Oasis cast

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Hi everyone,

I was wondering if anyone knows the steps to cast the foot using oasis casting technique? Is there any available website with the steps? I would really appreciated if you were detailed since it is part of my clinical practice module.

Thank you

 

Are you talking about the foam box casting? If so, see these threads
Isn't 'Oasis' a brand name for a type of floral foam?

 

Yes thats the one Craig.

Still I am unable to find how to actually use step by step guide to get the right impression of the foot. I have tried it a few times however I am not entirely sure what I am doing its entirely correct.

 

I think you will find very little by the way of step-by-step instructions as there are a zillion different ways to do it. Maybe someone needs to do a You Tube video.

 

Sheesh, what to they teach you guys? This is the sort of thing you really need to asking your lecturer to show you. Does'nt really work in text.

Notwithstanding. As Craig there are a buncha ways to do it.

My favourite.

Have the patient sit with their knee directly above their ankle and their foot resting on the ground. Hold the foot using three point pressure, under the nav, heel of the hand over the forefoot and lateral heel. Position the foot in the angulation you want the cast (STJ or other). Press the foot into the foam just enough to get it started. Check you still have the position you want, then push it the rest of the way in, evenly fore and rearfoot. If you want an intrinsic ff post the ff should be in varus. Check the foot has reached the base of the box and if need be press out the medial forefoot to get your intrinsic. Press out the forefoot corners to get a flat leading edge and reduce the lateral arch to whatever you desire (I generally get rid of it altogether.

Another way

Maximally invert the foot. Press it in until the lateral edge of the foot is at the bottom of the box. Pronate the foot until it reaches the position you desire.

Things to be aware of

Foam always gives a big ass lateral arch. Usually needs correcting out by hand. Remember, you're in charge of what shape the insole is, not the foot. Unless there is a specific reason to have a lateral arch it just takes up room and can cause tolerance issues.

Remember you get 71 % of soft tissue spread with 25 % of body mass so much less cast correction is needed.

Make sure the foot goes straight down. Often, especially with the latter method, it can slide sideways at the same time. B****xs up the cast.

Always use the right box. Trying to cast a 4 year old in a deep box is as hard as trying to cast a size 12 in a shallow one.

Regards
Robert

 

Robert, could you just remind me of the reference for this one please? Did they measure tissue spread in the "air" as it were, i.e. barefooot loaded from beneath or using a foam casting box, plaster bandage etc.?

 

I'll look it out for you. It's not going to be especially accurate, it was in air and of course it's an average so subject specifity will be lost. It basically just indicates that not a great deal of grf is needed to configure the soft tissue to it's Wb configuration. If we treat the soft tissue under the calc as a hydraulic unit then the amount of lateral force resisting soft tissue spread will be negligable compared to the vertical force causing it. Cut a foam block in half and see how many lbs you need to sink a 1 inch block by half a cm. Won't be much!

I find the big issue with foam (when other people do it) is the lateral arch. Creates all kinds of problems. Foam needs much less cast "correction" than pop but it DOES still need some. Of course it can be done in the foam rather than the cast, which is easier...

Regards
Robert

 

Why does foam impression result in increased height in the lateral arch? Is it increased tissue deformation from the "collision" between the foot and the foam, exagerated on the lateral side due to the greater compression of the foam that must occur on this side of the foot?

 

Actually I think it's more the position of the 5th met. I've rubbish spatial conceptualization on a sunday but I think it's to do with the length of the lever arms. On a flat surface the are are no external planterflexion moments on the 5th met past the sagittal plane because the plantarflexion moments don't start until the 5th met is horizontal. In foam, because the force is exerted basically evenly there is an external pf moment.

What I generally do is have the patient stand static Wb and manipulate the foot into my desired casting position, then look at the position of the 5th met relative to the ground. Generally the 5th met sits flat to the ground. If it does then I eliminate the lateral arch altogether.

I can't say what the "right" way to cast is, I suspect nobody can. But I DO know that casting is means to the end of an orthotic in the desired shape. If my design has a reason for having a lateral arch then well and good. But if it doesn't I see no problem with removing it.

Regards
Robert

 

Thanks Robert for the suggestion.

Lecturers unfortunately have different ways of doing it. Whilst one thinks this is the appropriate way of casting the foot then the other says its wrong!!! :bash: The end of the day when I have to do it during OSCE exam then I am not sure what I have to do?!? :bang:

I like both ways and I will give them both a try. With the 2nd method you have suggested, when will be the right time to place the foot in STJ neutral

Regards

 

LOL, I'll give you two answers.

To pass you're osce, whenever you were shown to. Or after the lateral border reaches the base of the box.

In the real world, who said you should cast the foot in neutral? Whats so special about a ST neutral position?

Ref your lecturers disagreeing on the "right way", if it produces a good end product, no technique is "wrong". Learn them all and pick what's best for you.

It pains me to say that some lecturers seem a little behind current events biomechanics wise, there is a lot of old theory being learned*, but I would consider it unwise to correct your course material! There was a dpm in America once (kelvin Curvey was it?) who disagreed with his professors a lot. Probably never amounted to much.

Regards
Robert

* i've no way of knowing if the outdated stuff being taught but it's certainly being learned

 

LOL I had a similar situation in may just before i qualified. I had to demonstrate ankle strapping techniques. We were taught how to do this by a physio lecturer 3 months before the exam. Like most students i forgot the technique due to only being shown how to do it once and on my part i didn't practice it. When it was approaching exam time i went to one of my pod lecturers and asked him to show me. After he did i was practising on clinic and another lecturer asked what on earth i was doing strapping like that??!!??. I told him it was how i'd been shown and in turn he showed me a prefered technique of his. This left me frustrated as i'd just perfected one technique. Another lecturer reassured me that its not that technique per say as long as it does its intended job.

To sum up :wacko: just do it however you've been shown and hope that your examiner doesn't prefer a different technique. As some of the other pods have said theres different ways to do it and as long as the result is the same it should be fine

 

This one

Regards
Robert