Welcome to the Podiatry Arena forums

You are currently viewing our podiatry forum as a guest which gives you limited access to view all podiatry discussions and access our other features. By joining our free global community of Podiatrists and other interested foot health care professionals you will have access to post podiatry topics (answer and ask questions), communicate privately with other members, upload content, view attachments, receive a weekly email update of new discussions, access other special features. Registered users do not get displayed the advertisements in posted messages. Registration is fast, simple and absolutely free so please, join our global Podiatry community today!

  1. Everything that you are ever going to want to know about running shoes: Running Shoes Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
  2. Have you considered the Critical Thinking and Skeptical Boot Camp, for taking it to the next level? See here for more.
    Dismiss Notice
  3. Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
    Dismiss Notice
Dismiss Notice
Have you considered the Clinical Biomechanics Boot Camp Online, for taking it to the next level? See here for more.
Dismiss Notice
Have you liked us on Facebook to get our updates? Please do. Click here for our Facebook page.
Dismiss Notice
Do you get the weekly newsletter that Podiatry Arena sends out to update everybody? If not, click here to organise this.

Measuring arch height

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Asher, Jan 6, 2008.

  1. Asher

    Asher Well-Known Member


    Members do not see these Ads. Sign Up.
    Hi everyone,

    Can I ask, as part of a biomechanical assessment for orthosis prescription, how do podiatrists measure arch height? And do you dictate the arch height on an script form or just decide on minimal, standard or max arch fill to determine arch height?

    I get my patient to stand on an off-the-shelf arch support, measure the height at stance and then estimate how much higher I would like it to be. And yes I ask for ?mm arch height on my orthotic prescription form.

    Rebecca
     
  2. Use a vernier caliper.
     
  3. Asher

    Asher Well-Known Member

    Yeah but where do you measure? :confused: Any particular point, the highest point of the arch, a particular bony landmark, where?

    Do you measure in STJ neutral Simon or some other position?

    I wouldn't know where to measure the arch height as the area rounds up from plantar to medial at the medial longitudinal arch unless on an arch support which compresses the soft tissues in the area a bit and gives you definite plantar and definite medial aspects.

    Actually, I use a ruler which is ground off at 0mm, it works fine.

    Rebecca
     
  4. I don't measure it routinely as part of clinical exam. In research studies we have measured to navicular tuberosity in RCSP. Why would you want to measure in STJ neutral?

    If you are trying to use this measurement as something to do with orthotic precription, you'd probably be better off measuring during dynamic function with a motion analysis system, since static measures are generally poor predictors of dynamic ones. Need to watch out for parallax though if using 2D.

    Demp used ellipsoids to classify the shape of the arch- maybe this would be more meaningful for you? Depends what you are trying to do with the data.
     
    Last edited: Jan 7, 2008
  5. Asher

    Asher Well-Known Member

    Thanks Simon. But a number of people have mentioned it on Podiatry Arena - I would love to hear from them.


    If not subtalar neutral then what?

    Even if I could, how would you come up with the arch height when the arch of the barefoot walking on the treadmill flattens to whatever height - how would you determine what arch height you want your orthosis to have.

    What is Demp and Ellipsoids?

    Rebecca
     
  6. efuller

    efuller MVP

    I measure arch height at the navicular tuberosity with the patient standing relaxed and pushing upward with my level finger. I use a mm ruler ground with the end ground to 0mm. Erorr is at least 1mm if the patient isn't squirming, in which case it would be greater. Some patients do not know they are constantly using their posterior tibial muscle in stance to raise their arch. I try to look and if I notice that they are I will try to get them to relax. I will push up less hard with my finger if they have a laterally deviated STJ axis.

    Reasoning:
    It is really hard to explain to a patient why there custom device does not touch their arch.
    Arch heights that apply too much pressure are painful and not tolerated.
    There is a wide range in the difference between neutral position arch height (casted) and relaxed standing arch height. This measurement gives me some idea about how much fill there should be.

    For me the goal of the medial arch of the orthosis is to apply some pressure, but not too much. There is a wide range in arch heights that can be tolerated. Some pople have a smaller range that they can tolerate. These are usually the medially deviated stj axis people.

    I hope this helps.
     
  7. Asher

    Asher Well-Known Member

    Hi Eric

    So you push up to what point? STJN? Eyeball of where you think device should come to? Another point?

    And your measurement is from the floor to where your level finger meets the skin?

    So do you quote the mm height on your script form or decide on minimum, moderate or maximal arch fill?

    Thanks Eric

    Rebecca
     
  8. DSP

    DSP Active Member

    Hi Asher

    I hope that this answers your orginal question.

