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Advice on best gait analysis system to purchase

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Bonnie, Mar 4, 2011.

  1. Bonnie

    Bonnie Active Member


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    I am considering buying RS Scan gait analysis system. I would welcome advice on this system or on any others that Podiatrists have found useful.
    Thanks
    Bonnie
     
  2. David Smith

    David Smith Well-Known Member

    Bonnie, Do you mean a pressure mat system? I wouldn't call this a gait analysis system but rather a a tool or component within a gait analysis system.
    For me RS Scan go too far in suggesting a reliable relationship between evaluation of applied normal forces and orthotic design.
    The data that you collect with a pressure measuring device be it insoles, short or long mat only tell you about forces applied to the mat and their time and location. They do not tell you anything about the biomechanics of the gait or the anatomy of the subject of interest.
    Any extrapolation of data outside of what is known is assumption, this assumption can be made more reasonable if, combined with the pressure mat data, there are other parameters considered like biometrics, visual and video data, anatomical variations, biomechanical variations, history, tests and other technical data, e.g. accelerometer.
    This, for me, constitutes a whole system of gait analysis and anyone of those on their own does not. How many of those system components you will require to reasonably asses your subject in terms of achieving a good outcome with your intervention is a matter for you to decide.
    I would say a pressure may system is not essential but good education and knowledge in the relevant field is.

    The pressure measuring device is very useful when used in the correct way otherwise it can be just an expensive toy to impress your customers.
    I have an interest in a certain PMD so I'm not sure it is valid for me to give you advise on which system you should buy. I have always preffered capactive PMD rather than ink resistive PMD but if your buying an insole system then the choice is restricted


    regards Dave Smith
     
  3. efuller

    efuller MVP

    It depends on what you want to do with it. Impress patients or get clinically useful information?

    Problems with gait analysis systems.
    Does the pain cause the gait or does the gait cause the pain?
    Little published research on outcome advantages using systems.

    Advantages
    If you want to think a lot, you can learn a lot.

    I wrote a chapter for Ron Valmassey's Clincal Biomechanics of the lower extremities 15 years ago. Some of the basic stuff in it is still useful.

    Eric
     
  4. Triaxial load cells are the way to go. This fella has all the answers with regard to that- https://www.eda.kent.ac.uk/school/staff_detail.aspx?id=40

    I'm going to be talking with a company in the next couple of weeks, who have a 2D system already, our initial conversations have touched on triaxial load sensing + 3D accelerometery. We'll see. 3d in-shoe is the way to go though.
     
  5. davidh

    davidh Podiatry Arena Veteran

    Hi Eic,
    I query the statement "does the pain cause the gait or the gait cause the pain" as being a problem.

    Does that matter, given that any gait analysis system, no matter how clever or complicated, can only capture certain aspects of gait? The common restrictive parameters for all gait analysis systems are that they only capture data taken at a specific time of day, and they all utilise a hard, flat surface (to walk on).

    Joint stiffness is affected by diurnal variation - I''m talking about joint stiffness in the spine, hips or knees rather than feet, but joint stiffness anywhere will affect gait. There is an old Paper by Ian Haslock and Tony Unsworth which shows how circadian (24-hour as opposed to 12-hour) variation affects joints - I don't have the ref and having recently moved house I cannot put my hands on it for the moment.
    Tony is a Prof in the Bioengineering Dept at Durham Uni. Ian is a Consultant Rheumatologist.

    Hard, flat surfaces in gait labs are of little or no concern provided the subjects are walking on hard, flat surfaces all the time, but I feel the diurnal variation factor is really quite important.

    I use a Tekscan mat system in my daily work. If a patient has an antalgic gait I would argue that there is value in having a record of that. The Tekscan is simple to use, works well given it's limitations, and costs are similar to the RS.
    It will record weightbearing foot-shape, and aspects of gait fairly accurately, and is a good patient education tool.

    Having met the RS team (including their MD) and talked to them at length about their product I'm rather inclined to agree with Dave S - they are very interested in providing insoles, and defending their system, and not so interested or even particularly well-informed about providing gait data.
     
