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Force / Time curve abnormalities

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Asher, Sep 16, 2009.

  1. Asher

    Asher Well-Known Member


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    Force / Time curves are characterised by two peaks separated by a trough. The apex of each of these three events occur at a coordinate, the two numbers defining the vertical component of GRF (y axis) and the timing (x axis). Kirtley (2006) cites Giakas and Baltzopoulos (1997) when providing normative ranges for these events.

    FIRST PEAK
    Timing ie: %age of stance (21-25%)
    Force ie: %age of body weight (108-126%)

    TROUGH
    Timing ie: %age of stance (45-51%)
    Force ie: %age of body weight (69-81%)

    SECOND PEAK
    Timing ie: %age of stance (74-78%)
    Force ie: %age of body weight (104-114%)

    In describing abnormal F/T curves, Dananberg (Tekscan case studies) discusses four basic shapes: heel plateau, central plateau, excessive central depression and forefoot plateau. However, F/T curves can be interpreted using the above six parameters and each can be either lower or higher than normal.

    My question is, what can cause each of these events to occur early / late and to be lower / higher in regard to force? Following is what I have taken from Dananberg and inferred myself:

    FIRST PEAK
    Timing: Early - ?
    Timing: Late - ?
    Force: High - delayed heel lift
    Force: Low - Dananberg's Heel Plateau - early heel lift eg: in lld or equinus

    TROUGH
    Timing: Early - ?
    Timing: Late - ?
    Force: High - Dananberg's Central Plateau - delayed heel lift
    Force: Low - Dananberg's Excessive Central Depression - equinus, flexed knee

    SECOND PEAK
    Timing: Early - equinus
    Timing: Late - ?
    Force: High - pes cavus, plantarflexed first ray?
    Force: Low - Dananberg's Forefoot Plateau - apparently hallux rigidus & limitus and pes planus

    Any advice would be appreciated.

    Rebecca
     
  2. Rebecca, with regard to timing I should imagine that surface stiffness (Ksurf), leg stiffness (Kleg) and foot stiffness (Kfoot) would be important factors. The shape of the foot-ground interface may also be significant, i.e. posterior directed heel flare on a shoe. In terms of magnitude, you also need to consider factors influencing the shear components, i.e. non-vertical force.
     
  3. Admin2

    Admin2 Administrator Staff Member

  4. Asher

    Asher Well-Known Member

    Hi Simon,

    Can you confirm for me that 'rate of loading' refers to the amplitude of the 'heel strike transient' or 'passive impact peak' normalised to body weight ... not the slope's gradient. Thanks

    Rebecca
     
  5. Rebecca, if we have a force /time graph then the rate of (un)loading is indeed the gradient of the line. This could be the gradient of the line at any area of the force/ time curve.
     
  6. Asher

    Asher Well-Known Member

    Hi Bruce,

    I am very interested in force/time curves. But I have not found much in the way of guidance for their interpretation. There must be more to it than the four abnormal curves described by Dananberg, as I have suggested in the initial post (and thanks Simon for the advice on stiffness).

    Also, I'm not keen on getting a separate curve for each peak, firstly because you might not select the same area (heel and forefoot) between feet and between patients, and secondly because there is even less information about how to interpret these individual curves. Why can't you get the information you need from the whole foot F/T curve?

    Rebecca
     
  7. Mart

    Mart Well-Known Member


    Hi Rebecca

    Just picked up on this thread.

    Firstly sorry not to have replied further as you requested to your very large document earlier in year; frankly it was too big a task and too little time and then I forgot to let you know that :eek:.

    After going through the same kind of thought processes for several years that you seem to be (on this issue and many others related to measurement of vertical GRFs and interpreting that data) I have as a generalisation come to the following conclusion.

    Because the data is most often so non specific to a particular problem (by inference this is usually clinically a potential pathology) there is no real specific interpretation if you expect to use it as a test with reasonable level of specificity (because there might be many plausable explainations for what you find).

    So then what is the point in using this technology?

