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Uncompensated forefoot varus - what do I prescribe?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by TEW, Nov 7, 2006.

  1. TEW

    TEW Member


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    A patient of mine presented with pain on the dorsal lateral aspect of her foot around the mid tarsal region. The area of pain is not local but a vague area in that region.

    She told me she saw a different pod a few weeks ago who tapped her foot (not sure exactly how - assume it was low-dye technique). The pod told her to purchase OTC orthoses from a sports shop if the tape helped.

    The tape helped (while it was on), she bought the orthoses and now the foot is getting worse.

    The BME revealled a true forefoot varus that was not fully compensated by the fully pronated STJ (the STJ had a small ROM or should I say - had excess stiffness). Consequently the lesser metatarsal heads were over loaded during static stance and the first Met head was under-loaded. I don't have the luxury of a gait plate or F-Scan to illustrate this objectively but any trained pod could see this when on hands and knees observing the foot from the medial aspect. While the patient was standing I could almost work my finger under the entire first met head - due to the minimal amount of weight resting on the first met head (and she is quite a heavy lady!). Contrastingly it was impossible to do the same with the lesser met heads.

    While she was standing the hallux was adducted (in relation to mid line of body not mid line of foot) and slightly plantar flexed to obtain ground contact. Consequently windlass is not being utilised and the foot is in a potentially pathological causing position.

    I hope I have explained the foot type adequately enough for you to understand.

    An X-ray showed OA changes at the Mid tarsal joint.

    Now I know I have to change the dynamics of the foot so that more weight is forced medially at the forefoot to allow for "high-gear" rather than "low-gear" push off to allow windlass to be utilised and have the foot working in a more functional manner. I was taught (at uni) with this foot type to place a varus wedge at the distal end of the orthotic, underneath the met heads (thicker under first met head and thinning out laterally under the 5th met head) so that I was bringing the ground up to the first met head and supporting the true forefoot varus position. The idea being that more load will be borne under the first met head and reduced under the lesser met heads.

    My only concern is how do I do this but still allow windlass to function (ie allow first ray plantar flexion and hallux dorsi flexion)?

    Having been to Craig Payne's courses I know he says to shift weight medially force needs to be applied laterally and vice versa. What I have explained is actually the opposite. But I don't think the foot has enough ROM (or too much stiffness) for Craig's principle to work. But I don't want to make the foot worse by jamming up the first ray and preventing windlass from functioning.

    She is due back in a few weeks for casting. I am open to any ideas, suggestions or similar situations that you may be able to share.

    I am a fan of what you teach Craig and do use a lot from your courses, hence my conundrum.

    cheers - any comments will be appreciated.
     
  2. efuller

    efuller MVP


    Hi TEW, don't be bashful about including your name. Some on the list won't reply unless people add their name.


    It sounds like sinus tarsi syndrome. How's that for an over the internet diagnosis. I don't quite know what you've been taught, but you have to look at the moments appiled to the foot. When the forces on the plantar foot are high lateral there will be a high pronation moment on the STJ. For the foot to be in equilibrium in stance there will have to be a high supination moment from some other source. That source can be the floor of the sinus tarsi. So to reduce stress on the sinus tarsi you need to decrease the pronation moment from ground reaction force. Treat with both forefoot and rearfoot varus wedging. Don't worry about the windlass unless first MPJ also has pathology. The structure that hurts is the sinus tarsi, treat it.

    Cheers,

    Eric
     
  3. Asher

    Asher Well-Known Member

    Hi TEW,

    You ask a question that I myself am struggling with at the moment. Frankly I'm surprised that this thread hasn't received much attention from other posters.

    I hope that bringing this post up again will prompt some suggestions / answers.

    So what prescription variables would be best used for a true FF varus with 1st MPJ pathology?

    Many thanks

    Rebecca
     
  4. efuller

    efuller MVP

    In TEW's example, the pathology was in the lateral dorsal rearfoot (Sinus Tarsi) So your question is a little different. The device should be aimed at what hurts.

