Tendons and ligaments L1: Biomechanics of tendons and ligaments Flashcards
1
Q
Tendons and ligaments are ______ connective tissue
A
dense, regular
2
Q
Tendons and ligaments are well adapted to resisting ____ forces.
A
Tensile
3
Q
What are 5 functions of ligaments?
A
- Transmit tensile forces (bone to bone)
- Strong enough to provide stability
- Flexible enough to permit joint motion
- Up to 5 degree varus –> flexibility
- >5 degree varus –> stiffness
4
Q
How do the fibres span in anterior & posterior longitudinal ligaments in the superficial layer?
A
fibres span several levels
5
Q
How do the fibres span in anterior & posterior longitudinal ligaments in the deep layer
A
- fibres cross only adjacent vertebrae, attach to annulus fibrosis
- short segment
6
Q
What are anterior & posterior longitudinal ligaments (vertebral)?
A
- Regional differences in size – thickest in thoracic region
- Different in composition, mechanical properties
- Natural brace- prevent injury ‘
7
Q
What is ligamentum flavum? 4 characteristics.
A
- Thick, elastic ligament connects lamina (vertebral canal wall)
- Under constant tension (elastic)
- Provides continuous compressive force
- Prevents buckling during movement (helps you ‘spring back up’)
8
Q
Which side of the ankle ligaments are more prone to injury? Why?
A
Lateral side is more likely to be injured- because there are fewer and less broad
9
Q
What are the 3 arches (plantar ligaments) of the foot?
A
2 longitudinal arches and 1 transverse arch
10
Q
What are the 3 components that are determine the plantar ligaments?
A
- Bony arrangement
- Plantar ligaments
- Plantar aponeurosis
11
Q
What is the windlass mechanism?
A
Windlass mechanism- lift first toe –> see plantar aponeurosis lift up
12
Q
What is the function of the plantar ligaments?
A
Functions to adapt to surfaces & dampen impact forces
13
Q
What are the functions of the anterior cruciate ligament (ACL)?
A
- Resists anterior tibial translation and rotational loads
- Ability to stabilise knee in various positions and loading conditions
14
Q
What is the anatomy of the ACL like?
A
2 bundles- complex anatomy
15
Q
ACL has a _____ curve.
A
Non-linear load-elongation
- First compliant (toe region)
- Stiff region
16
Q
Females are 4 times more likely to have a ACL injury due to sporting injury. True or False.
A
True
17
Q
What are the 4 functions of tendons?
A
- Transmit force from muscle to bone (joint motion)
- Absorb, store and release energy maximise exercise efficiency (conserve energy)…muscles are expensive to change length
- Power amplification (store slow and release fast – catapult)
- Protect muscle from damage (power attenuation – shock absorber)
18
Q
What are 2 specific energy storing tendons? Why?
A
Achilles and patellar tendons elasticity and fatigue resistance (most fail at 3.3%, Achilles > 12%)
19
Q
How does a tendon buffer?
A
During jump landing or walking down a hill, tendon lengthens before muscles to prevent eccentric damage
20
Q
How does a tendon act like an amplifer?
A
During stance, Achilles tendon slowly stores and quickly releases energy during push-off to propel to the next step
Slow Storage + Rapid Recoil = more power!
21
Q
Explain how the Achilles tendon structure can help when walking on uneven surfaces/movement of the calcaneus.
A
- Fascicles of Achilles tendon spiral 90 deg. during descent
- Allows elongation & elastic recoil for energy release
- MG fairly parallel
- LG and soleus insert onto calcaneus with strong torsion
- Helps calcaneus to accommodate for surfaces
- Important for intra-tendinous strain distribution
- Regional variations within Achilles tendon strains during walking (function?)
22
Q
Explain how the ITB is an energy storing tendon.
A
- The human IT band evolved for energy storage (chimpanzee vs human comparison)
- stores up to 7J of energy during running (14% of Achilles)
- 1J of energy during walking
- One of most common overuse running injuries
23
Q
What are 2 mechanical properties of tendon affect muscle output?
