Fundemental Physics Of Tissues Stress Model Flashcards
(41 cards)
Force
A push or pull on an object that can cause a change in motion (induce acceleration) or deformation of a mass
Stress
Intensity of internal forces within an object
Causes mechanical failure
Pressure
Force applied perpendicular to unit surface area
Surface stresses = pressures
Strain
Relative amount of deformation of an object when it is subjected to load
Describes change in length relative to the starting length of the object when loading force is applied
Stress and strain
Steeper = higher stiffness
Flatter = lower stiffness
Yield stress = ultimate stress
End = ultimate tensile stress
Issues with root theory
Reliability of measurement; no agreement on measurement of stj neutral as well as passive rom of the stj
Criteria for normal foot alignment - suggests criteria is too stringent and restrictive for the general population
What is the tissue stress mode,
“Injury occurs if the mechanical stresses acting on the tissue are beyond the tolerance of the tissue. Therefore, treatment is directed at reducing the load acting on the tissue and increasing tissue capacity
Stress on tissues - elastic and plastic region and biological responses to stress
Elastic - normal give and take of soft tissues, overuse avoided, tissue irritation and inflammation will be maintained at a tolerable level
Plastic - result in overuse injuries, damage to tissues
Biological - wolf and Davies laws
Mechanism of injury
When the stresses on the tissue are causing more damage than the body can repair
- one off very high stress
- moderate stress applied repetitively or for a long time
Stress and types
Ability of an object to develop internal resistance to loading force
2 types: axial and shear
Axial stress
Tensile stress
Compressive stress
Shear stress
Friction between structures
Non-uniform stress on muscle fibres
Stress between facial layers
Attachment of tendons/d fascia to bone
Bending
Induces compressive and tensile stress (greatest further away from the centre)
Torsion
Induces shear stresses - greatest further away from axis of rotation
Mcppoil and hunt 4 step to assessing and managing mechanical stress-related pathology
- History and identification of stressed tissues
- Application of controlled stresses to involved tissues
- Assessment of pt complaint
- Management program
Can stress be measurement
No directly measured
Outcome measures
Treatment progression and success is guided by symptom reduction, functional improvement and the person meeting their goals
Orthotics and root theory
If calc is x everted use a RF post of x to make the calc vertical
Saggital plane model and orthotics
If you have a functional hallux limitus use a 1st ray cut out
Tissue stress model and orthotic
Use an orthotic that reduces the stress enough
Described by Howard dananberg
Functional hallux limits and it’s relationship to gait efficacy
Principal: facilitate motion in the saggital plane, 15% of motion is found in the front plane and 70% of motion found in the saggital plane (15% may be more important than the 70%)
Facilitation of motion in the sagittal plane across the 3 rockers
Heel rocked
Ankle
1st MPJ
What happens if there is a block in one of the rockers
Body has to compensate to ‘psuh through or around’ the blocks
- more energy required
- early heel loft
- vertical toe odd
- abduction or addicted toe off
Principle of saggital plane
For the foot to function appropriately in the saggital plane, there needs to be a co-ordinated effort between the action of the foots auto supportive mechanisms and the creation of power for efficient forward motion
