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Clinical Methods for predicting the effectiveness of functional foot orthoses

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Dieter Fellner, Jul 16, 2006.

  1. Dieter Fellner

    Dieter Fellner Well-Known Member


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    When excessive pronation is the problem, functional foot orthoses are not always effective. How can clinicians know if treatment will succeed? Is trial and error the only option? Are there individual tests or are tests best grouped?

    Does this statement carry weight in 2006? What clinical indicators are of greatest value? What are the limits of orthoses when surgical intervention is indicated?
     
  2. Atlas

    Atlas Well-Known Member

    Effective at what in particular? I assume you mean symptom reduction.
     
  3. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    With due respect to Bill I think it was unfortunate to title that particular article with the title that was used as the article had nothing to do with Clinical Methods for predicting the effectiveness of functional foot orthoses ... it was all about different clinical tests to help orthoses prescription decision making .... of which none of the tests had or has since been shown to actually predict the effectiveness of foot orthoses (ie symptom changes).

    I am aware of only two study's that have actually tried to see what predicts outcomes with foot orthoses:
    One was ours that is in press at JAPMA that shows that changes in the pattern of rearfoot motion does not predict outcomes
    The other is also ours and is at the stage of data analysis in which some of the plantar force/time parameters do predict the outcomes and some clinical tests do predict changes in those particular force/time parameters- unfortunatly the are not rearfoot axis assessment, MTJ locking mechanism, physical and radiographic examination findings. With an emphasis on transverse plane motion assessment and ossseous relationship.. , so that statement does not carry weight in 2006.
     
  4. Patients don't usually show up to a podiatrist's office complaining of "excessive pronation". They instead complain of pain, disability and an inability to perform necessary or desired activities. Foot orthoses are known to be an effective conservative treatment method for symptoms due to pronation-related pathology. However, contrary to popular podiatric belief (based mainly on the teachings of Root et al), foot orthoses don't always "make the foot function in subtalar joint neutral position". Therefore, the goal of foot orthosis therapy should be to make the patient asymptomatic and improve their gait function without causing other pathology or symptoms. The goal of foot orthoses should not be "to cure excessive pronation".

    I don't always know in advance whether foot orthoses will succeed or not in achieving the goals of foot orthosis therapy. However, every year that I practice, I get a better idea of who will or not respond successfully to orthosis therapy simply from the clinical observations I have made over many years and the experience of treating thousands of patients with foot orthoses.

    In my practice, I prefer to give patients a certain percentage of possiblity as to whether the orthoses will make them better or not. For example, for a patient with plantar fasciitis I might say "From my clinical experience, you have a 90% chance of having complete relief from your plantar fasciitis with the foot orthotics I will be making for you." Whereas, for a patient with tarsal tunnel syndrome that has a pronated foot I might say "From my clinical experience, you have a 50% chance of having complete relief from your tarsal tunnel syndrome with the foot orthotics I will be making for you." I base this on my clinical experience and on modelling the mechanical effects that foot orthoses potentially might have at reducing the pathological tissue stresses that are causing the injury to a low enough magnitude so that proper healing may occur.

    The clinicians who are best at foot orthosis therapy will always use a trial and error process with their orthoses. The exact nature of how the human locomotor apparatus and its neurological control mechanisms will respond mechanically to foot orthoses intervention is very difficult to predict due to the complexity and large interindividual variation in ligament, tendon, muscle, cartilage and bone anatomy and mechanical qualities within the human population. In addition, the additional complexity that thousands of possible shoe design permutations have on foot orthosis function and foot and lower extremity biomechanics makes accurate prediction of orthosis function virtually impossible. It is for these reasons that trial and error modification of foot orthoses will always be used to "tweak" the orthosis prescription to achieve the goals of orthosis therapy (i.e. symptom relief, gait function improvement and avoidance of additional pathology or symptoms).

    There are a few tests and examination techniques that I have developed over the years that have certainly aided me to better understand the kinetic function of the feet and lower extremities of my patients and therefore better determine which patients may or may not respond successfully to foot orthoses. These tests are the maximum pronation test and supination resistance test, (Kirby KA, Green DR: Evaluation and Nonoperative Management of Pes Valgus, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchill-Livingstone, New York, 1992), palpation method of subtalar joint axis determination (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987) and standing method of subtalar joint axis determination. I have found that many of the Root et al measurements that I was taught to make 25 years ago to be relatively useless at predicting orthosis function. However, I do think that these same measurements are helpful in some cases in understanding the patient's structure and function, so I still perform them on all patients receiving foot orthoses.