    I think that if you have a reasonable handle on how GRF's are influenced by the forces acting above them, which as you know are very complex and variable, then there is a capacity to see if the measurements you make amount to what you might expect. Implicit though is an appreciation the limitations both of the reliability of the data and personal knowledge. I try and mittigate this by weighting the evidence according to how consitent it seems (interstep variability) and if it jives with other measures; ie the more the different measures seem to support a given hypothesis (for that individual) the more likely they are to mean what you think.

    Because this can be overwhelmingly time consuming and also questionable I try and reduce the data either to comparison to absolute normative pressure values for selected anatomic sites or generalised behavior such as trajectory of COP, timing etc. If there is deviation from expected of a measure, even if as broad as a total FTC, I will attempt to see if it can be explained by and consistent with the problem as seen by other measures; this might be Hx, PE, imaging, kinematics etc.

    I am linking the spreadsheets I promised you earlier to the Podarena Icon on my website (podarena doesnt allow spreadsheet postings) for you or anyone else to use. I have created 2 versions for tekscan. I'll link the FMat one first and replace it after a few days for the inshoe.

    It will only work with Research version 6.31.

    Please give me a couple of hours to modify my website otherwise you will get the earlier spreadsheet I posted on podarena last week.

    As vague as this seems I cannot see any alternative approach.

    Have a play around with the spread sheet and let me know what you think.

    cheers

    Martin
     
    Last edited: Nov 10, 2009
  8. Mart

    Mart Well-Known Member

    You should be able to download SS now, just doubleclick the podarena icon @

    http://www.winnipegfootclinic.com/resourses.html


    On opening the template excel automatically looks for 2 data sets

    These are the text files of data generated from the templated regions and saved from within FScan software for Left and Right foot data.

    Driving home I was thinking about some kind of illustrative exercise to try and clarify my point a little.

    Rebecca please give this a try.

    Although this may seem obvious to start out I am curious to see where it might lead other than exposing an embarrasing level of ignorance on my part.

    Anyone else, particularly Simon or Kevin K (if you are lurking and my silly cartoon didn't offend you) please jump in and criticise as we go.

    Scenario;

    You do a barefoot exam using FMat (good calibration using step method, equilibilbrilated sensor, 2 step protocol, no evidence of visual targetting, normal kinematics as defined by Kirtley, total contact time 620 msecs and normal forefoot contact timing) and notice that there is a consistently below normal left foot but not right foot peak pressures, force/time integrals as defined by 1st metatarsal head templating and elevated lesser metatarsal head values for same. This is based on 3 trials which all show abnormal values based on work by

    SCOTT, G., MENZ, H. B. & NEWCOMBE, L. (2007) Age-related differences in foot structure and function. Gait Posture, 26, 68-75.

    You have no other information at this time (this is a thought exercise not a reflection of good clinical practice).

    What might you deduce regarding stiffness of 1st ray MCJ from this data?

    would there be any justification in assuming this as

    1 possible
    2 likely

    given this evidence alone?

    After reply I will unveil another layer of the exam.

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  9. Bruce Williams

    Bruce Williams Well-Known Member

    Rebecca;

    first off please keep in mind that the curves cited in the tekscan case studies are gait curves. Gait curves are the curves derived from the entire foot pressures put into F/T curve. They do not represent either the heel or forefoot seperately, but the entire foot.

    Regarding the heel plateua: in this case the heel peaks then maintains the same level of force over time, a plateau, until the F/T curve will increase again in late midstance or early propulsion ending in a peak at the height of forefoot pressure and then decending towards toe off.

    see attachment 1:

    Heel Plateau basically represents a heel that starts to unweight but is then stalled into and thru midstance. It is usually associated with a shorter heel contact periods (time). It can denote either a shorter limb, equinus, or knee flexion compensation of the longer side. The patient will stall out in midstance due to lack of AJ rom and midfoot/FF compensation due to lack of stiffness. Prolonged midstance duration occurs.

    Bring the ground up to the foot via a heel lift and you will then equally distribute the FF and RF pressures and usually stop the delayed unweighting of the heel. A soft Heel lift sometimes works too to dampen or keep the heel on the ground for a longer period of time.

    Central Palateua: represents a peak at heel contact then a flat sustained curve that ends in peak forefoot pressure and falls towards toe off. Basically a rising curve, flat and then a drop off. see attachment 2.

