Structure Of Ligaments And Tendons Flashcards

1
Q

What is the tensile strength of tendons?

A

Up to 1260kg/cm2

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2
Q

What do the crimping regions of ligaments allow? (Reference?)

A

Allow stretch
Resist against injury
(Frank, 2004)

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3
Q

Describe a collagen molecule

A

Smallest discernible unit of tendons and ligaments
Triple helix molecule
~1nm long
Mechanically resistant due to cross-linking
Multiple types

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4
Q

What do collagen molecules bind into and what length are they?

A

Fibrils

~100nm long

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5
Q

Collagen fibrils can be heterogenous in composition, give an example of what this means?

A

Type I fibrils have collagen types I, III, IV and IX

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6
Q

What constitutes a collagen fibre?

A

Collagen fibrils plus fibroblast cells producing ECM

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7
Q

How long is a collagen fibre?

A

~1-20microm

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8
Q

What are collagen fibres bundled into?

A

Subfascicles (primary bundle)
Fascicles (secondary bundle)
Tertiary bundles

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9
Q

How does crossing-over in tertiary collagen bundles affect the structure?

A

Results in higher tensile strength

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10
Q

What loose connective tissue structure surrounds each collagen fibre bundle (fascicles)?

A

Endotenon

Endoligament

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11
Q

What connective tissue structure surrounds groups of fascicles?

A

Epitenon

Epiligament

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12
Q

What cells are ligaments rich in?

A

Proprioceptive

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13
Q

What is the reference for the collagen organisation of tendons and ligaments?

A

Wang, 2006

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14
Q

In what orientations do the fibrils of elongated fibroblast cells run in in tendons and ligaments?

A

Longitudinally
Transversely
Horizontally

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15
Q

In what orientation do bundles of collagen fibres run?

A

Longitudinally

But not always parallel = Crossing over

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16
Q

How do the orientation of collagen fibrils and bundles affect function? (Reference?)

A

Serves to buffer against forces acting on these tissues from different directions
(Kannus, 2000)

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17
Q

How can the structure of tendons under higher strains be described?

A

Thicker
Shorter
Bigger and denser packed bundles

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18
Q

How can the structure of tendons under low strains be described and how does this affect the movements they are parts of?

A

Longer
Thinner
Used in more precise movements

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19
Q

What is an epitenon/epiligament?

A

Loose connective tissue sac acting as a supporting sheath and fill with synovial fluid

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20
Q

What is paratenon? What is its function?

A
The very outer layer
Loose mesenchyme which carries:
- Blood vessels
- Lymphatics
- Nerves
Also assists in sliding
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21
Q

How much water is in the ECM of ligaments and how much in tendons?

A

60-80% water in ECM of both

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22
Q

How can the elasticity of both ligaments and tendons be described?

A
Ligaments = Stretchy
Tendons = Rigid
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23
Q

What is the level of organisation of collagen fibres in both ligaments and tendons?

A
Ligaments = Less organised fibres
Tendons = Highly organised fibres
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24
Q

What type(s) of collagen are present in both ligaments and tendons? (Reference?)

A
Ligaments = Type I most common but also Type III (Frank, 2004)
Tendons = Type I collagen chiefly (Kannus, 2000)
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25
Q

What is the DNA content of ligaments and tendons? What does this affect? (Reference?)

A

Ligaments = Higher DNA content so higher metabolic function
Tendons = Lower DNA content
(Amiel et al., 1984)

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26
Q

How much elastin is present in ligaments and tendons?

A
Ligaments = ~10% (up to 80% in nuchal ligament)
Tendons = ~2%
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27
Q

What is the peptidoglycan content of the ECM in ligaments and tendons?

A
Ligaments = Higher
Tendons = Lower
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28
Q

In what ligaments is the elastin level lower than the average level? What percentage is elastin present at in these?

A

Spinal ligaments = ~7% elastin (vs 10%)

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29
Q

When ligaments regenerate, what percentage of their original strain resistance do they retain and why?

A

10-20% original strain resistance

Cross-linking causes scarring

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30
Q

Tendons and ligaments are viscoelastic, what does this mean?

A

When a force is applied, they stretch to allow movement and will return to original structure

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31
Q

Why are tendons strong?

