Lower leg prosthesis/feet geometry physics ?

[barclay]

So - I have the 1C62 Triton foot which is a J-shaped carbon fiber type and so far, I am not very happy with it (though it's still whole, so that's good). A major difference to the low profile feet I have had before is the the angle between the foot and the steel pipe (pylon ?) is adjusted high up, where the foot meets the socket, with these J-types.

I have learned though trial and error that I get more push-off power if the foot (low profile) is adjusted so that the toe is pointed up. I have the feeling that i am standing on my toes/ forefoot with this angle - it's counter intuitive (to me), but that's what a lot of fiddling has proved.

So. with this J-type foot, the heel-down, toe-up adjustment was made much higher (about half way between the knee and the floor) and I have the feeling that this has the opposite effect. That is, with the adjustment made here, the feeling is that I am trying to push-off from the heel.

Does anyone else have this sort of J-type foot and any experience with changing the angle between the steel pipe and the the socket ?

As I have to give this back next Wednesday, I am sorely tempted to try to change the angle myself, but I don't quite dare. I will show up at 7 am on Moday though when my prosthetist is back from vacation.

[allenuk]

Dare, Barclay, dare.

Even the toe-out (or -in) by a few mill can make loads of difference. The pylon (that is the term) height similarly - with old-fashioned ones you could undo them and stick a coin (a UK £2 piece was handy) to raise them a couple of mill.

No, the NHS doesn't recommend making such adjustments to our legs or feet - and in the case of the Echelon, it's probably too technical for the average amp - but I've done loads of small 'fine-tuning' over the years. Some of it you only know after walking for a mile, which of course isn't possible in the limb-fitting centre, not usually.

There are some ankles which ARE made to be adjusted by the user - I'm thinking of the ones for people who wear heels of different heights. Hopefully one day most adjustments will be trusted to us, as after all we DO have to walk on the darned things.

A

[ann-]

Definitely altering just the feet can make an enormous difference, on how easy it is to walk. My feet are fairly basic single axis, but they contain rubbers, which are coloured differently for different grades, and whatever grade or colour is fitted affects the way I walk tremendously, not only does it affect the heel-toe movement, it also can affect the feel of socket and how much energy I am putting into walking.

[cherylm]

Feet are a really personal sort of thing...if you can't get your leg person to adjust it as you'd like, and you think you may be able to do so yourself, I'd say go for it. (Of course, I've not actually tried that for myself, so be forewarned that I'm no expert!)

[ann-]

Have to be wary about doing that if you are in the UK and have NHS legs though Cheryl, As Allen says, the NHS don't like you ajusting things .... also I think even with private provision there could be a problem with warranties, so be careful.

[oneblueleg]

I would say be cautious when making adjustments for yourself. Sometimes you may think that a certain adjustment might do one thing, when in actual fact it has the opposite effect. Prosthetists study the anatomy for years to become qualified and will make adjustments based upon the effect that adjustment might have on the rest of the body. My experience has taught me that sometimes, what feels right, in actual fact, eventually creates a problem elsewhere. For instance, you could lower the toe (planter flex the foot) to get more push off from the toe, only to find a few weeks later you start to get some lower back pain. This may be because you are having to climb over the toe, which initially felt great, but could eventually slowly show up a negative side to the adjustment. Because time has elapsed inbetween, sometimes, you might not link to two.... hope I make sense, just be aware, whatever you think of you Prosthetist, they see the bigger picture.... or they should! Almost imperceptable changes can have unknown consequences. If you make your own adjustments, no wonder the person responsible for your welbeing would have an issue with you, after all, they do what they do for a reason, and you are untrained. In every case, if you think you know better, just run your idea past your Prosthetist first, they will either explain why your idea is wrong, if he/she is worth their salt, will do what you want if it doesn't have any negative effect. Respect between the user and the Prosthetist is paramount in my humble opinion, you need them!
I'm not a Prosthetist by the way ;o)

[oneblueleg]

And Allen is right.... don't try and adjust an Echelon, you WILL get it wrong!

[barclay]

I didn't adjust it myself - here, if I did and anything happened, I wouldn't be covered by the insurance.

I did get in though first thing yesterday, and my thinking was correct (that when the adjustment is made at the top of the pylon instead of at the ankle, the affect is opposite, toe down for more push with the high adjustment, toe up for more push with the ankle adjustment) and I like this foot MUCH better now !. Unfortunately, I have to give it back tomorrow and I won't have played tennis or had a chance to do Scottish Country Dancing, so I will have to decide about this foot without really having tried it. The toe down foot is also better with shoes which is a big advantage as well. The heel is too soft for me though that may be the shock absorber more than the heel. It's got the hardest wedge in it now.

The next foot will be the Axtion, I am not sure if I get that tomorrow or not though.

Oneblue, I love my prosthestist and absolutely respect him (that's mutual - we have a great relationship), and I also realize that I am not a standard model and that he and I have to learn as we go - there just aren't that many tennis playing scottish dancing amps around.

Thanks for all the input !!
Cynthia