    Ideally, the static WB BMX exam is the most effective and practical way to measure arch height. Specifically, measuring from the supporting surface to the navicular tuberosity in RCSP using a ruler (mm) is probably the most accepted method. However, instead of using the navicular tuberosity as a reference point, perhaps measuring to the apex of the plantar medial arch area (underneath) would be more accurate. Perhaps that’s what an “ellipsoid” would be able to determine, as Simon suggested. IMO though, I don’t think MLA height is something that needs to be stressed over too much. If you do measure arch height then you should be using a technique that is reasonably accurate, repeatable and reliable. Arch height shouldn’t be a measurement that’s taken on its own to decide arch height, it should contribute to the overall picture. If you are able to clearly observe the general representation and profile of arch in static and dynamic assessments, this should give you a clear indication as to what you “feel” the height should be and the amount of fill (+/-).

    BTW, from how I would logically understand it, once you have determined the arch height that you want, you would then decide on the type of fill you desire. In other words, they go hand in hand. Personally, I dont measure arch height (apart from rare occassions), I only go by the amount of fill I think is appropriate.

    Regards,

    Daniel
     
  9. One that can be reliably found! Whatever rotational postional of the subtalar joint you think is important is probably the right answer, take your pick- it's the validity that I think is questionable- see below.


    How does standing in a foot position, say STJ neutral (on or off an orthotic) and measuring "arch height" tell you this? Show me the data! Given that it is dynamic function which you are trying to influence, surely a measure taken from dynamic function will be more useful.



    Demp is a well published researcher, I listed some of his publications here: http://www.podiatry-arena.com/podiatry-forum/showpost.php?p=28551&postcount=27

    Ellipsoids are a group of geometrical shapes that can be defined by equations that are unique to each shape and hence can be used as a taxonomy for arch structure: http://mathworld.wolfram.com/Ellipsoid.html
     
  10. Asher

    Asher Well-Known Member

    Thanks DSP but on my labs orthosis prescription form, you can either indicate the orthosis arch height you want only (I guess you get standard fill), the amount of fill only (actually I don't know if that effects the orthosis arch height) or both. Typically I indicate both, not saying that's right but that's why I ask ... what is the common / best way of deciding on prescription variables for this area of the orthosis.

    Fair enough Simon, I understand what you are saying. I certainly can't argue with you.

    Maybe dictating orthosis arch height is not done? So we depend on the contour we get from our cast and dictate the amount of fill?

    Rebecca
     
  11. DSP

    DSP Active Member

    After thinking about it now, I suppose the best approach is to either specify the exact arch height you want (mm) or request the amount of fill you desire. So basically, you either dictate the arch height by the measurements you obtained during your assessment (or the height you think is most appropriate), or, you can effectively do it by the amount of arch fill.

    The part I find challenging is that we record static and dynaimc observations, then we capture a non WB negative cast impression of the foot. How do all these systematically correlate with one another? IMO they dont! I still think that the majority of our assessments are predominantly qualitative i.e supination reisitance test, transverse position of the STJ axis, jacks test etc, which is where a lot of misconception stems from.... :eek:

    Cheers,

    Daniel
     
  12. When you use the term "arch fill" is this the same as medial addition?

    These variables are not really qualitative since if one wished they could all easilly be quantified. How does performing these tests as part of your clinical work-up lead to misconception?
     
  13. DSP

    DSP Active Member

    Yes, they are the same thing.


    Why aren't these qualitative tests? Aren't these tests predominately based on observations that don't involve numbers or measurements (clinically speaking). For e.g. medially deviated STJ axis, jacks test: easy medium hard etc. Even if we could quantify these tests, why aren't we taught to in the first place and why doesn't the majority of the profession do this already? Whenever tests like these are perfromed, there is always potential for a large degree of inconsistency, which, unless performed by experienced and competent clinicians, means, that there is greater potential for poor reliability, inaccuracies, and misjudgment. For e.g. clinician (a) might judge pt (x) as having a hard jacks test and delayed onset of the windlass mechanism, whereas, clinician (b) might interpret this test entirely differently, concluding that pt (x) has a medium jacks test and immediate onset of the windlass mechanism. Ultimately, this may result in two completely different orthotic prescriptions and different clinical outcomes. If these two clinicians were to coincide with one another, surely, wouldn't there be some degree of misconception...?

    Regards,

    Daniel
     
  14. Phil Wells

    Phil Wells Active Member

    Rebecca

    One solution for you is to use a foam impression box.
    If you can capture the foot in the box reasonably well, you can then take a measure very accurately of the arch height.
    I often get my customers to take a 'corrected foam box' and then a fully weight bearing foam box. They then send either both boxes into me or measure the difference between them to give an idea of the amount of arch 'collapse' of the patient.
    This is very important as it allows you to start making decisions of where you want the arch height of the orthotic to be to effect a clinical change.
    Alternatively go for a non wb POP cast and a fully weight bearing fb to get an idea of what is happening with the foot wtc.

    Hope this helps.

    Phil
     
  15. efuller

    efuller MVP

    That's a $5 dollar measurement that takes a couple of minutes that can be done with a ruler in less than 10 seconds. (Depending on how good your knees are.)
    It may be a bit more accurate, but how accurate do we need to be.