A

To withstand forces during muscle contraction

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32
Q

Why are tendons flexible?

A

To allow:

  • Movement around bone
  • Movement under retinacula
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33
Q

Why are ligaments flexible?

A

Offer resistance to movement

Hold joint together during movement (MCL and LCL)

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34
Q

What is the reference for the mechanics (strength and flexibility) of tendons and ligaments?

A

Nordin and Frankel, 2001

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35
Q

What are stress and strain?

A

Stress is a measure of force

Strain is the response of a system when stressed

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36
Q

What is strain a ratio of?

A

Change in length over initial length

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37
Q

What is the unit for stress?

A

N/m2 or Pa

Stress = Force/Area

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38
Q

Describe normal stress

A

Intensity of distributed forces are uniform
Dimensions change but not shape
Compressive or Tensile force
Symbol is delta

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39
Q

Describe shear stress

A

Equal and opposite force applied to opposite force (e.g. Book on table)
Changes shape of object but not dimensions
Symbol is tau

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40
Q

What is strain a measure of?

A

Deformation of a material

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41
Q

What is normal strain?

A
Ratio of amount of elongation to original length
Normal strain (E) = Change in length/Original length
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42
Q

If there is an increase in length, how is strain described?

A

Strain is tensile and positive

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43
Q

If there is a decrease in length, how is strain described?

A

Strain is compressive and negative

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44
Q

What is shear strain?

A
The ratio between horizontal displacement (d) and height (h)
Shear strain (gamma) = d/h
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45
Q

What is point P on the stress-strain curve?

A

Proportionality limit = Up to this point, stress is proportional to strain (Hooke’s law)

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46
Q

What is point e on the stress-strain curve?

A

Elastic limit = Point of stress at which all strain will totally disappear if force removed

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47
Q

What is point y on the stress-strain curve?

A

Yield point = Smallest amount of stress that will cause permanent plastic deformation

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48
Q

What is point u on the stress-strain curve?

A

Highest stress point

49
Q

What is point r on the stress-strain curve?

A

Rupture

50
Q

What is stress relaxation?

A

When a material is held at a constant strain, the stress required to do so decreases over time

51
Q

What is creep?

A

When a material is held at a constant stress, the strain increases over time

52
Q

What is the reference for stress relaxation and creep?

A

Matucci, 2012

53
Q

How is a load and elongation curve recorded for a tendon or ligament?

A

Tissue has a tensile force applied to cause a constant rate of elongation and this is applied until the tissue ruptures

54
Q

What is the first part of a load and elongation curve?

A

Toe/Primary region = Tissue elongated with a small increase in load as ‘wavy’ collagen straightens out

55
Q

What is the second part of a load and elongation curve?

A

Linear/Secondary region = Fibres straight. Stiffness increases and deformation begins

56
Q

What is the third part of a load and elongation curve?

A

End of secondary region = Load at this point is the limiting load (Plim). Progressive collagen failure after this point

57
Q

What is the fourth part of a load and elongation curve?

A

Max load = (Pmax). Ultimate tensile strength. Complete failure is rapid

58
Q

What is the reference for the load and elongation curve?

A

Nordin and Frankel, 2001

59
Q

How do the ligaments affect the vertebral column and its contents?

A

Range of movement limited by resistance of ligaments

Ligaments provide support and protection for Spinal Cord while maintaining mobility

60
Q

Where does the anterior longitudinal ligament run from and to?

A

From pelvic surface of sacrum
To:
- Anterior tubercle of C1
- Occiput

61
Q

Describe the layers of the anterior longitudinal ligament?

A
Superficial = Longest fibres (span 3-5 vertebrae)
Intermediate = Span 2-3 vertebrae
Deep = Extend over 1 vertebral body and blend with periosteum
62
Q

What does the superior part of the anterior longitudinal ligament blend with?

A

Anterior atlantoaxial ligament

Atlanta-occipital ligament

63
Q

How thick is the anterior longitudinal ligament and how well arranged are the collagen bundles?

A

1.3-2.5mm thick

Well arranged

64
Q

What are the references for the structure of the anterior longitudinal ligament?

A

Moore et al., 2010

Florian-Rodriguez et al., 2017

65
Q

What are the functions of the anterior longitudinal ligament?

