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Tissue Biomechanics > Ligaments And Tendons > Flashcards

Ligaments And Tendons Flashcards

1
Q

A bone-ligament or bone-tendon complex.

A

Enthesis

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2
Q

What is the overall function of an enthesis?

A

The progressive change from ligament/tendon to
bone protects against injury by allowing
better stress absorption and
transmission

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3
Q

What are the structural (mechanical) jobs of ligaments?

A
  • Stabilize joints (at end range)
  • Guide joint motion
  • Prevent excessive motion
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4
Q

What are the functional (sensory) jobs of ligaments?

A
  • detect rate and vectors of load via mechanoreceptors

- detect tissue damage via nociceptors

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5
Q

What are the structural (mechanical) jobs of tendons?

A
  • 99.9% collagen for strength, stiffness, ductility

- Parallel arrangement to transmit tensile strength

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6
Q

What are the functional (sensory) jobs of tendons?

A
  • Attach muscle to bone

- transmit tensile loads from muscle to bone for the purpose of joint motion and stabilization

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7
Q

The quality whereby a material exhibits large plastic deformation before FAILURE.
FAILURE > 5% total elongation of
material

A

Ductility

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8
Q

The quality whereby a material exhibits little plastic deformation before FAILURE.
FAILURE < 5% total elongation of
material

A

Brittleness

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9
Q

What is a deformation of a viscoelastic material
with time, when the load remains constant that results in a gradual rearrangement of collagen,
proteoglycans and water molecules?

A

Creep

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10
Q

What is the creep-relaxation phenomenon?

A

The deformation of viscoelastic material over time due to constant load. Over time, the tissue relaxes into its new length to decreases load over time. Results from stretching of tissue.

Ex: force needed to hold down a branch over time will decrease.

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11
Q

What are short term effects of a sprain?

A
  • temporary changes like hysteresis and slow return to baseline length
  • pain
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12
Q

What are long term effects of a sprain?

A
  • hypermobolity and instability
  • degeneration of joints
  • susceptibility to further injury
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13
Q

Strength of a ligament depends on what factors?

A
  • fiber composition (more collagen = stronger)
  • size and shape of fibers (increased fiber diameter and # of fibers = increased strength)
  • orientation of fibers (fibers parallel to direction of tension = more strength)
  • speed of loading (strength of tissue increases with speed of loading)
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14
Q

Of tendons, ligament and skin, rate them in order from strongest to weakest

A

Tendons > ligaments > skin

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15
Q

What types of injury can occur to ligaments?

A
  • sprain (% deformation has reached the plastic range and results in permanent deformation)
  • tear (% deformation exceeds plastic range/maximum stretch and tissue fails, resulting in lose of original form and energy)
    NOTE: microfailure of collagen can occur in the elastic range and is the beginning of a grade 1 sprain but does not actually sprain until plastic region
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16
Q

Progressive failure of collagen fibers with no change in gross appearance is seen in what type of ligament damage?

A

Grade 1 sprain

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17
Q

Tensile failure of collagen fibers and shear failure between fibers is seen is what type of ligament injury?

A

Grade 2 sprain - gross failure of ultimate loading. This injury results in:

  • partial rupture
  • joint instability
  • 50% decrease in strength
  • severe pain and swelling
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18
Q

Complete rupture, instability and dislocation is seen in what type of ligament injury?

A

Grade 3 sprain - complete failure with tissue loading that is characterized by severe pain initially but followed by little to no pain.

19
Q

How does loading speed affect injury?

A

Both the magnitude of the load and the rate that the load is applied affects injury. The strength of tissue (both bone and ligament) increases with speed but the bone increases more than the strength of the ligament, therefore the ligament fails first

20
Q

What are the characteristics of physiological loading of tendons and ligaments?

A
  • Under normal physiological conditions, the tensile load (stress) is only about 1/3 of its strength capacity.
  • But high loads (trauma) or repetitive loads or sustained loads can result in injury.
21
Q

What are the characteristics of the ligamentum flavum?

A
  • composed of 2/3 elastic fibers
  • functions to absorb shock and protect nerve roots and spinal cord
  • elongation reaches 50% before stiffness significantly increased
  • failure is at 70% elongation
22
Q

A high loading speed to the ACL will result in what type of damage?

A
  • ligament tears 2/3s of the time

- bone allusion in 1/3s of the time

23
Q

A low loading speed (1 minute) to the ACL will result in what type of damage?

A
  • bone avulsion
24
Q

Why is exercise needed during ligament remodeling?

A

Recovering ligament/tendon becomes:

  • stronger and stiffer with increased stress
  • weaker and less stiff with decreased stress

Strenuous exercise for a year after injury can increased the maximum load to failure, increase stiffness and increase the energy storage capacity of the tissue. This will result in tissue more resistant to re injury

25
Q

What are the effects of immobilization after an injury?

A
  • decreased maximum load to failure by 40%
  • decreased energy storage capacity by 30%
  • loss of stiffness

ALL this means that it is more likely to reinjury with less load

26
Q

How does age affect tendons and ligaments?

A
  • loss of strength
  • loss of stiffness
  • loss of energy storage capacity

All because collagen fibrils are getting smaller

27
Q

How does pregnancy affect tendons and ligaments?

A
  • laxity of ligaments and
    tendons in the pubic area
  • stiffness and tensile strength decrease
28
Q

How do steroids affect tendons and ligaments?

A
  • inhibit collagen synthesis

- prevents early strenuous rehab

29
Q

A change in length in response to a load?

A

Deformation

30
Q

The load divided by the dross sectional area (Newtons/meter)?

A

Stress

Example

31
Q

The amount of force on an object?

A

Load

32
Q

What are the three most basic types of load?

A
  • tensile
  • compressive
  • shear
33
Q

The amount of deformation: the change in length of tissue divided by the original length

A

Strain

34
Q

The ability of a substance or material to return to its original form following the removal of a deforming load.

A

Elasticity

35
Q

What characteristics will an elastic material have?

A
  • Returns to its original form
  • No loss of energy in one cycle of
    loading or unloading
36
Q

The property of a material to permanently deform and lose energy if loaded beyond its elastic range.

A

Plasticity

Ex: tearing a ligament, leading to hypermobility

37
Q

A measure of resistance offered to external loads by a material as it deforms.

A

Stiffness

stiffness = stress/load divided by strain/deformation

38
Q

A measure of compliance offered to external loads by a material as it deforms.

A

Flexibility

Flexibility = strain/deformation divided by stress/load

39
Q

A stiffer material needs _____ stress to deform

A

More

40
Q

A flexible material needs ______ stress to deform.

A

Less

41
Q

Loss of energy during a loading cycle, despite returning to its original form. It will lose elastic energy and therefor return to original form at a different rate than it was deformed

A

Hysteresis

42
Q

The process of plastic deformation or failure of a material from repeated loading.
Ex: Bending a paper clip repeatedly until failure.

A

Fatigue

43
Q

Resistance to speed: The faster the loading, the greater the load
necessary to deform an object a given amount.

A

Damping

44
Q

How does hysteresis occur with sitting?

A
  • After 20-30 minutes of sitting, creep and hysteresis results.
  • the loss of energy during the loading cycle and delayed return to original length, causes the tissue to no longer act as effective shock absorbers for 1-2 hours and during this time your spine is more unstable and susceptible to injury

Tissue Biomechanics (5 decks)

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