32 - Orthosis Theory Flashcards

1
Q

Why teach Root biomechanics?

A
  • It is the overwhelming choice of our profession which guides orthotic treatment
  • The following is accepted as fact: functional foot orthoses change the alignment of the foot and leg to improve function
  • I feel that its major use at this point is that it establishes a baseline of understanding (even if incorrect) which then needs to be proven/disproven over time as new investigational technologies evolve
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2
Q

2 major premises of West Coast (Root) Voodoo

A

o Neutral position of the STJ is the stable position of the foot
o Pathology occurs because the foot is not in neutral position (deviation from STJ neutral)

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3
Q

Describe the significance of neutral position in West Coast (Root) Voodoo

A
o	Root (correctly) determined that the neutral position of the STJ was necessary to identify in order to have a common talking point when discussing foot biomechanics
o	Neutral position exists for all joints in the body
o	It describes that position of the joint where the major planal motion of the joint is not predominately occurring in either direction
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4
Q

Describe motion of the STJ in relation to Root

A
  • For the STJ, since its motion is primarily frontal plane (inversion and eversion or pronation and supination), neutral position is where the STJ is neither supinated nor pronated
  • According to Root, the normal posterior bisection of the heel compared to the posterior bisection of the leg NWB should be 0° (STJ neutral position) (range is 0-3° varus)
  • With WB, the normal bisection of the heel to the ground also should be 0° (RCSP) (range is 2° varus to 2° valgus)
  • From this neutral position, one can then begin to describe deformities in the frontal plane, such as forefoot and rearfoot varus and valgus – any deviations from STJ neutral
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5
Q

Describe the function of orthoses in relation to Root theory

A
  • By trial and error only, Root determined that the best casts for making an orthosis were made when the STJ was held in neutral and the MTJ was fully pronated
  • The rationale behind this is not understood by his supporters
  • It is a logical assumption to allow the STJ to pronate after heel strike and to resupinate in midstance through toe-off
  • VERY IMPORTANT TO KNOW: The foot is locked and stable in supination making it a rigid lever for propulsion**
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6
Q

According to Root, what is the best way to achieve stable supination for propulsion?

A
  • The best way to achieve this is to cast the foot non-weightbearing in STJ neutral in order to get the orthotic to conform fully to the plantar contour of the foot in all three planes and prevent unnecessary, excessive, pathological motion that occurs when the foot bears weight
  • Fully pronating the MTJ during casting places the foot in its maximum position of osseous stability and resists deforming forces at the STJ and MTJ
  • This technique is easily reproducible among practitioners… OR IS IT?
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7
Q

Study on the variability of neutral positioning casting of the foot

A
  • 10 inexperienced and 10 experienced clinicians took a right foot cast of a single subject
  • 1 experienced clinician took ten casts of the same foot
  • Forefoot position of each cast was determined
  • Forefoot measurements – they were all over the place!

The question is then asked… Is it necessary to have an accurate cast if functional orthoses are effective in relieving pain either way?

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8
Q

What does an orthotic accomplish?

A
  • A custom functional orthosis (CFO) provides ground reaction force against the excessive plantarflexion and adduction of the talus (and hence, the T-N joint) during pronation
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9
Q

What does the concave heel of the orthosis do?

A
  • The concave heel of the orthosis resists calcaneal eversion which limits talar adduction and plantarflexion
  • Cast will capture the medial and lateral longitudinal arches and any forefoot frontal plane deformity
  • This prevents lowering of the arch and any compensation that an abnormal forefoot deformity (FF varus or valgus) will cause
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10
Q

Study on the effects of foot orthotics on lower extremity kinematics during running

A
  • “The potential of foot orthotics for reducing pain and injuries is convincing.”
  • The most important factor in determining a positive treatment effect was a mold of the foot taken in neutral position suspension cast
  • CFO’s caused a decrease in maximum tibial internal rotation, an INCREASE (?) in maximum rearfoot eversion angle, and an increase in maximum rearfoot inversion angle and velocity
    o The orthotic stopped the tibia from internally rotating
    o That however did not lead to a decrease in rearfoot inversion, it actually increased it
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11
Q

Study on the effect of foot orthotics and gait velocity on lower limb kinematics and temporal events of stance

A

The amount of tibial internal rotation was decreased in relation to the amount of tibial abduction

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12
Q

Study on the effect of foot orthotics on three-dimensional kinematics of the leg and rearfoot during running

A

The amount of tibial internal rotation was decreased in relation to the amount of tibial abduction

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13
Q

Study - Is there proof in the evidence-based literature that custom orthoses work?

