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Question about casting a foot with large FF supinatus?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by Berms, Mar 26, 2009.

  1. Berms

    Berms Active Member


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    I you are casting a foot with a significant FF supinatus (I didn't measure it) do you want to capture the full supinatus in the cast? Or do you want to cast it out by plantarflexing the 1st ray?

    The reason I ask is that technically speaking it is not a true deformity but rather a soft-tissue adaption, right?

    Any advice welcome,
    Adam
     
  2. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    I ALWAYS cast it out, by plantarflexing the first ray. For the larger ones (esp if early stage PTTD), I have started cautiously using the MASS method of semiweightbearing. Also plenty of mobs at orthotic issue.
     
  3. PodGov

    PodGov Member

    Please could you explain this last statement :wacko:.

    Thanks
     
  4. Graham

    Graham RIP

    I always cast it out.

    You don't want to ceate a FF varus appearance in the casting.

    Regards
     
  5. Craig Payne

    Craig Payne Moderator

    Articles:
    6
    Mobilisations and/or manipulations - we dealing with a soft tissue contracture here that needs help to be worked out
     
  6. efuller

    efuller MVP

    You want the orthotic to work. Presumably to reduce stress on the injured structure. (For that, you need a diagnosis to help design the orthotic.) What does casting out the supinatus do to the orthotic plate that the patient stands on. One thing it won't do is reach up and pull the first metatarsal down. However, when you cast out the supinatus you are often plantar flexing the first ray. So, why does this technique work. I believe that it works in two possible ways. First, plantar flexing the medial forefoot will increase the medial arch height in the cast. Secondly, it will more likely create a forefoot valgus in the cast and this may lead to an intrinsic forefoot valgus post.

    So, why would increasing the height of the medial arch of the orthotic help a foot. There will be increased force from the medial arch of the orthotic applied to medial arch of the foot. If the STJ axis is not too far medially positioned force in this position will supinate the STJ. As the owner of a foot with a much higher than average medially deviated STJ axis, I can tell you that too much pressure in this location is extremely painful. Pressure in this location can act as an uncomfortable stimulus that can lead to increased Posterior tibial activity taht will lead to a more supinated position of the foot.

    When you cast the foot with a lot of supinatus, the lab will have more leeway on the finished arch height, if you cast with the medial forefoot plantar flexed. The cast can be modified in the lab by increasing the medial arch fill to lower the finished arch height of the device. It is much more difficult to raise the arch height in the lab if the supinatus is left as is.

    I always measure the standing arch height of the foot, with some pressure applied, and ask the lab to make the arch that high. That way the lab does not have to guess on how high the arch should be.

    Cheers,

    Eric Fuller
     
  7. Berms

    Berms Active Member

    Thanks Eric, I appreciate your indepth reply.

    Yes, I always specify arch height when prescribing a device. But unfortunately in this case, I did not plantarflex the 1st ray during the cast and therefore the neg cast does represent a FF varus deformity..... Now that the cast is already taken (and I do not want to get the patient back in for casting again) would it be of benefit to use a 1st ray fill in the prescription to counter-act the "varus" captured and help allow the 1st ray to come down sufficiently?

    Thanks
    Adam.

    Thanks.
     
  8. Berms

    Berms Active Member

    Thanks Craig.

    BTW, could you explain what the "MASS method of semi-weightbearing" is?
    Adam.
     
  9. Craig Payne

    Craig Payne Moderator

    Articles:
    6
  10. Graham

    Graham RIP

    Adam,

    I would cancel the order and recast. If you add first ray fill you will increase the Varus deformity and decrease hallux extension - create a functional hallux limitus. If you don't want to re-cast I would add a reverse Morton's ext and a first ray cut away - to allow the ray to plantarflex.
     
  11. efuller

    efuller MVP

    The first question is what do you want the orthotic to look like. The second question is how do you get the lab to make what you want with what you started with. There are many ways to cheat in the lab. If you speak with a lab technician who is actually making the orthotic you may be able to get what you want and if you can't then you can recast.

    What do you want the orthotic to look like. How much arch hieght? Do you want an inverted heel cup? Do you want an intrinsic valgus post?

    Using classic Root technique for a forefoot varus cast and minimal arch fill you can get a quite high arch with an intrinsic forefoot varus post. A "Blake" inverted can also give you a lot more arch to play with. A medial or lateral heel skive can give you some more rearfoot variations.

