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Foam casting

Discussion in 'Biomechanics, Sports and Foot orthoses' started by markleigh, Jun 23, 2009.

  1. markleigh

    markleigh Active Member


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    I have recently attended Craig's bootcamp where we were able to experiment with foam impression casting (I have always used plaster for the last 17 years. Why change you could ask?). I've read the other posts on Pod. Arena concerning foam versus plaster casting but hoped those who are using foam casting could give me some more practical information on writing prescriptions. As the impression I am taking is semi-weightbearing, do you still ask for any additional lateral expansion? Do you still utilise posting of the forefoot or the rearfoot in the same way as you would on a traditional suspension cast & what allowances do you make for medial/lateral arch fill? Do you have any other suggestions that you have found are important when writing prescriptions for foam casting?

    Thanks.
     
  2. Yes, Mark, once you become a convert to foam-box casting, you will have completed your journey toward the Dark Side.:cool::butcher:
     

    Attached Files:

  3. markleigh

    markleigh Active Member

    Hello Kevin Vader. I know the force is strong in you (are your orthoses therefore appropriate?).

    I have not passed to the dark side but do seek to reduce the forces in others. Foam seems to be an alternative that Lord Payne highlighted & I seek knoweldge from others in this mystical art.
     
  4. Admin2

    Admin2 Administrator Staff Member

  5. Hey Mark.

    I have been a foam convert for some years so I was delighted to see this covered in the boot camp. I think its a much undervalued technique.

    The best bit about foam (for me) is the soft tissue expansion, which is captured "as is" and the base plane.

    In a POP cast the base plane is derived as perpendicular to the bisection of the calc. In foam it is derived from the ground.

    In POP the lab has to guesstimate the amount of soft tissue spread on wb for the "cast correction". In foam it is captured directly. 71% of soft tissue expansion takes place in the first 25% of weight bearing.

    In POP one has to rely on the lab for modifications. With foam you can do the modifications yourself on the foam. Want a PF groove? Extend the hallux, draw on the PF with lipstick. The line will come off on the foam, carefully depress the foam where the marking is and there's your pf groove exactly where you want.

    The only major complication I find with foam is the lateral arch. Possibly because of the way the foot is loaded by the foam I find I get a much higher lateral arch in a foam box than I would in POP. For fun, try casting the same foot both ways then hold a goniometer against the lateral foot and see for yourself. Bet you get much more in the foam. There's probably a study there.

    Aware as I am of High gear / low gear thing, I find this lateral arch causes more trouble than it saves so unless I specifically want to load the cuboid, or if there is a fixed forefoot equinus, I tend to remove the lat arch on the negative altogether. If I want a lateral forefoot wedge I modify the positive and make it intrinsic or use a valgus extention.

    But the rumour is that this is looked at askance by some (I have my sources ;)), so I look forward to a good debate on this!:boxing:.

    Kind regards
    Robert
     
  6. Oh and by the way, if you wish to learn the ways of the sith, mark, you're welcome to come spend half a day in my lab. I'll show you what happens to your casts once you send em off in both forms.

    I might be being unfair here but I think the lab element is not covered anywhere near enough at uni, certainly in my neck of the woods! Even if you never plan to pick up a rasp for the rest of your career, knowing how its done is of great value in prescribing!

    IMO of course

    Robert
     
  7. markleigh

    markleigh Active Member

    Thanks Robert for your response. I guess I have lots of questions & if I didn't live so far away (about 16,000km), I'd definately take you up & come & visit your lab. What is your process for positioning the foot i..e do you attempt to hold in neutral? Do you do anything to the hallux i.e. attempt to dorsiflex to increase arch height? Do you just press the heel down & forefoot/toes? Craig had us using a pen tip to assess whether we had bottomed out under the heel & 1st/5th mets i.e. that the pen tip would be the same diameter hole if everything was sitting in the same plane. Then in filling out a prescription, do you request further lateral expansion or request anything additional regards medial arch fill (I know all of these things may vary from patient to patient depending on their pathology)? I know that is a lot of questions Robert so I would be happy with anythign you can offer.

    Regards,

    Mark
     
  8. Here is a question for Robert or other foam boxers ( if thats a discription but thought it would fit with your boxing face )

    When don´t you use the foam casting technique, the list seems quite long in my head ?

    Michael Weber
     
  9. markleigh

    markleigh Active Member

    Robert, have you tried MASS positioning? Craig had us attempt it. I possibly performed it incorrectly but the orthos. produced from the cast were not particualry comfortable.
     
  10. Ah. That is a bit of a step.

    I don't particularly aim for neutral. I try not to think in terms of position, rather how much bulk / force the orthotic will exert and where. Although a cast, whatever the position, is a static thing it is well to remember that it will NOT "hold the foot in that position" or anything like. So the position depends on what i'm trying to do with the orthotic.

    Sometimes. If the problem is one with the planter apeurneurosis I will often dorsiflex the hallux as I press the foot in.

    I use three point pressure. So with the contralateral hand to foot (left foot right hand) I will have my thumb under the nav, my fingers under the lateral malleolus and the heel of my hand on the forefoot.

    Fantastic idea. Its a hell of a job trying to derive an orthotic from foam if its not to the base of the box because then you have NO reference plane! No heel to bisect, no base plane.

