32 - Orthosis Theory Flashcards
Why teach Root biomechanics?
- 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
2 major premises of West Coast (Root) Voodoo
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)
Describe the significance of neutral position in West Coast (Root) Voodoo
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
Describe motion of the STJ in relation to Root
- 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
Describe the function of orthoses in relation to Root theory
- 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**
According to Root, what is the best way to achieve stable supination for propulsion?
- 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?
Study on the variability of neutral positioning casting of the foot
- 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?
What does an orthotic accomplish?
- 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
What does the concave heel of the orthosis do?
- 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
Study on the effects of foot orthotics on lower extremity kinematics during running
- “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
Study on the effect of foot orthotics and gait velocity on lower limb kinematics and temporal events of stance
The amount of tibial internal rotation was decreased in relation to the amount of tibial abduction
Study on the effect of foot orthotics on three-dimensional kinematics of the leg and rearfoot during running
The amount of tibial internal rotation was decreased in relation to the amount of tibial abduction
Study - Is there proof in the evidence-based literature that custom orthoses work?
- “…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.”
Study - Do orthoses prevent injury? Foot orthoses in the prevention of injury in initial military training
- Randomized controlled trial
- ARR of .49 from using orthoses (NNT of 2), so it prevented injury HALF of the time
Casting outside of podiatry
- 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
Anti-Root thoughts
- 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