    Regards,

    Eric
     
  12. Berms

    Berms Active Member

    I'm not sure we are talking about the same thing. - By "first ray fill" I am referring to the use of additional plaster in the distal aspect of the medial long arch of the positive cast.... therefore theoretically, the orthotic will decrease the varus attitude of the forefoot and allow better plantarflexion of the 1st ray and better hallux function
     
  13. Asher

    Asher Well-Known Member

    Hi Adam,

    I don't plantarflex the first ray when casting (not saying its right nor wrong, I just don't).

    I feel you can get the same thing by asking for a first ray wipe (Biolab WA). Instead of a uniform arch contour, the lab will add less plaster proximal to your nominated 'peak of medial longitudinal arch' and more distally. The distal part is less curved / more straight down to the distal medial edge. So your orthotic will be exerting more upwards force proximally and less distally under the first metatarsal.

    When you nominate where you would like the peak of the MLA of the orthotic to be, think about where the STJ axis is, where you want the orthotic to push up and where you don't want it to push up.

    This is a great thread. Thankyou for your explanations Eric.

    Rebecca
     
  14. Adam:

    Like Eric said, you need to know first what you are trying to accomplish with the foot orthosis before you should be deciding how you are going to cast the foot. The "soft tissue contracture" which we call "forefoot supinatus" is probably present in many patients, even in those that don't have an inverted forefoot to rearfoot relationship. I sometimes plantarflex the medial column and sometimes dorsiflex the medial column during negative casting, depending on the foot and what I am mechanically trying to accomplish with the orthoses.
     
  15. Dananberg

    Dananberg Active Member

    Kevin and Eric are correct. Understanding what you ultimately wish to accomplish with the orthotic comes first. There are no rules where one technique works for everything.

    That said, if you determine that removing the supinatus while casting is appropriate, then try dorsiflexing the hallux (slightly) during the casting process. This will plantarflex the 1st ray and reduce the supinatus by using the foot's intrinsic mechanical properties, rather than guesswork, to achieve the appropriate positional correction.

    Howard
     
  16. Berms

    Berms Active Member

    Thanks Rebecca, yes I agree. I actually just added a 1st Ray Fill onto the prescription (I use the same lab as you) and I feel this will help in this case.
     
  17. Berms

    Berms Active Member

    Thanks Kevin that makes great sense.

    I just have one question, knowing that my "aim" of the device is to optimize foot mechanics by limiting the very excessive pronation present in resting stance and dynamic gait, as well as allowing the first metatarsal to properly plantarflex and aid windlass etc.....

    should I:-

    1. capture the supinatus forefoot "contracture" in the neg cast, and then utilise a first ray fill on the pos cast to bring the 1st metatarsal down.

    OR

    2. cast out the supinatus, and therefore allow the device to work mainly on the midfoot and rearfoot.

    Your thoughts are appreciated.
    Adam
     
  18. Berms

    Berms Active Member

    Thanks Howard, that makes good sense. I normally apply downward pressure on the 1st metatarsal to cast out supinatus, but your method of dorsiflexing the hallux is also a good suggestion.

    Cheers,
    Adam
     
  19. Atlas

    Atlas Well-Known Member

    These are feet that look horrid when standing on an orthotic device. The 1st met head is not plantargrade; and if you ever were going to get the golf-ball under my foot complaint, I would thing that this type of foot would help deliver it. In a shoe though I guess the orthotic might help to bring that 1st met down.

    Supinatus versus varus? If a supinatus doesn't respond to mobilisation, stretching etc...it might as well be a varus in my book. There are many frozen shoulders out there for instance that will not respond significantly to conservative stretching & mobilisation etc. I doubt that this is an osseous problem.

    Back to this foot-type and casting-orthotic implications...
    As long as the patient accomodates then all this theory is OK. If the patient doesn't accomodate with a device that is made with a plantar-flexed ray, well then we should go back to square 1 or 2. Again, pending presentation and symptomology, I would even consider some form of intrisic fore-foot varus...or dare I say it, a forefoot varus post. Of course the latter can be gradually ground down if needed.


    But it all comes back to the patient's main problem, and how successful the intervention is. When it is unsuccessful, we don't as a rule, go back to square 1 and do something radically different. Our subconscious tries to explain why the patient in front of us isn't responding to the current thinking aka EBP. In the physiotherapy profession, we refer to it as "patient compliance issues".




    Ron
    Physiotherapist (Masters) & Podiatrist
     
  20. Berms

    Berms Active Member

    Thanks for the input Ron, you make an interesting argument with Supinatus Vs Varus.

    I certainly hope he doesn't look as horrid on the device as you suggest! I am yet to find out in a week or so.