    A partly compensated varus foot (One in where there is insufficient ROM of the STJ to get significant medial forefoot weight bearing in stance) can have medial colum pathology. This pathology can be caused by more than one thing. Some patients will plantar flex their hallux with their FHL muscle and develop a hallux hammer toe. Others will have the pathology caused by an abducted gait where the MPJ recieves its stress as the foot rolls over the medial colum in late stance phase. (This is the time of highest stress on the MPJ because it is after heel lift and it can be before heel strike of the opposite foot.)

    If the pathology is caused by FHL contracture then I would support the MPJ with a forefoot varus wedge, extension.

    If the pathology is caused by abducted gait roll off I would try the usual windlass things and look for points of high stress from the device.

    If the forefoot varus has enough range of motion to get signiificant weight medially in stance, I would ignore the forefoot varus. If, in stance, their is eversion availble of the forefoot off of the ground, I would probably create an intrinsic forefoot valgus correction in the orthotic and consider a forefoot valgus extension.

    Remember treat the structure that is under stress, not the forefoot to rearfoot measurement. However, you have to be aware of modifications that can casue problems. If a little is good, more isn't always better.

    Eric
     
  5. Asher

    Asher Well-Known Member

    Thanks Eric.

    I have a 14 yr old boy who presented with no specific symptoms but wanted to partake in a school camp doing a section of the Bibbulmun Track (WA bush track). He explains that he can't be on his feet for longer than a couple of hours as his feet ache (vague) so he just keeps off his feet, and he can't run.

    He has an extremely abducted stance and gait, no areas were tender to palpation, no 1st MPJ pathology, no symptoms if he's not on his feet much.

    On my 4th attempt, I have him comfortable in orthoses with high (35mm) medial flange and 6mm PPT on the flange to cushion the block in transverse plane motion, spenco to toes, 30mm arch height and 10 degree medial heel skive. He didn't go well with a high lateral flange even when cushioned so i rely on the shoe to hold him on the orthotic and up against the medial flange - take it from me, there's not much room in the shoe for his foot to go anywhere else.

    It was interesting to see how his angle of stance and gait changed from very abducted without the orthoses to much less abducted (higher end of WNL) when he was with the orthoses.

    My only concern is that on his orthoses, his 1st MPJ is way up in the air, in fact, the whole first ray. I have a 6mm PPT pad under the 1st MPJ to 'bring the floor up to the foot' but it's not nearly enough.

    For anyone who might be able to provide advice, should I be looking to have the orthosis contour better to the 1st ray altogether, as I have explained, the whole region is elevated from the orthotic, and 'bring the floor right up to the foot'? Or need I not be concerned about this lack of contouring in the 1st ray area? What are the longer-term implications of this orthosis on the 1st ray?

    BTW, he can now do a decent run and his gait is much more 'normal' which he is thrilled about. He is doing a test run for his trek soon.

    Rebecca
     
  6. In this case, I would add a forefoot varus extension until the medial metatarsal heads were weightbearing sufficiently to allow him to propel off of his medial metatarsal heads, which will increase his speed and efficiency of running. By the way, the medial heel skive is measured in thickness, not only in degrees. How thick was your medial heel skive?
     
  7. Asher

    Asher Well-Known Member

    Hi Kevin,

    I have no idea on the thickness of the skive and actually thought it was more appropriate to prescribe / refer to the skive in degrees. Is the degrees vs the thickness prescribed relevant ... obviously or you wouldn't have asked ... how?

    Thanks for the advice but one further question, should I have done something different in casting / prescription so that the orthoses contoured the plantar surface of the medial met shafts or is it inevitable that they sit up off the orthosis?

    Rebecca
     
  8. Shane Toohey

    Shane Toohey Active Member

    Angles of medial skives

    "By the way, the medial heel skive is measured in thickness, not only in degrees. How thick was your medial heel skive?" Kevin Kirby

    Hi Kevin,

    I'll take some responsibility for a variation in medial skives in our region.
    Back in the early 80's we (an orthotic lab I was a partner in), used to offer a variable "intrinsic heel grind" on the positive casts. This was usually medial and was measured in degrees.