    Regards,
    Eric
     
  16. efuller

    efuller MVP

    Hi Rebecca,

    I push up under the navicular tuberosity, which is where I want the apex of the arch height of the device to be. I call it a comfortable amount of force. Usually it compresses the soft tissue a milimeter or two. The amount of force does not change the position of the foot.

    Yes, this measurement is floor to top of finger.

    Yes, I quote mm arch height.

    I choose resting position as opposed to Neutral because, I feel (am guessing) that this is the easiest way to estimate the dynamic arch height. Resting arch height is a lot easier to get than dynamic arch height. With the device being flexible, hopefully it will not cause pain as the foot tries to move from standing arch height to middle of midstance of gait arch height.

    This measurement is a best first guess. Some patients will prefer higher. A true story: I had a patient for whom I made orthotics using this measurement. She returned for follow up and felt that she wanted more arch height. I told her that it might be uncomfortable, so I suggested adding adhesive felt to the device in the arch to mimic what a higher arched device would feel like. It wasn't comfortable, but she liked having more "support". I remade the device with a higher arch.

    Using this measurement, I have had only one patient in the last 3 years complain of arch pain from the orthotic. On remeasuirng him I noticed that he used his posterior tibial muscle to raise his arch when being asked to stand relaxed.

    I've worn orthotics with too high an arch and I would not wish that pain on anyone. I don't really like saying to a patient, "Oh you'll get used to it. Just extend the break-in period." A lot of people will adjust there muscular activity so that they can tolerate a high arched device and this will quite often relieve there initial complaint. Like the man said "First, do no harm."

    Regards,

    Eric
     
    Last edited: Jan 10, 2008
  17. I thought so. How far proximally do you normally extend your medial addition?

    I see your point, it's because YOU don't have the ability to quantify these and so take a qualitative approach. When I measure variables such as these I quantify them; for STJ axial position I measure in degrees; for supination resistance I measure in Newtons etc..

    We can very easilly quantify these tests. I can't say why you weren't taught how to do this- ask your lecturer. The majority of the profession have never even heard of these tests.

    Lucky for me then that I am an experienced and competent clinician/ researcher / educator;). I've no idea what a "hard" Jacks test is but I am pretty certain that Jacks test has been demonstrated to have questionable validity when employed to make inferences to dynamic function- why weren't you taught that at School? If I based my orthoses prescriptions on this test I really would be a fool. Moreover, you make the assumption that the two different orthoses produced may not be equally as effective in terms of their clinical outcomes; you don't know that either.

    co·in·cide vi
    1. to happen at or around the same time
    2. to occupy the same place or be exactly alike in position or form
    3. to agree exactly

    Encarta® World English Dictionary © 1999 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.

    If the two clinicians agree exactly, I don't see how this would be a problem. If the two clinicians happen at or around the same time or occupy the same place or be exactly alike in position or form, I would question why it takes a pair of trained, MZ twin podiatrists, who can warp space to perform a clinical work-up on one patient.

    Daniel, perhaps if you quantified your measurements they would be somewhat less subjective. While there would still be inter / intra observer reliability issues you could then calculate 95% CI's and at least speak confidently with regard to your potential error.
    :drinks

    P.S. Qualitative research is for girls. That's not me being sexist, if you look at the origins of qualitative research it was developed as a backlash to the perceived masculinity of science.
     
    Last edited: Jan 10, 2008
  18. DSP

    DSP Active Member

    I usually leave this up to the lab to decide. I never thought that customizing this measurement was significant. Do you measure on an individual basis, and if so, what affect are you trying to achieve? Also, how far do you normally extend yours?

    I can appreciate that you are able to measure this test in Newtons. Is this something you do exclusively in your clinic? What apparatus do you use as part of your routine BMX assessment to obtain this measurement? Do the majority of podiatrists in your country measure this test in Newtons as part of there assessment like you do? Perhaps it’s performed differently here in Australia (anyone, please correct me if I’m wrong). Excuse my ignorance, but I’ve always assumed that the majority performs this test in accordance with how it was first detailed in the literature in 1992 by Kevin Kirby and Donald Green (Kirby, K.A., and D.R. Green: “Evaluation and Nonopertive Mangement of Pes Valgus”, pp. 295-327, in DeValentine, S.(ed), Foot and Ankle Disorders in Children. Churchhill-Livingstone, New York, 1992, p. 314.). They indicated that you perform this test by placing your fingertips plantar to the medial navicular and then apply a lifting force. Moreover, it also a test that allows the clinician to “feel” the forces that are likely to be occurring during weight bearing activities that would otherwise be difficult to measure. Hence, this is why I feel this specific test (and others) is qualitative in nature.

    So how do you measure the STJA spatial position in degrees then? I always thought we used the palpation method (as far as I'm aware) to determine the amount of deviation i.e. medially or laterally deviated (no numbers or measurements). Do you use computer software, radiographs, force plates, video etc? Again, is this method exclusive to yourself or any other podiatrists in your country? I am currently not aware of this specific test being measured or interpreted this way here in Australia (I could be entirely wrong though).

