TruStep & Vert Shock Pylon
Chris L Johnson
Description
Collection
Title:
TruStep & Vert Shock Pylon
Creator:
Chris L Johnson
Date:
1/27/1998
Text:
>I am going to get a new leg and the one that I have picked out is the
>trustep, I saw the literature in a nova care shop in Tucson and talked
with
>my prosthetist about it with my activities and we thought that it would
be
>a good choice, but he wants to add one more part and that is the
vertical
>shock. My question is will that help in the use with the leg or not?
>From the computer of <Email Address Redacted>
Thank you and your prosthetist for chosing the TruStep. I have
confidence you will be as happy as I am.
Very good question about the pylons. I think I can answer the question
in some detail through an experience I had plus other reflections.
To address the issue of what the added unit will do, I wore on one
experimental leg with a TruStep one of the more radical pylon-area
alternatives: Jerome Voisin's DAS ankle or MARS unit (pardon Jerome, I
forget the exact meaning of each acronym), the tall one with two big
springs, one titanium, and the other steel. That version weighs 708
grams, which is significantly more than the foot. He has other, ligher
units based on elastomer bumpers. The tall, spring version maximizes
motion. I assumed the added weight and motion would be real negatives.
I was wrong. I was somewhat right about the weight (less weight is
generally better than more), but found that the added motion added to the
'alive' feeling of the TruStep. The weight was not perceived as dead
weight and therefore did not feel as heavy as the numbers indicated. The
added motion, which was vertical as well, was appreciated. Gobs of
rotation! This combo may be the cat's meow for golf!
This experiment gave me confidence that components of this sort can
complement the TruStep. The original reason for doubt is that the
TruStep already has more motion potential that other prosthetic foot
designs, even vertically.
What is not always so evident with the College Park TruStep is that there
is already a measured 1/2 of vertical deflection as a result of the
unique dynamics of the 3-bone design, which creates a human-like
collapsing arch. Many assume there is no vertical deflection, and I am
sad to say we have not pushed this feature. It's like power steering for
free and we never say anything about it! Also, there is not so much
vertical deflection that gait symmetry is compromised as with some feet
with vertical shock pylons. I could argue that with excellent socket
design and a good residual limb, one does not need the added vertical
deflection an added pylon gives, because the leg can take a ponding. I
am at that point myself after many surgeries and fiddling with solutions.
Very good socket and 9 mm Alpha liner for cushioning, plus the vertical
deflection of the TruStep. However, there are benefits to the added
component that go beyond the detraction of the added weight. No everyone
has that tough leg and anything that reduces fatigue makes a big
difference in endurance.
What is nice about vertical shock pylons is that they spread the ground
reaction forces transmitted back up through the socket over more time.
The load spike felt on the unatural weight bearing serfaces of the
residuum is moderated. If the vertical shock pylon also includes some
rotation for torque absorption the benefit is expanded.
What you have to figure out is whether or not the TruStep alone, with its
anatomical specs for vertical deflection, will be something you prefer
over the added motions of the system as complemented by a vertical shock
absorbing pylon. To best assess that, I would respectfully suggest
starting with the TruStep alone for at least several months. The
adjustability of the foot alone is a learning experience worth embarking
on, though I suspect you will settle on close to what your prosthetist
and College Park gait match you with. Get to know the foot well first,
then add the pylon. I would suggest to not use a cosmetic cover during
that period to make access to components less of a hassle. I do not mean
the foot shell, but the cosmesis on the leg. Personally, I avoid
cosmetic covers as fluff. That's personal preference. I don't mind a
techie look in shorts, but some do. There will be a weight penalty with
the added pylon component. That's something you'll have to do your own
weight-verses-benefic analysis on. If you absorb or habituate the added
weight in the first 5 minutes of walking, the added weight may be a
non-issue, especially if you have a long residuum or good suspension. If
you sprint a lot, the reduced accelerations due to the added weight may
not be worth it. The added residuum endurance with running could be a
big benefit despite the weight.
