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PODMED3 > wk 5- manufacture of orthoses > Flashcards

wk 5- manufacture of orthoses Flashcards

1
Q

what can orhtotics do

A
  • Control alignment
  • Correct or accommodate deformity
  • Protect or support an injury
  • Assist rehabilitation
  • Reduce pain
  • Increase mobility
  • Increase independence
  • redistribute pressure/load/force
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2
Q

what is an orthotic

A

shoe device which alters forces acting on the foot during weight bearing

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3
Q

steps of traditional orthosis manufacture

A

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

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4
Q

ways you can perform a negative cast

A
  1. Non weight bearing plaster cast
    (Supine/prone)
  2. Weight bearing or semi weight bearing Foam box impression
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5
Q

what is the difference between WB and NWB negative casting

A

WB= lower arch, wider and longer foot

expansions need to be made for NWB

STJ neutral needs to be maintained for WB/SWB

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6
Q

Pros and cons of plaster cast

A

pro:
STJ neutral maintained/1st ray

con:
expansions required
physically demanding
time consuming, space, waste

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7
Q

pros and cons of WB foot impression

A

pro:
quick
easy
dont need expansions

cons:
hard to keep foot in STJ neutral
physically demanding
lower arch, wider, longer (deformation when applying pressure

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8
Q

what is involved in positive casting

A

Cast is filled with plaster of paris, while cast is angled, when set, the negative cast is removed

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9
Q

pour angles for positive casting

A

-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

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10
Q

steps in positive cast modification

A

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

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11
Q

what is pressing and steps

A

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

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12
Q

types of semi rigid or flexible material (shank dependent)

A

deformation occurs through compression

EVA
Foam rubbers
Cork
Thermoplastic polyurethane

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13
Q

types of rigid material (shank independent)

A

deformation occurs through bending of materials

Polypropylene
Polyethylene
Nylon
Carbon fibre
Resins

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14
Q

what is involved in posting

A

addition of material under the heel of orthosis

3 main types

  1. Extrinsic rearfoot post
    * frontal plane alignment of underside relative to
    the calcaneal bisection
  2. Heel pitch
    * Drop of rearfoot relative to underside of stabiliser
    * Important for footwear fit
  3. Heel raise
    * Thickness of material between underside of heel
    and underside of stabiliser
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15
Q

is covering necessary

A

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

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16
Q

what doesnt covering have effect on

A
  • Shock absorption/attenuation
  • Plantar pressures
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17
Q

Types of 3d scanners

A
  1. structured light- most accurate. projects patter of light on an object
  2. laser- expensive one in prac. captures depth and shape (NWB, WB, SWB)
  3. contact digitizer- not technically 3d scanning but expensive and same information. uses pins in the foot to capture data
  4. combination
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18
Q

pros of 3d scanning

A

accurate
low error
reduced capture time and processing time
easy redos
cost has reduced
types are portable

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19
Q

what is the assessment criteria of a 3d scan

A
  • 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
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20
Q

polypropylene material

A

-thin and lower profile compared to EVA
-tough, flexible and easy to mould
-limited adjustability

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21
Q

polyethylene material

A

-similar to polyproylene but easier to grind and more flexible and heavier

22
Q

carbon fire material

A

-lighter and thinner than propylenes but just as rigid
-more expensive
-less adjustable

23
Q

EVA material

A

-easy to modify
-can adjust lengths
-bulky orthotic can be hard to fit shoes

24
Q

poron material (open celled polyurethane foam)

A

-good for cushioning and pressure reduction
-different thickness and can bulk
-tears easily with shearing
-can bottom out. (lose rebound effect)

25
Q

plastazote material (closed cell polyethlene foam)

A

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

26
Q

top cover materials

A

EVA
Neoprene (synthetic rubber)
Vinyl (synthetic leather)- can be slippery
Leather (used for people allergic to synthetic)

27
Q

bottom materials

A

Cambrelle: protects lining of shoe and underside of orthosis and makes the forefoot thicker and easier to insert into shoes

28
Q

what does a plantar fascial groove do and how can you make it in the orthotic

A

reduces pressure on the fascia during propulsion to allow windlass mechanism

intrinsic: addition of plaster under fascia
extrinsic: removal of materail from shell

29
Q

cuboid notch and how can you make it

A

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

30
Q

what is a 1st ray accommodation

A

reduces forces and dorsiflexion of 1st met,
enables plantarflexion of 1st met and windlass mechanism

extrinsic: add plaster under 1st met

31
Q

what is a plantar 5th ray grind and how to make it

A

increases height of lateral arch and increases pronation moments during midstance

extrinsic: removal of plaster under 5th ray

32
Q

heel skive what does it do and how to make it

A

shifts GRF
medial: increases supination moments at loading
lateral: increases pronation moments at loading

extrinsic: removal of plaster at medial or lateral rearfoot

33
Q

what is a met dome and how to make it

A

increases pressure proximal to met heads, reduces ressure in nearby areas

intrinsic: removal of plaster between met 1-5

34
Q

what is a heel aperture

A

reduces pressure at centre of heel, increases pressure in surrounding areas

a hole in the heel and filled with poron

35
Q

what is a 1st ray cut out

A

removal under 1st met to reduce pressure and allow 1st ray platnarflexion

good for fnl hallux limitus

36
Q

what is a 1st ray cut away

A

removal of length of 1st met to reduce pressure and allow 1st ray plantrflexion goot for functinal HL

37
Q

what is a lateral plantar grind

A

reduces bulk and increases flexibility of orthoses

38
Q

what is a gait plate

A

increases force required to toe off over the long edge
-good for people in toeing

extension of a rigid shell distally

39
Q

what is a mortons extension

A

reduces dorsiflexion and compressive stress
good for hallux rigidus

intrinsic: extension of rigid shell
extrinsic: padding attached to top surface of orthosis

40
Q

what is a flange

A

midfoot extension (medial or lateral)
provides more stability

41
Q

what is a reverse mortons extension

A

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

42
Q

what is a heel raise

A

increases max ankle dorsiflexion

extrinsisc: addition material under heel

43
Q

extrinsic forefoot post

A

wedge applied to the forefoot (varus/valgus)

44
Q

computer aided design and manufacture pros

A

Repeatable
Reduces cost
Faster (less steps involved)
Accuracy
Remakes

45
Q

3 steps to computer aided design

A
  1. Scan (foot, negative cast, positive cast, orthosis)
  2. Model
  3. Manufacture (milling,3D printing)
46
Q

2 types of computer manufacuring

A
  1. subtractive (milling)
  2. additive (3d printing)
47
Q

pros and cons of milling

A

fast 15-30mins
manual finishing required
limited to homogenous materials
need space for machine
lots of waste
cost of blanks

48
Q

types of 3d printing

A
  1. powder bed fusion
  2. material extrusion(fused filament fabrication)
  3. vat photopolymerisation
49
Q

powder bed fusion

A

requires space
fast
no blanks required
post processing (removal of powder, time consuming)
cant have cavities
wide range materials

50
Q

material extrusion

A

wide range of materials
safe
minimal post processing
small space
affordable

51
Q

vat photopolymerisation

A

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)

52
Q
A

PODMED3 (5 decks)

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