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Normal function/tissue stress discussion biomechancis summer school 2011

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Craig Payne, Jun 24, 2011.

  1. Craig Payne

    Craig Payne Moderator


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    Trevor Prior ... he does not like the 'tissue stress' approach .... huh?

    As the discussion is getting interesting thought it should have its own thread - moved from live updates Biomechancis summer school thread .

    Last edited by a moderator: Jun 28, 2011
  2. Trevor Prior

    Trevor Prior Active Member

    Re: Live Updates from the Biomechanics Summer School

    So,let's clarify. Clearly, tissue stress is fundamental to what we do as clinicians as, without stress, we would not see many of the pathologies we manage. Whichever biomechanical concept you subscribe to, the end point will be to alter the stresses through the tissues.

    When we look at the scientific literature / studies. we always discuss normal and look to have normal function. In reality, this data shows us that normal is a range, a spread across the measure you are quantifying / evaluating.

    It is not a great leap of faith to therefore conclude that there will be 'normal' function.

    When I approach patient management I am trying to return the individual to normal function, or more accurately, less abnormal. I accept that the concept of normal function when it comes to the foot is difficult to define, but conceptually and clinically, this is the aim.

    It is my opinion that, as we restore this function, we are allowing the tissues to function more effectively and automatically reduce tissue stress - in other words, we do not need to have a tissue stress model as this is fundamental to whatever we do.

    My dislike of the concept is when it is applied to directly manage a complaint by relieving stress on a particular structure because the method applied, whilst reducing symptoms at that site, does not necessarily restore more normal function. A crude example would be immobilisng someone in a boot - fantastic tissue stress relief but not normal function.

    Thus, my approach is generally to try and restore as normal function as I can which involves restoring muscular flexibility / strength / control etc. The orthotic component tries to achieve more normal function and not prevent / compromise function.

    However, there are instances when this does not work sufficiently to relieve symptoms; in some instances, symptoms are sufficient such that compromised control may be required in the first instance and then move to more functional / dynamic control. Similarly, if the 'normal' approach is insufficient, then I would apply techniques to relieve symptoms but accept that this may be at the expense of function at another site, the effect of which, we do not know. In some instances, this may cause discomfort and cannot be tolerated. However, if you believe that pathology can occur as the consequence of low grade repetitive dysfunction over many months or years, then the affect can potentially manifest at a point that would not be attributed to the orthoses.

    An analogy would be the affect of a Wilson's osteotomy which is effective for correcting HAV but shortens the 1st metatarsal. It is common for this to cause transfer problems which manifest two years later and are often considered a separate entity by the patient.

    A ritchie brace for a TPD with ligament laxity is a good example of compromised control which is required due to the nature of the pathology and an inability to restore function.

    Tissue stress also comes into play when one considers if an individuals specific function can be contributing to their pathology although I tend to see this as functional anatomy.

    So, altering tissue stress is a fundamental process of all mechanical approaches to management and does not necessarily need a separate concept. To my mind, it only comes into play when normal function is insufficient to relieve symptoms. However, I would always try to restore normal function rather than start with compromised control unless this was specific and short term.

    I hope that makes sense but I am typing this as Kevin is lecturing (sorry Kevin) and am trying to listen to him at the same time.

  3. Trevor Prior

    Trevor Prior Active Member

    Re: Live Updates from the Biomechanics Summer School

    100% there are times it is appropriate but only whilst we address symptoms / pathology and my primary aim would be to transfer to more normal function as and if possible.
  4. efuller

    efuller MVP

    Re: Live Updates from the Biomechanics Summer School

    It comes down to a matter of emphasis. When I see a patient who is injured and wants to run, I could tell them to stop running to reduce the tissue stress. This is not what the patient wants. I can also try and reduce the stress on the injured structure as much as possible in their normal running gait. So, tissue stress is not about avoiding normal, its about returning to the desired activity without causing pain. On the other hand is wanting to run marathons normal?