    The process involved shaving off across about 2/3 of the width of the heel on the positive cast at the requested angle - which is very simply done, using a flat grinder at the heel and everting the forefoot of the positive cast with a platform which can be set at chosen angles. The angles requested were usually less than 10 degrees and were an alternative to inverting the casts to achieve increased rearfoot effect in the subsequent devices.

    It was with great pleasure we saw your papers on medial heel skiving published as it vindicated what we had been doing ( and we do feel a bit lonely sometimes).

    Your methodology was different, as it was measured in thickness (all at 15 degrees) and the theory behind it was very well outlined in far greater detail than had occurred to us. Nevertheless, we have been happy to continue on using the angle as the variable rather than the thickness and can make a case for it - I think it is easier to do in practice. We now, of course, do angles above 10 degrees. and mostly encourage a simple range of 5,10 & 15 degree skives.

    Where our technique came from is somewhat lost in time. I remember the name "Ganley" and a request from one of our clients and bit of 2+2= ? etc.

    So, Kevin, nothing but sincere respect for all you do and have done. I simply wanted to explain the apparent aberration.

    Cheers
    Shane
     
  9. Shane Toohey

    Shane Toohey Active Member

    Hi Rebecca,

    I'm concerned in this case about the 1st MPJ being in the air, despite even having a 6mm pad under the joint. I would be expecting trouble in the long if not medium term as "normal" function cannot be happening. The foot may look OK in the shoe at the STJ and the change has been beneficial but I'd expect a cost.

    My first thoughts on prescribing in this case would be to increase the medial skive, lower the arch and add a varus wedged extension. No matter what you need to get that 1st MPJ functioning.

    Personally, I think there is an over emphasis on getting the arch as high as can be tolerated. I don't think it is there to be pushed up. Even the varusw wedge may not be needed in the long term as the function improves.

    Just my thoughts

    Cheers
    Shane
     
  10. Rebecca:

    I described the medial heel skive originally as a constant angle of 15 degree skive at variable thicknesses 2 mm, 3 mm, 4 mm, 6 mm and 8 mm (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). However, certainly the technique can be altered to produce a similar effect in the resultant orthosis. Thickness of skive is important since this determines the percentage of the heel cup area that is in a varus attitude.

    I will tend to not use as much varus as you did in the walking orthoses I make, but will use more varus correction in running orthoses since symptoms often don't respond in running unless you do so. I will rarely add a varus forefoot extension in a walking orthosis but will commonly use it in a running orthosis. The varus forefoot extension does increase the ground reaction force and loading of the medial metatarsal heads but one must be careful that the tendency toward functional hallux limitus is not also increased. I don't think I am afraid of varus forefoot extensions as much as many other podiatrists obviously are on this forum, but I will use them with great care since they can cause problems when used in the wrong individual.
     
  11. Shane:

    Thanks for the posting. One very smart podiatrist (Steve DeValentine, DPM) said to me early in my career, "nothing new under the sun", when I asked him about whether a surgery like I was talking about had ever been done before.

    Actually the idea of the varus wedged orthosis heel cup probably started with P.W. Roberts who developed a deep, inverted heel cup metal orthosis with medial and lateral heel cups in 1912 (Schuster, R.O.: A history of orthopedics in podiatry. JAPA, 64(5):332-345, 1974.) I first saw a varus heel cup orthosis being used at CCPM as a podiatry student with Rich Blake making his first Blake inverted orthoses in about 1981. After making a number of foot orthoses for Rich as a student and using them on my own patients, I began to see the mechanical effectiveness of an inverted heel cup orthosis, even though most of the biomechanics faculty at CCPM at the time thought Rich Blake was crazy and was going to hurt people with his orthoses.

