wk 5- manufacture of orthoses

Question 1

what can orhtotics do

Answer 1

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

Question 2

what is an orthotic

Answer 2

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

Question 3

steps of traditional orthosis manufacture

Answer 3

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

Question 4

ways you can perform a negative cast

Answer 4

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

Question 5

what is the difference between WB and NWB negative casting

Answer 5

WB= lower arch, wider and longer foot

expansions need to be made for NWB

STJ neutral needs to be maintained for WB/SWB

Question 6

Pros and cons of plaster cast

Answer 6

pro:
STJ neutral maintained/1st ray

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

Question 7

pros and cons of WB foot impression

Answer 7

pro:
quick
easy
dont need expansions

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

Question 8

what is involved in positive casting

Answer 8

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

Question 9

pour angles for positive casting

Answer 9

-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

Question 10

steps in positive cast modification

Answer 10

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

Question 11

what is pressing and steps

Answer 11

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

Question 12

types of semi rigid or flexible material (shank dependent)

Answer 12

deformation occurs through compression

EVA
Foam rubbers
Cork
Thermoplastic polyurethane

Question 13

types of rigid material (shank independent)

Answer 13

deformation occurs through bending of materials

Polypropylene
Polyethylene
Nylon
Carbon fibre
Resins

Question 14

what is involved in posting

Answer 14

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

Question 15

is covering necessary

Answer 15

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

Question 16

what doesnt covering have effect on

Answer 16

• Shock absorption/attenuation
• Plantar pressures

Question 17

Types of 3d scanners

Answer 17

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

Question 18

pros of 3d scanning

Answer 18

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

Question 19

what is the assessment criteria of a 3d scan

Answer 19

• 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

Question 20

polypropylene material

Answer 20

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

Question 21

polyethylene material

Answer 21

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

Question 22

carbon fire material

Answer 22

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

Question 23

EVA material

Answer 23

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

Question 24

poron material (open celled polyurethane foam)

Answer 24

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

Question 25

plastazote material (closed cell polyethlene foam)

Answer 25

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

Question 26

top cover materials

Answer 26

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

Question 27

bottom materials

Answer 27

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

Question 28

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

Answer 28

reduces pressure on the fascia during propulsion to allow windlass mechanism intrinsic: addition of plaster under fascia extrinsic: removal of materail from shell

Question 29

cuboid notch and how can you make it

Answer 29

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

Question 30

what is a 1st ray accommodation

Answer 30

reduces forces and dorsiflexion of 1st met, enables plantarflexion of 1st met and windlass mechanism extrinsic: add plaster under 1st met

Question 31

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

Answer 31

increases height of lateral arch and increases pronation moments during midstance extrinsic: removal of plaster under 5th ray

Question 32

heel skive what does it do and how to make it

Answer 32

shifts GRF medial: increases supination moments at loading lateral: increases pronation moments at loading extrinsic: removal of plaster at medial or lateral rearfoot

Question 33

what is a met dome and how to make it

Answer 33

increases pressure proximal to met heads, reduces ressure in nearby areas intrinsic: removal of plaster between met 1-5

Question 34

what is a heel aperture

Answer 34

reduces pressure at centre of heel, increases pressure in surrounding areas a hole in the heel and filled with poron

Question 35

what is a 1st ray cut out

Answer 35

removal under 1st met to reduce pressure and allow 1st ray platnarflexion good for fnl hallux limitus

Question 36

what is a 1st ray cut away

Answer 36

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

Question 37

what is a lateral plantar grind

Answer 37

reduces bulk and increases flexibility of orthoses

Question 38

what is a gait plate

Answer 38

increases force required to toe off over the long edge -good for people in toeing extension of a rigid shell distally

Question 39

what is a mortons extension

Answer 39

reduces dorsiflexion and compressive stress good for hallux rigidus intrinsic: extension of rigid shell extrinsic: padding attached to top surface of orthosis

Question 40

what is a flange

Answer 40

midfoot extension (medial or lateral) provides more stability

Question 41

what is a reverse mortons extension

Answer 41

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

Question 42

what is a heel raise

Answer 42

increases max ankle dorsiflexion extrinsisc: addition material under heel

Question 43

extrinsic forefoot post

Answer 43

wedge applied to the forefoot (varus/valgus)

Question 44

computer aided design and manufacture pros

Answer 44

Repeatable Reduces cost Faster (less steps involved) Accuracy Remakes

Question 45

3 steps to computer aided design

Answer 45

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

Question 46

2 types of computer manufacuring

Answer 46

1. subtractive (milling) 2. additive (3d printing)

Question 47

pros and cons of milling

Answer 47

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

Question 48

types of 3d printing

Answer 48

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

Question 49

powder bed fusion

Answer 49

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

Question 50

material extrusion

Answer 50

wide range of materials safe minimal post processing small space affordable

Question 51

vat photopolymerisation

Answer 51

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)