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#2 Surg > 29 - Orthotic Fabrication II > Flashcards

29 - Orthotic Fabrication II Flashcards

1
Q

Rearfoot post

A
  • We’ve gotten to the point where we have a vacuum formed orthotic which has been trimmed distally and medially/laterally so it is not so wide
  • Now we have the opportunity to add an extrinsic rearfoot post to keep the orthotic stable in the shoe (because it is rounded without this)
  • The orthotic will have a rounded heel after it is shaped over the positive cast and will be unstable in the shoe
  • Rearfoot post only acts as a platform to stabilize the orthotic
  • Made from rigid material or shock absorbing material (cork or crepe)
  • An extrinsic rearfoot post is then applied to the shell
  • Functional devices that are milled have a rigid rearfoot post incorporated into orthotic – NOT going to be an extrinsic addition to the orthotic
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2
Q

Construction of rearfoot post

A

FLAT or ANGLED

  • FLAT = Rearfoot post may be constructed so that it is flat and parallel to the anterior orthosis edge (flat post)
  • ANGLED = Or it may be shaped so that the medial and lateral aspects are at different frontal plane angles (a rearfoot post that is angled and has motion)
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3
Q

How to write for a flat or angled rearfoot post

A
  • The first number is the amount of lateral grind on the post that holds the front edge inverted before forefoot loading. This is most often 4 degrees to accommodate the inverted position of the heel at heel contact.
  • The second number is the amount of motion the orthotic has during forefoot loading when the front edge comes down to the ground.
  • FLAT – A 0/0 post is ground parallel to the front edge of the orthotic and is intended to keep the front edge flat in the shoe regardless of foot movement.
  • ANGLED – A 4/4 post is one in which the lateral aspect of the post is inverted 4 degrees to the front edge of the orthosis and there is 4 degrees of motion (eversion) allowed to bring the medial half of the post parallel to the front edge of the orthosis.
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4
Q

Lateral skive

A
  • Lateral skive provides a prescribed amount of STJ pronation at contact phase.
  • This allows the STJ to function more normally and assist in shock absorption.
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5
Q

Prescription for rearfoot post

A
  • The prescription for the rearfoot post is based on the height of the STJ axis from the transverse plane
  • The lower the axis, the more inversion/eversion is available, the more pronated the foot, and the more motion control is necessary
  • Normal angle of inclination of STJ axis: 4°/4° (4° of inverted post and 4° of motion) – “normal”
  • Low angle: 6°/6° (a lot of pronation)
  • High angle: 2°/2° (not a lot of pronation)
  • 0°/0°: no inversion or motion – this is done to restrict motion
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6
Q

Inverted rearfoot post

A
  • Can also add a rearfoot post that is inverted (e.g. 4°) which does not allow any motion
  • RARELY DONE because it limits normal inversion and eversion of the foo
  • Does NOT mimic normal gait or foot position during gait – HOLDS it in the inverted position
  • No benefit or purpose for inverting a rearfoot post because it inverts forefoot at heel strike which then causes orthosis to evert at forefoot loading (creates a very unstable orthotic)
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7
Q

Medial heel skive

A
  • Can be done in addition to rearfoot post to increase pronation control for EXCESSIVE pronation
  • Unlike the rearfoot post which is an extrinsic modification to the orthotic itself, the medial heel skive is an INTRINSIC*** modification to the orthotic because it involves a modification to the positive cast, not the orthotic
  • Creates an additional wedge that inverts the heel
  • Inverts heel by increasing ground reaction force medial to the STJ axis
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8
Q

How to make a medial heel skive

A

Place positive cast upside down and divide the heel into thirds – all of the modification will occur in the medial 1/3 of the positive cast

Next, cut through the medial mark with a hacksaw to a prescribed depth
o 2 mm: mild pronation control (creates a little inversion)
o 4 mm: moderate (creates moderate inversion)
o 6 mm: large (creates large inversion)

Finally, remove the medial plaster at a 15° varus angle down to the level of the cut

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9
Q

Heel cup height

A
  • Puts plastic along the sides of the heel in order to physically limit how much the heel can rock in valgus and varus – helps to control motion of the STJ
  • The higher the heel cup height, the greater the control
  • Can do both sides or just one side (control just varus or control just valgus)
  • The disadvantage is that the higher the heel cup, the wider the heel, and the more difficult to fit into the shoe
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10
Q

Heel cup heights

A 
Average heel cup: 12-16 mm
o	Increase height of medial and/or lateral heel cup
o	High medial: 14-18 mm
o	High lateral: 14-16 mm
o	Low medial:  10-14 mm
o	Low lateral: 8-12 mm
  • Higher than normal cup height = to control excessive motion of the STJ
  • Lower than normal cup height = if patient would be irritated by the extra plastic (such as ulcers)
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11
Q

