Term
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Definition
| when an orthosis applies a force to the body there is an equal and opposite force also applied to the orthosis by the body |
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Term
| applying corrective forces |
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Definition
| essential to consider were and how the orthosis must apply corrective forces |
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Term
| failure to consider forces being placed on the orthosis by the body |
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Definition
| may cause structural failure or distortion of the orthosis |
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Term
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Definition
in clinical practice, forces must be applied over as large of an area as possible to reduce pressure
-P(pressure)=F(force)/A(area) |
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Term
| basic function of an orthosis |
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Definition
resist or control angular motion at a joint
-varus, valgus, knee hyperextension, etc |
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Term
| orthosis control angular motion at a joint by... |
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Definition
| applying a system of linear forces each pushing on a different part of the body in a specific direction |
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Term
| control of angular motion |
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Definition
| required because many of these linear forces are applied at a distance from the joint's center of rotation |
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Term
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Definition
| force acting at a distance from a joint causes a "turning force" known as a moment. |
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Term
| magnitude of force calculation |
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Definition
| M(moment)=F(force)x D(distance) |
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Term
| M(moment)=F(force)x D(distance) |
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Definition
| D (know as the lever arm) is defined as the perpendicular distance from the joint center to the line of action of the force. |
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Term
| applying oblique rather then perpendicular forces |
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Definition
| -if this happens forces will be less then effective in generating the required moment because the lever arm will be smaller |
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Term
| critical function of most lower limb orthosis |
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Definition
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Term
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Definition
-clinically useful strategy
-enables required moment to be generated while reducing the size of the force required |
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Term
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Definition
| reduces pressure on tissue which increases comfort. |
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Term
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Definition
-increase lever arm
-increase area over which pressure is applied
-increase both |
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Term
| maximizing pressure reduction |
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Definition
| -increase both lever arm and the area over which pressure is applied. |
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Term
| orthotic system of forces |
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Definition
| -in order to work successfully force systems in orthosis must be set up in equilibrium to balance each other |
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Term
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Definition
| both the forces applied as well as the moments created by these forces |
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Term
| to control angular motion at a joint |
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Definition
minimum number of three forces is required.
-three point pressure system |
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Term
| effective three point pressure system |
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Definition
-2 forces must be applied to the concave side of the joint.
-these forces must balance with the third force working in the opposite direction. |
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Term
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Definition
| this force should be located as close as possible to the center of joint rotation |
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Term
| mathematical expression of three point pressure system |
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Definition
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Term
| clinical importance of force systems |
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Definition
| it is important to recognize that it is impossible to alter one force in a three point pressure system without influencing the other two forces in the system |
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Term
| applying forces in orthosis |
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Definition
| important to use straps in the direction that the force is required to act |
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Term
| force systems for two joints |
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Definition
| if two joints are adjacent to each other some of the forces in a force system maybe shared. this can reduce the overall number of forces required to control joints. |
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Term
| significance of the masses of the orthosis and shoes |
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Definition
| The larger the mass to be accelerated and decelerated, the greater the muscle forces that are required |
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Term
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Definition
| whenever possible it is beneficial to minimize mass of the distally applied orthosis in order to reduce demand |
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Term
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Definition
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Term
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Definition
| -study of the effects of forces |
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Term
| ground reaction force (GRF) |
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Definition
| due to gravity the weight of body acts vertically downward. equal opposite vertical force acting upward is the ground reaction force |
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Term
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Definition
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Term
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Definition
| -all forces remain constant, with the magnitude equal to the body weight |
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Term
| GRF in dynamic situations |
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Definition
| forces typically vary in a repetitive fashion |
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Term
| GRF and center of rotation |
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Definition
-when line of action lies at a distance from the the center of rotation it creates a external moment
-greater the perpendicular line of action for GRF to joint cen |
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Term
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Definition
-GRF close, smaller external moment
-GRF farther, larger external moment
-GRF through joint, no external moment |
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Term
| presence of an external moment tends to cause: |
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Definition
-motion at a joint
-usually (not always) requires an opposing internal muscle moment to create equilibrium (control the motion) |
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Term
| balancing moments in dynamic situations |
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Definition
| moments generated by the muscles maybe greater or less then external moments in order to control angular motion at the joints |
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Term
| desirable effect of GRF at joints |
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Definition
may reduce or remove the need for muscle activity at a joint.
-paraplegic patient with KAFOs can achive hip stability by aligning the GRF posterior to the hip joints |
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Term
| exact magnitude of external and internal moments: |
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Definition
| influenced by the accelerations and inertial effects of the individual joint segments |
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Term
| normal gait basic definition |
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Definition
| highly controlled, coordinated, repetitive series of limb movements whose function is to advance the body safely with minimum energy expenditure |
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Term
| 5 attributes of normal walking |
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Definition
1. foot clearance in swing
2. adequate step length
3. prepositioning of foot for initial contact
4. stability in stance phase
5. conservation of energy |
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Term
| joint deviations in pathological gait |
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Definition
| potential deviations can occur in all phases of the gait cycle as well as all three planes |
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Term
| forward progression of the tibia |
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Definition
| -facilitated by the three rockers of gait |
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Term
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Definition
| -common feature is that the magnitude of the first peak of the GRF is excessively high in early stance, but the second peak in terminal stance is insufficient. |
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Term
| if GRF is less then body weight |
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Definition
| limb is not supporting the body weight sufficiently to remain functional as a support |
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Term
| if limb can not support weight sufficiently |
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Definition
| contralateral limb may make heavy contact with the floor generating an excessive first peak of GRF |
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Term
| normal gait patterns and GRF |
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Definition
| segments move in ways that align the knees and hip joints closely to the GRF so as to minimize lever arms and produce sufficient moments making gait efficient |
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Term
| 3 GRF alignment changes at knee in gait |
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Definition
1 during loading response moment changes from extension to flexion
2 in midstance-flexion to extension
3 preswing-extension to flexion |
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Term
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Definition
| GRF aligned anterior to the knee and posterior to the hip-creates external hip and knee extension moments producing stability |
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Term
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Definition
| GRF aligned anterior to the knee and posterior to the hip-creates external hip and knee extension moments producing stability |
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Term
| when segments are misaligned: |
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Definition
| GRF is also misaligned relative to the joints causing abnormal lever arms and moments that destabilize or excessively stabilize joints |
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Term
| what is external rotation angle of the ankle joint? |
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Definition
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Term
| what is external rotation angle of the ankle joint? |
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Definition
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Term
| reason for external rotation angle of ankle joint |
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Definition
| -motion of the ankle is then comparable with the antero-lateral movement of the center of gravity. |
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