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Biomechanics > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

Function of ligamen st

A

Ligaments contribute to joint stability by limiting excessive movements, and tendons facilitate joint motion by transmitting forces from muscles to bones.
-Ligament = ‘like’ to ‘like’ = ‘bone’ to ‘bone’

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2
Q

Role of Ligaments

A
  • Connect bone to bone
  • Stabilize joints
  • Guide joint motion
  • Prevent excessive motion (act as a static restraint)
  • Contribute to proprioception or position sense
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3
Q

Role of Tendons

A
  • Attach muscle to bone
  • Transmit the tensile load generated by muscles to the bone, to produce
    joint motion
  • Promote stability of the joint * Maintain body posture
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4
Q

Composition of Tendons

A

collagen fibres, water, proteoglycans, and cells.

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5
Q

Collagen function in tendons

A

predominant component of tendons; a strong and flexible protein. Type I collagen comprises approximately 70–80% of the dry weight of a normal tendon

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6
Q

Water function in tendons

A

tendons contain a significant amount of water, contributing to their flexibility & lubrication

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7
Q

Proteoglycans funtion in tendons

A

glycoproteins which help maintain the structural integrity of the tendon. Proteoglycans attract water, contributing to the hydration of the tendon and its resistance to compressive forces

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8
Q

Cells in tendons

A

tenocyes

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9
Q

Primary role of tendon cells

A

to control tendon metabolism and to respond to mechanical loads applied to the tendon

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10
Q

Composition of ligaments

A

primarily composed of collagen, elastin, water, cells, & proteoglycans

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11
Q

Collagen is Ligaments

A

Type 1 collagen (70% of dry weight)

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12
Q

Elastin in ligaments

A

provides elasticity, helps to absorb shock and adapt to joint movements

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13
Q

Cells in ligaments function

A

similar to tenocytes in tendons, ligaments have fibroblasts which
synthesize collagen and help in repair & healing

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14
Q

Mechanically passive meaning

A

only support joints

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15
Q

Ligaments vs. tendons

A

Compared to tendons, ligaments have:
* lower percentage of collagen (ligaments have higher elastin content) * higher percentage of proteoglycans and water
* less organized collagen fibres
* Fibroblasts vs tenocytes

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16
Q

Function of collagen

A

To sustain large tensile loads while allowing for some level of compliance for mechanical deformation

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17
Q

Collagen synthesis is an intricate process that contributes to

A

quality and stability of the collagen molecule

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18
Q

What type of collagen does tendons, ligaments and bone have?

A

Type 1

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19
Q

Where are cross-links formed?

A

Between collagen molecules

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20
Q

Purpose of crosslinks in tissue?

A

Give the tissue strength and give the tissue they compose the ability to function under mechanical stress
In newly-formed collagen, the cross-links are relatively few The cross-links are also easily denatured by heat  unstable

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21
Q

What is the function of a crimp formation

A

biomechanical role relating to the tissues’ loading state, with increased loading resulting in some areas of the ligt/tendon uncrimping, allowing the tissue to elongate without sustaining damage

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22
Q

What would happen if we did not have crimp?

A

The ability to manage the strain at the joint decreases due to the inability to manage high stress

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23
Q

The Vascular supply of tendons & ligaments

A

limited vascularization

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24
Q

How much do the blood vessels in tendons represent?

A

1 - 2%

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25
Q

Where does tendons get their bllod supply from ?

A

vessels of the perimysium

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26
Q

What is the outer layer in ligaments that connect directly to the periosteum of adjacet bones

A

Epiligamnet

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27
Q

Biomechanical properties of ligaments

A

Ligaments are pliant and flexible, allowing natural movement of the bones where they attach, yet strong and inextensible to offer enough resistance to applied forces

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28
Q

Biomechanical properties of tendons

A

Tendons are strong enough to sustain the high tensile forces from muscle contraction, yet flexible enough to angulate around bone surfaces to change the final direction of muscle pull

29
Q

Are tendons and ligaments ELASTIC or VISCOELASTIC materials?

A

Tendons and ligaments are both VISCOELASTIC materials.

30
Q

What are tendons capable of regarding muscle contraction and bone surfaces?

