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Biomechanics & Kinematics > Tissue > Flashcards

Tissue Flashcards

1
Q

which is more likely to rupture, muscle or tendon? Why?

A

-Muscle b/c tendon tensile strength 2x >muscle
-Tendon loading 5-10%

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2
Q

what is the injury & repair in tendon during the inflammation phase?

A

Cellular Reaction

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3
Q

what is the injury & repair in tendon during proliferation?

A

Collagen Synthesis

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4
Q

what is the injury & repair in tendon during maturation?

A

Remodeling

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5
Q

what does immobilization of tendon do to water content, PG/GAG & strength?

A

Reduces

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6
Q

where do muscle-tendon injuries most commonly occur & from what?

A
  • Myotendinous Junction
  • Due to stretching or combined stretching & contraction
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7
Q

what are age dependent behaviors of muscle tendon & Bone-Ligament-Bone failure under tension?

A

-Pre-epiphyseal closure (failure at epiphysis)
-Post-epiphyseal closure (failure at MTJ)
- Clinically mid substance tears of Bone-Ligament-Bone more common in adults

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8
Q

describe articular cartilage clinically relevant features/

A

-Avascular
-Aneural
-Tissue w/ low metabolic rate

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9
Q

what is articular cartilage designed to withstand?

A

-Rigorous loading w/o failure
- To distribute loads
-To provide low friction surface

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10
Q

describe the fluid compartment of articular cartilage?

A

-Key both structurally & mechanically in hydraulic tissue
-Water content decrease & PG content increased w/ increased depth of tissue

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11
Q

Describe the solid compartment of articular cartilage?

A

-Porous, permeable matrix primarily of type II collagen & PG
-Anisotropic tissue (Heterogenous CT)

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12
Q

what is the visco-elastic response of articular cartilage?

A

-Stress developed in collagen-PG solid matrix
-Frictional drag generated by interstitial fluid flow through matrix
-Greater PG aggregation = increase elastic response & rupture strength
-Aging reduces degree of PG aggregation

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13
Q

describe the mechanical behavior of permeability?

A

-Rate of creep is an indicator of tissue permeability
-Small pores result in low permeability & high friction to flow
-Compression further reduces pore size

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14
Q

what does aging due to structural macromolecules?

A

-Decreased GAG content & shorter chains
- Structural modification may be linked to changes in chondrocyte synthetic function

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15
Q

what is the creep response to compression?

A

-Rapid initial exudation of fluid from articular cartilage
-External compressive load creates creep, resisted by stress developed in collagen-PG solid matrix & frictional drag

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16
Q

what happens after prolonged compression to articular cartilage?

A

-Continued slower exudation until deformation equilibrium reached
-External compressive load ultimately equals stress developed in collagen-PG solid matrix alone

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17
Q

about how long does healthy cartilage take until it ends fluid flow?

A

4-16 hours of constant load

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18
Q

what is the response of stress-relaxation to articular cartilage?

A

-Stress is increased until deformation is reached & then deformation/strain maintained
-Stress decreases under constant strain until equilibrium stress is reached

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19
Q

what is fluid redistribution responsible for?

A

tissue stress relaxation

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20
Q

what does rapid redistribution of load throughout articular cartilage do?

A

-Reduced peak stresses & contributes to articular cartilage resilience

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21
Q

what is the AC lubrication system (Boundary)?

A

-Each load bearing surface is coated w/ lubricin (diarthrodial joints) = 2 surfaces don’t touch one another

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22
Q

when is the boundary ac lubrication system most effective?

A

-At low loads

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23
Q

what is the AC Lubrication system (Fluid)?

A

-Film of fluid interposed b/w 2 joint surfaces

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24
Q

what is adhesive wear?

A

-Osteochondritis dessicans (complete or incomplete separation of a portion of cartilage & bone)

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25
Q

what is abrasive wear?

A

joint mouse irritation

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26
Q

what is fatigue wear?

A

PG washout, aging, DJD

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27
Q

what causes loss of PG matrix?

A

Prolonged immobilization
-Anti-inflammatory drugs
-Trauma
-Infection
-Normal component of aging

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28
Q

true or false: Loss of PG matrix may be reversible dependent upon degree & duration

A

true

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29
Q

what are the early stage of development of OA?

A

-Fraying of collagen bundles in superficial layer
-Rapid progression once fraying has begun b/c of fiber orientation within tissue

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30
Q

describe tissue degeneration in chondromalacia?

A

-Degeneration appears to begin in layers 3 & 4
-Early visualization of pathology is difficut

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31
Q

what should the intensity be in order to facilitate AC growth?

A

-Use pain, edema, effusion as a guide
-Full body weight loading may be excessive

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32
Q

what should the duration and/or frequency be to facilitate AC growth?

A

-High reps (100-1000’s) cyclical loading

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33
Q

what should the mode be to facilitate AC growth?

A

-Attempt to mimic function loading characteristics
-May consider minimizing combinations of shear & compression

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34
Q

what is the gross function of bone?

A

-Protection for internal function
-Rigid levers for attachment of muscles to allow motion
-Harbors hemopoietic tissue for production of blood cells
-Serves as a reservoir for calcium, phosphate, & other ions

35
Q

what are the key features of bone structures?

A

-Highly vascular
-Innervated
-Dynamic CT
-Capable of repair & remodeling

36
Q

what is an osteocyte?

A

mature cells

37
Q

what is an osteoblasts?

A

young cells (growth)

38
Q

what is an osteoclast?

A

phagocytic

39
Q

what is the relationship of osteoblasts & osteoclasts during; aging, disuse, healing & exercise?