  6. Lee

    Lee Active Member

    Hello Simon,

    I used Matthew's triaxial in-shoe 'force plates' a few years ago on a research project on wearable technology for monitoring various aspects of lower limb function. Have these been developed into a clinic-ready product yet? When I used them they were far from being clinically useful (I still remember a very lengthy process of locating the 'right' positions for the tranducers followed by a labour intensive process of manually crafting the insole for each subject).

    Cheers,
    Lee
     
  7. efuller

    efuller MVP

    That is part of my point. It is very hard to use gait analysis as a diagnostic tool because you don't know if a subject is walking a certain way to avoid pain or if they are walking in the gait style that caused the pain. Additionally, there is step to step variation, even on hard flat surfaces. So, if you were going to make any conclusions on the data, you should average multiple steps.

    There is probably some useful data in gait analysis, but I'm not sure we have proven what is useful. For example, I just saw an article that showed that gait speed in folks over 74 was predictive for 5 year survival. Self selected gait speed might be useful clinically in the young as well.

    I also think that joint power, as calculated by inverse dynamics, might be useful in some evaluations. However, a plantar pressure map may have limited applications. For example, assessment of plantar pressures in someone with loss of sensation. Beyond that, there is debate. Howard Dannenberg has done some interesting things with the speed of progression of the center of pressure. I'd be very interested in seeing if this correlates with joint power and, or, is consistent over time.

    When they have an antalgic gait, what do you gain by recording it over just writing antalgic gait in the chart? Would measuring gait speed be a better measure?



    That is the point. What do you do with the data, other than impress patients.

    Eric
     
  8. I'm not sure, they are down to about 2mm thickness now. If you have the thickness of the transducer and the diameter, how hard is it to get a material of the same thickness and stamp out some apertures to fit the load cells into? Regardless, 3d load sensing at the foot orthosis interface is the future. Do you have a reference for the publication following the research project you performed?
     
  9. davidh

    davidh Podiatry Arena Veteran

    I don't conduct gait studies to impress patients. I use the data to educate patients, and to provide objective data about how that patient was ambulating on that day at that time.
    The hospitals I work in are designed to impress patients:D.

    My contention is that all gait analysis studies are limited as to the clinical usefulness of the data - some systems are simpler and less expensive to use than others and can provide useful objective data.
    I remember Vicon as being the most complicated and expensive system (£500,000.00 at the time) out there.
    Very impressive - told clinicians very little about how to treat a case.

    David
     
  10. efuller

    efuller MVP

    The definition of flat feet is subjective. You can measaure standing arch height with a ruler. Doesn't require much technology. Ok, using a video camera is probably the best way to measure the amount of intoing.

    Could you provide an example of how you educate a patient?

    What do you do with the data that you produce about how a patient was walking at a particular point in time?

    Eric
     
  11. Craig Payne

    Craig Payne Moderator

    Articles:
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    Useful for what?

    Useful to convince people to part with money or useful in that it gives information beyond what you get from a usual clinical assessment that actually is useful in the clinical decision making process.

    Call me cynical, but ask yourself some hard questions about what ever system you are considering ... will the information I get from this actually have the potential to change the treatment (ie foot orthotic prescription)?
     
  12. davidh

    davidh Podiatry Arena Veteran

    The data is stored. It becomes part of the clinical notes - there to be used again if needed, or there to be compared with a few years on. I should point out that my clinical practice is all musculoskeletal, that I only work in private hospitals (hence my reference to patients being impressed by the hospital, not a laptop, a mat and some wires) and pretty much all of my patients are referred, either by their GP or Medical Specialist (or Pod Surgeon). I don't think a vertical loading system would have as much application in general podiatry practice in the UK, although it would still be useful in some cases.

    From Craigs reply I surmise that vertical loading systems are not flavour of the month on Pod Arena. I'm not sure if this is because they are often mis-sold, mis-used, or whether this is simply a backlash against the hype put out by overly keen GA system salesmen.

    To paraphrase Dananberg (or maybe this is a direct quote, I can't remember - he made it a looong time ago.....
    "This is the age of the chip".
    These systems are now relatively inexpensive, easy and quick to use, accurate up to a point, and can provide repeatable and reproducible data. They also provide (unlike a video camera) easy data storage and accessability. I don't understand why anyone would still want to faff around with a video camera except for specialist applications like research or fast ambulation (running) outside.