A

Tendons are strong enough to sustain high tensile forces from muscle contraction and flexible enough to angulate around bone surfaces to change the final direction of muscle pull.`

31
Q

Describe the characteristics of ligaments.

A

Ligaments are pliant and flexible, allowing natural movement of bones where they attach, yet strong and inextensible to offer enough resistance to applied forces.

32
Q

What loads do tendons and ligaments chiefly sustain during normal and excessive loading?

A

Both tendons and ligaments sustain chiefly tensile loads during normal and excessive loading.

33
Q

What factors determine the degree of damage in tendon and ligament injuries?

A

The degree of damage is related to the rate of loading as well as the amount of the load.

34
Q

What information does the Load-Elongation curve offer regarding tendon-ligament structure?

A

The Load-Elongation curve offers information about the tensile capacity of a tendon-ligament structure after loading, including stiffness, ultimate load, and ultimate elongation.

35
Q

Describe the regions of the Load-Elongation curve.

A

Toe region: Nonlinear region where tendon fibrils un-crimp.

Linear region:
Physiological upper limit of tendon strain.

Yield and failure region: Tendon stretches beyond its physiological limit, resulting in irreversible plastic deformation and failure.

36
Q

Describe the regions of the Load-Elongation curve.
Toe region:

A

Toe region: Nonlinear region where tendon fibrils un-crimp.

37
Q

Describe the regions of the Load-Elongation curve - Linear region:

A

Linear region:
Physiological upper limit of tendon strain.

38
Q

Describe the regions of the Load-Elongation curve.
Yield and failure region:

A

Tendon stretches beyond its physiological limit, resulting in irreversible plastic deformation and failure.

39
Q

Why does the Load-Elongation curve for Ligamentum Flavum differ from typical curves?

A

Ligamentum Flavum (LF) has a high proportion of elastic fibers, allowing it to elongate significantly before stiffness increases appreciably and abrupt failure occurs.

40
Q

What are the stress-strain differences between tendons and ligaments?

A

Tendons carry higher loads, recruit fibers quickly, and have a smaller toe region, while ligaments recruit fibers gradually, leading to an elongated toe region.

41
Q

What does it mean when we say ligaments and tendons are viscoelastic?

A

Ligaments and tendons being viscoelastic means their mechanical properties change with different rates of loading.

42
Q

How do the mechanical properties of ligaments and tendons change with increased loading rates?

A

With increased loading rates, the linear portion of the stress-strain curve becomes steeper, indicating greater stiffness of the tissue, storing more energy, requiring more force to rupture, and undergoing greater elongation

43
Q

Describe the behavior of tendons at low strain rates.

A

At low strain rates, tendons are more deformable, absorbing and distributing mechanical energy generated during movements. They are less effective in carrying mechanical loads.

44
Q

Explain the behavior of tendons at high strain rates.

A

At high strain rates, tendons become stiffer and less deformable, efficiently transmitting large muscular forces to bone. They are more effective in transmitting large loads.

45
Q

What is stress-relaxation in the context of tendons and ligaments?

A

Stress-relaxation involves structures being stretched to a constant length, allowing stress to vary over time. Initially, stress decreases rapidly then more slowly over time.

46
Q

Define creep-deformation as it pertains to tendons and ligaments.

A

Creep-deformation occurs when structures are subjected to a constant load, resulting in gradual length (deformation) increase over time. Initially, deformation increases relatively quickly then more slowly.

47
Q

How do repetitive loading cycles affect tendons and ligaments?

A

Repetitive loading cycles displace the stress-strain curve to the right along the elongation axis with each cycle, leading to permanent deformation and micro-failure with progressive loading.

48
Q

What are the two general categories of injury mechanisms for ligaments and tendons?

A

Injury mechanisms include high levels of stress/load (e.g., external violent trauma), high rates of strain (e.g., whiplash), or a combination of both.

49
Q

The load-elongation curve for LF is not the typical curve. Why?

A

Has a higher proportion of elastic fibers.

50
Q

How do the viscoelastic properties of tendons and ligaments contribute to their function during dynamic movements

A

The viscoelastic properties of tendons and ligaments allow them to absorb and distribute mechanical energy during dynamic movements, providing support, stability, and flexibility to joints.

