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Foot orthoses outcomes and kinematic changes

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  #61  
Old 2nd March 2005, 10:39 PM
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Quote:
Originally Posted by Craig Payne
Jumping from a tall building (motion) does not kill you. Hitting the ground (forces) does.
Or put another way, it's not the acceleration that causes injury, it's the deceleration.
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Old 3rd March 2005, 03:42 AM
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Default Forces and motion.

Another analogy I would throw in, is that motion is the tired old saggy housewife, and force is the new sleek gravity-defying mistress. But lets not forget who would be more reliable at cooking the roast and picking up the kids.


I have two problems with its 100% force and 0% motion.
1. How can these 2 phenomena be independent of each-other?
2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.


1. How can these 2 phenomena be independent of each-other? How can the fellow who splatters himself on concrete do so without plummeting from a height. What else can provide such a FORCE?

What about the analogy of a baseball catcher or cricket wicket-keeper. When catching a ball at speed, the keeper wisely accepts the ball out in front of his body, but finishes the 'catch' behind him. The motion of his hands in the same direction as the ball gradualises the deceleration. How can motion be completely irrelevant here? No motion equals bruised hands.


2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.

Lets take a posterior impingement of the ankle for instance; for example a clinical os trigonum. End-range plantar-flexion is pathological and symptomatic. Restrict that range to short-of-its-limitation, and the patient is happy. (Restrict it for days and perhaps one has an impact on adjacent secondary soft-tissue inflammation if it existed concurrently). Yes a plantar-flexion moment around the ankle could be aggravating, but only at the end of (PF) range. Limit end-range plantar-flexion with an strapping technique, and the plantar-flexion moment provided by kicking a football or kneeling on your heels becomes tolerable.
Critics may suggest that the strapping is providing a neutralising dorsi-flexion moment, but how then can one extrapolate and suggest that motion is entirely irrelevant?

What about an unstable ankle? An ankle with a sloppy mobile anterior-drawer? An ankle that is multi-directionally hypermobile is an inevitable accident that will progressively happen. Osteoarthritis in the talo-crural joint is inevitable. Surrounding musculo-tendinous structures are then 'called up' to function in a manner that they were not intended; to remain hyper-tonically overactive to provide some motion check and joint stability. Stop the extraneous motion (albeit with stabilising FORCES), and reduce signs and symptoms.

Turning your head to do a head check in a car involves everyday movement and presumably everyday forces. But what happens if we sustain the position? Why the signs and symptoms. The forces haven't suddenly become pathological. They haven't increased. The forces have been sustained/prolonged. In terms of motion, this suddenly hasn't become pathological, nor increased; but the limit of motion has been sustained. In this limit of motion, agonists have shortened, antagonists lengthened, some passive tissues have stretched (tensile forces), while others are impinging (compressive forces).


If I was a post-tib musculotendinous structure, I would not want to be 'connected to' a foot that's motion permits my insertion to drift/drop further and further away. If you want me to jump from a building, give me the 1st floor, not the 6th. In the early part of stance, the navicular drop/drift is lengthening the unit. At the same time it is contracting eccentrically to control/decelerate/oppose this. IMO, low-dye taping has a significant impact (short-term at least) on tib-post dysfunction. The force crowd will suggest that the low-dye taping provides a sufficient force to counter-act this pathology. The motion person may suggest that it keeps the origin and insertion of tib-post closer together. Limit motion = limit length = reducing tensile stress.

Take motion out of the equation, and you don't get impingement and sprains etc. I could take one of Ali's punches if he was only allowed 20 degrees elbow extension. His force capacity (musculature) would be the same; but motion augments momentum and hence the force to floor me.



All the force talk makes sense and can be justified. But I have a problem with 100% force and 0% motion as contributing factors to injury. Despite what the latest research suggests, we need health clinicians (especially students) thinking about forces and motion…not just the former.




Ron.
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Old 3rd March 2005, 09:27 PM
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Quote:
Originally Posted by Atlas
I have two problems with its 100% force and 0% motion.
1. How can these 2 phenomena be independent of each-other?
2. Awareness of pathological motion and the ability to alter it is a powerful clinical tool.
Newton's Second Law of Motion states that the acceleration of an object is directly proportional to the net force acting on the object and inversely proportoinal to the mass of the object. F = ma.

Because of this interrelationship of motion and force, then you are correct, Ron, that one can not say that injury is caused only by force and not by motion. Acceleration is the change of velocity over time or for those that have had calculus, acceleration is the first derivative of velocity. Velocity is the change of displacement of an object over time. Therefore, accleleration is the second derivative of displacement. Therefore, force and motion are directly interrelated by using Newton's Second Law of Motion.


