wk 5- manufacture of orthoses Flashcards
what can orhtotics do
- Control alignment
- Correct or accommodate deformity
- Protect or support an injury
- Assist rehabilitation
- Reduce pain
- Increase mobility
- Increase independence
- redistribute pressure/load/force
what is an orthotic
shoe device which alters forces acting on the foot during weight bearing
steps of traditional orthosis manufacture
1.Negative cast (plaster or foam impression box)- inverse impression
2.Positive cast (fill with plaster)- impression of foot
3.Modified positive cast- changes made
4.Presing (vacuum forming)
5.Orthosis shell
6.Extrinsic posting, padding, etc
Unlikely to manufacture orthoses this way anymore, computerised technology used more often now
ways you can perform a negative cast
- Non weight bearing plaster cast
(Supine/prone) - Weight bearing or semi weight bearing Foam box impression
what is the difference between WB and NWB negative casting
WB= lower arch, wider and longer foot
expansions need to be made for NWB
STJ neutral needs to be maintained for WB/SWB
Pros and cons of plaster cast
pro:
STJ neutral maintained/1st ray
con:
expansions required
physically demanding
time consuming, space, waste
pros and cons of WB foot impression
pro:
quick
easy
dont need expansions
cons:
hard to keep foot in STJ neutral
physically demanding
lower arch, wider, longer (deformation when applying pressure
what is involved in positive casting
Cast is filled with plaster of paris, while cast is angled, when set, the negative cast is removed
pour angles for positive casting
-intrinsic posting
Neutral: calc bisection is vertical
Inverted: calc bisection is inverted relative to forefoot
Increases medial arch height
intrinsic varus wedge under heel
Increases STJ supination moments in loading response and midstance
Everted: “
Decreases medial arch height
Intrinsic valgus wedge under heel
Increases STJ pronation moments in loading response and midstance
steps in positive cast modification
Step 1: forefoot platform - flat expansion under met heads and toes which allows for clear distal edge of orthotic shell
Step 2: lateral expansions- lateral border expansion of foot, allows soft tissue and thickness of any covering materials. Standard = 5mm
Step 3. Medial expansion- creates MLA contour of orthotic device
Optional steps: heel skive, intrinsic domes, notches, etc
what is pressing and steps
Shell material is now vacuum formed to the shape
1.Chosen material is heated in oven until flexible
2.Placed on top of modified positive cast in vacuum former
3. Membrane is closed and air is evacuated from former
4. Membrane forms the material to shape the cast
5. Material is allowed to cool ad harder before being removed
types of semi rigid or flexible material (shank dependent)
deformation occurs through compression
EVA
Foam rubbers
Cork
Thermoplastic polyurethane
types of rigid material (shank independent)
deformation occurs through bending of materials
Polypropylene
Polyethylene
Nylon
Carbon fibre
Resins
what is involved in posting
addition of material under the heel of orthosis
3 main types
- Extrinsic rearfoot post
* frontal plane alignment of underside relative to
the calcaneal bisection - Heel pitch
* Drop of rearfoot relative to underside of stabiliser
* Important for footwear fit - Heel raise
* Thickness of material between underside of heel
and underside of stabiliser
is covering necessary
no but can be used for:* Change shear forces at skin
* Protect foot from minor imperfections in shell finish (pressure concentrators)
* Enhance durability of EVA devices and padding
* Protect device from sweat, wound exudate etc
* Improve appearance to device
what doesnt covering have effect on
- Shock absorption/attenuation
- Plantar pressures
Types of 3d scanners
- structured light- most accurate. projects patter of light on an object
- laser- expensive one in prac. captures depth and shape (NWB, WB, SWB)
- contact digitizer- not technically 3d scanning but expensive and same information. uses pins in the foot to capture data
- combination
pros of 3d scanning
accurate
low error
reduced capture time and processing time
easy redos
cost has reduced
types are portable
what is the assessment criteria of a 3d scan
- Are there holes in the scan
- Can you see the rearfoot bisection
- Forefoot to Rearfoot alignment
- Have you capture the height of the MLA
- Toe alignment
- Does it match the foot
polypropylene material
-thin and lower profile compared to EVA
-tough, flexible and easy to mould
-limited adjustability