Other negatives about these components are their height, added
maintenance, and potential for noise. Some BKs with long residua, do not
have the room between the foot and socket for the shock absorbing pylon.
Some designs are more compact than others. The added maintenace will be
there as the bearing on the slider will take a beating. As with any
added component, there will be a noise potential. I'm sure these
objections will become more and more minor as the technology improves,
even as it has with the TruStep.
I must admit I am a fan of vertical shock and torque absorbing pylons. I
may have been the first (who knows?), or one of the first to concept one
in 1983. At the time, I knew nothing about the O&P industry, and didn't
even know any other amputees. I was in a hard socket with SACH foot and
bone spurs at the time. Boy did I ever wish for vertical deflection!
Poor student and knowing no one, I sat on the concept for years until
taking a renewed interest in O&P just a few years ago. A vetical shock
absorbing pylon was to be the first product of my budding little company,
Techniks. After hearing Walt Harris of M+IND describe what he/I was
working on, I lost heart and shelved the project. I shouldn't have. One
reason I did was College Park became at that time my primary engineering
consulting client. I was quite busy pursuing other projects. Later, I
signed on full time. Now many have jumped on the vertical shock band
wagon since then. My hat is off to those of you who did not sit on your
concepts as I did! I still have one embodiment of the original left to
be expressed....
Anyway, I'm blabbering. The point is, I think the components are an
added value for some people and their particular activities. You have to
decide if you are one of them. You will already have vertical shock
absorption in your TruStep, whether or not it will be enough will be a
matter of experimentation and choice. Then there are many different
brands to chose from. They are quite different from one another in many
respects.
I hope you and the list find this info helpful.
Chris (CJ) Johnson
Director of Engineering,
College Park Industries, Inc.
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
<Email Address Redacted>
_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at <URL Redacted>
Or call Juno at (800) 654-JUNO [654-5866]
>trustep, I saw the literature in a nova care shop in Tucson and talked
with
>my prosthetist about it with my activities and we thought that it would
be
>a good choice, but he wants to add one more part and that is the
vertical
>shock. My question is will that help in the use with the leg or not?
>From the computer of <Email Address Redacted>
Thank you and your prosthetist for chosing the TruStep. I have
confidence you will be as happy as I am.
Very good question about the pylons. I think I can answer the question
in some detail through an experience I had plus other reflections.
To address the issue of what the added unit will do, I wore on one
experimental leg with a TruStep one of the more radical pylon-area
alternatives: Jerome Voisin's DAS ankle or MARS unit (pardon Jerome, I
forget the exact meaning of each acronym), the tall one with two big
springs, one titanium, and the other steel. That version weighs 708
grams, which is significantly more than the foot. He has other, ligher
units based on elastomer bumpers. The tall, spring version maximizes
motion. I assumed the added weight and motion would be real negatives.
I was wrong. I was somewhat right about the weight (less weight is
generally better than more), but found that the added motion added to the
'alive' feeling of the TruStep. The weight was not perceived as dead
weight and therefore did not feel as heavy as the numbers indicated. The
added motion, which was vertical as well, was appreciated. Gobs of
rotation! This combo may be the cat's meow for golf!
This experiment gave me confidence that components of this sort can
complement the TruStep. The original reason for doubt is that the
TruStep already has more motion potential that other prosthetic foot
designs, even vertically.
What is not always so evident with the College Park TruStep is that there
is already a measured 1/2 of vertical deflection as a result of the
unique dynamics of the 3-bone design, which creates a human-like
collapsing arch. Many assume there is no vertical deflection, and I am
sad to say we have not pushed this feature. It's like power steering for
free and we never say anything about it! Also, there is not so much
vertical deflection that gait symmetry is compromised as with some feet
with vertical shock pylons. I could argue that with excellent socket
design and a good residual limb, one does not need the added vertical
deflection an added pylon gives, because the leg can take a ponding. I
am at that point myself after many surgeries and fiddling with solutions.