    The reason why I don’t think I was taught how to quantify these specific tests i.e. jacks test, supination resistance test etc, is because it isn’t practical for the average clinician (unless they are doing it for research purposes), and because they were never designed to be interpreted that way in the first place.

    I don’t understand what you mean, Simon? Are you saying that the majority of the profession has never heard of how to quantify the actual tests I’ve already mentioned, or, are you saying that the majority has never heard of tests such as STJA palpation technique, supination resistance test, jacks tests etc? If you are referring to the latter, I would beg to differ???

    Sorry for being vague regarding the Jacks Test. I commonly assess two variables during this test: The force required to dorsiflex the hallux, hence my terminology hard, medium and easy, and the timing i.e delayed or immediate onset of the windlass. Despite some the flaws associated with this assessment, it still allows us to get an overall impression of the windlass mechanism. Shouldn’t our design parameters within the orthotic prescription be aimed at improving the windlass where necessary? I think so. The Jacks Test is one way of being able to try and determine the need for this.

    In addition, Simon, I wasn’t implying that this test alone would dictate mine or anyone else’s reasoning to justify an orthotic prescription. It is extremely important that we observe the overall picture to derive our prescription. I was using this example to simply explain how the interpretations of this test (and other tests) may differ from clinician to clinician, which may potentially affect the clinician’s decision making process when prescribing an orthotic.

    I know that you have only referred to the Jacks Test, but this is the point I’m trying to make with the tests I have already mentioned, Simon, which is what can lead to misconception.

    I do quantify some of my assessments but not the ones I have mentioned, as I can’t understand (yet) how this would be practical and conducted in a timely manner. If you have any current ideas or if you can provide me some examples as to how you regularly quantify these tests during your BMX assessments, then I'm open to suggestion...
    Daniel
     
    Last edited: Jan 11, 2008
  19. Asher

    Asher Well-Known Member

    Maybe it isn't Daniel. It would be good to hear from a few more podiatrists.

    I'd love to have the equipment to measure supination resistance and STJ axis spatial location and others. Did you make these yourself? Can you get such equipment from a supplier?

    I'm with you on the above Daniel.

    Just looking at my biomechanical examination form, I quantify lunge test and modified lunge test (in degrees), navicular drift and navicualr drop (in mm) and lateral FF elevation test (in mm). I only estimate nwb 1st MPJ dorsiflexion range (in degrees) and nwb STJ inversion / eversion range (in degrees) (yes I know but its still on my form).

    Rebecca
     
  20. Asher

    Asher Well-Known Member

    Thanks Eric for describing your technique.

    That's interesting Eric. I always feel like (with any foot that I think pronates too much) I want to get significant control by contouring pretty well in the medial longitudinal arch, particularly proximally. So I always measure it in some degree of corrected position, not necessarily STJN, but not in resting position. I don't always rely on applying that force with the poly shell, typically I get a 1st ray wipe (to allow 1st ray planatrflexion) and add a PPT (which I believe is the same as the low density 120 EVA) arch pad so that some force is applied but its not as severe as it would be if the polyprop contoured at the same arch height.

    So say the arch height I want is 28mm, I'll request the orthosis shell to be made at 25mm and add a 4mm PPT arch pad (allowing for a bit of compression for the static measurement).

    Not saying I'm right, its just what I do. It is nice to know what you and others do, it makes me question what I do, which is good.

    However, I fully understand what Simon means when he says "Given that it is dynamic function which you are trying to influence, surely a measure taken from dynamic function will be more useful". Its just that what dynamic measure is there to use?

    Rebecca
     
  21. DSP

    DSP Active Member

    I've always considered this to be at the labs discretion. I haven't read of anything specific regarding this addition before. Will be interesting to hear more about this...

    Me too.

    Every test you have mentioned above I also "quantify", however, I still question the level of subjectivity when it comes to assessing NWB 1st MPJ ROM and STJ ROM (I'm not picking on you, I'm just generalizing; I do this too). I hope people don't get the impression that I am criticizing all the tests (which I'm not), as I am only referring to ones I have specifically mentioned, yet, these tests IMO, are still regarded as being important in order to facilitate an orthotic prescription.

    I think we might be moving slightly off topic though. Another thread might have to be initiated.:dizzy:

    Regards,

    Daniel
     
  22. See Michaud p.205. It depends what I'm trying to achieve in terms of orthosis effect on first ray. Most labs will blend the medial addition to end roughly in the area of the navicular. The point is though, that if the medial addition is blended to zero thickness at this point, what influence does the medial addition have on arch height, given that in most feet the navicular is the heighest point of the arch?