    Central Plateua represents geriatric gait. picture an elderly person taking small steps with little or no hip extension, a flexed knee and landing with essentially no heel rolling and no mpj extension or propulsion as they transition to the opposite limb.

    Rocker bottom shoes work well for these patients. I'd utilize the FF rocker more than a RF rocker, if the patient has stability issues with their gait. If you use a heel rocker, make it smaller in most cases. MBT is an over kill for heel rockers in this demographic.

    Excessive Central Depression: This is a very high initial heel curve wiht a deep central depression in midstance adn then ends in a high curve for the FF.
    Basically what I tell people is this... Since this curve represents normality in most instances you need to understand that usually you will still see delays in the heel and FF curves in these patients. They will be very subtle, but will be the primary cause of teh assymetries that will lead to CLBP due to acceleration differences L to R. These are usually the easiest patients to get better!

    Treatment: treat the to the heel and FF curves, ie cutouts and Heel lifts adn the problem is usually easily resolved.

    Howard may jump in here at any time and say I'm completely wrong! ;) I hope not, but it would not be the first or the last time!

    Finally, Forefoot Plateua: This is a "normal" heel curve that transitions into a flattened mistance curve that tapers off gradually to toe off.

    This curve basically represents a blockage of normal propulsion. We will see this in patients with significant FnHL or structural hallux limitus. Answer to these patients or curves is to use a very large 1st ray cutout, FF valgus posting and digital pads, ie cluffy wedge at the hallux and also 1-5 in most instances. Make it so the FF rolls to eliminate this problem. Rocker bottom FF adjustments work too at the sole of the shoe.

    I hope this helps!
    Bruce
     
  10. Bruce Williams

    Bruce Williams Well-Known Member

    Rebecca;

    The F/T curve of the whole foot, the gait curve, provides confusing information at times.

    I try my best to focus on the seperate heel adn FF curves first adn foremost adn then the Gait curves lastly. It is much easier to identify delays in forward motion in the heel and FF curves, and also to correlate this with the delays in motion in the frames in the center of pressure trajectory that I call the earthworm for I think obvious reasons.

    I then try, as Mart stated, to understand where the delay is, what joint is probalby causing the problem and then whre to put my attention in the orthotic modificaiton.

    So, if there is a heel delay and no FF delay I don't have to usually worry about a 1st ray cutout, but instead address a potential LLD or manipulate for AJE.

    If there is no heel delay and only FF delay in the curve, then I treat with either a cutout, a FF valgus posting and or a digital wedge a la cluffy wedge.

    Usually it is a combined problem so will take a little of everything. No worries, just treat it sequentially and you should see significant improvements!

    BTW I just got back from Orlando Florida this weekend and we did a Tekscan users meeting there with Norman Murphy. Tekscan usually does at least two of these in the states per year. I was fortunate to have done one in Seattle and the one Orlando.

    If you guys have interest in having one in the UK, Norman can do those, or if you bend Tekscans arm, maybe they might be willing to send me over sometime to help out! hint, hint! :D

    Cheers!
    Bruce
     
  11. Asher

    Asher Well-Known Member

    Hi Martin,

    Thanks for your reply.

    I don't have the mat. Would you mind emailing me the in-shoe version?

    Regards

    Rebecca
     
  12. Asher

    Asher Well-Known Member

    Hi Bruce

    Thanks for those explanations. But have you described the Gait Curve or the individual curves? Howard describes these same abnormalities but for the Gait Curve only. Does Tekscan have something that shows the individual curves for the four F/T curve abnormalities? (your attachments haven't come up).

    Don't you think Bruce that F/T curves have the potential to be more informative than just to highlight four problems ie: if we knew the normal timing and amplitude range for each peak/trough for in-shoe measurements, as per Kirtley, 2006 (citing Giakas and Baltzopoulos, 1997) for floor-mounted measurements? For example, maybe a late first peak indicates the need for a stiffer material (shoe, orthotic material, heel lift) to be used?

    What is not provided by Dananbergs 4 abnormal F/T curves is what it means when, and what you do for:
    First peak - early, late and high pressure
    Trough - early or late
    Second peak - early, late or high pressure

    Do these things not occur?