    Cheers,
    Adam
     
  21. Griff

    Griff Moderator

    Adam,

    I think its fair to say that we don't really understand whether orthoses actually do this as we once thought they did; 50% of the research out there suggests they have little kinematic effect (and when they did it has been queried whether it was of biological significance). As Craig repeatedly says, motion doesnt cause tissue damage --> forces do.

    Out of interest what is this patients pathology? (i.e. what is the injured structure?)

    Just to add to the above comments/common practice I also always plantarflex the first ray in a foot with a significant supinatus deformity when capturing the negative cast (again not claiming there is a right or wrong way - just the way I have always done it)

    Ian
     
  22. Melvita

    Melvita Member

    I am a little confused by the discussions.

    When doing a quantitative biomechanical assessment I usually measure forefoot to rearfoot angle and then measure "reduced forefoot to rearfoot angle" by placing the foot in STN and applying pressure to the navicular bone, the difference between the two angles I call the supinatus (which is to me a soft tissue contracture that originates in the midtarsal joint).
    When casting, I correct supinatus by pressing on the navicular, this does not cause a plantarflexion of the first ray. I also ensure the hallux is slightly dorsiflexed as to allow my cast to pass the oil drop test in cast evaluation.
    I think that supinatus and a dorsiflexed first ray are two different animals and as such should be addressed and assessed individually.
    I agree that a rigid supinatus should be treated as a forefoot varus (how would you know the difference anyway?). A semi-rigid supinatus I would try physio/ART/manipulations to regain as much motion as possible.

    I am crazy? or is this a matter of semantics?
     
  23. Asher

    Asher Well-Known Member

    Hi there,

    As I said, I don't plantarflex the first ray (cast out a supinatus) when casting. However, I would like to at least try and maybe put it in my bag of tricks, so I'm after some advice.

    I know how to do it (downwards pressure on 1st metatarsal and/or dorsiflex the hallux). But to what degree do you plantarflex the first ray (cast out the supinatus)?. Do you do it to a neutral forefoot to rearfoot relationship? Or as far as it can go, even if that reflects as a FF valgus in the cast?

    If the answer is "It depends on your aim / what you want the orthotic to do / look like", I would ask in what circumstances would you do it (cast the supinatus out) to varying degrees?

    Thanks for any advice.

    Rebecca
     
  24. Adam:

    Good questions. I will never have the lab add a "first ray fill" to the positive cast that will "bring the first metatarsal down". This, to me, makes no sense and would likely result in a poorly performing orthosis or uncomfortable orthosis. In addition, casting "out the supinatus", such as by plantarflexing the first ray/medial column during casting, will tend to work for some patients, but may produce an uncomfortable orthosis for other patients.

    In general, I will plantarflex the medial column during negative casting much more in young children (e.g. juvenile pes plano-valgus under the age of 13) than in adults and will rarely use this negative casting modification in adults over the age of 50. Children seem to tolerate increased medial arch height in their orthoses much better than do older, weaker [for their body weight] adults. In addition, if I plantarflex the medial column during negative casting to either increase the forefoot valgus or decrease the forefoot varus deformity in the cast, then this allows me to also invert the positive cast more without having the inverted positive cast then having too much intrinsic forefoot varus correction within it, which may tend to make an orthosis that may overdorsifex the first ray.

    Of course, these modifications will all change in mechanical effect depending on the stiffness of the plate material you use, what type of rearfoot post you use (or don't use), whether a topcover or forefoot extension is being used, what type of shoe being worn, the patient's foot shape/function, the patient's activity level, etc.

    Lastly, the soft tissue contracture, "forefoot supinatus", which is commonly taught in podiatry schools to occur only in patients with an inverted forefoot to rearfoot relationship will commonly also occur in those patients that have everted forefoot to rearfoot relationship (i.e. forefoot valgus). What do we then call those feet with an inverted forefoot soft tissue contracture that also have an everted forefoot to rearfoot relationship, ''forefoot supinatus-valgus"? My suggestion?......get rid of the term "forefoot supinatus"!!

    Overall, it is my firm belief that we call "forefoot to rearfoot relationship" is simply a positional measurement of the plane of the metatarsal heads to the rearfoot at one point in time and is not a permanent "deformity", but is rather a fluid relationship of the forefoot to the rearfoot that may change a little or a lot over the lifetime of the individual. In other words, the "forefoot to rearfoot relationship" is not set in stone and is not a "deformity" as has been taught for years by the podiatric profession. Rather the "forefoot to rearfoot relationship" that we measure is only a temporary position of the forefoot to the rearfoot that is dynamic in nature and may change over time due to the time-dependent load-deformation (i.e. viscoelastic) characteristics of the tissues of the foot that will alter their shape in response to the prevailing internal and external forces and moments acting on the foot over time during weightbearing activities.
     
