wk 5- plantar pressure Flashcards
difference between force and pressure measurement
f- a vector quantity which means that it has both magnitude and direction. allow measurmeent of the foot as a whole. measured in (N) newton.
p- measure of force per unit area. it shows the distribution of load across different regions. measured in (kPa) kilopascals
how can foot/body structure relate to plantar pressure
high arch, pes cavus = force over a smaller area = higher pressure
lower arch, pes planus = force over larger area = lower pressure
shape and BMI matters for plantar pressure
plantar pressure assessment refers to the study of
pressure acting between the
plantar surface of the foot and a supporting surface (ground, shoe or insole)
* Pedography (or pedobarography) is another term for this.
clinical applications include?
-sports biomechanics
-gait biometrics
-offloading diabetic feet
formula for pressure
force / contact area
pressure has a relationship with
force, stance time and contact area
different equipment for plantar pressure
pressure plates
instrumented treadmill
insole systems (in shoe)
outcome measures for plantar pressure assessment (7)
stance time
* Contact area
* Peak pressure
* Maximum force
* Pressure-time integral
* Force-time integral
* Centre of pressure line
what does the stance time tell you
shorter stance time = faster walk
faster walk= more pressure
same stance time for trials = consistent gaits
important that the stance time is consistent for your trials
what does contact area tell us and what can it be used for
pes cavus, high arch
pes planus low arch`
used for offloading high pressure areas by increasing contact area in the foot
what is peak pressure
indicates magnitude of peak pressure but not how long this pressure is applied to the foot
pressure time integreal and force time integral
area under the curve of the pressure time graphs and force time graphs
indication of magnitude and time in specific areas
what is centre of pressure pathway
also known as gait line. green dot is start, red dot is toe off. dots close together moving slowly through region, dots further apart moving quickly through region.
looking for sharp changes of direction or asymmetry between feet
what is the step to step variation of gait measures and how this is quanitfied
Normal amount of variation in gait due to
motor control / human factors
- Also consider the amount of error/variation
that might be introduced by the
measurement procedure itself, e.g. - Skin movement
- Marker placement
- Targeting force plate
- Calibration issues
- Knowing how much variability to expect can
help us determine the amount of difference
is clinically significant
whats the clinical applications of plantar pressure analysis in podiatry 7
diabetes and other high risk populations
musculoskeletal deformities
pre/post surgery
effect of orthoses/footwear
gait analysis in neurological conditions
sport and biomechanics
running technique analysis
methodological considerations 7
- Sensor size
-(can underestimate peak pressure values due to the area its assessing) - data collection protocols and instrumentation
- Frequency and responsiveness (sensor type)
-ability of the sensor to change quickly
*calibration
- Individual step-to-step variation (reliability/repeatability)
-extent to which a consistent measure is obtained on different occasions - in shoe vs barefoot pressure plate
how many regions to mask for analysis
different protocols for platforms
Mid-gait protocol
* Data are collected after the subject has taken a few steps (approx 5)
* Subjects may “target” the force or pressure plate
-most representative of a standard gait pattern
-can be fatiguing or difficult for patients
Two-step protocol
* Data are collected from the subject’s second step
* Reported to be almost as reliable as mid-gait method
-better protocol for those with difficulties of prolonged standing or understanding instructions
also 1 and 3 step protocols
and two step XL emed platform- overcomes targetting and measures TSP
and instrumented treadmill (zebris)-no targetting, but overground vs treadmill walking
methodogical factors influencing plantar pressures (7)
gait speed
sensor size
reliability
contact area and site
walking protocol
instrumentation
population studied
individual factors that influence plantar pressures
- body composition- extra pressure due to weight
- insensate or painful feet
- foot deformities
4.altered kinetics/kinematics
- atrophy of muscle/fat
- footwear and offloading
- walking speed
the differences between 5x5mm and 10x10mm sensors
5x5- lesser toe error is still atleast 8%. used in most contemporary systems
10x10- may underestimate true pressure by between 17% and 70%, lesser toes, bony prominences, soft tissue atrophy
frequency and responsiveness
frequency response - ability of sensor to change with force/pressure changes
scanning frequency- rate at which measurements are taken and recorded
disadvantage of emed and pedar system with sensor type
sensor is larger than most other sensor types- can underestimate pressure in sites
adverse effects of pressure on the diabetic foot
-pressure ischaemia
-tissue atrophy
-hypertrophy (callous formation)
-pain
-ulceration
in diabetics how can injury form? 4
-high pressures over long period
-low pressure over very long duration
-moderate repetitive pressure
-shearing pressure
reducing plantar pressure does what
interventions aim to reduce load or pressure in certain areas of the foot
reliability of measures
what does it mean, what is it reported as, how to interpret this?
the extent to which a consistent measure is obtained on different occasions, commonly reported as intra class correlation coefficient (ICC)
ICC: >0.9 very good
>0.75 good
0.5-0.75 moderate
<0.5 poor
ICC does not help us determine how much variability to expect
coefficient of variation
standard deviation of gait values
coefficient of repeatability
variation less than 10% is considered a reliable measure
why do patients with neuropathy have very high pressures
they do not feel the pain and therefore do not alter their gait to avoid the high pressure point
ways you can reduce plantar pressure 6
Total contact insoles/orthoses
* Metatarsal pads
* Rocker sole shoes
* Footwear
* Felt pads
* Walking devices