    Rebecca
     
  13. Asher

    Asher Well-Known Member

    How? And why? Can you show me an example of the gait curve providing confusing information that has been solved by separating the heel and forefoot region?

    But what do you use to determine what's abnormal and what's OK? Do you just have to use it for years to get the hang of it?

    Rebecca
     
  14. Bruce Williams

    Bruce Williams Well-Known Member

    Rebecca;
    see my replies below:

    Sorry the attachments did not work. Send me your email and I can send you the ppt slides I used this weekend. The curves are highlighted in the ppt.

    [/QUOTE]Don't you think Bruce that F/T curves have the potential to be more informative than just to highlight four problems ie: if we knew the normal timing and amplitude range for each peak/trough for in-shoe measurements, as per Kirtley, 2006 (citing Giakas and Baltzopoulos, 1997) for floor-mounted measurements? For example, maybe a late first peak indicates the need for a stiffer material (shoe, orthotic material, heel lift) to be used? [/QUOTE]

    Absolutely! Unfortunately at this point you have to intuit some of this information.
    You also have to keep in mind that there is more than one way to skin a cat! Sometimes soft heel lifts work as effectively as a hard heel lift. You can't usually know this unless you try it though. There may be numerical information that the curves are derived from that could help with a more specific assessment of this, and the CoM'nalysis software might help with that as well.

    I realize you want hard facts here. Unfortunately at this point it is not that easy. It does take time to appreciate what to look for within the curves, compare it to your physical exam, adn how the patient moves/walks/runs in video. From there you make a decision on your next move. There is a "learning curve" no doubt!


    [/QUOTE]What is not provided by Dananbergs 4 abnormal F/T curves is what it means when, and what you do for:
    First peak - early, late and high pressure
    Trough - early or late
    Second peak - early, late or high pressure

    Do these things not occur?[/QUOTE]

    I'm not sure what you mean in this last question. Can you be more specific?
    send me your email and I'll attach the curves. I copied all the curves and turned them into a picture, but they don't seem to want to upload. If anyone has a suggestion I can try that first to post them for everyone.'

    Bruce
     
  15. Bruce Williams

    Bruce Williams Well-Known Member

    Rebecca;

    finding exact curves for demonstration can be time consuming. If I stumble upon something I'll post it with an explanation.

    My suggestion still stands, focus on the heel and FF curves, where they cross over, when then initiate and end, their impulse, etc. Compare it to the static images with the CoP trajectory and also to the side by side "bunny hopping" comparison of right and left feet and check for delays in acceleration from side to side and the timing for when certain areas of the feet load and unload.

    That was a brief synopsis of what I teach in the users meetings.

    Finally, abnormal is a plateau or 'stoppage" of forwrd motion in the curves. Normal is a minimally or non delayed transition of the curves. I wish my syntax could be better as I know you want hard and fast specifics. Mart may answer this better than I. Suffice to say, there is no true normal, only what works best for each individual.

    Achieving "normal" F/T curves will not guaruntee a cure for your patients. I still have "failures" or patients that improve but not completely. This is where Kevin Kirby is right in saying the plantar fascitis, and other diagnoses, are a potential combination of causes. You treat what you can and hope for the best sometimes.

    Bruce
     
  16. Mart

    Mart Well-Known Member

    Will do. Consider that the absolute values for masked data for in-shoe pressure measurement studies are extrapolated from the barefoot data. Therefore a bit dodgy in that respect. That is why I use the Mat since it is the only way to make comparisons with normative data (the effects of shoe are unknown without this).

    When I do in-shoe pressure measurement studies I do a Mat exam at same appt. That way I feel I can get a bit of a feel for the effects of the shoe on pressures and timing.


    Please reply to the example I posted - I think it will be a useful learning exercise for us both.

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  17. Bruce Williams

    Bruce Williams Well-Known Member

    Mart;
    I downloaded your matscan info. Now what? I unzipped it, but i can't seem to open it.

    any help appreciated. I'm not a big excel user, so please be gentle! ;-)
    Bruce
     
  18. Mart

    Mart Well-Known Member


    Hi Bruce

    Shouldn't need to unzip this is not compressed file. It does require excel 2007 for macros to work and you need to set security level to allow macro to run.