  25. Berms

    Berms Active Member

    Hi Rebecca,
    As Kevin has just mentioned, I also only cast out the supinatus in cases which are clearly soft tissue contractures and usually associated with kids or young adults (in their 2nd decade of life). In adults, any supinatus is usually more "fixed" and therefore need less "casting out" IMO.

    As far as the amount or force needed to plantarflex the 1st met during casting --> its not very much.... just get a feel for the 1st ray position by gently but firmly moving the 1st met up and down before the plaster starts to set and make sure that it is gently plantarflexed (ie not forcefully). Or if you are using the hallux dorsiflexion method, then it is probably a little easier to gauge (but I havenot used this method).

    Give it a try.
    Adam
     
  26. Berms

    Berms Active Member

    Thanks Kevin, they are excellent points you have made. :good:

    I learn something new everyday here on Podiatry Arena.
    Adam.
     
  27. Asher

    Asher Well-Known Member

    Hi Eric,

    I have not considered this before. Would it be reasonable to think that if one can plantarflex the 1st ray enough (I'm imagining large supinatus, large forefoot inversion/eversion range, younger patient, ligamentous laxity...) to show as a FF valgus in the cast, which then provides an intrinsic forefoot valgus post in the orthotic (assuming the cast is poured with heel bisection vertical) this would be a legitimate aim / favourable outcome.

    Rebecca
     
  28. efuller

    efuller MVP


    Hi Rebecca,

    For example, if I wanted an intrinsic forefoot valgus post in the orthotic I would evert the forefoot to rearfoot relationship (This is essentially what you are doing by plantar flexing the first.) until I got the desired amount of forefoot valgus in the cast.

    I decide how much forefoot valgus intrinsic post I want by looking at the maximum eversion height measurement.

    There are still a lot of tricks you can do with a cast in the lab. For example you could take a cast with a varus forefoot to rearfoot relationship and add an intrinsic forefoot valgus post. This would evert the calcaneus further, but you could counter this by doing a medial heel skive so that heel cup of the device will appear how you want it.

    Another reason for plantar flexing the medial forefoot is to increase the medial arch height of the finishied orthosis, assuming the lab does not fill the arch right back in.

    Regards,

    Eric
     
  29. Asher

    Asher Well-Known Member

    Thanks for that Kevin. That is a very helpful insight!

    ... unless you ask for a 'first ray wipe'. The lab will angle the distal part of the arch fill plaster (distal to the peak of the arch) straight down so as negate the first ray dorsiflexion force that you would get from a standard arch contour.

    Rebecca
     
  30. markleigh

    markleigh Active Member

    Thanks Eric for your thoughts. I've searched but I can't find an explanation for "maximum eversion height measurement". Can you explain this further. Thanks.
     
  31. Berms

    Berms Active Member

    Rebecca, my thoughts are the same as yours, however see post #24 and Kevin's thoughts regarding this. Now I am confused! :dizzy:

    Adam
     
  32. efuller

    efuller MVP

    I've mentioned it before on the arena, but have not published it. It comes from an idea that John Weed taught. John weed described placing fingers under the lateral column of standing feet. Sometimes your fingers really hurt and others there is no problem. Why? Eversion range of motion varies between individuals.

    Have patient stand and ask them to evert without moving their legs. Some people will not be able to lift their lateral forefoot off of the ground, others will be able to get their fifth met an inch off of the ground. I call the distance that the person has off of the ground the maximum eversion height. Interestingly, it is not a 100% correlation with how much your fingers hurt. There are feet that will hurt your fingers that have significant range of motion available. (these feet have laterally deviated STJ axes.) A vast majority of feet that cannot lift the lateral forefoot off of the ground will hurt your fingers in proportion to the weight of the person.

    Clinically, I've found that if you make an intrinsic forefoot valgus post higher than this height you will get pain either in the sinus tarsi or under the lateral column of the foot, because you are trying to evert the foot farther than the available range of motion.

    The theory is that feet that have very little force under the lateral forefoot will overload the medial forefoot and an intrinsic forefoot valgus post will increase load on the lateral forefoot and decrease load on medial forefoot.