Quote:
1. How can these 2 phenomena be independent of each-other? How can the fellow who splatters himself on concrete do so without plummeting from a height. What else can provide such a FORCE?

What about the analogy of a baseball catcher or cricket wicket-keeper. When catching a ball at speed, the keeper wisely accepts the ball out in front of his body, but finishes the 'catch' behind him. The motion of his hands in the same direction as the ball gradualises the deceleration. How can motion be completely irrelevant here? No motion equals bruised hands.
Helpful here is the Principle of Conservation of Linear Momentum. Here we should use the concept of the impulse-momentum theorem where:
impulse = change in momentum. Impulse of a force is a product of the average force and the time interval during which the force acts: Impulse = F x t.

Momentum of an object is the product of the object's masss and velocity: Momentum = m x v.

Using the Principle of Conservation of Linear Momentum, it can be said that the total linear momentum of an isolated system remains constant (i.e. is conserved). Therefore, for the baseball catcher, the average velocity of the decelerating baseball times its mass will equal the average velocity of the catcher's hand and mitt times its mass. The faster the ball is thrown and the greater the mass of the ball, then the more momentum, so that the catcher will need to absorb more momentum during catching the ball due to conservation of momentum.

Quote:
All the force talk makes sense and can be justified. But I have a problem with 100% force and 0% motion as contributing factors to injury. Despite what the latest research suggests, we need health clinicians (especially students) thinking about forces and motion…not just the former.
I would agree that we should not say that it is 100% force and 0% motion, since force and motion are tightly interrelated. But I would say that clinicians and students need to know about forces, motion, mass, moment of inertia, moments, moment arms, linear and rotational equilibrium, stress, strain, elastic modulus, and all the other basic mechanical concepts that affect the structural components of the human body. However, it is unlikely that all podiatrists or podiatry students will have a firm grasp on these concepts during my lifetime. Because of this, for many years to come, these important topics of biomechanics will be thought of as "advanced concepts" for podiatrists and will not be considered as basic concepts as first year engineering students consider them.
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  #64  
Old 8th March 2005, 07:55 AM
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Fallacies:

Applying a linear equation to a number of joints that move in three axes of motion, thereby oversimplifying the issue so it does not consider angular impulse

Oversimplifying forces that act on the stance foot as an average force that is then applied to the linear equation; ignoring the fact that the swinging limb contributes momentum (constantly changing in a fashion that is unrepresentative by being averaged) to the stance limb.

Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.

Current and past methods in empirical Biomechanics (with and without podiatric input) cannot discern statistically significant differences with and without CFO intervention. However, therein lies numerous clinical significances, which makes these practices successful.

Perhaps in future, as methodologies and apparatus evolve, such clinical success, "may" be empirically explained.

I for one look forward to such prospects.

-Kerry
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  #65  
Old 8th March 2005, 08:38 AM
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Quote:
Originally Posted by Kerry_Rambarran



Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.
Hi Kerry,
You missed out diurnal variation as it applies to the human lower limb.

I have to point out that applying Newtonian concepts to a system that is clearly neither closed nor isolated is not an activity exclusive to podiatriy.

Newtonian concepts are widely used in bioengineering - when designing replacement joints for example, and by orthopaedic surgeons, when replacing worn joints.
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  #66  
Old 8th March 2005, 10:08 AM
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It is true that other professions use this approach during Finite Element Analysis. Currently initial research and testing by companies such as Smith and Nephew use simulators for data pertaining to joint kinematics and durability. Based on trial data presented at academic conferences this is an apparently rigorous process.

Eventually, as dialogue between patients and practitioners makes its way back to the drawing board (bioengineers), refining the model indirectly makes the model less finite and more real. Which (relating back to the original topic of discussion posted by Dr. Payne) may account for more clinical versus statistical significance. Again this is a product of research methodologies.

I have noticed less gait "noise" in those with only a knee arthoplasty rather than the hip. Perhaps this may be due to the fact that during stance the knee mainly flexes and extends through the sagittal plane (medio-lateral axis), i.e. mainly one degree of freedom rather than three of the hip.

While this curent approach with the hip may never return patients back to their previous state (of 100%), postoperatively their quality of life is mostly better….a great thing!