A

Maintain vertebral column stability between individual vertebral joints
Restrains movement of each vertebral segment - limiting extension

66
Q

Why is the anterior longitudinal ligament very stiff?

A

Due to high % of collagen fibres

67
Q

What is the reference for the functions of the anterior longitudinal ligament?

A

Butt et al., 2015

68
Q

True or false - The ALL is the strongest and longest vertebral ligament?

A

True

69
Q

Why is the posterior longitudinal ligament narrower than the ALL?

A

Lies within vertebral canal on posterior aspect of vertebral bodies

70
Q

What is the structure of the PLL in the cervical and upper thoracic regions?

A

Uniform

Broad (10-15mm)

71
Q

What is the appearance of the PLL in the lower thoracic and lumbar regions?

A

Saw-toothed

72
Q

What happens to the PLL as it descends over the lower thoracic and lumbar vertebral bodies?

A

Narrows as vertebral bodies increase in size

73
Q

How do the collagen fibres in the PLL compare to those in the ALL?

A

More compact than in ALL

74
Q

What are the references for the structure of the PLL?

A

Moore et al., 2010

Butt et al., 2015

75
Q

What are the functions of the PLL?

A

Prevents separation of posterior aspects of VBs - limiting Flexion
Avoids posterior IV disc herniation

76
Q

How much stronger/weaker is the PLL than the ALL? What forces can the PLL withstand?

A

2x weaker than ALL
Can withstand:
- 70N in thoracic regions
- 50N in cervical and lumbar regions

77
Q

What are the references for the functions of the PLL?

A

Butt et al., 015

Tubbs et al., 2007

78
Q

What is the structure of the ligamenta flava?

A

Connect adjacent laminae
Thin and broad superiorly
Thickens towards lumbar region
Higher % of elastin than other vertebral ligaments (appears yellow)

79
Q

What are the functions of the ligamenta flava?

A

Counteracts vertebral lamina separation during Flexion

Helps return vertebral column to upright position after Flexion

80
Q

What does the elastic quality of the ligamenta flava prevent?

A

Buckling

81
Q

What is the course of the supraspinous ligaments? What does it blend with superiorly and how does its structure change inferiorly?

A

Runs from tip of spinous process of C7 to sacrum
Blends superiorly with nuchal ligament
Broadens towards lumbar region

82
Q

What are the references for the structure of the supraspinous ligament?

A

Moore et al., 2010

Johnson and Zang, 2002

83
Q

What are the functions of the supraspinous ligaments and when does it hold its maximum load?

A

Limits Flexion
Resists separation of spinous processes
Holds max load during torsion
- When vertebral column rotates

84
Q

What is the structure of the interspinous ligaments? Where is is small and where is it thicker? What does it merge with?

A

Thin membranous ligament between spinous processes
Poorly developed in cervical region
Thickens as it descends through thoracic and lumbar regions
Merges anteriorly with supraspinous ligament

85
Q

What are the functions of the interspinous ligaments?

A

Works with ligamentum flavum and supraspinous ligaments
Vertebral stability
Limited resistance to flexion
Counteracts separation of spinous processes

86
Q

What is the appearance of the intertransverse ligaments?

A

Fibrous between thoracic vertebrae

Thinner and more membranous between lumbar vertebrae

87
Q

What are the functions of the intertransverse ligaments?

A

Limit Flexion

Carry max load during lateral flexion of vertebral column

88
Q

What is the course of the nuchal ligament?

A

From external occipital protuberance and posterior border of foremen magnum
To spinous processes of cervical vertebrae

89
Q

What is the elastin content of the nuchal ligament?

A

~80%

90
Q

How does the nuchal ligament divide the posterior neck muscles?

A

By forming a midline septation

91
Q

What are the references for the structure of the nuchal ligament?

A

Moore et al., 2010
Kerr, 2010
Tubbs et al., 2011

92
Q

What are the functions of the nuchal ligament?

A
Supports the head
Resists hyperFlexion of cervical spine
Returns head to anatomical position
Helps maintain c-spine alignment
Muscle attachment (due to broad lateral surfaces)
93
Q

Why is the nuchal ligament thicker in quadrupeds?