    I can assure you that the Tekscan mat is a useful piece of clinical kit. I only have experience with one other vertical loading system, the Musgrave mat. Good, but fussy to set up, and expensive when I bought mine. The Tekscan mat is less accurate, but accurate enough, and useful clinically for the reasons I've outlined above. I don't believe it is particularly useful in diagnosis, again for the reasons I've given.
    In fact, and to repeat myself, I don't believe any gait analysis system is particularly useful in diagnosis.

    David
     
  13. Really?
     
  14. Lee

    Lee Active Member

    Hello Simon,
    From memory, there were a variety of issues beyond the simple tasks like stamping out cut outs for each transducer. I can't find the reference, but it was a poster presentation at one of the Salford biomechanics conferences (2005 probably) about the realprof project that I did with Chris Nester. Hopefully the technology has moved on and is more instantly useable in the clinical setting now. Matthew was a really nice bloke too and good to work with.
    Cheers,
    Lee
     
  15. davidh

    davidh Podiatry Arena Veteran

    Yes - you'll no doubt have noticed that I deliberately didn't mention quantifying arch height, which it can't do, being a 2-D based system.
     
  16. Ok, so how does it "show standing arch height clearly?
     
  17. davidh

    davidh Podiatry Arena Veteran

    Think about a wet footprint on a tiled floor.
    That would show standing arch height pretty clearly wouldn't you agree?
    That's what the Tekscan shows, but it's a permanent record, not a wet footprint.

    Of course - you already knew that.............:rolleyes:.
     
  18. I´m a bit confused here -

    Ive drawn a diagram .

    Arch height to me is picture x measured in mm.

    picture y represents the amount of foot that come in contact with the ground.

    Which may mean the arch height is 3mm or 15 mm. So a wet foot print type of test only shows the amount of surface of the foot that come in contact with the ground right ? There maybe a lose correlation the height the arch height in mm the less foot comes in contact with the ground but clearly showing arch height ? Maybe it´s just me?
     

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  19. davidh

    davidh Podiatry Arena Veteran

    Mike,
    We're kind of going off-topic here. I agree with your reasoning BTW.

    Arch height is not too important clinically except to ensure that the contour of the orthotic fits. I do that with a cast, like most of us. I don't believe that either the Tekscan or RS Scan show arch height accurately. With Tekscan it doesn't matter, because all we want to verify in a foot which may have been referred in as being flat is "is there an arch". Tekscan or a wet footprint can show this - Tekscan can store the information.
    With RS Scan it does matter, because that system is used to measure accurate arch height prior to prescribing orthotics. This is difficult to do with a 2D system, as has been discussed here before.
     
  20. efuller

    efuller MVP

    I also think that this is a misuse of the system. You can't get arch height from 2-d and you are misrepresenting the capabilities of the system. When people come to me with an arch and say they have flat feet, I just tell them they may be low average and they seem to accept that and that there problem is not that their feet are flat, it's that there feet hurt. I don't need a force plate to do that.


    I usually point to the inside of their shoe to show that they are overloading an area.

    I concede the point on a measurement of intoing, if you take multiple passes and average them. But do you actually treat intoeing. And if you do, don't most of the results come from external hip rotation, which is something that you would see better with video.

    I do know this, I'm just questioning whether you need the cool looking computer screen to get the value that you say you are getting.

    So, does the data change the treatment plan? How often have you retrieved data on a patient? A good analogy is an x-ray. It is sometimes nice to compare to prior films to assess progress.

    My problem is the efficiency of use of health care money. I'm questioning the value added by the amount spent on gait analysis. I think a very interesting study would be to look at the use of inshoe pressure on the evaluation of pressure reduction insoles prior to the patient walking out the door. Modifications of the insole based on pressure data might prevent some problems. There might be some value there, but a lot of information can be obtained in other, less expensive, ways.


    It appears to be pretty easy to put a picture into EMR. It shouldn't be much harder to put a digital video clip in as well. I have no experience here, but I do have experience with a force plate. It was hard to decide how much of the footprint data to save. How often do you go back to look at the data?

    Agreed. So, your reasons are patient education and recording how they walk at a certain time? Were there any others? What I'm saying is that you may be able to do those tasks equally as well without the gait analysis system.

