Ligaments | Tendons | Nerves Flashcards
What elements make up the structure of capsule, ligaments and tendons?
~20% cellular material
~80 Extra-cellular material (70% water, 30% solids: collagen, ground substance - proteoglycons, amino acids -, elastin
Describe the role of type I and Type III collagen
Type I: resists tensile forces (stretching).
Type III: more elastic; increased recoil capacity
Collagen is primarily type….
Type I: important for resisting tensile forces
Collagen fibres and cells align in the direction of the force. What process is this called?
Reorientation
Name Six types of loading
Compression Tension Shear Torsion Bending Combined (tension + compression)
What are 3 measurements of force?
- Strain gauge (ligaments)
- Instrom testing (compression/tensile)
- Insitu muscle testing (change length)
What are the biomechanical variables of interest (load:elongation graph)
Toe-in Region (Stiffness) Elastic Limit Ultimate Load Ultimate Elongation
The tissue is at what point when it is stretched to the point of rupture?
(biomechanical variables of interest)
Ultimate Load
Stiffness describes the relationship between a change in load and a change in elongation. T or F?
(biomechanical variables of interest)
True: it is represented by the linear region of the Load:Elongation curve and is experienced between the Toe Region and Elastic Limit
What does the area under the load:elongation curve represent?
(biomechanical variables of interest)
Energy absorbed. When a muscle is unable to absorb sufficient energy, it’s risk of rupture will increase
Describe the Toe-in Region
Observed at the start of stretch where there is little resistance to stretch.
Influencing factors include: fibre orientation, slippage of collagen fibres, injury
Fibres are slight crimped. As stretch increases, they straighten out as they transition from Toe-in region to elastic region
Tension (stretch) lengthens fibres, stretch tissue, cause collagen fibres to slip. This increases toe-in region.
What structures prevent overstretching of sarcomeres during toe-in region?
Endomysium and perimysium: stretch to protect contractile elements from damage
What at the toe-in region of damaged tissue?
There is little resistance when load is applied resulting in length without resistance. More movement will occur with less resistance, reducing the stability of the joint
Describe Elasticity
the ability of a material to resume its original size once the force is removed
The return to normal position indicates no damage to tissue
Describe Plasticity
Continued application of force lengthens tissue to a point of damage (collage fibrils may be torn). Once force is removed, tissue does not return to original length resulting in permanent deformation.
Factors that influence the biomechanical parameters when tissue is stretched
Size and strength of ligaments and tendons
Ageing
Velocity of stretch
Intrinsic factors (within musculo-tendinous unit: contractile elements)
_____ is important to the strength of the tissue
size
The larger the tissue, the greater the strength and energy capacity (how much it can absorb)
- has a higher ultimate load before rupture
How does age effect ligaments
Stiffness decreases by ~30%
Ultimate load up to 3x lower in older people
Rupture site: mid-substance of tissues in older people, closer to insertion points in younger people
Explain how tissues respond differently to fast and slow velocities of stretch and what damage is likely to occur.
Fast: higher load applied to tissue, demanding greater strength and resistance from tissues. This results in stiffness.
More likely to result in tearing; damage to mid-substance of tissue
Slow: lower force levels applied, allowing tissues to lengthen with less strain as they build their capacity for elongation/withstanding load/stretch. Used in recovery stage to reduce risk of further damage
More likely to result in avulsion (separation); damage at point of insertion
What are the effects of immobilisation on ligaments?
Disorganisation of collage
Varied shape to fibroblasts
Changes in water and proteoglycan content
These lead to:
- change in size of ligament
- reduced strength
- increased compliance: less stiffness/resistance capacity
> > > weaker tissue
(Characteristic elements of ligament + biomechanics variables related to strength, stiffness, and energy absorption)
Why might complete ruptures occur when low level forces (intensity) is applied?
When there are pre-existing degradation of the tissue, reducing its strength and point of ultimate load
Why is immobilisation important when repairing tendons?
What other tissues may be impacted due to immobilisation?
It allows the ends of tendons to start healing; ideally to a similar length prior to injury
Other Tissues: ligaments around joint, intrinsic muscles may experience atrophy, changes in collagen, reduced strength etc. as a result
Weight Bearing impacts the about of energy stored and therefore the _________ of the tissue
Elasticity.
The greater energy stored, the greater the capacity for tissues to recoil.
Two steps to rebuild tendon function following immobilisation
- reorganize collagen
2. remodel scar tissue
What is creep?
change in length of tissue when load is applied and held constant.
Sliding of collagen occurs at fasicle/fibre level, and water is redistributed resulting in the gradual lengthening of the tissue.
When does the greatest amount of change occur during creep?
In the first 5 minutes, sliding of collagen fibres and redistribution of fluid and proteoglycans is evident, before becoming gradual after 20 minutes
____ creep occurs when the same loading level is applied repetitively i.e. on the achilles tendon during running
Cyclic
Less force leads to less tension in tissues which leads to a reduced…….?
Risk of injury
