BIOMED 10/11b Soft Tissue and Bone Mechanics

Question 1

external loads that the body

Answer 1

1. Gravity
2. Wind
3. Friction
4. ***Impact

Question 2

how does tissue deformation result in loads arising within tissue

Answer 2

• deformation to match external force
• meniscus in th eknee
• accommodates external load with internal forces

Question 3

healthy tissue response to load

Answer 3

• deforms as much as it needs to
• goes back to original shape/position after unloading
• load response is tissue dependent

Question 4

what do we need to focus on when doing an examination for a patient?

Answer 4

1. what was the mechanism of injury?
2. what tissue structures might be involved?
3. what are the appropriate treatments for the patient

Question 5

how do we define the mechanism of injury?

Answer 5

• was the injury a trauma or insidious onset?
• what does the MOI tell you about the potential movements and forces that occurred to cause the injury?
• what tissues were susceptible to damage through this MOI?

Question 6

how do we determine the tissue’s response to load?

Answer 6

1. tissue stress
2. tissue strain
3. stress strain diagram

Question 7

what is tissue stress?

Answer 7

• pressure = force/area
• forces resisting the additional pressure added to a tissue
• measure of load or energy that stored within a tissue
• ex: rubber part of a balloon is stress as air is added into it

Question 8

what is tissue strain?

Answer 8

• how much does it stretch out?

- the delta of the stretch

Question 9

stress strain diagram

Answer 9

• y axis = stress
• x axis = strain
• helps estimate the behavior of the tissue
• the linear slope is the stiffness of the tissue
• young’s modulus determines how the tissue deforms in response to certain amounts of loads proportional to stiffness

Question 10

nonlinear base region in the stress/strain diagram

Answer 10

-slack that is inherent to the tissue at rest

Question 11

linear portion in the stress/strain diagram

Answer 11

stiffness of the tissue

-young’s modulus

Question 12

at a high stiffness behavior, what is the young’s modulus?

Answer 12

high

Question 13

at a low stiffness behavior, what is the young’s modulus?

Answer 13

low

Question 14

Truly elastic material

Answer 14

returns back to its original state after load is released

Question 15

Plastic Deformation

Answer 15

After yield point, tissue starts to change permanently

• serial casting
• muscle building
• stretching
• joint mobs

Question 16

do tissues have a fluid like component to their behavior?

Answer 16

Yes, tissues have viscosity

-they have time dependent visco-elastic behaviors

Question 17

at fast loading behaviors, what happens to the tissue?

Answer 17

it breaks fast

Question 18

at slow loading behaviors, what happens to the tissue?

Answer 18

it stretches out

Question 19

what determines how tissues respond to stress?

Answer 19

the organization of the tissue

Question 20

creep in regards to serial casting

Answer 20

• over time, when something is subject to continuous load, it changes
• serial cast puts someone in a cast when they have a contracture
• tissue adapts to the stress from the cast
• it is essentially a prolonged low-load stretch

Question 21

how does tissue deformation occur?

Answer 21

under continuous load

Question 22

how do you evaluate if a tissue is elastic?

Answer 22

• stiffness

- young’s modulus

Question 23

ankle sprain motions

Answer 23

plantar flexion and inversion

very high loading rate

Question 24

in vivo

Answer 24

in human body

Question 25

in silico

Answer 25

sillicon/computer based modelling

Question 26

in vitro

Answer 26

outside of the body/pitri dish

Question 27

as moment increases, what happens to the ACL strain during pivot landing

Answer 27

strain inceases as the moment increases

Question 28

Important factors that impact MSK loads

Answer 28

Loading variables that determine how the tissues respond 1. Loading Magnitude 2. Loading Rate 3. Loading typ

Question 29

Define the significance of the loading magnitude

Answer 29

- High vs low load - Cumulative load: keep increasing the yield capacity; can reach yield much faster because you are cumulatively loading and getting stronger

Question 30

what eventually happens when you have cumulative loading over time?

Answer 30

you may reach the yield point much faster

Question 31

what is the significance of loading rates with MSK loads?

Answer 31

- biological tissues are sensitive to load - when loading occurs at a rate that the object is not built to respond to, the object will break - slower rate = stretching/pulling/plastic deformation - faster rate = injury/tear/ligamentous "explosion"

Question 32

different loading types

Answer 32

1. unloaded 2. tension 3. compression 4. bending 5. shear 6. torsion

Question 33

tension loading

Answer 33

two forces pull on an object in different directions | -lateral ankle sprain => severely tensioned as the foot rotates inward

Question 34

compression loading

Answer 34

forces that push or pull the surfaces of objects together or brings the end of an object closer -humerous is pulled against the glenoid by the deltoid muscle creating a compressive load between the bones

Question 35

Bending Loads

Answer 35

deformation tissue that occurs at right angles to its longitudinal axis - top is bending, bottom is stretching (concave side undergoes compression, convex side undergoes tension) - Coxa vera results in an increased bending load on the neck of the femur (predisposed to fractures)

Question 36

Shear loading

Answer 36

unaligned parallel forces that move on a part of the body in one direction and another part in the opposite direction -delaminated articular cartilage away from acetabular roof (square peg in a round hole)

Question 37

Torsion Loading

Answer 37

twisting force applied to tissue around its longitudinal axis -ACL tear is a torsion load

Question 38

describe process of delamination

Answer 38

think you were pulling up a carpet and pushing under it with your foot from the floor -this pathology results in abnormal shearing at the joint and peels the articular cartilage off of the acetabulum

Question 39

factors that influence a tissue's ability to accept loads

Answer 39

- Age - Disease or trauma - Overuse or Underuse

Question 40

Impact of overuse on the tissue

Answer 40

tissue gets damaged, then it starts to change/repair overtime, but is not able to ever reach equilibrium, then the pt starts loading again, and loading exceeds the tissue's ability to repair itself

Question 41

impact of underuse on the tissue

Answer 41

tissue atrophy | -Wolff's law is unable to function => bone doesn't get stronger because there is no stress to respond to

Question 42

soft tissue genetic disorder that influence collagen

Answer 42

you can have hyperelastic tissue and if you don't have the rebound of tissue, you can be prone to injuries and it will affect tissues that affect breathing