Medial arch fill (AKA medial expansion)

A
  • Reduces irritation of medial arch from the orthotic
  • Plaster is added to the medial arch of the positive cast, now when you press the plastic against this, you will create a space between the orthotic and the skin
  • The orthotic is now not pressing up on the foot as much
  • You would use this if you thought the main use of the orthotic would be to control the STJ motion and you thought the plastic would irritate the bones of the arch
  • Average medial arch: 4mm of fill
  • High medial arch (cavus foot): 2 mm of fill = minimal arch fill
  • Low medial arch (flat foot): 6 mm of fill
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12
Q

Foot types and medial arch fill

A
  • Flatfoot: extra medial arch is added to the positive cast-when orthotic is formed to shape of cast, medial arch of the orthotic is lower than the foot’s medial arch which will reduce irritation of the orthotic on the arch
  • However, if extra pronation control is desired, minimal arch fill will make the arch of the orthotic higher, helping to prevent pronation, especially if it is the result of increased frontal plane motion at the MTJ
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13
Q

Inverted pour or Blake modification

A
  • Can also affect arch height of orthosis by performing an inverted pour or Blake modification
  • NEGATIVE cast is wedged up medially, increasing varus position
  • Not a good modification, other methods provide better control and comfort – DON’T USE THIS
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14
Q

Lateral expansion

A
  • Makes the orthotic wider to allow for soft-tissue spread – used in fat feet and flat feet so that the lateral grind does not dig into the feet
  • When you send in your prescription, you also send in a weightbearing trace of the foot, so they know how the foot expands when weightbearing
  • A functional orthotic is made from a negative cast taken in NWB position; thus, when foot bears weight, soft tissue is displaced laterally and medially
  • Lateral expansion allows for spread of soft tissue in WB
  • In order to prescribe the correct amount of lateral expansion, need to observe the amount of soft tissue expansion in WB
  • A lateral expansion is done by adding extra plaster along the lateral side of the positive cast
  • Standard lateral expansion (3-5 mm): average soft tissue displacement
  • Wide lateral expansion (5-10 mm): excessive soft tissue displacement
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15
Q

Top cover

A
  • Most people like something soft between their foot and the orthotic – that’s all a top cover does

Uses:
o Keep foot from slipping on orthotic
o Make anterior edge of orthotic more comfortable
o Cushion or accommodate bone that may rub against the orthotic

  • Can extend to metatarsal parabola, to sulcus of the toes, or to the ends of the toes
  • If you need more room in the toebox, you can use a top cover that does not extend all the way to the tips of the toes
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16
Q

Soft tissue supplement materials

A
  • Neoprene (Spenco®)
  • Polyurethanes (PPT®, Poron®, plastizote)
  • Visco elastomers (Sorbothane®)
17
Q

Neoprene (Spenco®)

A

o Notes: Keeps its shape longer, not as much cushioning, not a lot of movement so you can prevent blisters, sticks to plastic of orthotic, but can be pulled off easily to replace
o Best for anti-shear material
o Closed cell makes them more adhesive resistant
o Closed cell permits excellent rebound

18
Q

Polyurethanes (PPT®, Poron®, plastizote)

A

o Notes: Deforms more readily, but per square inch of pressure, it provides more cushioning and sticks better to the polypropylene plastic , but that makes it really hard to pull off to replace (ends up coming off in pieces)
o Best memory gradient and vertical force resistance
o Open cell material makes them adhesive friendly, but retain odors

19
Q

Visco elastomers (Sorbothane®)

A

o Notes: do not use this ever, it has better shock absorption, but it does not stick to the plastic and it is too thick and too hard so patients don’t like it
o Best shock attenuator
o Adhesive resistance
o Sticky surface inhibits motion of foot within shoe

20
Q

Tissue interface materials

A
  • Neoprene (can put this right on the skin)
  • Leather
  • Naugahyde, or vinyl
21
Q

Leather as a tissue interface material

A

o Notes: not good for someone with sweaty feet
o Poor moisture and acid resistance
o Hypoallergenic

22
Q

Naugahyde or vinyl as a tissue interface material

A 
o	Notes: a lot easier to put on, lighter than leather, slide around on it more, generates heat
o	Moisture and acid resistant
o	Excellent adhesive retention
o	Stretchable
o	Highly tear resistant
o	Generates heat
23
Q

Additions to orthotics

A
  • Forefoot extension
  • Heel lift
  • Metatarsal pad
  • Morton’s extension
  • Reverse Morton’s extension
  • “Sweet spot”
24
Q