    Some years later, I was lecturing at a seminar one day on Blake inverted orthoses and after the lecture, another podiatrist came up to me and said that he does a similar thing by putting varus heel wedging under his cork and leather orthoses which he found worked well. Something "clicked" after that, and it was soon after that, in 1990, that I started having Precision Intricast put the medial heel skive into my patient's orthoses. I liked the medial heel skive because it was so much easier to perform than the extra positive cast work that was needed to be done with the Blake inverted orthosis. In addition, I liked the medial heel skive because it didn't modify the medial arch of the orthosis like the Blake inverted orthosis did which then allowed me to vary the medial arch height of the orthosis independent of the changes to the heel cup that were occuring due to the medial heel skive.

    Now, over 15 years later, I think the technique of how the medial heel skive is performed is of secondary importance since the same varus heel cup effect can be accomplished in many ways. However, I believe that the theory of how a varus heel cup works (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; Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992) is of major importance since the inverted heel cup orthosis design variable has been used in orthoses for nearly a century now and, as far as I know, did not have a good mechanical explanation in the literature until the concept of STJ axis location variation was applied to it.

    Shane, thanks for the information and keep us informed if you are doing any other creative things with your positive casts that you have found to be effective.
     
  12. Shane Toohey

    Shane Toohey Active Member

    Kevin thanks for history and it all seems so logical up to this point.

    You also wrote; "Shane, thanks for the information and keep us informed if you are doing any other creative things with your positive casts that you have found to be effective.
    I just spent probably the best part of an hour writing a couple of paragraphs in response only to have server drop out and lost the lot. Is there a 'save' button we can use along the way?

    I'll just have to be more brief. Medial arch fills became a matter of how much and what shape? Particularly when casts were inverted.
    We developed a system of describing the medail arch fill that is quite specific and gives the technicians a good idea of what the prescriber wants.
    Firstly, the arch fill height (AFH), can be measured in mm. This is the max height of the arch on the positive cast. The prescriber can nominate the height or ask for high, standard or low and the lab can then work out the measurement on the negative cast with the rearfoot reference vertical.
    Having heights above that of the cast vertical is a recipe for disaster I think and that is obviously where the device for Rebecca's patient now is.

    We combine the AFH with descriptions of the contour of the shape of the medial arch. This arch contour (AC) is desribed as "minimal fill", "standard fill" and "maximal fill". I think virtually self explanatory with the minimal fill being more aggressive anteriorly in the arch. We also identified two more descriptives for the contour. The first we call "peak" which describes a shape more like that for a cavus foot, with the maximum height more anterior in the arch and slightly extra fill in the proximal arch, which reduces the severity there which can happen with the usual fills. The shape then is more of a regular cup shape. The other we call "wrap" and just requests that after the original shape above (AFH and AC) the medial side of the fill is rounded off substantially to produce a shape suitable for the high medial flare.
    Originally we offered an "hypermobile" correction which included the high medial flare and a large medial skive. I'm sorry I couldn't come up with a better word than "wrap".

    Overall this all happened as a response to inverted corrections, and variations in casting techniques and qualities.

    I'll press the button again without checking!

    Cheers
    Shane
     
  13. efuller

    efuller MVP

    If you placed your cast on the grinder at 10 degrees for 2 seconds as opposed to 15 seconds you would get a significantly different shape that could be characterized by the depth of the skive.

    Now that you are deep into experimenting (Not always a bad thing) you should look at the wear pattern of the current device. In other words, when he stands on the device in your clinic the first met head is up in the air. The question is whether or not the wear on top of the orthosis is the same or does the first met get down when he wears the orhtosis for a long time. Without that information, I would agree with Kevin that a forefoot varus wege/extension should be added so that the entire forefoot can be loaded in propulsion. In my opinion, the ideal gait should have the force on the forefoot spread over as much as area as possible so that no one structure bears too much of the stress.

    If the wear pattern on the orthosis was entirely lateral then put the varus wedge in right away.