    Cheers,

    Eric
     
  33. Foot Doc

    Foot Doc Active Member

    How do i "cast out" a forefoot supinatus? And is an intrinsic post the same as casting the supinatus out?

    Hi all,
    When "casting out" a forefoot supinatus is it a simple case of dorsiflexing the first metatarsal head so it is parallell with the fifth when the stj is in neutral? Or as i have read in several textbooks.......................if the forefoot post is intrinsic the forefoot supinatus will reduce and therefore the be touching the ground? And therefore there is no need to "cast out" the supinatus. is this correct? If this is correct why would we need to reduce the supinatus when casting the foot?
    Please help as i am thoroughly confussed!!!!!!!!
    Cheers in advance to anyone who has any ideas!
     
  34. Griff

    Griff Moderator

    Re: How do i "cast out" a forefoot supinatus? And is an intrinsic post the same as casting the supinatus out?

    Hi,

    You need to plantarflex the 1st met - this can be done by either applying downward pressure dorsally, or alternatively by dorsiflexing the hallux

    Hope this helps

    Ian
     
  35. Griff

    Griff Moderator

  36. Foot Doc

    Foot Doc Active Member

    Re: How do i "cast out" a forefoot supinatus? And is an intrinsic post the same as casting the supinatus out?

    thanks for the reply. sorry, i did mean plantarflex.
     
  37. footdoctor

    footdoctor Active Member

    Re: How do i "cast out" a forefoot supinatus? And is an intrinsic post the same as casting the supinatus out?

    Hi,

    As Ian correctly stated either applying force plantarly to the dorsal aspect of the 1st MPJ or dorsiflexing the hallux will reduce the forefoot supinatus.


    "If the forefoot post is intrinsic the forefoot supinatus will reduce and therefore the be touching the ground"?

    Not true, If at cast correction stage you do not push out the supinatus your distal arch shell contour will be higher under the 1st ray than necessary, this if anything may hinder the reduction of the supinatus unless the lab uses extra plaster fill under the 1st ray/distal arch, uses a flexible shell/flexible area in the distal portion of the shell, reduces the shell width to 75% or applies a 1st ray cut out.

    Also" If the forefoot post is intrinsic the forefoot supinatus will reduce"

    This is not necessarily true either, the forefoot supinatus will only 'reduce' if the excessive force under the 1st mpj is counteracted by the device. It is important that there is sufficient correction applied to the rearfoot of the device to create a supinatory moment/reduce the pronatory moment at heel strike and midstance.
    Think medial heel skive, extrinsic rearfoot posting, high medial heel cup, inverted cast, very minimal cast fill in proximal arch area.Ensure that the orthotic doesnt deform on load in the proximal arch area of the device also. If it does apply korex/med density eva/cork to the plantar surface of the arch of the device.

    If sufficient correction is present, the supinatus should reduce.

    Cheers

    Scott
     
  38. Foot Doc

    Foot Doc Active Member

    Thank you for the helpful replies, but im still a little confused................does that mean when a pateint has a forefoot varus (and i know its rare) and its captured in the cast (As it should be) and the correction is intrinsically posted at the forefoot the pt's forefoot varus is accomidated and the rearfoot will stop pronating?
    In the text book i've read, they say that if you intrinsically post the forefoot will be touching the ground.....and in the case of a fully compensated or uncompensated forefoot varus this just isn't possible, right? or have i got it wrong?
    Any help would be very much appreciated!
    Thanks again to vereyone who posted. Im getting there.....slowly but surely!
    Cheers,
     
  39. Foot Doc

    Foot Doc Active Member

    Or is it a case of correcting the pronation with an intrinsic forefoot post and then addressing the forefoot varus with an extrinsic forefoot post? is that how we would treat a fully compensated forefoot varus foot type?
     
  40. efuller

    efuller MVP

    When I was a student this was an area that gave me a lot of confusion in Root biomechanics. How does an intrinsically balanced orthotic allow the first met head to get to the ground within the theory. What happens when the heel lifts of of the ground, is the foot no longer supported and should there be compensation of STJ pronation to get the first met head to the ground. If you are working within the theory, as a student, then you also think the STJ should be in neutral position.

    It's one of those times where the orthotic worked, but the explanation of why it worked was not very good.

    Yes, if your forefoot varus is not entirely compensated, you do need to add a forefoot varus extension.

    Looking at the not fully compensated varus foot in the tissue stress approach, you have high load on the lateral column and at the sinus tarsi. You want to decrease load in those areas by increasing load on the medial forefoot and increasing the supination moment from the ground.

    Regards,

    Eric
     
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