Data from my last research what suggested (within subject) significant differences between CFO conditions. However statistical differences were not noted after ensemble averaging of data (a common practice in empirical research).
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Old 8th March 2005, 02:06 PM
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Kerry - thanks for the input...
Quote:
Eventually, as dialogue between patients and practitioners makes its way back to the drawing board (bioengineers), refining the model indirectly makes the model less finite and more real. Which (relating back to the original topic of discussion posted by <Craig>) may account for more clinical versus statistical significance.
The approach we are trying to take is to measure using different "models" what actually happens to the patient mechanically and correlate that to outcomes --- not outcomes as a change in the biomechanical parameters, but outcomes in terms of symptom reduction (using validated measures, such as the FHSQ) .... the ultimate aim to to find predictors of outcomes. from the study I mentioned in the first post, changes in the pattern of rearfoot motion was not related to clinical outcomes ---- some things are getting clearer. We have just started recruiting for a couple of RCT's to test what we found.

Kerry - thanks for those abstracts of a few weeks ago. Also, I will be in Ottawa in November.
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Old 8th March 2005, 06:47 PM
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Quote:
Originally Posted by Kerry_Rambarran
Fallacies:

Applying a linear equation to a number of joints that move in three axes of motion, thereby oversimplifying the issue so it does not consider angular impulse
Kerry, I have found that in my 20 years of teaching podiatrists and podiatry students biomechanical concepts there must be some simplification of concepts so that they can grasp the basics. As they become more knowledgeable, they can more easily understand more complex concepts. In biomechanical modelling, using uniplanar, simplified models are acceptable as long as you understand their inherent limitations.

Quote:
Oversimplifying forces that act on the stance foot as an average force that is then applied to the linear equation; ignoring the fact that the swinging limb contributes momentum (constantly changing in a fashion that is unrepresentative by being averaged) to the stance limb.
Both internal and external forces acting on the stance phase foot need to be considered when determining the forces acting internally within the foot. Of course the swing limb needs to be included if one is interested in the energetics of locomotion. However, if one is interested in something such as the direction and magnitude of moments acting across the subtalar joint axis at any instant in time, the mechanical contributions of the swing phase limb may be ignored as long as the spatial location of the subtalar joint axis is known, the center or pressure is known and the direction, magitude and line of action of the ground reaction force vector is also known.

Quote:
Attempting to apply these Newtonian “concepts” to a system that is clearly neither closed nor isolated.
Newtonian concepts are still used in physics, engineering and biomechanics, to this day. I agree with David Holland that they are widely used in many fields. I don't understand which of Sir Isaac Newton's concepts you don't like??

Quote:
Current and past methods in empirical Biomechanics (with and without podiatric input) cannot discern statistically significant differences with and without CFO intervention. However, therein lies numerous clinical significances, which makes these practices successful.
Have you read the papers by Mundermann et al and Williams et al?(1. Mündermann, A, Nigg BM, Humble, RN, Stefanyshyn, DJ: Foot orthotics affect lower extremity kinematics and kinetics during running. Clin Biomechanics, 18(3):254-262, 2003. 2. Williams, D.S., McClay-Davis, I., Baitch, S.P.: Effect of inverted orthoses on lower extremity mechanics in runners. Med. Sci. Sports Exerc. 35:2060-2068, 2003.) These researchers were able to discern statistically significant biomechanical differences with and without custom foot orthoses. As I have been lecturing for years, orthoses affect moments more than motion.
[/quote]

I enjoy your input and criticisms, Kerry. You are obviously very knowledgable in biomechanics. I am interested in your research at Ottawa Hospital if you could let us know more about it, it would be greatly appreciated. We are always looking for new lecturers on biomechanics here in the States. Have you published any of your research yet?
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  #69  
Old 14th March 2005, 02:01 PM
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Ahh, good. I think it is important to acknowledge the inherent limitations of applying linear physical equations to the foot.

With respect to the two research articles by Mundermann et al. and Williams et al., both discussed kinematic parameters of the whole foot (i.e. one segment models).

The Kinetic parameters discussed by Mundermann et al. included peak vertical loading rates (whole foot). Significant differences were found up the kinetic chain including the foot.

Conversely, Williams et al. kinematic found no significant differences in ankle eversion / inversion, however, peak rear foot inversion moments and work were significantly reduced during inverted CFO trials. The methodology used by this paper still analyses the foot as a single segment, due to limitations. is this acceptable? Perhaps for now.