A

They must hold their head up while on all fours

94
Q

What is the structure of the transverse ligament of the atlas?

A

Extends between tubercles on medical aspects of lateral masses of C1
Running transversely across anterior arch of atlas

95
Q

What does the transverse ligament of the atlas divide the vertebral canal into and what structures run through each?

A

Anterior compartment = Dens

Posterior compartment = Spinal Cord and CN XI

96
Q

How much force can the transverse ligament of the atlas support? What does this say about it?

A

350N

It is the largest, strongest and thickest craniocervical ligament

97
Q

What does the smooth anterior fibrocartilage surface of the transverse ligament allow?

A

The odontoid process to glide against it

98
Q

What are the functions of the transverse ligament of the atlas?

A

Contributes to craniocervical joint stability (strongest)
Aids stabilisation of atlantoaxial joint
Permits rotation of atlantoaxial joint
Limits Flexion at:
- Atlanto-occipital joint
- Atlantoaxial joint
Prevents anterior displacement of axis by pushing ventral surface of dens against posterior aspect of the anterior arch of atlas

99
Q

What are the references for the structure and functions of the transverse ligament of the atlas?

A

Panjabi et al., 1998

Tubbs et al., 2011

100
Q

Where do the lateral aspects of the alar ligament attach?

A

Odontoid process

101
Q

What are the potential superior attachments of the alar ligament?

A

Anterolateral aspect of foremen magnum
OR
Medial aspects of occipital condyles

102
Q

What are the mean dimensions of the alar ligament?

A

Mean length = 8.8mm

Mean diameter = 7.3mm

103
Q

How much force can the alar ligament resist before rupturing?

A

200N

104
Q

What joints does the alar ligament stabilise?

A
Atlantoaxial joint
Craniocervical junction (with transverse ligament)
105
Q

What movements does the alar ligament resist?

A
Excessive rotation (at atlantoaxial and atlanto-occipital joints)
Lateral bending (contralaterally)
Anterior displacement of atlas
106
Q

What can cause alar ligament damage and what can it result in?

A

RTAs
Results in further axial rotation causing compression/damage to:
- Vertebral artery
- CN XI

107
Q

What are the references for the alar ligament structure and function?

A

Iwanaga et al., 2017
Panjabi et al., 1998
Sardis et al., 2017
Tubbs et al., 2011

108
Q

How much can ligaments stretch beyond their original length before disruption? What happens after this point? At what percentage is there complete rupture?

A

Can stretch up to a max of 4% beyond original length
Strain >4% = Rupture of up to 50% of fibres and moderate tearing
Complete rupture at 20% which may also damage connected structures

109
Q

Why are crosslinked fibres susceptible to tearing?

A

Ageing > Crosslinks mature > Regen with scarring > Reduced strain resistance

110
Q

What can cause a rupture of the transverse ligament of atlas?

A

Falls/accidents with direct blow to head and forced hyperFlexion

111
Q

When the transverse ligament of the atlas tears, where in the ligament is most susceptible to tearing?

A

The body of the ligament

112
Q

Why are ruptures of the transverse ligament of the atlas rare in kids? (Reference?)

A

Weaker synchondrosis of dens compared to ligament

Floman et al., 1991

113
Q

What can result in rupture of the alar ligament?

A

RTAs resulting in:

  • Hyperextension
  • Excessive rotation
114
Q

Why are ligaments of the craniocervical junction susceptible to high energy injuries?

A

High % of collagen content

Little stretch due to low elastin

115
Q

What are the references for ruptures of the craniocervical ligaments?

A

Mesfar and Moglo, 2913
Kaufmann et al., 2015
Tubbs et al., 2011

116
Q

How can ossification of the PLL and ligamentum flavum affect the Spinal Cord? How does this present? (Reference?)

A
Compress Spinal Cord
Causes:
- Neck pain
- Limb dysfunction
(Jian et al., 2011)
117
Q

In what individuals is ossification of the PLL and ligamentum flavum more common? (Reference?)

A

Females (Tsuyama, 1981)

Asians (Wang et al., 2017)

118
Q

After what surgery in what region is ossification of the PLL a significant risk?

A

Atlantoaxial fusion after lower lumbar spine surgery