    When you open the template file it will ask you to identify location of the .txt files generated by the template module within the 6.31 version software. You need to generate the left and right foot data and save that from tekscan software first.

    Then the SS will import that data via the macro into page 2 and 3 of the SS (speadsheet). Then if you look at page 1 I have programmed in a bunch of calculations which compare the data to the normative data, made some boolian calculations on that data representing it as graduated colour, the key is at bottomn of page. I have also included timing data and a IPP and IPF ratio calcs for PD1 and 1st MTH as a possible index of presentce FHL.This idea is based on the work done by David Smith for his MSc thesis on the nature of FHL in relation to timing and tensile loading.

    let me know if you still have problems and I'll try and troubleshoot for you


    cheers


    Martin
     
  19. efuller

    efuller MVP

    Bruce,

    I'm curious as to how a heel lift can both cause an earlier heel off ("stop the delayed unweighting of the heel") and cause a later heel off. Any thougths as to why this would happen? How much between step variation is there in the timing of heel off in a single condition?


    Regards,

    Eric
     
  20. Asher

    Asher Well-Known Member

    Hi Martin

    So low first metatarsal head pressure and high lesser metatarsal head pressure would indicate that propulsion is occuring laterally not medially (low gear Bojsen Moller) which likely means functional hallux limitus. BTW, does a FnHL produce high hallux pressure? It could also indicate a structural hallux limitus, but I would think that hallux pressures would be elevated. It could be a pain avoidance gait. These are my first thoughts.

    I wouldn't have even thought about the first metatarsal cuneiform joint stiffness but it would indicate low stiffness. Unless its stiff and sore and its a pain avoidance mechanism to toe off laterally.

    Or maybe its a metatarsus adductus or internal tibial torsion causing the lateral toe off.

    Rebecca
     
  21. Asher

    Asher Well-Known Member

    Bruce
    That's so frustrating. I'm not good at intuition. I make assumptions and conclusions that are incorrect because of this shortcoming. Is FScan only good for top class biomechanists who already have a superior knowledge of all things biomechanics?

    [/quote]What is not provided by Dananbergs 4 abnormal F/T curves is what it means when, and what you do for:
    First peak - early, late and high pressure
    Trough - early or late
    Second peak - early, late or high pressure

    Do these things not occur?

    I'm not sure what you mean in this last question. Can you be more specific?
    [/quote]
    Please see the opening post of this thread Bruce.

    Rebecca
     
  22. Bruce Williams

    Bruce Williams Well-Known Member

    What is not provided by Dananbergs 4 abnormal F/T curves is what it means when, and what you do for:
    First peak - early, late and high pressure
    Trough - early or late
    Second peak - early, late or high pressure

    Do these things not occur?

    I'm not sure what you mean in this last question. Can you be more specific?
    [/quote]
    Please see the opening post of this thread Bruce.

    Rebecca[/QUOTE]

    Not sure why it would be frustrating to intuit. We all do it everyday as we gain more experience in situations. We see patterns and intuit the cause adn effects from those patterns.

    F-Scan can help you to become a much better biomechanist because of the information it provides. As you start to think about why and when there are variations in the curves, the trajectories, the pressures, you start to understand foot function much better than ever before. It definitely helped me and continues to do so regularly.

    Finally, I reread your into post and I still don't understand what you are asking. Maybe you can pick one example and phrase it in a way that might be more understandable to me?

    Bruce
     
  23. Bruce Williams

    Bruce Williams Well-Known Member

    Eric;

    if the heel begins to lift off the ground, but then cannot rise any further, there is a delay in its unweighting. This can be caused by lack of AJ rom, and / or increased compliance within the metatarsals or midfoot.

    Adding a heel lift in some of these circumstances may bring the ground to the heel and eliminate the delay in teh F/T curves. It may also help to elevate the midfoot thereby positioning the mpjs in more extension to potentially eliminate and FnHL. It might also allow for more AJ rom due to the positioning of the foot in a more PF'd position during heel contact.

    How can there be step variation in heel off in a single condition? I don't understand what you are asking.