    We are back to the definition of normal. Root et al had two competing definitions. There was it doesn't hurt in everyday activities definition and there was the biophysical criteria of normalcy. And there are more definitions. If we cannot define normal we have to look to tissue stress. We can't make someone normal unless we define normal. Some feet are abnormal. If we identify an anatomical structure that is in pain we reduce stress on it and hopefully it will feel better.

    So, if normal function is heel off at x% of stance phase, do we always want to restore to normal. Suppose a patient has a stress fracture 2nd metatarsal caused by a long 2nd metatarsal. A normal heel off will tend to make this problem worse as compared to the patient choosing to walk flat footed with a really late heel off. So, if we emphasize the tissue stress by creating an environment in the shoe where there is less ground reaction force under the metatarsal, then we can return to normal function. I think the emphasis should be more on tissue stress than "normalcy" Tissue stress gives you the plan to return to normalcy.

    How else do you return a fractured metatarsal to normal other than by reducing the stress on it.

    Tissue stress is the recipe you use to return a subject to normal function. If you know what normal is, you have to know how to make someone normal. What do you change to make someone more normal.

    Thanks for posting.

  5. Re: Live Updates from the Biomechanics Summer School


    I think you are misinformed about the tissue stress approach. Eric Fuller and I will hopefully have our chapter on the tissue stress approach published on this subject which we wrote over 5 years ago published by the end of the year. The final proof of our chapter has just been finalized.

    The three primary goals of the tissue stress approach are as follows:

    1. Reduce the pathological stresses on the injured structural components of the foot and/or lower extremity.

    2. Optimize gait function.

    3. Not cause further pathology or symptoms while performing goals #1 and #2.

    Therefore, you see, Trevor, the tissue stress approach does not simply perform goal #1 with no regard for goals #2 and #3. Rather, the tissue stress approach combines all three goals together into an approach which probably is exactly the way you currently practice. I think once you read the 60 page chapter that Eric and I wrote, you will agree.

    Great seminar....the rest of you guys are really missing out!!:drinks
  6. Re: Live Updates from the Biomechanics Summer School


    I believe that the most valid point that you made on the tissue stress approach this last few days was emphasizing the point that treatment should never be designed solely just to reduce tissue stress, without regard to optimizing gait function and reducing potential complications from the "tissue stress treatment". All three goals of the tissue stress approach must be used together in order to achieve rapid resolution of symptoms and improve gait function, while, at the same time, not cause harm to the patient.

    It was great fun lecturing with you after not seeing you for many years. I greatly enjoyed your lectures. Hope you had a safe trip home.:drinks
  7. Re: Live Updates from the Biomechanics Summer School

    Just Read this after being away for the weekend.

    I see Kevin has replied but I also would add that this come back to Simon Zones Type approach as well.

    instead of Normal maybe would should be discussing Zones of optimal stress.
  8. Trevor Prior

    Trevor Prior Active Member

    Re: Live Updates from the Biomechanics Summer School

    Kevin / Eric

    Hoefully, by now, you will have appreciated that I do believe that what we do modifies tissue stress although the method of how this is achieved can vary between practitioners.

    On reflection, my comment should have ben supported by more clarification than it was but it has stimulated interesting debate.

    My concerns remain that there is a risk that all three of the components you highlight may not be achieved and how each practitioner determines that they have optimised gait - there are clearly a number of ways but some form of assessment is required.

    Part of Eric's first post on this thread was:

    In this instance, the issue is a structural problem with a long second met and the altered heel lift is a compromised function. Offloading the metatarsal head may be sufficient to resolve the problem and allow the gait to return to normal. Alternatively, one could consuider shortening the metatarsal although there would be a risk of MTPJ stiffness and abnormal function. By contrast, if a process was used to alter the heel contact and this was left in situ, the presenting problem may resolve but the resultant gait be abnormal - this has the potential to lead to other problems. So reducing stress may be a temporary intervention or, if it in itself restores a more normal gait etc., then a long term intervention.

    I enjoyed the question and answer session we had on the Saturday as this really gives the opportunity for debate. Without risking opening up the barefoot running debate I looked at the thread which relates to this.

    In the barefoot thread, Eric posted the following reply:

    On the face of this, this does not necessarily address the three components to which Kevin alludes in my first quote and thus clarification is important.

