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Info regarding ink pedograph and arch index

Discussion in 'Biomechanics, Sports and Foot orthoses' started by anhtar, Feb 17, 2006.

  1. anhtar

    anhtar Member

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    Dear all,

    A colleague told me that one can calculate the "foot Arch index' from an ink print pedograph by measuring the width of the arch and the width of the heel and finding the ratio of them both.

    If the ratio is >1 then the foot is considered 'flat' foot and if the ratio is <0.3 the foot is considered 'high arched' foot.

    Does anyone have any information regarding this Foot Arch Index and using a ink print pedograph. I am trying to find out more the validity of this method.

  2. admin

    admin Administrator Staff Member

  3. DrPod

    DrPod Active Member

    There are many diffeent indicies and ratio's out there - all pretty useless as far as I am concerned.

    What do you want it for?
  4. anhtar

    anhtar Member

    Googling only gives me abstract of journal articles which I don't have access to.

    Anyway, as part of our clinic we are using these ink pedographs to take prints of people's feet and then 'screening' them to see whether they have flat foot are high arched foot. Our pod assisstants are the ones doing this mass screening at public places and are interpretating the results purely from the measurements they make using this "foot arch index'.

    As I have never used this before, I wanted to find out the medthod for measuring, reading and interpretating them. I just wanted to find out if anyone are familiar with the use of these ink print devices.
  5. admin

    admin Administrator Staff Member

  6. Since the 1930's, the height of the medial longitudinal arch has been indirectly measured using arch height index systems (AHI), charted on footprints, obtained using inked rubber mats. A review of the literature illustrates that the validity of AHI's when used to infer the level of arch height is a contentious issue (Cobey and Sela 1981, Hawes et al. 1992)

    Hawes et al. (1992) contend that AHI's are poor predictors of arch height and conclude that the use of footprint parameters are not valid as measures of height of the medial longitudinal arch. The conclusion of these workers are in strong contrast to the results reported by Irwan (1937) and McCrory et al. (1997) who present strong correlation's between direct measures of arch height and AHI's. From the analysis of 100 footprints, Irwin (1937) reported a reliability coefficient of r=0.98 (rsquare= 0.96). Mccrory et al. (1997) analysed footprints and weightbearing lateral radiographs of 14 women and 31 men. The authors report a correlation of r=0.67 (r square =0.45) between arch height index and navicular height. When navicular height was normalised to foot length a correlation of r=0.71 (r square =0.5) was yielded. The authors conclude that arch height index provides useful indirect measurements of medial longitudinal arch height.

    Thomson (1994) investigated the validity of AHI in a compariative study of AHI and frontal plane goniometric measurements of RCSP. Thomson (1994) concluded that the valgus index (a form of AHI) is a useful measure of rearfoot position, being less judgemental and possibly more sensitive to small amounts of rearfoot deviation than frontal plane measurements. Several workers who have demonstrated excellent correlation coefficients for the calculation of AHI from footprint data echo these views. Indeed many authors suggest that structural characteristics of the arch can be assessed from the analysis of footprints, with decreasing AHI mirroring increases in the height of the medial longitudinal arch (Schwartz et al. 1928, Clarke 1933, Cureton et al. 1935, Irwin 1937, Cavanagh and Rodgers 1987, McCrory et al. 1997).

    There are many forms of AHI's.

    I've run out of time now- got to go to work! Will come back to this if interested.
  7. davidh

    davidh Podiatry Arena Veteran

    Hi Anhtar,

    May I ask the rationale for "screening" people for flat or high-arched feet?
    To my certain knowledge there is not one "normal" arch height out there.
    Are you UK-based, and if so I have to also ask "is this really a good way to use our NHS pod resources?"
  8. anhtar

    anhtar Member

    Hi David,

    To answer your question, no, I am not from UK but from Singapore.

    One of the reason behind these 'mass screening' exercises is to promote foot health and podiatry awareness to the public. Unlike the Western countries, the podiatry profession and foot health awareness here is woefully lacking in the general population. Most people here will think reflexology when you talk about feet care.

    So as part of our 'marketing' strategies, we are involved with health screening programmes with our partner organisations. We would send our podiatry assistants to these events and get them to take a pedograph print of people and from the results of the Arch Index, let the participants know whether they have a low arched foot or high arched foot and where to go seek help if they have any problems.

    Yes, I realise this does not constitue a proper foot assessment and they are not meant to be so. They are simply a 1 minute foot screening job to give the participant a general idea of their foot type and let them know that the podiatrist exists.

    I was not involved in the setting up of this screening programme but as I am the one reviewing it, I wanted to find more on the procedures for taking a pedograph print, and the method for calculating and reading the results. I saw some of the pod assistants taking a print, derive a foot arch index that indicated 'flat foot', but clearly on my observation, the individual did not have a 'flat foot'.