    Bruce
     
  24. Mart

    Mart Well-Known Member

    Hi Rebecca
    My intention was that you would likely comment that this could be evidence of elevated MCJ compliance but that with this limited information there was no justification for assuming this to be true.

    You are way ahead of the game here and have already re-enforced the point that a single gait measure in isolation has limited specificity and I agree with your analysis/interpretation and won’t patronize you by carrying on with my idea further. Logically, it seems to me that the more that different measures stack up to support or refute a theory the more likely it is that you will arrive at the truth and/or mean what you think they do.

    For what it is worth this is my experience;

    I find that I am able to filter out many possible interpretations simply from PE. In this instance some-one with a very high MCJ stiffness would be identified from PE, so interpretation of low 1st metatarsal head peak pressures in this case might be; compensation occurring for 1st metatarso-phalangeal joint dysfunction, abnormal lower limb position or pain as you already mentioned. It may be useful to understand this for example if presenting problem appears to be pain associated with Tib Anterior tendon overload.

    It may not be possible to determine the behavior of the foot during gait from static exam or simply watching someone walking up and down the hallway. However gait “abnormalities” may be entirely incidental to the presenting problem.

    I am not convinced by the arguments which I have seen which support the idea of trying to create symmetry in measures from in-shoe pressure measurement studies for things like centre of pressure trajectory, and timing simply because symmetry is somehow intuitively desirable. It seems probable to me that interfering with asymmetry may actually create problems given that feet are often asymmetric both morphologically and in loss of functional headroom.

    I have stopped looking for the holy grail of ” an algorithmic analysis of gait data as means to determine diagnosis”. The problem is way to complex for this little brain of mine and I suspect that is an impossible task anyway given the limitations in measurement systems and what we can actually usefully measure.

    For me a decent Hx, PE, look at lesion pattern and shoe wear, and cursory look at walking gait will most often create a very strong impression of nature of complaint to work with and gait exam not indicated.

    I tend to do “gait exam” when; there are apparently multiple problems intertwining, nothing obvious explains symptoms and am looking for clues, prior evidence is conflicting, there are intermittent symptoms and non when presenting, what you do doesn’t work or makes things worse for no apparent reason, or gait seems abnormal and you want to slow things down and get a chance to look over again to check things carefully rather than rely on memory or a potentially flawed record of what you thought you saw.

    It seems worthwhile to me to question premises in detail as you are and I look forward to trying to learn from what you are doing with this.


    Cheers

    Martin
    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  25. Mart

    Mart Well-Known Member

    Bruce's approach presumes an important understanding of what the total FTC represents. It simply examines the vertical acceleration of the body wt above the point of contact. So whilst the curves typically represent the effects of the 3 rockers seen in the saggital plane on body acceleration so does a bunch of other things.

    Simon posted a neat study on the effects of proprioception on IC. So 1st rocker may well be a function of this but you may add to that the other things he mentioned too. Therefore without concurrent kinematic data, what is actually going on is not clear. Thats what bothers me about Dannenberg's work, he doesn't mention this let alone control for it. It doesn't mean that his ideas are wrong, for me at least though it makes them less convincing. If the normal camel humps are not present in your exam you might want to go looking for a reason. If you have an elderly appropulsive pt with slow gait , chances are the FTC will be flat simply because there is little vertical acceleration, not particularly a big deal.

    I think what is much more interesting and better use of time is to look at the so called 3 box approach to GRFs.

    What this does is gives you more insight into the timing because you can see very quickly when those rockers are happening because you isolate the forefoot from the rear foot and estimation the loading and unloading rates is more intuitive because the data is separated out. In the total FTC the forefoot and rear foot accelerations are superimposed (along with mid foot and toes).

    Another important feature of the loading / unloading is what the contra lateral foot is doing. The faster you walk the shorter the double stance period becomes and this also effects the loading / unloading rates, that is the disadvantage of the short mat. it doesn't see what the other foot is doing at IC and HO. You can see this if you wire yourself up in shoe and walk at different velocities then do a 3 box and sample through the range. Watch how the FTCs change.