This is the paradox:
1.To better understand the foot and ankle, dynamic, rather than static physical measurements are necessary (methodological limitations).
2.To better understand the both internal and external forces (both are important) that act on the foot and ankle we need to move towards a more fluid model that encompasses more than two segments (a team at Penn State is currently working on that).

Looking at the GRF with respect to the STJ is acceptable when looking at instances during stance. What methodologies can we use to the question is how does one take several of these instances and put them together to get a better understanding of foot function (normal or pathological).

If we look at GRF or CoP with respect to the STJ at best we can view the foot a two segment model. Again is this an appropriate approach?

-Kerry
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Old 14th March 2005, 06:21 PM
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I will not even dare to enter a debate far beyond my capabilities (advanced kinematics and kinetics).

Students and young graduates (and maybe a few oldies) have enough trouble with the biomechanics in day-to-day musculo-skeletal medicine. And in view of this, and my feeling that simple basic (albeit slightly flawed) concepts adequately describe what may be wrong and what we as clinicians must do to address it, teaching must remain simple. And teachers should be comfortable with this.


Even if and when we discover the complex answers, I can't see how this can be re-formatted in a simple teaching version.

In the ideal world though, yes, lets get the complex correct answers and transfer all of this across to the learners.
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Old 14th March 2005, 09:29 PM
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Quote:
Originally Posted by Kerry_Rambarran
Ahh, good. I think it is important to acknowledge the inherent limitations of applying linear physical equations to the foot.

With respect to the two research articles by Mundermann et al. and Williams et al., both discussed kinematic parameters of the whole foot (i.e. one segment models).

The Kinetic parameters discussed by Mundermann et al. included peak vertical loading rates (whole foot). Significant differences were found up the kinetic chain including the foot.

Conversely, Williams et al. kinematic found no significant differences in ankle eversion / inversion, however, peak rear foot inversion moments and work were significantly reduced during inverted CFO trials. The methodology used by this paper still analyses the foot as a single segment, due to limitations. is this acceptable? Perhaps for now.
The prevailing research seems to indicate that moments are affected much more than motion by foot orthoses. Benno Nigg has his "preferred movement pathway" theory that states that the individual will tend to move in a certain movement pattern during gait. Therefore, this is why he feels that motion is relatively unaffected by foot orthoses. However, when I lectured with Benno at the University of Calgary a few years back, he said his knee feels better with foot orthoses so he knows that foot orthoses do work, he just couldn't be certain how they work at the time.

I believe that one of the reasons that much of the foot orthosis research to date has not shown much difference in motion of the foot is the foot orthoses used were not corrective enough or were not custom foot orthoses. Clinically, if one wants to see a change in kinematics, the foot orthosis must be quite corrective, often with medial heel skives, inverted balancing positions, rigid plate materials. Without these corrections (i.e. vertically balanced foot orthosis made with a semi-flexible material) the foot orthosis will not resist the motions of the foot enough to show a change in kinematics.

Neil Humble was wise to use such corrective orthoses in the Mundermann et al study and I think that this was one of the main reasons why Mundermann's study showed the changes in kinetics that it did. In addition, in the study by Williams et al, Steve Baitch made Blake inverted orthoses that were used to demonstrate the kinetic changes. The moral of this story is that if you want your research study to show that orthoses change gait kinetics or kinematics, the more corrective the orthosis, the more likely that changes will be seen. In other words, don't use vertically balanced foot orthoses without medial heel skives or without inverted heel cups!

Kinetics of the rearfoot can be changed without a change in kinematics during both walking and running. If the subtalar joint (STJ) is maximally pronated throughout the midstance phase of gait and the patient wears a foot orthosis that relieves their sinus tarsi pain by decreasing the interosseous compression force within the sinus tarsi, but the orthosis is not corrective enough to supinate the STJ out of the maximally pronated position in midstance, then the kinematics of the rearfoot during midstance will not likely change (Kirby, KA.: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989). This is a fact that few biomechanics researchers mention in their papers on the kinetic effects of foot orthoses.

Quote:
This is the paradox:
1.To better understand the foot and ankle, dynamic, rather than static physical measurements are necessary (methodological limitations).
I agree. However, quasi-static models may be used quite effectively to model the internal forces within the foot and lower extremity. In addition, finite element analysis can be quite effective at determining internal forces. Simon Bartold's research group at Asics currently is using such a model that has defined nearly all the ligaments, muscles and bones of the foot and lower extremity as a way to test mechanical effects on the foot with different sport shoe designs. Dynamics is nice, but statics can tell you a whole lot also.