    Our ink pedograph printer did not come with any instructions on proper usage hence i wanted to find out from fellow colleagues if they had any experience with using them.

  9. davidh

    davidh Podiatry Arena Veteran

    Interesting -.
  10. Jamie

    Jamie Active Member

    I think the UK has the same issues as Singapore about Foothealthcare awareness. It is an interesting way to look at marketing Foot Healthcare and promoting the "Value" of Podiatry services to change Public Perception of Foot Healthcare. If you have toothache - you see a dentist, if you walk into a lampost - you see an optician. If you have a sore foot what percentage of people will go and see a Podiatrist. A 2D ink impression might not be Scientifically the best way to treat specific foot problems but if it helps people link Podiatry with Feet, then as an initiative it should be applauded and I know has been used in the States with Community Diabetes screening. I also know of cases in Ireland when Podiatry patients have shown their computer generated plantar pressure images around the pub.

    Is there any Research done on %age recognition of the Podiatry (Chiropody, FHP whatever) in UK. It would then give those of us who have a vested interest in a Healthy Proffession a target to aim at. Maybe even a banner to rally the masses behind - Now theres a thought.


  11. OK back from work.

    The footprinting mat has a long history of use in large scale foot surveys, the afore mentioned Harris and Beath (1947) survey of Canadian army recruits probably being the most famous, but other surveys include that by Staheli (1987) and Rao and Joseph (1992).

    In my Phd study:
    Predictors of Hallux valgus: A study of Heritability. Spooner S.K. University of Leicester (1997), I used the arch height index (AHI) described by Rao and Joseph (1992)- simplest easiest to calculate. I used the Berkemann pedobarograph- this is the least messy (and they are messy!) of the systems I could find. Unlike the traditional Harris and Beath mat, it does not give the pressure sensitive grid within grid print. But for AHI's you don't need it. It is also worth noting that footprint systems have also been used for both dynamic and static measurement of hallux abductus angle. I would be tempted to suggest that this may be a better thing to calculate, if all you are trying to do is raise foot health awareness, but then if you are doing this, you might as well use goniometric measures- something about giving them a footprint to take away though as Jamie said.

    Rao and Joseph method: A line is drawn between the lateral most aspect of the heel and the most lateral aspect of the metatarsal region (line AB) The narrowest region of the midfoot area of the print is identified. A line perpendicular to line AB is drawn through the narrowest point of the midfoot. The points at which this line contacts the medial and lateral borders of the print are identified and denoted as point 1 and 2 respectively. the distance between points 1 and 2 is measured (mm). The widest region of the heel area of the print is identified and transected by a line perpendicular to line AB Similarly the points at which the line contacts the print are identified and denoted as points 3 and 4 and measured. AHI = width of arch contact area / width of heel contact area. Sorry don't have a digital pic on hand :(

    I recorded AHI, Age, Met. formula, digital formula gender, 1st ray sagittal plane position, and family history (+ve or -ve) from nearly 600 individuals from about 300 families. Of these AHI was the best predictor of hallux abductus angle with an r square of .40425 in the model. (BTW if I was starting again, I wouldn't necessarily include these variables, given 20:20 hindsight- I did start taking measures to calculate STJ axial position ala Phillips and Lidtke- but guess what it takes an epic amount of time and the measures themselves are just a tadge unreliable :mad: ) but it did mean that I got SALRE theory really early doors which has stood me in good stead (cause I soon forgot all my undergrad dogma) meant that Kirby kinda likes me (and I kinda like him) and enabled me to travel the world teaching :cool: . But that was way back then ;) .

    Conclusion: AHI's have their place, but recognise you are assessing an AHI, not necessarilly a measure of anything other than the AHI. AHI's can be significant predictors of other measurements taken from the foot such as RCSP and HA angle. But why not just measure these? In my PhD I was predictive model building and trying to find simplistic measures that could be applied to broad populations without harming them and without the need for technology and as such the footprint mat was a perfect tool. But technology has moved on since then...
  12. anhtar

    anhtar Member


    You are a gold mine! What I really wanted was the details on methodology like that you described for the Rao & Jospeh method. I just didn't know where to begin. Anyway, I shall search for this article and begin from there. unfortunately I can't really picture what you was describing.

    Just some question:

    1) Will it make a difference whether the subject's print is taken in dynamic or static stance? My concern is that in static stance, the subject might subconsciously over invert/evert their feet because they can't stand relaxed.

    2) So far, we have been getting our subjects to do a natural walk over our pedographs and in some prints, the most medial arch areas come out as very feint lines. Would you then still measure from the most medial feint ink lines? Or would you only measure from the solid square ink lines that appear?

  13. Sorry to make you forget all your wonderful undergrad biomechanics teaching, Simon. Yeah, the Phillips and Lidtke method....what a chore!! The STJ axis locator will eventually make a difference some day, but that's another thread for another day.

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