair (3-28 days)
- maturation/remodeling (3 days - 1 year)
what are the main characteristics of acute inflammation
- injury and vasoconstriction (arteriolar)
- vasodilation (edema)
- clot formation
- cellular infiltration
- cytokine production
how do clots form at the site of injury?
prothrombin > thrombin > fibrin > scar tissue gets laid down
what is the purpose of cellular infiltration during acute inflammation?
initiates repair and remodeling phase
what is the overall purpose of acute inflammation?
- removes necrotic tissue
- provides more fluid and nutrients to the site of injury
how is acute inflammation treated?
POLICE
□ Protection - reduce further injury, pain, and muscle spasm
□ Optimal Loading - stress informs tissue what it needs to break down and remodel to
□ Ice - Gate theory of pain (tricking the system to think about another stimulus away from the pain stimulus), vasoconstrict and reduce blood flow
□ Compression - principles: tighter distally
Elevation - help fluid to move back
what are the main factors of repair in the inflammatory response?
- growth factor expression
- new vessel formation
- collagen synthesis exceeds lysis
- increased cross-links (H+ bonding)
- collagen type III gradually replaced and turned into type I
- increased cells, GAGs and water
how do we get growth factor expression during the repair phase of tissue healing?
- produced mainly by activated macrophages and platelets
- -all: proliferation of fibroblasts, collagen synthesis, collagenase secretion to promote turnover of collagen - pro-inflammatory cytokines
- -all: help with proliferation and fibroblast creation, too much of these lead to negative cascades
what does increasing the number of cross-links (H+ bonding) do for tissue strength?
it increases tensile strength
what does the presence of increased cells, GAGs, and water do to inflammation?
provides negatively charged particles that attract water
Thus, allowing the scar to be more pliable
what occurs during the maturation/remodeling phase of inflammation?
3 days - 1 year
- collagen synthesis = lysis
- conversion to type I collagen completed
- more mature cross links (covalent)
- orderly alignment of collagen
- decreasing cellularity and vascularity
what is the significance of collagen synthesis = lysis
there are equal amounts of new collagen being laid down and old collagen being removed
why is it important for tissue to hace more mature corss links?
it is harder to break them down and makes the tissue stronger
how do you change up your treatment style if you know that your patient is in the repair phase of inflammation?
Alter the Level of activity - open chain with no load, isometrics, distal on proximal stability and strength
how do you alter your treatment style if you know that your patient is in the maturation/remodeling phase of inflammation?
Performance based progression!
- Initially with grade I and grade II injury, you have to teach the patient to step back
- Think about progressive reloading
- How do you know if you’ve loaded the tissue too much?
- Sx come back
- Motion decreases
- Swelling Increases - Think about long term prevention
connective tissue response to loading and immobilization
- Growth Factor Pathways
- When you apply stresses to tissue, growth factors are relased and communicate with the nucleus
- GFs bind to receptors and signal tranduction pathway
- That produces more collagen - Stress activated Channels
- Play a role in cytoplasmic transduction signals to produce more collagen and fibroblasts - Complex Running from ECM
- ECM communicates through nucleus through integrins that live on cell membrane
- Integrins and actin filaments tell the nucleus to generate more collagen and fibroblasts to generate more tensile strength
response to loading in normal connective tissue without trauma
- Consistent, prolonged exercise
- Initiates a low-level inflammatory response (acutely)
- Upregulates collagenase
- Upregulates type I collagen synthesis (acutely and chronic)
- –>Increase net type I collagen synthesis
response to immobilization with normal connective tissue?
- decreased collagen biosynthesis
- decrease enzyme activities
- decrease mRNA for type I and III collagen
- stretch sensitive - increased collagen degradation
- Increased expressionofmatrixmetalloproteinases (MMP’s)
what is an MMP
too much causes more break down than needed. Don’t want over-expression of MMPs
what happens during immobilization of healing CT?
- biochemical changes
- morphologic changes
- biomechanical changes
what are the biochemical changes during immobilization of healing CT?
- Decreased collagen
- Decreased collagen synthesis
- Increased collagen lysis - Increased weak cross-links (decreased tensile strength)
- Decreased GAG, HA, Water Content
what are the morphologic chagnes during immobilization of healing tissue?
- Adhesions
- Contractures
- Less orderly arrangement of collagen fibers
what are the biomechanical changes during immobilization of healing tissue?
- Decreased tissue stiffness (elastic modulus)
- Due to structural changes:
- Decreased ability to withstand forces and biomechanical changes
- Stiffness is Lower - Decreased load to failure (creep)
-Due to structural changes, it has a decreased ability to withstand forces and biomechanical changes
»>This makes the tissue more pliable to improve the tensile strength of the tissue
-Creep for scar tissue is higher than for normal tissue
what happens to collagen in healing immobilized tissue vs normal tissue?
- In scar, the collagen is smaller
- In normal, there is more variability in the collagen fibers
- In normal, there are more gaps
- In scar, there are less gaps, but there are scar defects which have blood vessels entering
what are the steps for remobilization of healing CT
- biochemical
- morphologic
- biomechanical
what are the steps in biochemical remobilization of healing CT?
§ Increased secretion of growth factors, collagen synthesis, ECM proteins, and PGs □ TGF-Beta □ PDGF □ bFGF □ IL-6 □ IL-1 □ IGF-I 3 groups of rats: sham control, ambulatory (free cage activity), unloaded (suspended healing)
what are the morphologic factors of rembolization of healing CT?
- Controls (tissue integrity was the same)
□ 3 weeks - increased cellularity
□ 7 weeks - parallel appearance - Ambulatory
□ 3 weeks - increased cellularity, more than the control
□ 7 weeks - starting to look like the control, but still not as organized - Hind Limb Unloaded
□ 3 weeks - disorganized re-grouping of collagen fibers and BVs
□ 7 weeks - defects are less, no parallel appearance
what are the biomechanical factors contributing to remobilization of healing tissue?
- Ultimate stress is much lower for those pose injury vs non-injured
- Stiffness of the tissue has really decreased as well (specific to tendon and ligament, not the joint!)
