Fundemental Physics Of Tissues Stress Model Flashcards
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
Auto support mechanism 1
Calcaneocuboid locking
Secondary to tightening of the plantar fascia
Stabilisation in the rear foot and mid foot complex by compression of the calccuboid joint prior to heel lift
Auto support mechanism 2: windlass mechanism
DF of the hallux pulls plantar aponeurosis, shortening the distance between the met heads and calc
Supinates the foot and externally rotates the lower leg
Auto support mechanism 3: closed packing of bone
Reflects the radical tightening and the ‘locking wedge effect’ - packing the bones
Final piece of the stabilisation process
Foot can now resist highly repetitive loads
What are the 3 auto support mechanisms depend on
Saggital plane motion of the 1st MPJ
Heel rocker prevents
Heel roll
Injury and fracture
Ankle rocker
Decrease rom
Forefoot equines - forefoot is lower on the ground relative to the heel , creating an uphill position that can impede forward advancement
Consequences of the restrictions in ankle
Steppage gait (vertical toe off)
Early heel lift (bouncy gait)
Midfoot pronation
Shorter step length
Unstable mtj
1st MPJ
Functional hallux limitus
Hallux rigidus
Stiff shoe
Amputation
High jacks force
Consequences of restrictions in 1st mpj
Altered heel lift
Timing of heel can be adversely effected
Delay in heel lift
Compensatatorg pronation through mid foot
Vertical toe off
Inverted step
Weight flow directed to the lateral column and fails to shift medial,y web pace prior to heel lift
Comes at the expense of one or more of the auto support mechanism
Not related to stj supinated
Abducted and abducted toe off
Body will follow and alternative pathway of least resistance to permit saggital plane motion
Abductory twist
Flexion compensation
Flexion occurs at torso during the middle of the mid stance
Failure of knee to fully extend
Lumbar spine will straighten
Head is flexed forward
Lower back pain
Heel rocker interventions for restrictions
Surgery
Footwear modification
Bracing
Ankle rocker interventions for restrictions
Stretches
Manual therapies
Heel raise
Surgery
Forefoot rocker interventions for restrictions
Allow 1st ray to PF, 1st ray cut out, reverse Morton’s extension
Rocker sole
Functional hallux limitus (FnHL)
The functional inability of the proximal phalanx to extend on the 1st met head
Full range of motion non wb
Restriction is only thought be be during gait
Bruce test
Help you determine where to place the 1st ray cut out