    Going back to my original response, structural alignment has been demonstrated to be predictive of a degree of dynamic function. One can apply tissue stress to a paradigm such as Root as one would determine if the observed function (or dysfunction) would explain the presenting symptoms. If this was the case, then optomising that function could well be sufficient to resolve the problem.

    Similarly, the practitioner that utilises a range of concepts can make this assessment across the concepts (i.e. fhl, deviated axis etc.). To my mind, this has to be supported with at least some form of video gait analysis although pressure analysis provides greater detail.

    However, there are instances whereby dynamic function does not marry structural alignment etc. (this is what gets picked up by the gait analysis) and may be the instances whereby the control provided is contrary to such alignment / structural approach.

    It would seem logical that, however a foot works, there must be something driving that function. So, if it is not the structural alignment, then what is it - searching for these variables may allow a broader treatment plan. Indeed, it may prove that function can not be optimised by orthoses and other interventions utilised.

    I could go on for hours, but I would get further behind and you would get bored.

    Kevin, it was great to catch up and I look forward to the chapter.

  9. Re: Live Updates from the Biomechanics Summer School

    Which "degrees"?
  10. Trevor Prior

    Trevor Prior Active Member

    For instance the papers realting FPI scores to a % of function during dynamic gait
  11. Which ones are they?
  12. efuller

    efuller MVP

    Re: Live Updates from the Biomechanics Summer School

    I can see how shortening the metatarsal would reduce load on the metatarsal and could possibly return the person to normal function.

    How would altering heel contact help high pressure on the 2nd metatarsal in normal heel-toe gait? This is why I like tissue stress. It makes you try and explain how your treatment would work. Also, how would altering heel contact return normal function?

    Again, I think we are debating emphasis. I'm saying that if you address the stress on the anatomical structure then normal function will return. (If you pay attention to the other two points.) You are saying that if you have the person return to normal function then the stress will be reduced. I'm saying that the tissue stress gives you the most logical interventions to get a reduction of stress and a return to normal function. Although I did not explicitly say it, the other two points should be implied as I am thinking about them.

    What drives foot function is forces and moments from the ground, body weight and muscles and forces on anatomical structures. Structural alignment is part of that equation. Trying to accommodate structural alignment will alter the forces on the foot.

    It is very hard to define function. However, it is possible to measure forces and motion. If your definition of foot function uses motion and position then you have to look at forces and moments to explain that function. After all F=ma and moment = moment of inertia x angular acceleration. It's the law. How do you define/ measure foot function?

    Regarding video gait analysis and pressure analysis. I'm going to contradict myself a bit here. You don't have to measure exactly the forces involved, but you do have to think about them and how to reduce them on the injured structure. If you reduce the force on the injured structure enough it will heal and the pain will go away. That is probably the most important indicator of whether you have reduced the force enough. Visual analysis is probably enough to see if you have returned to normal function. Certainly those modalities (video, pressure plate) can be helpful in making your diagnosis. However, there are times when I would prefer looking at the sock liner of a six month old, often used, shoe than a pressure platform analysis. You are more likely to know if the gait caused the pain.

  13. Trevor:

    I do look at foot and lower extremity structure and take that into consideration as to how it contributes to foot function and the pathology/pain that the patient presents with. Foot and lower structure forms one of the bases for determining how and why a foot functions the way it does and why certain pathologies occur, which will then allow the skillful tissue stress clinician to determine how best to reduce the stress on the injured tissue, improve gait function and decrease the risk of new pathologies developing. Whether one uses video gait analysis, visual gait analysis and/or in-shoe pressure analysis, some form of gait testing needs to be done to evaluate the function of the foot pre and post treatment.

    I don't think we are very far apart from each other in the ways we treat patients.
  14. Griff

    Griff Moderator

    Only paper I can think of off the top of my head is the Nielsen et al research published last year in Gait & Posture where they correlated FPI with dynamic midfoot kinematics. Pretty certain they still talked about unpredictable subject specific responses however.
  15. hontas

    hontas Member

    Here's another

    Attached Files:


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