    In your patients if you see a lot of asymmetry in 1st rocker (IC) loading you might want to look at the tibial angle at that 50ms mark prior to IC (according to proprioception paper), how the hip or knee is behaving during 1st rocker etc. If the heel unloading rate is high it probably reflects early heel rise, but then what is causing this, could be pain, posterior group contracture, ankle block and so on. Again lack of specificity but non the less useful info if you want to see if your PE is relevant to possible gait effects. This MUST be helpful if you suspect an injury is likely caused by compensation for another problem. If your suspicion is warranted you will likely be able to detect it, unless of course you observe an uncompensated sample or the sample is unrepresentative of typical walking because of the clinic environment and/or act of measurement alters the gait pattern.

    Don't panic the more you think about this the more tuned in you will become.

    hope that makes sense (and is accurate!!)

    cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    phone [204] 837 FOOT (3668)
    fax [204] 774 9918
    www.winnipegfootclinic.com
     
  26. Asher

    Asher Well-Known Member

    Bruce,

    Yes, I agree. I use my 15 years experience to intuit everyday and it serves me well most of the time. However, I am trying to use a bit more evidence to back up my interventions.

    I think it would be great to actually see that a 3mm heel raise is better than a 5mm raise in patient A because I can see that 3mm is what it takes for the windlass mechanism to work, as shown by plantar pressures or the F/T curve or whatever. Or that an arch height of 20mm is better than 25mm for patient B because the F/T curves are within normal limits or the CoM is perfectly sinusoidal.

    When I provide an in-shoe device, there are degrees of intervention. I don't just decide to "use a heel raise", I get tied up with what thickness heel raise: 3mm, 4mm, 5mm, 6mm, 8mm, 10mm? How do I know? Let's say they all fit in the shoe and they all feel comfortable. I would like something to show me that its the 3mm or the 8mm that I need.

    But as several colleagues have told me, I'm much too recipe-oriented and as Martin suggested, there is no holy grail. My expectations of FScan in-shoe are unrealistic.

    Rebecca
     
  27. Bruce Williams

    Bruce Williams Well-Known Member

    Rebecca;
    You can "see" all of the changes you talked about above. You can tell, the majority of the time, whether the patient is doing better with a 3mm or 6mm heel lift. There will be a change in pressures, trajectory and almost always in the F/T curves unilaterally or bilaterally!

    You can see pressure, trajectory and F/T curve changes due to a higher arch height between devices. If the patient excepts the arch height, as comfortable or whatever, then you will see full pressure of the medial arch. If the device doesn't match up or they supinate the foot away from it, then you have a problem adn have to figure out whether it is the height of the arch, the opposite foot causing a problem or if you need to add a cutout or heel lift etc.

    Everyone wants a cookbook approach. I'm pretty sure I could retire if I could create one. It's not quite that easy since there are som many differeing variables from patient to patient. I'm also not a very good carnival hawker or used car salesman. I see to many hairs to split in the way I do things and I'm just happy when it works out, often regardless of what we did.

    there are those days though when yoiur intuition is on high and every move you make does exactly what you think it will do when using Fscan and doing orthotic mods. In actuallity, that happens much more often for me now than ever before.
    I get to do the same thing in front of an audience when I to the Tekscan users meetings. So far, knock wood, i've only had one relative failure in that venue! ;)

    cheer!
    Bruce
     
  28. Bruce Williams

    Bruce Williams Well-Known Member

    Martin is correct, the 3 box approach is what works best adn supplies the greatest amount of information. My apologies if it was unclear that this was what I was advocating all along!

    Bruce
     
  29. Mart

    Mart Well-Known Member

    I have started a sub thread @

    http://www.podiatry-arena.com/podiatry-forum/showthread.php?p=122931#post122931

    The idea is to look at nitty gritty of using observational video gait examination and cheap/fast/dirty clinical kinetic data for evidence of foot behaviour. Also to consider limitations, value and justification for doing this. It should eventually include discussion of force/time curves and their interpretation.

    Cheers

    Martin

    The St. James Foot Clinic
    1749 Portage Ave.
    Winnipeg
    Manitoba
    R3J 0E6
    Phone [204] 837 FOOT (3668)
    Fax [204] 774 9918
    www.winnipegfootclinic.com
     
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