    If you are asked to consult on a patient, you will add your expert opinion to the report. That is what referring people want from you. The question is what is added by the gait analysis system.

    Eric

    Eric
     
  21. davidh

    davidh Podiatry Arena Veteran

     
  22. You could perform an arch index, but that would require quantification, and as you were at pains to point out, you don't quantify. Moreover, the relationship between something like Staheli's arch index and the actual height of the arch is questionable. http://www.ejbjs.org/cgi/reprint/69/3/426


    So, do I agree that the static stance print that you get from the activation of sensors in a pressure mat, or a wet footprint test "show standing arch height pretty clearly"? Not really, no. "Of course - you already knew that.............:rolleyes:"
     
  23. David Smith

    David Smith Well-Known Member

    Craig,

    Useful is a great word and a well --- useful, principle to aim for.

    To answer the question 'what useful information can you glean from a pressure measuring device (PMD) that you cannot get from other clinical evaluation techniques?'

    These could be defined as corporate or universal usefulness

    1) A permanent precise record
    2) Comparable data from a inter and intra clinician repeatable technique
    3) Confirmation of standard references and the variation from that standard reference.
    4) Standard references that are precisely communicable
    5) Standard references that are testable and falsifiable.
    6) Quantifiable data

    To answer the question ' Does this information change your prescription values and orthotic design?'

    This could be defined as personal or singular usefulness - in other words these are relative to my / a person's acceptance of the truthfulness or reliability of the interpretation (human and machine) of the data output.

    1) Yes
    Saying more than that requires me to validate each statement and that would take hours and could only be successfully concluded when/if you accept my initial assumptions and axioms. NB I do have a 1 day training seminar on that subject.

    For example I would say that FncHL is indicated when the peak of the force time curve applied by the hallux occurs later than that of the 1st MPJ. I.E. hallux force is increasing while 1st MPJ force is decreasing. Confirmation of FncHL would result in a definite orthotic design.

    Regards Dave
     
    Last edited: Mar 9, 2011
  24. Craig Payne

    Craig Payne Moderator

    Articles:
    8
    I am not disagreeing with you, I just want those who are considering buying any system to ask those questions rather than buy them for the "bells and whistles".
     
  25. davidh

    davidh Podiatry Arena Veteran

    Leaving Tekscan alone for a minute, you don't think you can show standing arch height (not quantified of course) with a wet footprint? Just to clarify, because I don't want this taken out of context, I discussed this in terms of showing whether a foot was flat or not.
     
  26. Yeah, really. Your contention being that you can infer the height of the medial longitudinal arch from a qualitative viewing of a 2D pressure mat read-out. Tell me how you do this?
     
  27. davidh

    davidh Podiatry Arena Veteran

    Please see the last line of my last post.

    I think I've put enough info on this thread to show how I use a pressure mat.
    I hope some find it useful.
     
  28. You said regarding a foot pressure mat:
    Now that last line of your post was a question:
    No, I don't think you can show standing arch height clearly with a wet foot print or a 2d pressure mat output, which is why I started asking you about this. So enlighten me as to how you do it....
     
  29. David Smith

    David Smith Well-Known Member

    I'm talking timing, relative rate of loading and relative magnitude of load. There are many ways FncHL is initiated and so a number of ways to reduce it.
    This paper highlights a typical example of how you would judge the usefulness of data and in particular the usefulness of data from the PMD. You first have to accept one assumption of truth or axiom before you can accept the validity of the interpretation applied to that data.

    If FncHL was shown to be a fictitious condition then any interpretation of PMD data that indicated the concept of saggital plane progression perturbation (that may for instance result in some sub optimal angled trunk posture)as manifesting from FncHL, would be useless. This phenomenon of rational thought would not be exclusive to PMD data alone though.

