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Leather
- Ex: : shoes, cover metal components, supportive components
- Pro: Can make porous or stretch or stiffen
- Cons: Heavy, archaic
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Steel
- types: carbon steel, low alloy and high alloy steel, stainless steel
- Pro: strength, rigidity, many of the uprights, durable, can heat and bend it
- Cons: high density, susceptible to corrosion
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Aluminum
- Cast Aluminum
- Ex: Prefab prosthetic components
- ----Stiffen toe for gait cycle
- Wrought AL
- Ex: Pylons, Uprights, UE devices
- ----Pylon is the shaft
- ----Uprights are the sides
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Titanium
- Pros: stronger than Al, comparable to steel, resistant to corrosion
- Cons: expensive
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Magnesium
- Corrosion resistant, lighter than titanium and aluminum
- Not used often
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Wood
Ex: prosthetic foot (Keel, SACH) or knee units
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Plastics
- Thermoplastics
- Thermosetting Materials
-
Low temp vs. High temp
- Low temp, can heat right onto the pt, but not as durable as high temp
- Ex: resting hand splint
- Ex: high temp: LE
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Polypropylene
- Ex: hinge joints, spring assist, prefab AFO, prosthetic sockets, pelvic bands
- Many AFOs we see
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THERMOSETTING MATERIALS
- • plastics applied over positive model
- • common resins: acrylic polyester and epoxy
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FOAMED PLASTICS
- Protective interface; microcell structure
- Next to skin
- Compress over time so have to be replaced
- Disperses pressure
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FORCES IN ORTHOTICS DESIGN
- spread forces/ pressure of distance and increase lever arm to increase comfort
- goal to maintain mechanical advantage 2:1-5:1, i.e. lever arm of applied force 2-5x longer than lever arm of applied resistance
-
bending moment:
- location of max orthotic control or correction
- least deforming/most effective if central force and maximum bending moment coincide/congruent with actual joint axis
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TYPES OF CONTROL SYSTEMS
- 1. First class lever system
- ----Forces equal 0
- ----Two arrows pointing left on first model
- 2. Balanced parallel force system
- ----Controlled jt motion
- 3. 3 point loading or control system
- ----2 forces
- --------one proximal and one distal that counter act the primary force (MCL stability) ← second picture
- ----used most often in orthoses
- 4. Balanced 4 point system
- ----control rotation/ translation
- ----use bands
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