Tissue Biomechanics Flashcards

1
Q

What effect do mechanical forces have on tissues?

A

Important for:
Development (of tissue and damage/disease)
Maintenance
Remodeling

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2
Q

What is the definition of tissue biomechanics?

A

Study of how different parts of the human body react to external forces

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3
Q

What is the definition of tension?

A

When a structure is stretched longitudinally

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4
Q

What is the definition of compression?

A

When a load produces forces that push the material together

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5
Q

What is the definition of shear?

A

Forces acting parallel to each other in opposite directions

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6
Q

What is the definition of torsion?

A

Forces twisting/rotating in opposite directions about the long axis

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7
Q

What is the definition of bending?

A

Combination of tensile and compressive loads

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8
Q

What kind of a force is tension?

A

Stretching or pulling force

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9
Q

What are the tension elements of the body?

A

Soft tissues (fascia, muscles, ligaments, and connective tissue)

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10
Q

When do tensile forces occur in the intervertebral disc?

A

During rotational movements

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11
Q

What part of the intervertebral disc tends to bear the tensile loads?

A

Annular fibers

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12
Q

What is the compressive force continually being transmitted to the vertebral bodies and intervertebral discs of the spine?

A

Gravity

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13
Q

How does the structure deform during a shear injury?

A

Internally in an angular manner

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14
Q

What type of bone is most at risk for a fracture?

A

Cancellous bone (ex. femoral condyles and tibial plateaus)

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15
Q

What spinal structures are able to resist shear forces?

A

Facet joins and fibers of the annulus fibrosus

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16
Q

What areas of the spine are at risk for damage by excessive rotational force (torsion)?

A

Facet joint
Pars interarticularis
Capsule
Annulus

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17
Q

What kind of long bone fracture would be an example of a torsional load failure?

A

Spiral fracture

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18
Q

Long bone fractures frequently occur through what mechanism?

A

Bending (combination of compression and tension)

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19
Q

What are the three common tissue responses to mechanical loading?

A

Deformation
Growth and remodeling
Failure

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20
Q

What is the definition of deformation?

A

Local shape change under the effect of applied forces

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21
Q

What kind of deformation occurs when an object is subjected to external forces but is in static equilibrium?

A

Some local shape change within the object

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22
Q

What four things does the extent of deformation depend on?

A

Material properties
Size and shape of object
Environmental factors (ex. heat or humidity)
Force

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23
Q

What is the difference between the measurement of a stress or strain?

A

Stress - measure of the intensity of the force

Strain - measure of the degree of deformation

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24
Q

What is the definition of “stress” in terms of deformation?

A

The external force acting to deform the material

25
Q

What is the definition of “strain” in terms of deformation?

A

Magnitude of deformation as a result of the applied stress/loading

26
Q

What determines the strength of a tissue?

A

The maximum stress a tissue can withstand without permanent deformation

27
Q

What kind of tissue strength is considered the level of stress at the yield point of a material beyond which permanent deformation will occur?

A

Yield strength

28
Q

What kind of tissue strength is considered the maximal stress that a material can withstand prior to the initiation of failure?

A

Ultimate strength

29
Q

What kind of tissue strength is considered the stress at which the material actually breaks or ruptures?

A

Failure strength

30
Q

What is the definition of ductility?

A

Force per unit area required to deform a material, represented by the steepness (slope) of the stress/strain curve

31
Q

What kind of tissues fail at low stress by can withstand a large strain (ductile/pliant or brittle/stiff)?

A

Ductile (pliant)

32
Q

What kind of tissues can withstand high stress but fail with relatively low strain (ductile/pliant or brittle/stiff)?

A

Brittle (stiff)

33
Q

How can the amount of “toughness” of a tissue be estimated?

A

Observing the total area under the stress/strain curve

34
Q

What is the definition of “toughness” when referring to tissue?

A

The total energy required to cause material failure

35
Q

What type of tissue, (bone, tendon, or ligament), is more brittle but very strong with low overall toughness?

A

Bone

36
Q

What type of tissue, (bone, tendon, or ligament), is moderate for both strength and ductility with high overall toughness?

A

Tendon

37
Q

What type of tissue, (bone, tendon, or ligament), is more pliant but has lower strength with moderate overall toughness?

A

Ligament

38
Q

What is the definition of elasticity?

A

Ability to return to the original shape when the load is removed

39
Q

What is the yield point of elasticity?

A

Point at which the applied stress can lead to permanent deformation

40
Q

In terms of elasticity, what is the nonlinear response of the material after the yield point?

A

Plastic region

41
Q

In terms of elasticity, once reaching the plastic region, will some degree of deformation persist after the removal of the stress?

A

Yes, some

42
Q

What is the term for the property of materials to resist loads that produce shear or tensile forces?

A

Viscosity

43
Q

Is the linear deformation produced by tensile stress alleviated even after the stress is removed?

A

No; it remains

44
Q

What is another name for viscous stretch?

A

Plastic (putty-like behavior)

45
Q

Are most soft tissues viscous or elastic?

A

BOTH (viscoelastic)

46
Q

What affects the viscoelastic property of a material?

A

Both the rate of loading and the length of time that it is subjected to a constant load

47
Q

What is the definition of creep?

A

Continued deformation over time when CONSTANTLY loaded

48
Q

What is the cause of the creep in tissues?

A

Expulsion of water

49
Q

What is the definition of relaxation in terms of viscoelastic tissue?

A

The corresponding eventual decrease in stress that will occur as fluid is no longer exuded

50
Q

What is the definition of hysteresis?

A

Energy loss exhibited by viscoelastic materials when they are subjected to loading and unloading cycles

51
Q

What effect does load size have on hysteresis?

A

Increased load = increased hysteresis

52
Q

What happens to hysteresis levels when a load is applied a second time?

A

Decreases (less capacity to absorb the shock energy)

53
Q

What is the “toe region” of a tissue?

A

Its normal range of motion

54
Q

When does micro-failure of a tissue occur?

A

After taking out the slack

55
Q

What kind of sprain is an example of a micro-failure?

A

Grade One

56
Q

At the micro-failure stage, is a tissue still elastic?

A

Yes

57
Q

What kind of stress is present when plastic deformation starts?

A

Yield stress

58
Q

What kind of sprain is known as a macro-failure where the tissue undergoes plastic deformation?

A

Grade Two

59
Q

What kind of sprain occurs when a tissue ruptures?

A

Grade Three