A
- A more compliant tendon requires a higher level of muscle contraction before force is generated around a joint.
- There is a delay between the activation of a muscle and its production of force – the electro-mechanical delay.
- more compliant tendon = greater electro-mechanical delay, less force transmitted for given change in length.
- Ca2+ pump
24
Q
A more compliant tendon requires a _____ level of muscle contraction before force is generated around a joint.
A
higher
25
What is a electro-mechanical delay?
There is a delay between the activation of a muscle and its production of force
26
A more compliant tendon = _______ (greater/less) electro-mechanical delay, ______ (greater/less) force transmitted for given change in length.
greater less
27
What is an aponeurosis?
* Broad sheet of dense regular connective tissue
* Attaches muscle to bone or muscle to muscle or muscle to fascia
* Both tendons and aponeurosis are highly organized elastic (parallel collagen fibres)
28
An aponeurosis is a broad sheet of _______ connective tissue
Dense, regular
29
Aponeurosis attaches from ____ to _____ \_\_\_\_ to _____ \_\_\_\_ to \_\_\_\_\_
Attaches: muscle to bone muscle to muscle muscle to fascia
30
What is an enthesis?
Tendon/ligament to bone insertion
31
What is the function of the enthesis?
Aids load transfer between elastic tendon/ligament and rigid bone (100x stiffer than tendon/ligament)
32
What are the 3 types of fibres in the enthesis?
1. Fibrous (inserts directly onto long bone)
2. Fibrocartilaginous (4 distinct zones with a gradual transition)
3. Muscular (attachment of muscle to bone without a tendon)
33
What is a muscle-tendon junction?
* Abrupt rather than gradual transition
* Collagen fibres and muscle cell membrane interdigitate (join/combine) to increase surface area and reduce stress between tendon and muscle
34
What are 3 different surrounding structures?
¥ Fibrous sheath/retinacula e.g. hand o Assist in joint stability ¥ Synovial sheaths +/- peritendinous fluid o Reduce friction ¥ Bursae e.g. subacromial o at sites of compression o Pillow sacs o Help lig. &tendons stress
35
Connective tissue is split into 2. What are they?
Cells and ECM
36
What are 4 ECM splits?
Fibres, proteoglycans, glycoproteins and tissue fluid
37
What is the most abdundant protein in the body?
Collagen
38
What collagen type accounts for 90%?
Type I
39
What collagen type accounts for 10%
Type III
40
Elastin has a ____ dimensional branching pattern.
3
41
Elastin is highly ____ and ____ resistant
Elastic Fatigue resistant
42
Elastin resists _____ and _____ deformation.
Transverse and shear
43
What are examples of elastin?
Aorta Ligamentum flavum Achilles tendon
44
What is the most abundant non-fibrous protein?
Proteoglycans (PGs)
45
Core protein attached to ______ side chains- negatively charged, which attracts \_\_\_\_\_.
glycosaminoglycan (GAG) Water
46
\_\_\_\_\_\_ distribution varies along the length of the tendon.
PG (proteoglycan)
47
\_\_\_\_\_\_ is the most abundant PG in tendon, helps transfer loads between collagen fibrils & regulate collagen fibrillogenesis
Decorin
48
\_\_\_\_\_\_ provides lubrication allowing gliding at tendon surface
Lubricin
49
Cartilage associated proteoglycans predominate in areas of tendon subjected to _____ (attract water to resist compression)
compression \*Tendons don’t like compression
50
Composition and structure
51
\_\_\_\_\_\_ (additional loose connective tissue layer) surrounds tendons in regions away from joints, to facilitate movement of tendons below the skin.
Paratenon
52
\_\_\_\_\_\_ (additional covering where a tendon passes around a joint) to ensure smooth gliding past surrounding structures.
Synovial sheath
53
Are tendons isotrophic or anisotrophic?
Anisotrophic
54
Tendons are heterogeneous. True or false.