Very good socket and 9 mm Alpha liner for cushioning, plus the vertical
deflection of the TruStep. However, there are benefits to the added
component that go beyond the detraction of the added weight. No everyone
has that tough leg and anything that reduces fatigue makes a big
difference in endurance.
What is nice about vertical shock pylons is that they spread the ground
reaction forces transmitted back up through the socket over more time.
The load spike felt on the unatural weight bearing serfaces of the
residuum is moderated. If the vertical shock pylon also includes some
rotation for torque absorption the benefit is expanded.
What you have to figure out is whether or not the TruStep alone, with its
anatomical specs for vertical deflection, will be something you prefer
over the added motions of the system as complemented by a vertical shock
absorbing pylon. To best assess that, I would respectfully suggest
starting with the TruStep alone for at least several months. The
adjustability of the foot alone is a learning experience worth embarking
on, though I suspect you will settle on close to what your prosthetist
and College Park gait match you with. Get to know the foot well first,
then add the pylon. I would suggest to not use a cosmetic cover during
that period to make access to components less of a hassle. I do not mean
the foot shell, but the cosmesis on the leg. Personally, I avoid
cosmetic covers as fluff. That's personal preference. I don't mind a
techie look in shorts, but some do. There will be a weight penalty with
the added pylon component. That's something you'll have to do your own
weight-verses-benefic analysis on. If you absorb or habituate the added
weight in the first 5 minutes of walking, the added weight may be a
non-issue, especially if you have a long residuum or good suspension. If
you sprint a lot, the reduced accelerations due to the added weight may
not be worth it. The added residuum endurance with running could be a
big benefit despite the weight.
Other negatives about these components are their height, added
maintenance, and potential for noise. Some BKs with long residua, do not
have the room between the foot and socket for the shock absorbing pylon.
Some designs are more compact than others. The added maintenace will be
there as the bearing on the slider will take a beating. As with any
added component, there will be a noise potential. I'm sure these
objections will become more and more minor as the technology improves,
even as it has with the TruStep.
I must admit I am a fan of vertical shock and torque absorbing pylons. I
may have been the first (who knows?), or one of the first to concept one
in 1983. At the time, I knew nothing about the O&P industry, and didn't
even know any other amputees. I was in a hard socket with SACH foot and
bone spurs at the time. Boy did I ever wish for vertical deflection!
Poor student and knowing no one, I sat on the concept for years until
taking a renewed interest in O&P just a few years ago. A vetical shock
absorbing pylon was to be the first product of my budding little company,
Techniks. After hearing Walt Harris of M+IND describe what he/I was
working on, I lost heart and shelved the project. I shouldn't have. One
reason I did was College Park became at that time my primary engineering
consulting client. I was quite busy pursuing other projects. Later, I
signed on full time. Now many have jumped on the vertical shock band
wagon since then. My hat is off to those of you who did not sit on your
concepts as I did! I still have one embodiment of the original left to
be expressed....
Anyway, I'm blabbering. The point is, I think the components are an
added value for some people and their particular activities. You have to
decide if you are one of them. You will already have vertical shock
absorption in your TruStep, whether or not it will be enough will be a
matter of experimentation and choice. Then there are many different
brands to chose from. They are quite different from one another in many
respects.
I hope you and the list find this info helpful.
Chris (CJ) Johnson
Director of Engineering,
College Park Industries, Inc.
(810) 294-7950 (at CPI), (616) 664-4173 (home office)
<Email Address Redacted>
_____________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at <URL Redacted>
Or call Juno at (800) 654-JUNO [654-5866]
Citation
Chris L Johnson, “TruStep & Vert Shock Pylon,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 2, 2024, https://library.drfop.org/items/show/210209.
