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Measuring arch height

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

  1. Asher

    Asher Well-Known Member

    Unfortunatly I am one of those who don't fully appreciate that there are big differences between running and walking. I have read Novacheck's paper from an earlier thread of yours and I learned a lot. And will read Simon's suggestions over the coming days ... thanks to you both!

    Rebecca
     
  2. Smilingtoes

    Smilingtoes Active Member

    The most influential biomechanics/ advice I can recall;

    "If in doubt, pad it out."

    In making my own and 5 other podiatrist’s (4mm poly) orthoses for 14 years I believe an important balance needs to be found.

    Too much and the arch will irritate or blister. Too little and the arch falls down onto the device leading to reports of "hard". Both unacceptable outcomes as rigid orthoses are joint specific.

    I have recently (3yrs) started using a lab which also looks for a measurement of arch height. For me this is a very difficult question as Im use to determining orthotic arch height from a combination of assessment findings (to a lesser extent), arch contour and foot type.

    To assist with your prescription writing I might suggest 75% of NCSP measured inferior to navicular then 60% inferior to the highest point of the arch.

    I say might, because I’m still having troubles communicating the arch height each orthotic requires to my lab. Caution! My opinion as it is based on experience, not controlled trials.
    Of equal concern to me is lack of recognition as to where the medial arch starts in the frontal plane.

    The lab that I use 3D scans my neutral plaster casts before as they modify using computer software. They have described this as draping a sheet over the cast and lifting it medially. This concerns me greatly! When modifying casts myself I would identify the transverse arch of the orthotic at the tarsal joints before carrying this through to the forefoot. I believe this directly relates to the arch height you need, as stability through the tarsals will influence Post. Tib., Peroneus L, STJ etc etc.

    I look forward to reading further comments as for me I am still looking for the one arch height measurement my lab expects me to identify during my assessment. :craig:Hope this helps.
     
  3. fixmyfeet

    fixmyfeet Welcome New Poster

    Hi Rebecca
    We use a small rectangular shaped tool with 'arch height' measurements in millimeters, printed on a sticker and placed on the long sloping end of the triangle. We then slide this under the apex of the arch with the person sitting, and then again standing. It is not an exact science, but can help show how much the arch drops during weight bearing compared to non-weightbearing.
     
  4. JFAR

    JFAR Active Member

    Arch height change during sit-to-stand: an alternative for the navicular drop test

    Thomas G McPoil , Mark W Cornwall , Lynn Medoff , Bill Vicenzino , Kelly Forsberg and Dana Hilz

    Journal of Foot and Ankle Research 2008, 1:3doi:10.1186/1757-1146-1-3

    Published: 28 July 2008

    Abstract (provisional)

    Background
    A study was conducted to determine the reliability and validity of a new foot mobility assessment method that utilizes digital images to measure the change in dorsal arch height measured at 50% of the length of the foot during the Sit-to-Stand test.

    Methods
    Two hundred - seventy five healthy subjects participated in the study. The medial aspect of each foot was photographed with a digital camera while each subject stood with 50% body weight on each foot as well as in sitting for a non-weight bearing image. The dorsal arch height was measured at 50% of the total length of the foot on both weight bearing and non-weight bearing images to determine the change in dorsal arch height. The reliability and validity of the measurements were then determined.

    Results
    The mean difference in dorsal arch height between non-weight bearing and weight bearing was 10 millimeters. The change in arch height during the Sit-to-Stand test was shown to have good to high levels of intra- and inter-reliability as well as validity using x-rays as the criterion measure.

    Conclusions
    While the navicular drop test has been widely used as a clinical method to assess foot mobility, poor levels of inter-rater reliability have been reported. The results of the current study suggest that the change in dorsal arch height during the Sit-to-Stand test offers the clinician a reliable and valid alternative to the navicular drop test.
     
  5. Smilingtoes

    Smilingtoes Active Member

    Thanks, that’s helpful and clinically relevant.:good:
     
  6. joejared

    joejared Active Member

    For my own customers (orthotic labs), we don't request arch height, but rather arch fill, simply because it is calculated from the actual patient's digitized/scanned cast. I believe most of my customers have about a half dozen settings of arch fill to cover your requirements. Specifying an arch height will work but arch fill is simpler and goes back to the roots of manufacturing orthotics by hand, even in automated systems. Unless you're designing a whitman roberts, or UCBL type of device for your patient, measuring arch height directly is irrelevent to the manufacture of custom orthotics. Oh, prefabs. :eek: Well, stay below 50% of your patient's arch height as it climbs to more than 45 degrees relative to the plane defined by the center of the first metatarsal, 5th metatarsal and heel and you'll be able to provide your patient some comfort. You may also want to consider the cuboid longitudinal position both in midstance and in a neutral non-weight bearing condition to be sure that there is no undue pressure on the midtarsal joints. The arch is somewhat forgiving, but the cuboid isn't, and an improper amount of pressure in the mid tarsal joints can cause cramping. I wouldn't suggest exceeding 50% of arch height simply because you could do more harm than good.
     
  7. Bill Bird

    Bill Bird Active Member

    Hi Rebecca

    The ancient way to do is is to trace the foot with a fine pen held vertically. Then hold the pen at 45 degrees to the ground and 90 degrees to the axis of the foot and trace the arch onto the paper. You can make a simple device with a triangle of wood and an elastic band to make this tracing consistant.