    I haven't ridden a BMX since I was 14. In terms of quantification of supination resistance see:

    Payne CB, Oates M, Mitchel A: The response of the foot to prefabricated orthoses of different arch heights. Australasian Journal of Podiatric Medicine 36(1)7-12 2002
    Payne CB, Noakes H, Oates M, Munteanu S: Resistance of the foot to supination. (Published online - Nov 2002)
    Payne CB, Noakes H: Foot posture and the force needed to supinate the foot Journal of the American Podiatric Medical Association (in press)
    Payne CB, Munteanu S, Miller K: Position of the subtalar joint axis and resistance to supination Journal of the American Podiatric Medical Association 2003 93: 131-135

    I just cut and pasted these from Craig's online CV, so there may be others.

    There are several ways of doing this, given that you obviously already use a palpation technique I'll tell you a couple of ways of quantifying this: 1. Use a goniometer and measure angulation to midline of foot 2. Use a perspex sheet with a grid and Cartesian coordinate system- use trigonometry to calculate the angulation.



    So how does your qualitative assement allow you to arrive at a quantitative prescription?



    Beg to differ all you like, the fact remains that the majority of podiatrists around the world have never heard of these tests. Think a bit further than podiatrists specializing in biomechanics in Australia Daniel.



    The fact that the test lacks validity suggests that it is fundamentally flawed and doesn't give you an overall impression of the windlass mechanism during gait. So if a test lacks validity, why would you still perform it? It's like assessing a persons favourite colour and then using that to predict their height.

    Never disputed this, but if you base your assessment of need on Jacks test, which lacks validity....


    The point you raised re: misconception was based on the premise of inter-observer error using these assessments. Take a look at the literaure which was produced by researchers in your own country:

    Noakes H & Payne CB: Reliability of the manual supination resistance test Journal of the American Podiatric Medical Association 2003 93:185-189

    Abstract

    Several decisions need to be made when prescribing foot orthoses for abnormal foot pronation. One of these decisions is how much force is needed from orthoses to supinate the foot. The supination resistance test has been described as one technique to help determine the amount of force needed. The aim of this project was to determine the reliability of the manual supination resistance test. Four clinicians of differing levels of experience performed the test on 44 subjects (88 feet) on 2 separate days. The test had good reliability overall, with an intertester intraclass correlation coefficient of 0.89. For the two more experienced clinicians, the intratester intraclass correlation coefficients were good (0.82 and 0.78), but for the two inexperienced clinicians they were poor (0.56 and 0.62). The supination resistance test may be clinically useful in the prescription of foot orthoses, but more work is needed to determine its validity and its relationship to clinical outcomes. (J Am Podiatr Med Assoc 93(3): 185-189, 2003

    Practice makes perfect, malpractice makes perfect even sooner.

    Daniel the real misconception here, in my opinion, is the rationale and blind faith that appears to be being attached to these techniques. Read the last sentence of the abstract above.
     
    Last edited: Jan 11, 2008
  23. Rebecca,
    You wrote:
    And when I'd begun discussing this topic with Daniel you wrote:
    SO I kind of get the impression you'd sooner talk to someone other than me about this, sorry ;-)

    Payne CB, Oates M, Mitchel A: The response of the foot to prefabricated orthoses of different arch heights. Australasian Journal of Podiatric Medicine 36(1)7-12 2002

    ABSTRACT
    A number of different design parameters are used in foot
    orthoses, one of which is the height of the arch. The aim of
    this study was to investigate the response of the foot to
    prefabricated foot orthoses of different arch heights. Sixteen
    subjects stood in static stance on six different pairs of foot
    orthoses and changes in navicular height and frontal plane
    calcaneal angle were measured. All devices resulted in
    statistically significant changes in the frontal plane calcaneal
    angle and height of the navicular. The changes to the
    calcaneal angle were correlated to the amount of force
    needed to supinate the foot. The changes in navicular height
    were correlated to the posture of the foot. Further work is
    needed to determine if these changes are related to dynamic
    changes and clinical outcomes.


    In other words- we don't know.
     
  24. efuller

    efuller MVP

    Hi Rebecca,

    If you think about STJ axis position relative to the medial arch of the device versus the position of the medial tubercle of the calcaneus relative to the STJ axis. Feet that tend to pronate more tend to have more medially positioned axes. A more medially positioned STJ axis will exit the foot around the medial arch. So pressure in this location will not cause a supination moment of the STJ. It may cause discomfort and the patient will use there posterior tibial muscle to supinate. So, with a higher arched device you will STJ supination, but it is more likely from muscular activity rather than a direct push from the orthoses. (There are orthoses out there with high arches that have the most wear under the lateral forefoot, 5th met shaft, which is consistant with the muscle causing supination.) The only time that using the muscles to cause supination is a problem is when there is active poterior tibial tendon pathology. It might happen in the future if the arch of the device is too high.

