Mountain Bike Modifications

Mountain Bike Modifications

Chris & Mary Lake

8/14/1999

Thanks for all the responses. Below are all the responses received that
contained suggestions. Befor responding back, we tried several
different modifications in an effort to provided some feedback to the
list. I suggest all interested prosthetists go to
www.amputeeonline.com. There is a article on the subject which was very
helpful.

Shortening the crank appears to be the best. Be careful - the article I
referred to above suggests drilling and tapping a hole every inch or so,
severely compromising the structural integrity of the crank. Since this
sounded somewhat aggressive we tried shortening the prosthesis at
increments of one inch. We found this not to provide good function (one
inch was not enough and two inches worked but was uncomfortable).
Trying a random amount of increments it was observed that 1 1/4 seemed
perfect. We plan on installing a Otto Bock adjustable tube clamp so the
patient (who is very compliant) can fine tune the length. We will then
drill and tap one hole, shortening the crank accordingly.

We plan on trying out an articulating ankle foot such as the college
park Trustep to see if we can further benefit the patient. Thanks for
your assistance.

Chris Lake, CPO

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You may want to try Advancing the pedal on the prosthetic side so that
it
is always about 10-20 degrees ahead of the non-prosthetic side. For
example, when the sound side pedal would be at the 12:00 position, the
prosthetic side would be at the 7 or 8:00 position. This may allow the
sounds side to always have a mechanical advantage. What type of pedal
attachments does he use? Typically, Mountain biking makes use of the
upstroke as well as the downstroke so trying different setups there
may
be helpful, maybe only on one side... maybe on both. There are quick
disconnect pedals which require special shoes to be worn, and there are
also
the strap systems that tie the feet into the pedals. It may not be the
prosthesis that needs to be changed.

Best of luck.
Paul
----------------------------------------------
Chris & Mary,
Try going to CYCLING TIPS FOR LOWER LIMB AMPS @
www.amputee-online.com/amprtee/onyerbike.html or e-male:
<Email Address Redacted> : janet <Email Address Redacted>
I am taking about 20 amputees and non amps. on a 900 mail bike ride in
Sept. going from Busch Gardens, in Va. to Sea World in Fl. If you know
of
someone that would like to join us , have them e-mail;
<Email Address Redacted>
or go to web @ www.asahr.org
Robert Sandlin
Chairman
RIDE 900 FOR AN AMPUTEE - 99
--------------------------------------------------------
You're headed in the right direction with the advance pedal position.
But
what I thought would happen apparently did excess pedal travel thru
the
pedal arc. You need to design an elliptical pedal that screws into
current
pedal position that does give you advance pedal postion at 1200 position
but
takes it back on the back of the stroke. Given that this might cause
pedalling imbalance you may have to put this on the sound side also.
Next
please consider not only advancing the operative pedal but also
lengthening
the radius length to give power to the transtibial leg. I apologize
that I
don't have one of these elliptical' pedals laying around my orthotic
lab,
point is that this is a wonderful challenge but a difficult one indeed.
I
would be glad to lend my physics background, my drawing capacity, and my
creativity to the project if you want.
-------------------------------------------------------
First I would like to know what kind of foot the patient is wearing. I
would
also suggest that you try to shorten the crank arm on the affected side.
This is a good way of reducing the amount of travel needed on the
prosthetic
side. I have seen a lot of advantage from the use of a College Park
TruStep
foot in cycling. The motion of the foot in all axis is very conducive to
the
demands of the sport. Mike
--------------------------------------------------
I do a lot of biking myself but am not an amputee. I have in the past
for a patient of mine suggested the use of a shorter crank on the
affected side. By placing the pedal closer to the axis, the knee won't
have to bend as much. When we tried this we found that we were able to
comprimise by shortening the crank some and lowering the posterior wall
some. Later, after the liner was trimmed down to follow the trimlines of
the socket anteriorly, he was able to put the longer crank on again
because the liner was not streatching over the knee as much. I hope
this helps.
Kevin Warner CP.