L1 Intro Flashcards
Orthotist
refers to professional
Orthotics
refers to field of study
Prothesis
an externally applied device used to replace a missing body part
Orthosis
an externally applied device used to replace a missing function (refers to singular device)
Force
a push or pull exerted by one object on another
when a force is applied to an object, it can cause it to accelerate or decelerate
forces on human body can produce or restrain a movement
External force
push or pull from a source outside of the body
gravity, weight of body, ground reaction force
Line of gravity
line from the object’s COM to center of the earth
the location of the line of gravity with the respect to the axis of rotation of a joint can produce or limit movement at that joint
LOG anterior to hip causes
hip flexion
LOG anterior to knee causes
knee extension
LOG posterior to knee causes
knee flexion
LOG anterior to ankle causes
dorsiflexion
LOG posterior to ankle causes
plantarflexion
Ground Reaction Force Vector
the force of the ground on the foot
line connect the body’s COM and the point of contact of the foot with the ground
the location of the GRFV relative to the joints will affect joint movement
Midstance forces
GRVF should pass anterior to the knee and posterior to the hip
causes knee and hip extension
Internal Forces
produced by sources within the body
muscle, connective tissues
these forces can produce joint movement, counteract external forces that act on the body
Knee buckling during stance
Ankle DF will move GRFV posterior to the knee, causing knee FLEXION
if the body doesn’t have sufficient enough muscle force to maintain knee extension, the knee will buckle
you will want a AFO that prevents ankle DF to keep GRFV anterior to the knee, keeping it extended
Tensile Forces
distracts or moves the surfaces apart
a dynamic progressive splint applies end-range tensile loads to trigger elongation and increase joint ROM
Compression
perpendicular force by the direction of force is towards one another
would be used for swelling
Shear
forces applied parallel to a surface to move one object along the surface of another
Friction
special type of shear force
Skin breakdown
can be caused by shear and friction forces
Bending Forces
applied to an object that results in equilibrium
Three point bending systems
a proximal and distal force applied in the same direction are countered by a third force applied in the opposite direction at a point inbetween
used to control unwanted motion
The force required _____ in a three point system as….
decreases as the point of application is moved further from the axis of movement
Central force
anteriorly directed force applied at the posterior knee
4 Point Control System
force should not be applied directly over a bony prominence
alternative is a four point force system to distribute the counter-force on either side of the bony prominence
Dynamic Devices
devices designed to generate forces that produce movement
determined by design, materials, alignment
Functional Electrical Stimulation
alternative to a conventional orthosis
E-stim applied to nerve or muscles to improve function
can be used by itself or with an orthosis
Orthosis to Limit, control, or prevent movement
use of materials or appliance designs that produce high levels or rigidity at unstable joints
rigid materials, increased thickness, and more surface area provide stability
Heel lift will
move the GRF more posterior because the tibia tilts forward
Stop
prevents motion in a particular direction but allows movement in the other direction at the joint
named for the direction it is stopping
Lock
component that can be engaged to lock the joint in a selected position preventing all motion at the joint while its engaged
Goals of prosthetics/orthotic devices
apply sufficient force to achieve effectiveness
-minimize pressure to insure comfort and safety
-devices should be designed to apply the least effective force
To achieve the balance between effective control and comfort
- minimize the magnitude of the force requirements
- minimize friction and abnormal movements between device and the user
- minimize pressure between the device and user
Minimize magnitude of force requirements
-done my maximizing the length of the moment arm
-increasing the length of lever arm allows for decreased force application
also longer residual limbs have greater leverage, helps to produce greater moment arm
Minimize friction and abnormal movements between the device and user
Remember skin tolerance –> some areas handle forces better
congruence between the anatomical and mechanical joint reduces shear
perspiration increases the coefficient of friction of the skin
Minimize Pressure
the amount of force per surface area = pressure
increasing surface area will decrease pressure
prosthetic sockets and orthoses are designed to spread force over a large area
Loss of limb due to amputation
COM sifts away from the amputated limb
Weight of orthotic or prosthetic device
COM moves lower and toward the additional weight
Psychosocial considerations of orthotics
body image
ability to resume normal activities
reduced motivation due to self image
Orthotic Classifications
- method of manufacture
- biomechanical terminology
- types of materials or components
Method of Manufacture
Custom Made
Prefabricated–off the shelf or over the counter
Custom Made orthoses
manufactured and fit by an orthotist for a specific individual
Prefabricated orthoses
mass produced for the general population
off the shelf or over the counter
off the shelf
provided to pt by a practitioner, with custom fit
Over the coutner
without individual fitting, can purchase from a pharmacy or store
Biomechanical naming by joint or body region
named proximal to distal
includes the name of major joints that are enclosed within the orthosis
Biomechanical naming by type of control exerted by orthosis
Free
Assist
Resist
Stop
Hold
Lock
Free
no control is exerted and the joint is free to move in a designated plane
Assist
assists the motion by applying an external force to increase range, velocity, or force of a desire motion
Resist
resist unwanted motion by applying force to decrease the velocity or force of an undesirable movement
Hold
controls and eliminates all motion at a joint in all planes
Naming by materials and components used in fabrication
Conventional
Molded
Hybrid
Conventional Orthosis
made primarily from metal components and leather
Molded Orthosis
made from thermoplastics and composite materials. manufactured over custom mold of client. no moving parts. plastic one piece shell. total contact
Hybrid orthosis
hinged or articulated and uses a combination of conventional and molded compenetry
Stiffness
amount of bending or compression that occurs when a material is loaded
increased stiffness means it is less flexible
Density
material’s weight per unit volume
prime determinant of energy cost during functional activity
Thickness
increasing thickness of material means increased rigidity. Also increases weight and bulk of the device
Strength
determined by max load that a material can sustain or support