    Eric
     
  14. efuller

    efuller MVP

    Wow, with all the diffrences that we see in podiatric biomechanics, you and I have come up independently with same idea. Kevin and I have independently done this on occaision. (dorsiflexing the first ray, when casting, on a flexible cavus foot comes to mind.) I was looking at the standing arch height and looking at the arch height of the neutral position cast and seeing almost no correlation. I started measuring standing relaxed arch height and then started making my orthoses this high. When I do this, I have had very little problem with toleration of the arch. John Weed taught that if you had an ankle equinous you had to take a cast with the STJ more pronated. This would lower the arch. I think this acomplishes the same thing. In some feet I've had the lab call me and ask if I want the arch of the unmodified cast ground to make it as high as I asked for. On other feet, I will reduce the neutral positoin arch height by half or more.

    Anyway, telling the lab that I want a 20mm medial arch height makes the prescription much more precise. When the orthosis comes back with a 15mm arch height, I have no problem sending it back when I asked for 20mm.

    Cheers,

    Eric
     
  15. Griff

    Griff Moderator

    Eric,

    Please forgive my ignorance, but could you explain further why you slightly pronate the foot whilst taking the negative cast for someone with an ankle equinus?

    Respectfully,

    Ian
     
  16. Shane Toohey

    Shane Toohey Active Member

    Hi Eric,

    Thanks for your response, it's great to get into this type of chat.

    You wrote; "Wow, with all the diffrences that we see in podiatric biomechanics, you and I have come up independently with same idea."

    I think we come up against the same problems when following similar systems and ideas just wait to be tried out. The medial arch fill was also a problem from a lab perspective in having the wants of different pods with different expectations explained to technicians so that they could satisfy the different wants. It wassn't our job to say you can only do this our way. As the system became more precise it also then presented as having benefits for different foot types.
    It can also be difficult at the lab when a prescriber says 'you've done it wrong', when their prescription was very vague (and the devices, obviously, were having problems). We really appreciate the pods who prescribe arch heights and contours. We've been basically doing this since the early 90's with the peak and wrap shapes for about 5 years.

    You also wrote: "If you placed your cast on the grinder at 10 degrees for 2 seconds as opposed to 15 seconds you would get a significantly different shape that could be characterized by the depth of the skive."
    Our system has been to skive off the same proportion of the width of the heel of each foot (~2/3) but with the variable being the angle. You get to be very consistent at this and you can visually and quite easily match up a pair of casts. So we get used to doing skives at different angles, but the same proportion of each cast and the effect it will have. Similarly a 6mm depth skive will be quite different for a small child than what it would be on an elite basketballer. You make allowances for that and don't just say that 6mm is causing a moderately supinatory momment at the STJ in both cases. We just have a different way of manufacturing a scale of response.

    And lastly on Ian' query: 'explain further why you slightly pronate the foot whilst taking the negative cast for someone with an ankle equinus?' Personaly, I'd not pronate the foot more in casting, but simply lower the arch a few mm and be less aggressive in the contour. In general, with modified corrections on positive casts, the shape of the corrected arch is not fully prescibed by the shape of the arch taken in the cast as it was more fully in the Root system.

    Cheers
    Shane
     
  17. Asher

    Asher Well-Known Member

    Hi Shane, you quoted: "Having heights above that of the cast vertical is a recipe for disaster I think and that is obviously where the device for Rebecca's patient now is"

    I'm not sure if I fully understand your statement. My pour was vertical, arch height 30mm. No plaster was scraped from the positive model.

    From the previous posts, I can see that with a forefoot that is true varus with no MTJ motion to get the 1st MPJ down, that 1st MPJ is always going to be sitting up in the air. So the foot has to do one of two things, either STJ pronation inspite of the orthosis to get it down, or toe-off will go through the lateral MPJs (low gear). Either way, a FF varus extension will reduce both.

    I can understand your reasoning Shane that the arch height ideally would be less and compensate somewhat by increasing the medial heel skive angle and I will definitely try this in the future. My only thought is that with his serious Subtalar Joint Tip-over sign, once he starts to pronate, he'll keep going and get irritation from the friction of his midfoot sliding over the orthosis.