    One of the most effective tests that I use daily in my practice to see if the patient may respond to the mechanical effects of foot orthoses is the use of in-shoe padding or modification to the shoe insoles. This test is very effective at determining whether altering the location, magnitude and temporal patterns of ground reaction force on the plantar foot will give the patient any level of positive therapeutic results. This information will not only give me additional insight as to how best to construct the optimal foot orthosis for the patient but will also give the patient additional confidence that their money will be well-spent by having me make custom foot orthoses to treat their condition.

    Finally, in regard to foot orthosis therapy versus surgical therapy, one must realize that foot orthosis therapy and foot surgery each has its individual limitations as to what it can and cannot do. It is not always best to make foot orthoses for a patient before surgery is done on a patient. For example, if a patient had a displaced midshaft fracture of the first metatarsal I would first recommend surgical open reduction and internal fixation and then possibly recommend foot orthoses if the patient had sequellae from that trauma. However, if the patient has plantar fasciitis, I will generally treat them for at least 6 months with multiple treatments before I started to discuss a surgical procedure such as a partial plantar fasciotomy.

    One thing that foot orthosis therapy and surgical therapy do have in common with each other is that they are both mechanically-based therapeutic methods of treatment. Surgery has the benefit of being able to cause permanent and quite dramatic alterations within the structure of the anatomical components of the foot and lower extremity to cure or treat deformity, which foot orthoses have little chance of accomplishing in most cases. However, foot orthoses have the benefit of being able to quickly and effectively treat a wide variety of mechanically-based pathologies of the foot and lower extremity with a minimum disruption of the patient's life, no risk of harmful surgical risks and virtually no risk of permanent side effects. In other words, the experienced podiatric surgeon who is also well-trained in foot orthoses therapy is able to offer their patients the full range of treatment options available to them and provide their patients with expert opinion on how those options may affect their current complaints and affect their lives in the future.
     
    Last edited: Jul 17, 2006
  5. slaveboy

    slaveboy Member

    Hi

    If we are saying that orthoses are a hit and a miss then surely this opionion applies also to surgery, physiotherapy etc. I see many patients who attend my clinic who have had knee surgery or foot surgery who have had a reducement in pain or total pain relief and others who have had the same pain or worse. So i think any treatment modality can be classified as a hit or a miss just some have better outcomes than others, but surely the research that has been done by Root, kirby, fuller etc allows us to at least have a fighting chance as a prediction on whether your patient will get better and decide on the best option. I like to use kevins max pronation test, hubsher and supination resistance test.

    chris
     
  6. Dieter Fellner

    Dieter Fellner Well-Known Member

    Kevin - a frank and informative response, as usual. Thank you for the references. I note the text you refer to cannot be easily obtained (at least from Amazon!). Are you able to describe the tests?
     
    Last edited: Jul 17, 2006
  7. Atlas

    Atlas Well-Known Member

    With few exceptions, low-dye-taping aint a bad indicator either.
     
  8. Dieter:

    Send me your e-mail address and I'll send you a copy of the chapter.
     
  9. I suspect that predictors of orthoses success are pathology specific. It would be great if we could build predictive models for orthoses success for each pathology, even better, but possibly even more difficult to build a model which encompasses all pathologies. However, I suspect that this is more difficult than it first appears.

    How is the dependent variable: "effectiveness" measured? The independent variables should include orthoses design specifications, not just clinical measurements taken from the individual patients. Otherwise how do we define "orthoses"? Since by their very nature each custom orthosis is unique, how can you just lump them all together as "orthoses" in the model? Alternatively, you could start building "orthoses specific models"- you then end up with lots of models. If "effectiveness" is only predicted by patient specific variables which are not easily changed, it makes for difficult manipulation to ensure "effectiveness" is achieved- and thus the model is impracticable and useful only as an academic exercise- nice PhD- waste of time and money.

    A few words of caution though and some things those less experienced in research should be aware of when interpreting research about relationships and prediction: Measurement scale: Sometimes we measure variables in a clinical environment which appear to be poor predictors of dependents, but when we perform scale transforms they are then stronger predictors. An example of this is the monofilament- Although cliniians talk about 10g monofilaments, in reality a log scale of the monofilament weight is used. The use of linear models can also provide misleading conclusions. For example if we perform a Pearsons correlation and get weak association, this does not mean that there is no correlation, nor should we conclude this. Since what this shows is only that a linear model does not fit the data well, in this case a scale transform may provide a better fit for the data, and/ or the relationship may be defined better by curvi-linear models.
     
    Last edited: Jul 17, 2006
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