Forefoot extension

A

o Added under topcover distal to edge of orthotic to support or accommodate metaheads
o Can have a valgus or varus wedge
o Even though you have already made the orthotic for a valgus or varus, you may want a little more, so you can add a wedge
o Example: If you have a painful 2nd metatarsal head, you can cut a hole out of this extension so there is no pressure on the 2nd met head and the other metatarsal heads will bear more pressure

25
Q

Heel lift

A

o Treat limb length inequality, ankle equinus, heel pain, scoliosis, calf or hamstring strain, hip pain
o There is a limit to this – a maximum of ½ inch can be added for athletic shoes, three-eighth’s inch in men’s lace-ups, one-quarter inch in men’s loafers or women’s flats

26
Q

Metatarsal pad

A

o Sits under topcover just proximal to metaheads and off-loads metaheads
o The ideal placement distance for the most consistent pressure reductions is 6.1 to 10.6 mm proximal to a line identifying the met head
o Example: if you added an extension and cut a hole by the 2nd metatarsal head, you can also add a pad more proximal on the 2nd metatarsal head so you can further off-load the 2nd metatarsal head, but this one takes pressure off of all the metatarsal heads instead of increasing pressure on the other ones
o There is an exact place you need to place this – make sure the leading edge of the metatarsal pad is 8 mm from the metatarsal head

27
Q

Morton’s extension

A

o Pad that extends under the 1st metatarsal head and great toe to restrict 1st MPJ motion
o If you have hallux limitus (DJD of first MPJ), so surgically you treat it with a first MPJ fusion (no movement – preferred surgical approach) because the pain is due to movement in the joint. You can also treat this conservatively by restricting motion of the first MPJ by having a stiff material under the joint, so the joint is immobilized.

28
Q

Reverse Morton’s extension

A

o Pad that sits under the 2nd through 5th metaheads to accommodate 1st metahead for a lesion or allows plantarflexion of 1st metatarsal to improve 1st MPJ dorsiflexion
o Another surgical approach to DJD of the first MPJ would be positioning the 1st metatarsal plantarly, and by putting it closer to the ground, allow the 1st toe to bend more dorsally – you can mimic this conservatively by allowing more plantarflexion of the first ray by dorsiflexing the rest of the digits
o The patient will often say that they have less pain in soft shoes – more likely for this to work better

29
Q

“Sweet spot”

A

o Extra padding depressed into the body of the orthosis while the plastic is still hot to cushion prominent bones (navicular)
o Can also pad around bones to “float” them

30
Q 
Intrinsic modifications to correct pronation include:
o	Medial heel skive
o	6/6 rearfoot post
o	Shallow heel cup
o	2/2 rearfoot post
o	Morton’s extension
A

Answer: 1 – KNOW THE DIFFERENCE BETWEEN INTRINSIC AND EXTRINSIC MODIFICATIONS***

31
Q 
-	To alleviate the pain with hallux limitus modify an orthosis with:
o	A Morton’s extension
o	A reverse Morton’s extension
o	A lateral expansion
o	A varus forefoot extension
A

Answer: 1, 2

32
Q

Now I’m going to make it easy for you…

A
  • Although I have presented all the modifications available across the industry
  • Orthotic companies want your money, so they try to make it easy for you
  • On the front side of their prescription form is all the possible modifications available
  • On the back side of their prescription form is “what is your patient’s problem?”
  • If your patient has plantar fasciitis due to a forefoot valgus, that’s all you have to do – they tell you what you’re going to do
  • What they are depending on from you is the only important step – that you have gotten an accurate mold of the foot
  • If you use this company, you don’t need to know anything about what we just talked about, but they are one of the only companies that does this
  • If you look at the form, it tells you all the modifications they will make for each of the pathologies
33
Q

Orthosis prescription simplified (if you aren’t using ProLabs)

A
  • Semi-rigid or flexible polypropylene (regardless of weight)
  • Full length 1/8” Spenco® or PPT® topcover
    o Glue only the proximal portion of topcover to orthosis
    o Allows one to make additional modifications (adding extra pads) to forefoot if needed
  • Post the rearfoot to vertical (because most of us have already comfortably compensated to vertical)
  • Post the forefoot to cast (this is the step where you add a nail and add a platform so the orthotic sits flat on the table)
34
Q
  • Need 3 things if you are going to do orthotic modification in your office:
A

o Glue
o Cheap roll of 1/8 inch felt and ¼ inch felt to make modifications and add extra padding
o Grinder for plastic

#2 Surg (14 decks)

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