polyethylene material
-similar to polyproylene but easier to grind and more flexible and heavier
carbon fire material
-lighter and thinner than propylenes but just as rigid
-more expensive
-less adjustable
EVA material
-easy to modify
-can adjust lengths
-bulky orthotic can be hard to fit shoes
poron material (open celled polyurethane foam)
-good for cushioning and pressure reduction
-different thickness and can bulk
-tears easily with shearing
-can bottom out. (lose rebound effect)
plastazote material (closed cell polyethlene foam)
similar to poron
-range of densities
-moudable
-shock absorbing
-can be used as top cover to reduce pressure
-strong and soft
-can bottom out quickly
top cover materials
EVA
Neoprene (synthetic rubber)
Vinyl (synthetic leather)- can be slippery
Leather (used for people allergic to synthetic)
bottom materials
Cambrelle: protects lining of shoe and underside of orthosis and makes the forefoot thicker and easier to insert into shoes
what does a plantar fascial groove do and how can you make it in the orthotic
reduces pressure on the fascia during propulsion to allow windlass mechanism
intrinsic: addition of plaster under fascia
extrinsic: removal of materail from shell
cuboid notch and how can you make it
applies pressure plantar to cuboid and a pronatory forces across midtarsal joint . this can help prevent with peroneal injuries
intrinsic: removal of plaster plantar to calcaneocuboid joint
extrinsic: applied to shell
what is a 1st ray accommodation
reduces forces and dorsiflexion of 1st met,
enables plantarflexion of 1st met and windlass mechanism
extrinsic: add plaster under 1st met
what is a plantar 5th ray grind and how to make it
increases height of lateral arch and increases pronation moments during midstance
extrinsic: removal of plaster under 5th ray
heel skive what does it do and how to make it
shifts GRF
medial: increases supination moments at loading
lateral: increases pronation moments at loading
extrinsic: removal of plaster at medial or lateral rearfoot
what is a met dome and how to make it
increases pressure proximal to met heads, reduces ressure in nearby areas
intrinsic: removal of plaster between met 1-5
what is a heel aperture
reduces pressure at centre of heel, increases pressure in surrounding areas
a hole in the heel and filled with poron
what is a 1st ray cut out
removal under 1st met to reduce pressure and allow 1st ray platnarflexion
good for fnl hallux limitus
what is a 1st ray cut away
removal of length of 1st met to reduce pressure and allow 1st ray plantrflexion goot for functinal HL
what is a lateral plantar grind
reduces bulk and increases flexibility of orthoses
what is a gait plate
increases force required to toe off over the long edge
-good for people in toeing
extension of a rigid shell distally
what is a mortons extension
reduces dorsiflexion and compressive stress
good for hallux rigidus
intrinsic: extension of rigid shell
extrinsic: padding attached to top surface of orthosis
what is a flange
midfoot extension (medial or lateral)
provides more stability
what is a reverse mortons extension
increases pressure under 2-5mets, reduces pressure under 1st, increases STJ pronation moment during midstance and terminal stance, reduces dorsiflexion moments of 1st met
extrinsic: extension under 2-5 met heads
what is a heel raise
increases max ankle dorsiflexion
extrinsisc: addition material under heel
extrinsic forefoot post
wedge applied to the forefoot (varus/valgus)
computer aided design and manufacture pros
Repeatable
Reduces cost
Faster (less steps involved)
Accuracy
Remakes
3 steps to computer aided design
- Scan (foot, negative cast, positive cast, orthosis)
- Model
- Manufacture (milling,3D printing)
2 types of computer manufacuring
- subtractive (milling)
- additive (3d printing)
pros and cons of milling
fast 15-30mins
manual finishing required
limited to homogenous materials
need space for machine
lots of waste
cost of blanks
types of 3d printing
- powder bed fusion
- material extrusion(fused filament fabrication)
- vat photopolymerisation
powder bed fusion
requires space
fast
no blanks required
post processing (removal of powder, time consuming)
cant have cavities
wide range materials
material extrusion
wide range of materials
safe
minimal post processing
small space
affordable
vat photopolymerisation
wide range of materials
high detail and accuracy
fast
range in prices
materials are health hazards, long term degrdation and stinky
lots of manual post processing required (washing and additional curing)