51
Q

Explain the concept of stress-relaxation and its significance in the context of injury prevention and rehabilitation for tendons and ligaments.

A

Stress-relaxation involves structures being stretched to a constant length, allowing stress to vary over time. It is significant in injury prevention and rehabilitation as it helps reduce the risk of overloading tissues during prolonged stretches and aids in gradual tissue adaptation to loading, promoting healing and preventing re-injury.

52
Q

Describe a real-world scenario where creep-deformation might occur in tendons or ligaments and its potential implications for injury risk.

A

A real-world scenario of creep-deformation might occur during prolonged sitting or standing positions where tendons or ligaments are subjected to constant load over time. For instance, prolonged sitting with poor posture can result in creep-deformation of spinal ligaments, potentially increasing the risk of back injuries.

53
Q

Discuss the importance of understanding the biomechanical properties of tendons and ligaments in the context of designing rehabilitation programs for sports-related injuries.

A

Understanding the biomechanical properties of tendons and ligaments is crucial for designing effective rehabilitation programs for sports-related injuries. Tailoring rehabilitation exercises to the specific viscoelastic properties of injured tissues can optimize tissue healing, prevent re-injury, and enhance athletes’ return to sport safely and efficiently.

54
Q

How are ligament injuries clinically categorized according to severity?

A

Ligament injuries are categorized into three grades: Grade 1, Grade 2, and Grade 3 sprains based on the level of symptoms and joint stability.

55
Q

What are the symptoms and characteristics of Grade 1 ligament sprains?

A

Grade 1 sprains exhibit negligible symptoms with minor pain and no joint instability. There may be micro-failure of collagen fibers, but no macroscopic disruption to the ligament.

56
Q

Describe Grade 2 ligament sprains.

A

Grade 2 sprains involve severe pain, partial ligament rupture, and some degree of joint instability.

57
Q

What defines a Grade 3 ligament sprain?

A

Grade 3 sprains are characterized by severe pain during the trauma, followed by less pain after the injury. These sprains result in complete joint instability and mostly or total rupture of the ligament.

58
Q

What additional factors contribute to tendon injuries compared to ligament injuries?

A

Tendon injuries are influenced by the force produced by the attached muscle during contraction and the cross-sectional area of both the muscle and tendon.

59
Q

How does the tensile strength of a healthy tendon compare to its muscle?

A

The tensile strength of a healthy tendon may be more than twice that of its muscle.

60
Q

What role does the cross-sectional area of the tendon play in injury risk?

A

The larger the cross-sectional area of the tendon, the greater the loads it can bear.

61
Q

Describe the phases of healing and repair for tendons and ligaments.

A

Healing involves inflammation, proliferation, and remodeling phases, with scar tissue formation. Limited vascularity slows down the process.

62
Q

What are the characteristics of scar tissue formed during healing?

A

Scar tissue has persistent flaws, abnormal extracellular matrix (ECM), reduced diameter and length of collagen fibrils, making it biomechanically inferior to normal tissue.

63
Q

How does maturation affect the mechanical properties of tendons and ligaments?

A

Maturation increases the number and quality of collagen cross-links, resulting in increased tensile strength.

64
Q

What happens to collagen and tissue properties as aging progresses?

A

Collagen reaches a plateau in mechanical properties with aging, followed by a decrease in tensile strength and stiffness.

65
Q

Why is mobilization important for tendon and ligament recovery?

A

Mobilization promotes realignment of collagen fibers, conversion of weaker collagen III to stronger collagen I, and overall tissue recovery.

If you dont use it you lsoe it

66
Q

How do ligaments and tendons respond to changes in mechanical demands?

A

Ligaments and tendons become stiffer and stronger when subjected to increased stress, and weaker and less stiff when stress is reduced.

67
Q

Types of injury mechanisms

A

 High levels of stress/load e.g. external violent trauma
High rates of straine.g. whiplash
 High levels of both stress and strain e.g. ligament injury in contact-collision sport

68
Q

Collagen III

A

Patch up - laid down after injury less quality than Type I

Need the load to fix the fibres and imporve the quality Type ! collagen

Biomechanics (6 decks)

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