True Varies along a tendon
55
Tendons and ligaments are viscoelastic. True and false.
true visco- resists deformation (depends on PG/GAG) elastic- return back to original (depends on collagen/elastin)
56
Behaviour is ____ and _____ dependent.
Time History
57
Structural properties depend on the object’s _____ and \_\_\_\_\_.
size and shape
58
\_\_\_\_\_ properties are normalized for the object’s size and shape and describe the properties of the underlying material from which the object is made.
Material
59
What is the toe region?
Compliance is quite high
60
What is the elastic region?
When load is removed the tissue returns to its pre-stressed dimensions (although this return is time dependent)
61
What is the plastic region?
Recovery requires time
62
What is the ultimate failure?
Remaining collagen fails progressively (ligament) or rapidly (tendon)
63
Tendon has _____ (graded/abrupt) failure. Why?
Abrupt
Complete (parallel alignment)
64
Ligaments has _____ (graded/abrupt) failure. Why?
Graded progressive failure (different organization)
65
What is stress?
Force/area (pascals)
66
What is strain?
Change in length/original length (no units)
67
What is Elastic (Young's) modulus
slope (measure of material’s stiffness)
68
What is compliance?
Inverse \*more stiff = less compliant
69
Forces and deformation values depend on ____ of structure (CSA & length) and its composition
size
70
Stress and strain depend on the ______ of the structure but are independent of its size.
composition
71
Typical stress-strain curve for tendon
1. Adequate match between stress/strain &existing form – Most physiological loads within this range – Fibres will regain their original configuration after removal of load
2. Inadequate match between stress-strain & existing form – Plastic deformation has different forms – Δ conc electrolytes & transmembrane voltages without disruption of structural integrity – Cross linking fails (Microtears)
* Pull tendon won’t return to original length
* Need to be here- for adaptation remodeling
3. Tendon rupture
* Depending on type
* 3.3% 8%
* 12% Achilles
72
What are rate-dependent and time-dependent properties?
* Creep
* Stress-relaxation
* Hysteresis
* Loading rate
* Temperature
73
What is creep?
When a tissue is loaded to a fixed force, length will increase with time (recovery non-linear)
74
How might creep impact joint stability?
Extra slack = decreased stability --\> injury can occur (even doing non-strenuous activity)
75
What is stress-relaxation?
If tissue is stretched to fixed length, the force will decay with time
76
How might stress-relaxation impact splinting of joint?
When healing tendons- want tendons under some stress (for rehab)
77
What is hysteresis?
As the tissue is loaded and unloaded, some energy is dissipated through heat • not all energy stored during loading is given back during unloading (ie: not ‘perfect’ springs)
78
If tissue is loaded rapidly, _____ force is required to deform the tissue.
More
79
Low loading rates cause ______ injury.
Avulsion fracture more common
80
High loading rates cause _____ injury.
Mid substance tear- more force required
81
Heating connective tissue to about 40° C ________ (increases/decreases) creep (affects tropocollagen bonding)- bonding properties changes
Increases
Note muscles are much more sensitive to temp changes than tendons/ligaments (q10)
82
How does rehabilitation (triphasic model) in ligament tears vary in regards to tendinopathy?
In tendons, there is no inflammation phase
83
What is the triphasic model in healing of ligament tears? How should physio help with rehabilitation? (Give the timeframe as well)
1. Inflammation
* Swelling, bleeding, redness, pain, heat
* POLICE
* Manage pain
* Don't load
* 10 days
2. Proliferation
* New layers of tissue are laid down
* Start to add load along tensile axis
* 3 weeks
3. Remodelling
* Load more and in different directions
* 14 weeks
84
Where are children more likely to be prone to tendon injuries? Why? Give an example.
* More prone to tendon-bone insertional problems
* Reason: the bone is less developed and has less bone mineral density
* Example: avulsion fracture (a bit of bone gets pulled off, while tendon is still attached to the bone)
85
Which region of a ligament is more predominately affected in children?
Enthesis
Bone has not fully developed, still close to the growth plate
86
Which region of a ligament is more predominately affected in adults?
Mid-substance