A
  • “…peer-reviewed scientific evidence to confirm our speculations that custom orthoses are effective in treating plantar fasciitis, metatarsalgia, hallux limitus, adult acquired flatfoot, rheumatoid arthritis foot, tarsal tunnel syndrome, and lateral ankle instability.”
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14
Q

Study - Do orthoses prevent injury? Foot orthoses in the prevention of injury in initial military training

A
  • Randomized controlled trial

- ARR of .49 from using orthoses (NNT of 2), so it prevented injury HALF of the time

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15
Q

Casting outside of podiatry

A
  • Outside of podiatry, most casting is done in semi-weightbearing or full weightbearing position
  • These people claim that they capture the true pathological condition of the foot by having them casted in weightbearing
  • Orthosis most accurately reflects the true position of the foot as it functions
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16
Q

Anti-Root thoughts

A
  • Root followers believe that this position captures the foot after it has compensated for a deformity
  • This would only preserve this abnormal position in the orthosis and not restore normal alignment and function
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17
Q

Study on the comparison of negative casting techniques used for the fabrication of custom ankle foot orthoses

A
  • Right foot of 34 y/o w/f had slipper casts applied in neutral suspension (NS), semi-weightbearing (SWB), full weightbearing (FWB)
  • Total length of foot increased in SWB and FWB due to lower arch configuration
  • Maximum width of heel increased in SWB and FWB
  • Width of forefoot remained the same with all techniques
18
Q

SWB and FWB

A

KNOW THIS
o **SWB and FWB resulted in supination of the forefoot; 7° for SWB which was even more inverted than FWB
o **
NS resulted in 4° everted forefoot position
o ***Heel is not rounded in SWB and FWB which is considered essential for rearfoot control in an orthosis

“In most pathologies treated with functional [AFO’s], maximal rearfoot control and accurate medial arch contour are critical to a successful outcome.”

19
Q
  • According the Root biomechanics:
    o Controlling the arch limits abnormal movement
    o Controlling the forefoot limits abnormal movement
    o Controlling the STJ around neutral position at midstance limits abnormal movement
    o Pathology occurs because the foot in not in neutral position
    o Weightbearing impressions capture the true position of the foot before it compensates for pathology
A

Answer: 3, 4

20
Q

East Coast (Schuster) Voodoo

A
  • Arch support is more important in controlling foot pronation than is maintaining the foot as close to its neutral position as possible
  • STJ neutral is a range rather than a distinct point
  • SWB and FWB is more accurate because it more closely captures closed chain biomechanics
21
Q

Origin of East Coast (Schuster) Voodoo

A
  • Root used a study by Wright et al (Action of the subtalar and ankle-joint complex during the stance phase of walking. JBJS 1964; 46A:361) to describe STJ neutral
  • According to Root, STJ neutral is reached during midstance
  • MAJOR FLAW
  • However, Wright observed that it was only the relaxed calcaneal stance position that was achieved during midstance and it was in a pronated position
  • KNOW THIS *****Root took data he thought was for his neutral position when actually it was for RCSP
  • Root claims that the STJ must resupinate to his STJ neutral position during midstance and that the negative cast must be made to capture this midstance position
22
Q

Study on rearfoot inversion/eversion during gait relative to the subtalar joint neutral position

A

In 100% of asymptomatic individuals, the position of the foot in stance and gait was in a position more pronated than neutral position***

23
Q

Study on functional characteristics of the foot and plantar aponeurosis under tibiotalar loading (Sarrafian)

A
  • His anatomical study showed that “With vertical loading and internal rotation, the hindfoot and midfoot are PRONATED, and the forefoot is supinated. The medial longitudinal arch is lower, the foot is longer, and the plantar aponeurosis is tense. The foot is then more rigid and a better lever arm
24
Q

Sarrafian theories

A
  • Sarrafian also claims that the normal STJ neutral NWB position is 3.5° inverted, not 0°
  • RCSP is between 3 and 7° everted, not 0°
  • As a result, orthoses should not be made from neutral position casts – MAIN DIFFERENCE*****
  • Proponents of Schuster believe that NWB casts are not coordinated to standing and running and that SWB or FWB casts are most appropriate*
  • “Just because you capture the plantar contour of the arch with a negative cast does not mean the orthosis will put the joints of the foot in the same position when the foot is on the orthosis.”
  • “…there is about an inch of compressible soft tissue between the plantar skin and the bones of the medial arch…”
  • Painful to apply significant force to this tissue
  • “…can easily move your foot while standing on…orthoses.” (round heel MOVES in the orthotic)
  • “…the heel cup of an orthosis is not capable of holding the heel in a selected position.”
  • Difficult to stabilize a round object like the heel on a round surface of the heel cup of an orthosis
25
Q

Forefoot question

A
  • Because a Root orthosis ends behind the metaheads, how can it support a forefoot deformity?
  • “Neutral position theory looks at the positions of joints and not necessarily the forces that alter those positions.”
26
Q
  • According to Schuster biomechanics:
    o Controlling the STJ limits abnormal movement
    o Controlling the forefoot limits abnormal movement
    o Soft material is better than firm material for an orthosis
    o Controlling the arch position is more important than keeping the foot in STJ neutral
    o Controlling the position of joints is more important than the forces that act on those joints
A