Quote:
2.To better understand the both internal and external forces (both are important) that act on the foot and ankle we need to move towards a more fluid model that encompasses more than two segments (a team at Penn State is currently working on that).
I am currently working with Steve Piazza and Greg Lewis from Penn State on STJ axis location in cadavers. They have been trying to determine STJ axis location mathematically by optimization techniques for calcaneal to tibial motion. I recommended some changes in technique that we applied to cadavers last fall when I went to Penn State to help them with their research. Greg is presenting our work on STJ axis location at the GCMAS meeting in Portland, Oregon in a few weeks which I will be attending. In addition, Neil Sharkey is still using his Dynamic Gait Simulator at Penn State to research kinematics and kinetics of gait in cadaver specimens that are "walked" using servomotors attached to the tendons of the foot. Neil and I will be presenting together this June at the WPC at Disneyland Hotel and I hope to collaborate with their group in the future.

Quote:
Looking at the GRF with respect to the STJ is acceptable when looking at instances during stance. What methodologies can we use to the question is how does one take several of these instances and put them together to get a better understanding of foot function (normal or pathological).
Quasi-static modelling is an acceptable method of taking "snap-shots" of each instance of gait to determine the approximate STJ moments that are occuring at any instant in gait. This can be used to give the clinician a better idea of how STJ moments are affected by pathologies such as PT dysfunction or metatarsus adductus and how treatments such as medial heel skive or Blake inverted orthoses affect STJ moments. That is not to say that gait dynamics is not important, but for the clinician, I have found that the static model is a much better starting point to allow them to progress intellectually toward the greater complexities of gait dynamics.

Quote:
If we look at GRF or CoP with respect to the STJ at best we can view the foot a two segment model. Again is this an appropriate approach?
The more segments, the greater the complexity. I think a better question is how much complexity do students and clinicians need to optimize their understanding of foot and lower extremity function. I think that this will depend greatly on their previous comfort and knowledge with mathematics and physics.

Chris Nester and Andrew Findlow will be introducing a new model for the midtarsal joint in a new article to be published soon in JAPMA. I have read the article and discussed this model quite a bit with Chris and I really like the direction that Chris and coworkers are headed with the midtarsal joint. I think that having more segments is great for those clinicians who have the capacity to "soak it all in". Unfortunately, in my 20 years of teaching, I have found that most clinicians either don't want to spend the time learning biomechanics or don't have enough basic biomechanics knowledge to understand the complexities of foot and lower extremity biomechanics.

By the way, Kerry, I enjoyed your article and please tell Gordon Robertson that I greatly enjoyed his book "Introduction to Biomechanics for Human Motion Analysis" and have recommended it to many of my students and clinician-students to increase their knowledge of biomechanics.
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Default Re: Foot orthoses outcomes and kinematic changes

The research that started this thread has been published:

Relationship Between Positive Clinical Outcomes of Foot Orthotic Treatment and Changes in Rearfoot Kinematics
Gerard V. Zammit and Craig B. Payne
J Am Podiatr Med Assoc 97(3): 207–212, 2007
Quote:
Background: Previous two-dimensional kinematic studies that assessed the effect of foot orthoses on rearfoot motion have yielded mixed results regarding whether control of rearfoot motion is related to symptom relief.

Methods: We sought to determine the effect of foot orthoses on rearfoot motion and to correlate these changes with the degree of symptom improvement in 22 individuals with excessive rearfoot pronation (17 women and 5 men; mean ± SD age, 44.3 ± 16.7 years; mean ± SD weight, 74.9 ± 15.9 kg). Two-dimensional motion-analysis software was used to assess frontal plane rearfoot motion with and without foot orthoses. The mean ± SD Foot Posture Index of the left foot was 8.83 ± 3.54 and of the right foot was 9.22 ± 3.64). The pain and function subscales of the Foot Health Status Questionnaire were then used to determine the degree of symptom relief associated with the orthoses at baseline and 4 weeks later.

Results: Orthoses had a small but statistically significant effect on rearfoot motion, although no significant correlations were found between differences in rearfoot motion with and without foot orthoses and the improvements demonstrated in the Foot Health Status Questionnaire subscales of pain and function.

Conclusions: The effect of orthoses on frontal plane rearfoot motion is considered small and probably insufficient to account for the extent of symptom reduction found in this study. Other parameters of orthotic function, such as kinetic and neuromechanical variables, should be further investigated.
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What is the "normal foot"? Craig Payne Biomechanics, Sports and Foot orthoses 79 31st January 2008 11:54 AM


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