    Dave
     
  30. Mark2

    Mark2 Member

    Bonnie,
    I have a matscan system which I do not use with every biomechanical patient, but I do find it useful in determining 1st MTPJ and IPJ loading.
    Initiallly I will assess their feet and gait then tell them what I believe are the causative factors of their pain. I will then get them to walk over the mat a few times to assess their weightbearing, comparing both feet.
    I then use strapping and padding for example: low dye strapping with 5mm felt lateral wedge attached to their foot and then get them to walk over the mat again and see what the changes in their gait have been.
    I use it as an educational tool to show the patient how I am altering the gait to make it more efficient. It is often useful in showing gait speed i.e. from heel contact to toe off.
    I have found that patients get a better idea of their foot function and the reasons that areas need to be off loaded.
    Mark
     
  31. Mark2

    Mark2 Member

    Bonnie,
    I have a matscan system which I do not use with every biomechanical patient, but I do find it useful in determining 1st MTPJ and IPJ loading.
    Initiallly I will assess their feet and gait then tell them what I believe are the causative factors of their pain. I will then get them to walk over the mat a few times to assess their weightbearing, comparing both feet.
    I then use strapping and padding for example: low dye strapping with 5mm felt lateral wedge attached to their foot and then get them to walk over the mat again and see what the changes in their gait have been.
    I use it as an educational tool to show the patient how I am altering the gait to make it more efficient. It is often useful in showing gait speed i.e. from heel contact to toe off.
    I have found that patients get a better idea of their foot function and the reasons that areas need to be off loaded. It seems to be a good way of educating patients about forces rather than alignment.
    Mark
     
  32. davidh

    davidh Podiatry Arena Veteran

    To repeat myself (post 29) - please see the last line of my post - post 27.
    You posted #28.
     
  33. Instead of trying to weasel, try answering the question. I saw the last line of your post No 29, I even quoted for all to see, it talks about how you use a wet-footprint test to infer arch height, so how do you do it?
     
  34. davidh

    davidh Podiatry Arena Veteran

    Dr Spooner, The last line of my post,#27 reads (quote) "Just to clarify, because I don't want this taken out of context, I discussed this in terms of showing whether a foot was flat or not. "
    Go back and look it up. Follow the posts from there - you'll see I'm right.

    What you are doing is taking this out of context.

    I have stated in this thread that I cannot quantify arch height with a 2D pressure mat system - I don't believe anyone can. I even made a point of saying it.
    But I can tell if a foot is flat or not with said system. Heck, my seven year-old granddaughter can do that.
     
  35. Mr Holland,

    You said:
    I questioned this, so then you said:
    I questioned this too, so now you're saying:
    So, that's not really the same as
    But nice attempt at the weasel. We could go on to talk about defining when a foot is flat or not........ but lets just leave it there for now, with your high tech and expensive method of dichotomising feet into "flat" and "not flat".
     
  36. davidh

    davidh Podiatry Arena Veteran

    Dr Spooner,

    I have made it absolutely clear how I use the Tekscan.

    I have not made any wild claims as to what I do, or what the Tekscan is capable of.

    Nowhere have I said that I use wet footprints to find arch-height, as you assert in your post #35.
    To quote you from that post "I even quoted for all to see, it talks about how you use a wet-footprint test to infer arch height, so how do you do it?"

    Although I have repeatedly said that arch-height cannot be quantified using a 2D system, you persist in asking me to explain my statement "it shows standing arch height clearly".

    And so it does. It doesn't quantify the height - by which I mean that one cannot measure the arch height.

    As you say - lets leave it there.

    Just to be clear - I posted on this thread in answer to the OP. I have absolutely no financial or other interest or connection in the Tekscan Company, other than I use the Tekscan mat system and software in clinical practice.
     
  37. efuller

    efuller MVP

    Since the title of this thread was asking about purchase of a gati analysis system....

    Your logic is fine, once you own the system. The additional cost per use is not that great, so why not use it. I enjoyed playing with the EMED when I was at CCPM. It taught me a lot. However, my point still stands. You can do a lot of what you claim to do with the pressure mat, without the pressure mat. Why buy it?

    Eric
     
  38. davidh

    davidh Podiatry Arena Veteran

    Hi Eric,

    I can't fault your logic either.

    Owning and using a vertical loading system is a personal choice. I like it, but I agree that some at least of what I do can be done with other equipment.

    I think Craig makes a good point asking what the potential user will do with the kit once they have it. It does cost, and although most of us know not to buy into the sales hype, some companies are very good at selling a dream.

    Good to debate with you.

    Regards,

    David
     
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