    Regards,

    Eric
     
  25. DSP

    DSP Active Member

    Could you please provide more info re: the above reference

    I concur with the literature. What I do object to though is whether or not this is possible in a clinical setting. Personally, I don’t know of anybody literally quantifying this test in private practice (e.g. using a supination resistance test device). Therefore, as I’ve originally stated from the beginning, the majority of the profession, in a clinical setting, are still likely to perform this test qualitatively.

    Simon, providing you believe this test still has some merit, could you please indicate what apparatus you regularly use (discarding research) on your pts during a typical BMX assessment in order to quantify the supination resistance test?

    Okay, so how is measuring an angle going to be an advantage though? Are you saying that once I’ve already determined the axis i.e. via the palpation method (which BTW is subjectively plotted), you then measure the angle of this axis to the midline of the foot?

    In your second example, are you basing this on the assumption that I have used the palpation method? Again, what advantage is this going to provide the “clinician”?

    I thought the gist of this test was to observe and estimate if there is any deviation of the STJ axis, thus it being a qualitative assessment? Quantifying this angulation is probably more useful for research purposes.

    Again, you’ve given me examples, but you didn’t indicate what your preferred method is for quantifying the STJA spatial position (in a clinical setting)?



    Simon, you seem to imply that all my assessments are qualitative, which they are not. To rely solely on qualitative assessments would be ridiculous.

    Honestly, I’m reluctant to admit it, but it generally comes down to an educated best guess in end. Ideally, I would love to have the equipment and expertise to quantify all my tests. I still find it hard to comprehend how we come up with numbers for RF post angles, skives, balanced position of the negative cast etc.

    Simon, I think it would be helpful if you could provide a list outlining the assessments you do during your BMX assessment which enables you to determine an orthotic prescription. I would be very grateful.

    Fair enough.

    I use it because it makes sense to me and it allows me to visualize the windlass mechanism. When I dispense my orthotics, I usually ask my pts to stand barefooted on the devices and perform this test again. I am generally satisfied if I can see a lowering in the force and an improvement in the timing.

    How do you measure the windlass mechanism in private practice? Do measure it dynamically? If so, how then?
     
  26. Asher

    Asher Well-Known Member

    That's a great explanation Eric. But rest assured, where the STJ axis exits the foot on the medial side is foremost in my mind.

    Regards

    Rebecca
     
  27. Asher

    Asher Well-Known Member

    You must be joking Simon, I am very grateful for the insight into the knowledge and mindset of greats like you and Eric. I've learned bucket loads from your's, Eric's and Daniels responses and discussion already ... but I don't think for minute Simon that you are that fragile. ;)

    I thought that a lot of podiatrists would enter this thread because I thought nominating arch height of an orthosis was common practice, probably because its on my labs script form, becasue I do it and becasue I have heard it mentioned before on Podiatry Arena ... though it seems not.

    Rebecca
     
  28. Asher

    Asher Well-Known Member

    I've just thought of something ...

    I almost always use poly or EVA rearfoot posts on the orthoses I prescribe. I think this is important to provide an orthosis that resists pronatory forces. But as a result, the poly shell in the area of the proximal MLA is very stiff.

    To my way of thinking, this stiffness is also necessary to resist these pronatory forces. On the other hand, it would be beneficial to have some 'give' in the orthosis shell in this area to ensure comfort (activity-dependent).

    A PPT arch pad gives a higher orthosis arch height when standing but allows a lower orthosis arch height when walking and even lower orthosis arch height when running.

    So I have come to use the PPT pad for this reason. I'm not saying that this is the ideal way to go about it but do you agree that the ideal would be an orthosis that provides the appropriate support in the proximal MLA for different situations? The 'appropriate' degree of support or control would reduce from static stance to functional situations from walking, running, jumping etc.

    I guess this works on the premise that one orthosis arch height is not adequate for the range of weightbearing activities from walking through to running and jumping. It also works on the assumption that an orthosis with a rearfoot post does is very stiff and does not reduce in arch height in the area of the proximal MLA.

    Just thinking out loud, if I had a pod mate nearby I would chat about this over coffee ...

    Thanks for listening ...

    Rebecca
     
  29. Tell that to my right supraorbital process that got "dented" when it made contact with somebody's knee at high speed on the rugby pitch yesterday. Lots of haemorrhaging into the eye, plenty of double vision, nice shiner and a nice headache today. Oh well cup match next weekend.:bash:
     
  30. Depends whether you think the rate of deceleration of pronation is significant. Orthoses have been shown to decelerate rearfoot eversion. This may or may not be a good thing.

    Historically the orthosis shell was usually of a uniform thickness material due to the limitations of the manufacturing process. As you have noted, the addition of a rearfoot post stiffens the device. One of the points I was trying to make in the shank thread is that by applying modern manufacturing techniques the stiffness of the shell can be selectively manipulated by varying the shell thickness, this is a far more "flexible" and potentially more accurate method of differentially altering orthosis stiffness when compared to sticking an angled block on the heel. This is one of the reasons I was trying to get you to think about how orthoses alter forces.