A

-Aging : increase clastic (old)
increase blastic (young)
-Disuse: more absorption
-Healing: clastic balance w/ blastic
-Exercise: lay more bone down less clastic

40
Q

what happens when effective applied load is decreased?

A

-Bone deposition decreases
-Disuse atrophy

41
Q

what may you see during casting & NWB status?

A

-Following 8 wks of immobilization
-May see 3 fold decrease in load to failure, stiffness, & energy storing capacity

42
Q

what does plates/screws implanted do?

A

-Reduce stress at fracture site may reduce/slow healing to normal strength
-Fixation site strength may increase

43
Q

which is stiffer & has a steeper slope of stress/strain curve?

A

cortical/compact bone

44
Q

what is cancellous/ Trabecular bones porous structure allow?

A

-Great capacity for energy storage

45
Q

when is bone more brittle?

A

-With age
-More brittle w/ increasing velocity of loading (time dependent if things happen quickly)

46
Q

what type of behavior does bone demonstrate & what does that mean?

A

-Anisotropic
-Strength is greatest in direction in which loading is most common

47
Q

what is the order of direction of loading from strongest to weakest?

A

-Compression
-Longitudinal Tension
-Oblique Tension
-Transverse Loading

48
Q

since cortical bone is stiffer than cancellous what does that mean?

A

-Cortical bone can withstand greater stress but less strain than cancellous bone

49
Q

how much strain can cancellous bone sustain before failing compared to cortical bone?

A

-Cancellous bone (75%)
-Cortical bone (2%)

50
Q

why is bone deposition increased on the side of compression & absorption on side of tension?

A

(-) charge on side of compression & (+) charge on side of tension
-Osteoblasts tend to migrate toward (-) electrode & osteoclasts migrate toward (+) electrode

51
Q

what is the effect of muscle contraction on bone?

A

-Usually oppose antagonist or gravity to counterbalance bending
-Acting independently create bending of bones
-Create tension at tendon-bone junction
-Create tuberoisties/trochanters developmentally
-Pathological may create avulsion fx

52
Q

what does constant compressive loading of bone produce?

A

-Increase endosteal diameter & increase in intracortical porosity

53
Q

what does intermittent loading on bone produce?

A

-Increased bone mass

54
Q

what occurs as a result of torsion on the bone?

A

spiral fractures

55
Q

what is most sensitive to torsion forces?

A

-Epiphyseal plate
-Under torsional load, newly formed bone will grow away from epiphysis in spiral fashion

56
Q

what does a greater area of cross sectional area indicate?

A

-Stiffer & stronger bone

57
Q

what does healing of a fx begin with?

A

large callus

58
Q

what should the intensity be when treating bone?

A

-Loading within tissue structural tolerance
-Move carefully into plastic zone
-Pain free loading

59
Q

what is the duration/frequency when treating bone?

A

-Many reps (cyclical loading)

60
Q

what is the mode when treating bone?

A

attempt to mimic functional loading characteristic

61
Q

what is the mechanical factors that strength depend?

A

-Rotary component of muscle force & length of MA

62
Q

what is the physiological factors that strength depend on?

A

-Length of muscle
-Velocity of contraction
-Fiber orientation
-Cross sectional area
-Fiber type

63
Q

when are type I muscles predominately called?

A

-Stability, postural, tonic muscles

64
Q

when are type ii fibers predominately called?

A

-Mobility
-Non-postural
-Phasic muscles

65
Q

what do epimysium, perimysium, & endomysium surround respectively?

A

-Epi (surround whole muscle)
-Peri (surrounds the the fascicules)
-Endo (surrounds the individual muscle cells)

66
Q

what is the contractile element?

A

contractile proteins

67
Q

what is the parallel elastic element?

A

peri, epi, & endomysium

68
Q

what is series elastic element?

A

tendons

69
Q

what occurs with an isometric contraction?

A

-Contractile element shortens
-Series elastic element lengthens

70
Q

when will the PEC stretch?

A

-Passively pulling on muscle beyond “rest” length & contribute to tension

71
Q

what does muscle force have to do with cross sectional area/

A

-Fiber arrangement is key issue in determining cross sectional area
-Muscle force varies with cross sectional area of the muscle

72
Q

what ages does cross sectional area increase?

A

0-20

73
Q

when does cross sectional area decrease?

A

30+

74
Q

what age does one have maximal strength?

A

20-30

75
Q

is cross sectional area loss reversible?

A

yes, and can be minimized

76
Q

when does max shortening speed occurs?

A

-No resistance to shortening
-No tension is developed in muscles b/c no resistance

77
Q

during concentric what is the relationship b/w shortening speed & tension?

A

as shortening speed decreases , tension increase

78
Q

why is there greater tension generated during isometrics than concentric?

A

speed is 0 so tension generated compared to concentric

79
Q

what is the relationship b/w speed of lengthening & tension in eccentrics?

A

-As speed of lengthening increases, tension increase

80
Q

what happens as the velocity of muscle contraction decreases & eventually become neg?

A

tension produced by muscle increase

81
Q

when is isometric contraction good at strengthening?

A

-Great strengthening but only at joint angle that +/- 10 degrees

82
Q

what is the issue with concentric contraction at strengthening?

A

-Dynamic but velocity-tension relationship often limits strengthening at higher velocites

83
Q

Eccentric is great at strengthening but what is possible issues?

A

-Tissue damage (micro tears) due to potential for large muscle force production

84
Q

what is the limitation of isotonic contraction?

A

-Dynamic contraction
-Intensity limited by capability in weakest part if ROM (typically end range)

Biomechanics & Kinematics (10 decks)

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