Prothstetics Flashcards
Example Gait Faults
Observed Deviations
* bilateral internal hip rotation
* increased knee flexion
* short step length
Potential Impairments
* femoral anteversion
* tibial torsion
* hip weakness
* knee flexion contractures
Mechanical Consequences
* poor leverage for ankle plantar flexion
– reduced gait economy
– decreased gait speed
* incr. retropatellar pressure
What are the main causes of amputation?
Vascular disease (54%) + Trauma (45%)
The majority of amputations are ___
transtibial (below knee) or transfemoral (above knee)
Prosthetic considerations:
Suspension method, socket, limb interface
Suspension def
Method of attachment to residual limb
Socket def
Encases residual limb and disperses weight
Pressure wounds often seen here.
Patient Orthosis Prothesis - What is it?
- Junction between the body tissues and support surface which forces are transmitted
- Seat cushion, prosthetic limb, AFO (Ankle Foot Orthosis)
Reaction forces are due to:
- Reaction forces (Newton’s 3rd Law)
– May be partial - 5x’s BW
– May be due to the orthosis, prosthesis itself - Loads on soft tissue may lead to tissue breakdown
Osteointegration
Metal placed into the bone. Don’t have to worry about skin problems because it is solid.
What do we need to think most about with a prosthetic?
- Pressure and the relationship with Load Transmission and Load Distribution
Load Transmission
- Forces traveling through kinetic chain (Try to reduce reaction force)
- Body Weight
- Nature of the activity (walk, run etc.)
- Assistive devices (yes/no)
Ex: Cane for someone with below knee amputee
Load Distibution
- Pressure at the interface (Try to reduce pressure)
- Musculature
- Bony geometry of the interface
- Mechanical properties of the tissue and surface
Must consider load distribution early vs late on in injury because throughout time muscle with atrophy.
Putting in foam or something else that forms around the body.
Interface Mechanics
Compliant: Put something soft inside that will conform to you.
Rigid: Get entire shape between device and limb to match.
Improper can lead to shear stress or bottoming out (sink so far no material left).
Energy Return
- SACH: Solid Ankle Cushioned Heel; Doesn’t move. Minimal energy return.
- High energy retun in flex prothesis. Moment of inertia significantly affected (mass x radius^2). Leg is shorter and mass is reduced. Won’t fatigue as much. At sprinting speed is faster than normal person at top speed but when starting is much harder to get going to get spring to react.
Prosthetic device - degrees of freedom
No DOF
1 DOF: DF and PF
2 DOF: DF/PF and Inversion/Eversion