    Taking your PPT pad- why not just make this section of the orthoses thinner, i.e. more compliant?

    I believe that it's time to rethink orthoses designs in light of 21st century technology and knowledge. Much of the reason orthoses are the way they "classically" are, is because of the limitations imposed on the pioneers when they were developing the production methods. Lets pretend that foot orthoses don't exist. With the current knowledge base and technology at your disposal, how would you design them?

    Don't tell me. Instead, run straight to the patent office. But since I've disclosed these ideas in public they are no longer patentable- doh, what a bummer- I won't loose any sleep over it.;)
     
  31. Just thinking- amazing what a blow to the head can do! I'm also going to start experimenting using this angle on the internal oblique external rearfoot post design that we investigated here: http://www.japmaonline.org/cgi/content/abstract/96/5/383

    At the moment I pretty much randomly create an angle for the distal edge of the post, but if I use this to position the distal edge of the external stabilizer and add medial addition back to this point it should give maximal opportunity to add additional STJ supination moment through the orthosis.
     
    Last edited: Jan 13, 2008
  32. A further thought, perhaps the point that the STJ axis exists the medial column, is the point to which we should bring 1st ray cut-outs back to. Hit me again, it helps with my thought processes.
     
  33. Originally Posted by Simon Spooner
    Quantification of the axial position allows me to more precisely document the patient's axial position. I do use it for research purposes and also use this in determing the position of the heel skive on the orthosis (which incidently Rebeccca is an ellipse- http://en.wikipedia.org/wiki/Ellipse). We use the subtalar joint axial angulation relative to the midline of the foot as the major axis of the heel skive ellipse. I picked up this technique from colleagues who were employing it in Spain on plaster of paris positives. I found that when I began using computer aided design (CAD) to design orthosis, employing this method enabled me to more easilly locate the heel skive on the shell.

    See the above? That was part of a post that took over an hour or two to compose in response to Daniel. I think I might have deleted it by accident, or maybe it was deleted for me? ;-) Sorry Daniel, I have neither the time nor the patience right now to re-type it all in. I'll get back to you when I have a moment.
     
  34. Simon, Eric, Rebecca and Daniel:

    Lots of good stuff going on in this thread. Please let me add a few thoughts.

    1) I don't specifically measure actual medial longitudinal arch (MLA) height of the patient either weightbearing or non-weightbearing. However, I do clinically assess MLA height both weightbearing and non-weightbearing and note the change that occurs with loading from ground reaction force (GRF). If I want to increase MLA height in a prescription foot orthosis I will order a decrease in medial expansion plaster thickness and/or an increase in inverted balancing position of the orthosis. If I want to decrease MLA height in a prescription foot orthosis I will order an increase in medial expansion plaster thickness and/or an increase in everted balancing position of the orthosis.

    2) Subtalar joint (STJ) spatial location will tend to be associated with MLA arch height in human feet for a few reasons. First of all, in order to have a more medially deviated STJ axis, the talar head must be more adducted relative to the calcaneus than normal and this talar head adduction will be nearly always associated with plantarflexion of the talus relative to the calcaneus which will, in turn, cause decreased MLA height. Secondly, a medially deviated STJ axis will increase the GRF on the medial metatarsal heads relative to the lateral metatarsal heads due to the increase in magnitude in external STJ pronation moment (Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989; Kirby KA: Foot and Lower Extremity Biomechanics: A Ten Year Collection of Precision Intricast Newsletters. Precision Intricast, Inc., Payson, Arizona, 1997). Increased GRF on the medial metatarsal heads will increase the medial forefoot dorsiflexion moment which will tend to, over time, cause gradual decrease in MLA height (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).

    3) I first wrote about the correlation of STJ axis spatial location to orthosis irritation to the MLA over 7 years ago in the June 2000 Precision Intricast Newsletter titled, "Effect of Subtalar Joint Axis Location on Arch Irritation in Orthoses" (Kirby KA: Foot and Lower Extremity Biomechanics II: Precision Intricast Newsletters, 1997-2002. Precision Intricast, Inc., Payson, AZ, 2002, pp. 29-32). This is one of my favorite of the 240+ newsletters that I have written over the past 21 years for Precision Intricast. In this newsletter, I explore the ideas of the foot structure having a relatively deformable outer soft tissue layer and a relatively nondeformable inner osseous core that will respond to forces acting on it that will be determined by the location of its axis of rotation.

    To summarize the thoughts of this long newsletter, if the orthosis reaction force (ORF) is pressing directly toward the STJ axis, then only compression forces, and no rotational forces, can occur on the soft tissues and bone since there is no moment arm for ORF to produce rotational force on the STJ axis. As the STJ axis becomes more medially deviated into the MLA of the foot, the medial orthosis edge in the MLA may then become a source of irritation since this area of the orthosis is not only being subjected to MLA flattening forces but also is not causing any external STJ supination moment, only soft tissue compression forces.