    But thanks for the posts to date, they have been very helpful.

    How are you going TEW?

    Rebecca
     
  18. efuller

    efuller MVP

    Hi Ian,

    I was just reporting what I was taught in school. As I understand it, through trial and error the Root et al (Well it was John Weed who spent about two hours on this topic in a 30 hour course) found that people without adequate ankle dorsiflexion could not tolerate their orthoses. They found when they casted the foot in a more pronated position the patients could tolerate the device. My interpretation of this information is that the pronated cast produced a device with a lower arch. However, in examing many feet as the STJ is moved from a pronated to a supinated positoin, there are some feet whose shape does not perceptibly change. Therefore I believe it is not the STJ position that matters so much, but height of the arch of the device.

    Craig mentioned his wall test where assess ankle joint dorsiflexion. He adds a heel lift when there is not adequate dorsiflexion. If I recall correctly, he said that there was better tolernece of thedevice with the lift. I wonder what would happen if those devices were made with a lower arch ( more arch fill)?

    Cheers,

    Eric Fuller
     
  19. Griff

    Griff Moderator

    Eric - thank you for your reply.

    Eric/Craig: Is this a modification you would use on all orthoses for patients with limited ankle joint ROM?

    It is my understanding that whilst running you do not need as much ankle joint ROM and whilst walking for example. With this in mind is this a modification that would be routinely done on a sports/running device?

    Ian
     
  20. Shane Toohey

    Shane Toohey Active Member

    Arch heights.

    Hi Rebecca,

    My apologies for taking a few days to get back to you and for a messy sentance - the one you quoted. That was a quick re-write after losing the lot and a couple of ideas got collapsed into one sentance (difficult for males).

    Nevertheless, a point, that seems important to me. You had the arch height at 30mm which I presume was about as far as you could go and then added also a 6mm pad into the arch? You've stated your reason but the device is now probably higher in the arch than the arch itself would be if the STJ was ~neutral. So you do this with good reason and you're not alone, but I'm just not convinced about this approach or in fact any that delivers a device that has the 1st "up in the air".

    Some thoughts that cross my mind include:
    Your arch will be on the high side because you have captured a large F/F varus.
    Some common casting methods seem to exagerate a F/F varus.
    If you measured the arch of the foot weightbearing as in the method Eric mentioned it would probably considerably lower than in the cast.
    If you did this could the first get down to the ground (or assisted to).

    And, of course, a varus wedged extension will bring the ground up to the joint, but I have the impression that the 1st is too high up at present to achieve this. And in the long run I'd expect problems including digital imbalances to develop.

    Pardon my ramblings, it's just on one of my buttons.

    Cheers
    Shane
     
  21. Asher

    Asher Well-Known Member

    Shane, you quoted: "You had the arch height at 30mm which I presume was about as far as you could go and then added also a 6mm pad into the arch?"

    The 6mm arch pad was put on the medial flange to cushion transverse midfoot motion not under the arch to prop it up, so my arch height is 30mm only. But as you say, it is too high due to the fact that the 1st MPJ is up in the air still. I will keep a close eye on 1st MPJ pathology and next time, I will definitely reduce arch height.

    By the way Shane, do you consider Subtalar Joint Tip-over Sign in your orthotic prescription...please be assured that I have the highest regard for you expertise...that is why I ask.

    Rebecca
     
  22. Shane Toohey

    Shane Toohey Active Member

    Hi Rebecca,

    You wroter: "By the way Shane, do you consider Subtalar Joint Tip-over Sign in your orthotic prescription"
    You'll have to explain what that is to me! So, at present, the answer is no. If I did hear of it it's been forgotten.

    Briefly, I think there are many ways and how's that arches can get too high in orthoses, and that's the cause of many problems I see in existing orthoses, which is mostly what I seem to be doing: seeing folk who already have devices and having problems. So I've come to the point of not letting someone go on with a device where the 1st does not get to the ground. If the varus wedged extension can get it weightbearing then well and good and hopefully it will.