    You can do this weight off in neutral position and then weight on. You will get two lines the weight off one being further in than the weight on one. When you come to rectify your casts, lay it on the tracing and rectify it so that the pen draws a line half way between the two arch traces you took from the foot. Under-rectify for light patients and over rectify for heavy ones. (Get some scales and weigh them)

    This is analogue rather than digital method but it really works.

    Bill
     
  8. efuller

    efuller MVP

    I have to disagree. As a practitioner, I see the patient standing and have some idea of how high I want the arch of the device. To get what you want when you send a cast off to a lab, you have to know what that lab's definition of medium, minimum or maximum fill is. If you ask for a 20 mm arch height and the lab sends you an orthotic that has a 16mm arch height, the lab should fix it for free. If you wanted 20 mm and asked for medium fill and got back an orthotic with 16mm arch, the lab can just say "that is what you asked for, medium fill. Do you want to buy another orthotic?"

    Regards,

    Eric
     
  9. Phil Wells

    Phil Wells Active Member

    Dear all

    I have working with scans of feet for about 6 years (Manufacturing orthoses commercially) and have always been an advocate of specifying the required arch height. However there is a problem with this. The method for raising or lowering the arch height digitally is variable and can distort the orthotic. Its concavity or convexity can be effected when moves of 5mm plus are specified. This is ok if you are using 'freehand' CAD software but if you are using a pre-designed orthotic specific CAD system, it may be a problem as the method of movment is fixed.
    The solution is to give the CAD design package to the clinician who an see the changes on their patients scan and make the decision themselves. This at the moment is too costly but in the future it may be the panacea for all issues with translation between lab and clinician.


    Phil
     
  10. Phil,

    Craig, Phillip Hartshorne, Dave Kingston (LCB) and I started discussing this briefly at PFOLA in San Diego in 2007. Basically, the clinician needs to be able to access a version of the CAD software (maybe dumbed down, maybe not) to gain an understanding of what is being done within the software rectification.
     
  11. Berms

    Berms Active Member

    Hi Rebecca. Well done for being the catalyst in an excellent and informative thread.

    I know you posted this a while ago (apologies if you have covered it elsewhere) but could you explain how you measure/quantify navicular drift and drop? And what is the lateral FF elevation test you speak of?

    And for what its worth, I am one of those who both measures and prescribes an exact arch height, simply so I know exactly how high I want the highest part of the medial aspect of the arch area of the device - I then choose the arch "profile" that I want ie where I want this highest point to actually sit relative to the anatomy of the foot. For example if I want the peak arch height to be mid arch, or if I want it to be further proximally eg under the navicular.... I believe both the arch height and the correct arch contour of the device are both important in achieving maximum efficacy and comfort of the device.

    Cheers,
    Adam
     
  12. Asher

    Asher Well-Known Member

    Hi Adam,

    For drift and drop, I have a business card and an A4 piece of paper, and I have the navicular tuberosity already marked. Have the patient stand with one foot on the paper in STJ neutral (in angle and base of gait). Place the business card on one edge so it is standing flat on the ground and place it up against the foot (at the navicular tuberosity). Mark the business card where the navicular tuberosity mark is, and mark the paper where the edge of the business card sits on the paper. Ask the patient to relax and remark these two spots. So you will have two marks on the business card and two marks on the A4 paper. The distance between the two marks on the A4 paper is navicular drift (transverse plane) and on the business card is drop (sagittal plane). Navicular drift and drop measurements give you an idea if the foot is compensating more in the sagittal or transverse plane or equally in both planes.

    Eric Fuller has discussed the forefoot elevation test a few times in past threads, hopefully Admin might provide you with a link to those threads. You can use this test to determine if / how much lateral forefoot extension / posting you can use.

    Rebecca
     
  13. Berms

    Berms Active Member

    Hi Rbecca,
    Thanks for the explanation.

    As you have said before, getting all this qualitative and quantitative data about the patient's foot is great.... but the tricky part (I find) is taking all this great info and translating it into exactly how we do our orthotic precription. This is the bit where I get unstuck, eg I know the patient has a medially deviated STJ axis, great!! now what does that exactly mean in terms of how I prescribe? - ok maybe a little inversion? Maybe a medial heel skive? maybe both? How much of each one? Will I over-correct?

    Your thoughts are welcome.
    Adam.
     
  14. Asher

    Asher Well-Known Member

    Hi Adam,

    I follow Craig Payne's thoughts mainly, on orthotic prescription. He is big on examining things only when the result of that examination directly effects an orthotic prescription variable. I've been to a Bootcamp a couple of years ago - thoroughly recommend it Adam. Things like symmetry of hee-off, supination resistance, Jack's test, prominence of plantarfascia, functional foot drop, forefoot supinatus.

    I'll send you a PM with a few notes I have.

    Rebecca
     
  15. Berms

    Berms Active Member

    Thanks.
     
  16. joejared

    joejared Active Member

    There is no reason you can't specify an arch height within 1mm with any of my customer's, but in practice, the type of fill specified is common practiice. In a production environment where thousands of pairs per month are processed in a lab, however, usually the type of fill only is specified. Going back a couple decades, I doubt that a lab technician did more than add plaster according to fill. It's the newer automation that attempts to make such a precise statement. and more importantly, labs that make libraried parts that want actual arch height.
     
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