    Even though I have been asked this question hundreds of times at seminars that I have given on STJ axis location over the past two decades, I have never been too keen on trying to align any angles of rearfoot posts or corrections on the orthosis exactly to the STJ axis location. The reason for this is I believe it is more important to design the orthosis based on all the patient's foot and lower extremity mechanical characteristics rather than just designing the orthosis on only one parameter from the biomechanical examination, such as STJ axis spatial location.

    Instead of exactly measuring the STJ axis in every patient, which is too time consuming for my busy practice, I estimate the STJ axis and then, along with all the other measurements and observations I make, I use my knowledge of mechanical modelling and lower extremity mechanics to design the orthosis that will A) optimize reduction of pathological stresses on the patient's injured structural components of their foot and/or lower dxtremity, will B) optimize their gait function, and will also C) prevent other pathologies or symptoms occurring in the patient.

    Hope these ideas and observations stimulate further discussion.
     
  35. DSP

    DSP Active Member

    Thanks for clarifying. I didn’t actually do my training in Australia, so I wasn’t familiar with the text.


    Thank you for your explanation Simon. I suppose it is a question of scale like you said, but I doubt that many will deviate from using the 3 point scale.


    Well firstly, it would probably be due to lack of resources, motivation, finances. Secondly, we don’t all have the ability to become the researcher/clinician


    Neither do I. Actually, it was my senior lecturers that used this abbreviation while I was in school, so I’ve gotten into the habit of using it.


    The only apparatus I’m familiar with is the supination resistance test device which was used in the study by Noakes H & Payne CB: Reliability of the manual supination resistance test Journal of the American Podiatric Medical Association 2003 93:185-189. At a later stage, when I get the time, I’ll read the previous articles you listed so I can compare the different quantification methods used. Consequently, it was suggested in this article, that the supination resistance test device was not necessarily suitable for routine clinical use in order to determine the supination force that may be needed to counter pronation related forces. Furthermore, they indicated that the supination resistance test device could be substituted for the manual supination resistance test, but reliability will be dependent on the clinician’s experience.

    Once again, I doubt many practitioners will be measuring this test in Newtons.


    Thanks for that.



    Relying on qualitative assessments alone would lead to more subjectivity, less reliability, making it more difficult when I’m trying to rectify errors. Even if I have made educated guesses, the fact that I still perform a mixture of quantitative and qualitative assessments means that I still have a reasonable point of reference which I can refer back to. It might be possible to achieve this with qualitative assessments, but it would probably be a lot more difficult and frustrating because assessing errors would be predominantly based on what you observe and feel as opposed to modifying actual measurements.

    Thanks for the above. I currently dont have/use F-scan (would love to get my hands on it) nor do I have/use anything to evaluate/scan my negative casts.

    Thanks. When I first read this post I figured that it must have been around 7ish on your side. That’s a bit harsh for a Sunday morning don’t you think?

    I definitely see your point here. I’m fairly neutral when it comes to assessing dynamic and static data. In other words, I don’t necessarily favor one over the other. I make my decisions based on what I collectively see as a whole i.e. static/dynamic. I would say at this stage though, because of my lack of clinical experience (and probably more so resources), this would be the main reason why I don’t feel comfortable with predominantly assessing the windlass dynamically.
     
    Last edited: Jan 14, 2008
  36. QED. So why not just go for all quantitative assessments?
     
  37. Asher

    Asher Well-Known Member

    Reliability??

    This seems a good point. Most of my assessments are not quantitative, they are high/mod/low, Yes/No, 0/1/2/3 etc. But even if they were quantitative, how does that necessarily direct you to a certain orthotic prescription? Even if you had degrees and newtons etc for every measure, we still make an educated guess as to orthotic prescription.

    What is the reference that shows that Jack's test lacks validity - sorry, I am not very well read!

    I would think another good point Simon but it is an improvement in what we have had in the (recent) past - possibly not so recent for you. To me, I am pretty much where Daniel is and it is a whole lot better than where I was a few years ago. You seem to be playing devils advocate which is frustrating but I guess you are basically saying there is a long way to go?

    rebecca
     
  38. Asher

    Asher Well-Known Member

    I don't know if it is or isn't. What do you think? It sounds reasonable.

    Sounds good, can it be done currently for a non-shank-dependent orthosis?

    Rebecca
     
  39. Asher

    Asher Well-Known Member

    Simon, I'm lost - what is the internal oblique external rearfoot post?

    And what's the external stabiliser?

    Rebecca
     
  40. DSP

    DSP Active Member

    Too time consuming and I don’t have the available resources for me to do so.

    Simon, there is obviously a huge knowledge gap here in terms of how you quantify your assessments, and how I conduct my own, which I respect. It may seem like a simple question to you, but if everyone were to quantify every single assessment to the nth degree and we completely eradicated qualitative/subjective assessments, do you think there would be a significant enhancement in orthotic success?
     
Loading...

Share This Page