Answer: 2, 3, 4

27
Q

** Schuster SUMMARY **

A
  • Weightbearing casting instead of non-weightbearing
  • Soft instead of plastic orthotic
  • Deep heel cup instead of rounded heel cup
  • Since it is soft, you can extend under the forefoot to control pathology there
28
Q

2-axis concept

A

It supposes that the C-C and T-N joints have their own separate axes of motion

29
Q

Study on clinical and experimental modes of the midtarsal joint

A
  • “…navicular and cuboid can be considered one rigid body…, they always move principally in the same direction. When the navicular bone everts relative to the ground, so too does the cuboid bone, and vice versa for inversion, and likewise for dorsiflexion/plantarflexion and adduction/abduction.”
30
Q

Midtarsal joint

A
  • It has been assumed that it is the midtarsal joint which solely determines the motion of the forefoot to the rearfoot
  • What about the navicular-cuboid-cuneiform-metatarsal complex?
  • 2 axis theory assumes that the MTJ either pronates (eversion, dorsiflexion, abduction) or supinates (inversion, plantarflexion, adduction)
  • It has been proven that the MTJ undergoes different combinations of the three planal
  • Movements (inversion with dorsiflexion and abduction, for example)
  • The one-axis model allows for this, not the two-axis model
31
Q

Study on orthotic basics for running activities

A
  • Flexible, not rigid materials are best for foot support, especially with extended forefoot posting
  • Schuster claims that it is not the rearfoot that is important to control, but rather the forefoot
  • His orthosis with its post extends underneath the metaheads, not proximal to the metaheads, like Root
32
Q

Study on the correction of the pronated foot

A
  • Heel fat pad is subjected to deformation due to compression, and would allow shearing motion
  • Therefore, “cup” the heel bone by higher medial and lateral flanges and use less rigid material
  • Heel is contacting the ground for such a short period of time, especially in running, that it does not leave time for the Root orthosis with its posted rearfoot to work
33
Q

Study on the comparison of custom and pre-fabricated orthoses in the initial treatment of proximal plantar fasciits

A
Are Custom Orthoses Better Than OTC Devices?
-	236 patients with 6 months or less of heel pain assigned to one of 5 groups which all did, at least, Achilles and plantar fascia stretching: stretching only, silicone heel insert, rubber insert, felt insert, custom made neutral casted functional orthotic (Prolab) 
-	Pain relief at 8 weeks:
o	Stretching only: 	72%
o	Silicone:		95%
o	Rubber:			88%
o	Felt:			81%
o	Custom orthosis:	68%
34
Q

Personal opinion

A
  • Using an over-the-counter orthotic and padding it with felt is the best option in terms of cost effectiveness and best outcomes
  • TAKE HOME MESSAGE: other things work – not JUST custom orthotics
35
Q

Flaws with the Pfeffer study (plantar fasciitis study from above)

A
  • Orthotics varied in flexibility, heel cup depth, width, use of a rearfoot post, and use of a topcover
  • Patients were encouraged not to change their regular footwear
  • Negative casting methods varied (13 different individuals casted the 42 individuals in the custom orthotic group)
36
Q

Unified theory

A
  • “Unified Theory” as proposed by Harradine and Bevan

- Published study below, claiming that there is some merit in both schools of thought

37
Q

Study published regarding unified theory

A
  • At contact, lower limb internally rotating (both theories agree on this)
  • STJ pronates in response to lower limb internal rotation to translate this leg movement into foot movement
  • ***Normal pronation makes foot stable as it puts tension on plantar fascia which compresses midfoot (“reverse windlass mechanism”) – their conclusion is that pronation is GOOD
  • The leg then begins to externally rotate in midstance which leads to STJ supination and arch raising – their conclusion is that supination is UNSTABLE (in midstance)
  • This could lead to lost tension (as the origin and insertion of the fascia and tendons move closer) and the midfoot might become unstable
38
Q

According to the “unified theory” of biomechanics:
o The tibia internally rotates in early stance
o The STJ then pronates
o The pronated position of the foot is unstable
o The supinated position of the foot is stable
o The windlass mechanism is not activated

A

Answer: 1, 2

39
Q

Heel off conclusion from “Unified Theory”

A
  • At heel off, the great toe dorsiflexes, which activates the normal “windlass” mechanism and this causes continued midfoot compression and resultant stability
  • If pronation is too prolonged or there are not enough forces to resist pronation, pathology can develop in the foot, leg, hip, or back
40
Q

FOCUS

A
  • Schuster’s main claims
  • Root’s main claims
  • Understand there is evidence for 1 axis of motion of MTJ (midtarsal joint)
  • Understand what the unified theory is trying to do