    As you say, depends on what I want from the orthotic. If I want to exert ORF under the lateral mid / forefoot I'll leave the lat arch alone. If I don't I'll correct it out. I rarely need to modify the heel, unless to use a skive or intrinsic wedge. I will modify out the arch (equivilent to adding plaster to the sides of the cast) if I'm making a device which does not sweep up around the arch but I don't generally modify the height of the arch. If I wanted it lower I'd have cast it that way.

    The joy of boxing for me is the option for a wyciwyg cast. What you cast is what you get. You make the foam the exact morphology you want the orthotic with as much medial arch, lateral arch or intrinsic modification as you like. Then you just tell the lab that is what you want. Puts you in controll.

    If I want to capture the dorsum of the foot (for dorsal wrap on, for eg, a UCBL or smafo)

    If I want a deeper cast than the box.

    If I cannot press down through the knee hard enough to take the cast (for EG if they've just had a TJR)

    They're the ones which spring to mind.

    Ro
    Yes I have. I use it on some patients, but not many. Like the neutral position, I don't feel there is any inherent merit or demerit to Mass. It'll produce an insole with a very high arch. Good for some, not for others.

    The Mass technique, to push the foot in in an inverted position, evert the forefoot, then pronate the foot until the forefoot contacts, is one I have used from time to time. Of course you can start from the inverted position then evert the foot as much as you want it be that Mass, Neutral or sub neutral. I sometimes find the foot slides into the foam at an oblique angle that way which B*****rs the cast. However it can be useful if you are of slight build. I've never met a foot I could not cast, however I'm about 6 ft and 14 stone. If you are slim and petite (like twirly or Derek) you might struggle to push hard enough the other way so this might work for you.

    Kind regards
    Robert
     
  11. Phil Wells

    Phil Wells Active Member

    Mark

    Re expansion etc, try an alternative approach that I encourage my foam box casting customers to use.
    Measure the width of the heel and than the width of the shoe they are hoping to go into. The difference is the amount of expansion needed (Quick tip, it is not always a positive addition.) We use CAD which means we do it digitally to fit the shoes - compliance is excellent.

    Cheers

    Phil
     
  12. markleigh

    markleigh Active Member

    I have done suspension plaster casts my whole professional life. Using a foam box seems to have some good uses but for some reason it seems more unknown when I can't see what I am doing (seems to be what Kevin Kirby & others said was their dis-like of foam versus plaster). It is maybe just a mindset thing & obviously very much what you get use too. I purchased some foam boxes so I will give them a try & see what results I achieve.
     
  13. markleigh

    markleigh Active Member

    Thanks Phil for your thoughts. I gather if the shoe is narrower than the heel then you suggest a wider shoe? I also assume you measure the heel width weightbearing? I hate burdening practitioners with comments at times. I think I have a small amount of knowledge about a lot of things & therefore not much help for many people. You get so many people on here that have a lot of knowledge about some specific things that are incredibly helpful & they get "used" by myself (& I guess a lot of others). We pay these people often a lot of money to hear them speak at conferences & seminars & on this site they speak & answer questions for free. But it feels almost selfish because one question & answer leads to more questions & answers.

    In saying this above (& humbly meaning it), Phil, do have any basic points you would make that would make foam impression taking & following on from that prescription writing for a foam impression, more succesful? Or what mistakes do you see from those Pods you deal with when they take foam impressions?

    Gee I can rave on!!!
     
  14. Phil Wells

    Phil Wells Active Member

    Mark

    Please feel free to rave on, its my favourite time of raving!
    I have a few subjective comments I can offer on the foam box foot capture and I hope they help.
    1. Rigid foot types seem to be captured really well just by having the patient stand in them.
    2. Flexible feet need more careful placement as the foam can distort the plantar surface of the foot when pressed into it. There are many techniques that work but I would suggest using a semi weight bearing approach and trying to control as much as possible - tricks such as externally rotating the tibia, apply a finger under the navicular, dorsiflexing the hallux and toes etc can all work some of the time.
    3. Try doing a 'corrected/supported' cast then have the patient do a fully weight bearing, non-corrected cast. It is very interesting to see the difference and can give you some guidance on cast corrections required. Labs are capable of lowering the arch, raising the arch etc to your Rx
    4. Don't be scared of using your finger/hand to shape the cast. This allows you define the plantar surface of the orthoses.
    5. ALWAYS send in a template of the shoe, the shoe itself or measurements. Use an inside calliper and a ruler to do this.

    Re your comment about finding wider shoes, this is not usually needed. It depends on the compliance of the material that makes up the heel counter. If it is flexible, then the orthoses will bed in well. If more supportive (My preference) then the orthoses should be made to fit the shoes not the foot. I then use lower heel cups, sometimes at 0mm, as I believe the shoe will do a far better job.

    Hope this helps

    Phil
     
  15. Boots n all

    Boots n all Well-Known Member

    As to which ones not to cats in a foam box l would like to add if l may.
    Osteoporosis, we would not like to add another fracture to their collection
    Diabetics with ulcers on the dorsum of the foot.

    For us the foam box is quick, clean and you have a very stable unit to pour your plaster into, if you are making your own Orthosis.
     
  16. markleigh

    markleigh Active Member

    Robert, when you said "Extend the hallux, draw on the PF with lipstick. The line will come off on the foam, carefully depress the foam where the marking is and there's your pf groove exactly where you want." - I gather you meant to dorsiflex the hallux?
     
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