    Cheers
    Shane
     
  23. docstivers

    docstivers Welcome New Poster

    Forefoot posting

    I find that a true forefoot post is one that extends under the metaheads at least to the sulcus. Hard plastic is uncomfortable in that area so I have used one quarter inch poron or PPT extending from the orthosis to the sulcus grinded down to nothing by the time it reaches the 4rth or 5th metahead. Anything thicker makes most shoes too tight and even that amount barely makes it in lace up shoes. Any plantar flexed or rigid metaheads need a cut out also in that extension. Any time an orthotic ending proximal to the metaheads fails to control pronnation I find this extension solves that probem and most symptoms associated from the pronnation. I have been using this extension since I made my first pair of orthotics in podiatry school around 1981. Stephen
     
  24. TEW

    TEW Member

    Hi all, sorry for not responding until now after being the one who actually started this post.

    After reading the replies it has given me confidence to prescribe what I first thought would do the trick. I have casted the patient and am expecting the devoces back from the lab tomorrow. The patient went on a holiday the day after casting hence I'll have to wait 2-3 weeks after casting before I can dispense.

    So that is where it's at Rebecca. I will let you know how it all goes after I have dispensed and the patient has worn them for a while.

    TEW
     
  25. Asher

    Asher Well-Known Member

    Hi Shane,

    The subtalar joint tip over sign is, as I understand it, when dorsiflexion is applied to the foot (in neutral position), the STJ will in some individuals fall 'tip over' into maximal pronation. It is more likely to be evident with a medially deviated STJ axis. As far as I know, Craig Payne explained it first ... but I may be wrong ... I'm sure someone will set the record straight there.

    www.interpod.com.au/research/supination_resistance.pdf

    Rebecca
     
  26. Shane Toohey

    Shane Toohey Active Member

    Hi Rebecca,

    Thanks for your reply - I now have a reference for the " subtalar joint tipover sign". I really do appreciate you getting back on this.

    I also sent you a private message with the last posting a fortnight ago which you can access under your name where you log in at the top of the page.
    This explained also that I thought this was a huge topic and I was selectively only addressing part of it etc.

    Even though casts may be taken that increase the forefoot varus (and some techniques will exagerate this even further), I will not fundamentally accept a device which does not allow the first MPJ to weightbear and have seen devices that do this cause problems. It's like the cure being worse than the bite. I excpect that Craig would not advocate doing this to the foot and we'll have to ask him (I may be wrong). I'm happy that if hefty rearfoot supinatory momments are built into a device then a varus forefoot wedging may be needed to get the 1st weightbearing, but am not happy with having the arch so high that the first is beyond that. It's just one of those lines I've drawn in the sand!

    I'd like to know what Craig has to say. I'll post him.

    Cheers
    Shane
     
  27. efuller

    efuller MVP

    Be aware of STJ axis positoin. There are some feet with medial column pathology that have a laterally deviated STJ axis. Large amounts of rearfoot varus wedging are not good in these people. These people will respond to rearfoot varus wedging by using their peroneal muscles to pronate, and the forces in late stance phase, will still be high on the medial forefoot.

    In relation to rearfoot varus wedging lifting the 1st met off of the ground. This would theoretically happen with feet with laterally deviated STJ axes. However, these feet should not get rearfoot varus wedging. And there is a tendency for these people to use their peroneal muscles to get their forefoot onto the ground. Feet with medially deviated STJ axis will probably not have enough change in moment to actually cause the foot to supinate.

    The above is reference to heel wedging. Things are different in response to high medial arch device. When the arch height of the device is significantly higher than the standing arch height something has to give. Often it is the supinatory musculature that casue the foot supinate and this causes the first met to be up in the air. Earlier in this thread there was reference to a 30mm medial arch height. I measure the arch height standing relaxed in patients and I have very rarely seen an archt height that high. I agree that when the arch is so high that you get the first met up in the air, you are going to have problems.

    Eric Fuller
     
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