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  1. #1
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    Trying a biking prosthesis

    I am trying to see if I can use a prosthesis specific to biking, with a locking pin liner suspension. I am a longtime left below knee amputee.
    I've had the unit for a week.

    The distal end of my residual limb is small - generally smaller than the umbrella on these liners, and is quite bony. I have a silicon pad for extra cushioning. but it is not enough so far. It feels like the edge of the umbrella hits the distal end of fibula.

    I can pedal bike on trainer, but I can only stand or walk for less than 5 minutes. I can almost pedal standing, I just have one dead spot at top of pedal stroke. I can do one-leg pedaling drill with the prosthetic side. I am working to strengthen hip flexor on the prosthetic side.
    I'm going to return to prosthetist, and see what he can do to add more cushioning.

  2. #2
    LBKA punkncat's Avatar
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    Well, it seems that I might offer you some suggestions now, as this is exactly what I do. I have found that the trimline on my "walking" leg to be too high so we took one of my old legs and adjusted it for the purpose.

    As to the liner...I have that exact problem with the large umbrellas common to "BK" amps. It rubs right along the scar line and irritates the crap out of it. Through a bit of trial and error I found an above elbow liner that was large enough and had a really small umbrella; like the size of a quarter. The front of the liner is thicker than the back. I want to say its 6mil to 3mil from front to back to help cushion the knee and other bones in the front where I have no protection or padding either.

    Keep in mind while working with your prosthesist that the movements of riding as opposed to walking are totally different. Don't forget to leave room for the tendons behind your knee and the distal end to clear from the more circular motion of pedaling. I suggest putting on an adjustable pylon so you can easily adjust height and toe to find what works best for you. Be aware also that the best adjustment for biking is not going to work for crap walking and will be awkward.
    For pedaling I have found using my hips and glutes to power through the front part of the pedal stroke and then "coast" through the rest of the motion tends to hurt least and cause less problems than attempting to use my quads the same way. YMMV

    I have also found it rather useful to have more socks with a cycling leg fit than what might be comfortable to a standard walking leg.

    Best of luck.
    One Foot Less

  3. #3
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    Thanks for the input.
    I will talk to my prosthetist about using an AE liner.
    The trimline on this socket is cut way down behind the knee.
    I don't have prominent tendons behind the knee, and I am not experiencing any shortage of room for those.

    The alignment on this prosthesis is very unlike my regular limb. I am using 10 ply in that unit, and I don't want to have more socks than that.

  4. #4
    LBKA punkncat's Avatar
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    I would imagine not, 10 ply is a lot. I find I get too much bell clap and slop when I have a fit that far out. I will typically pad the inside of the socket in order to avoid needing that many socks. I have about a 2-3 ply difference in the cycling leg as opposed to my walking leg.
    One Foot Less

  5. #5
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    I had the 2 week follow-up visit with Prosthetist.
    Version 1 had a SACH foot. Version 2 has the old Flex Foot installed on it.

    Prosthetist tweaked alignment, and gave me a foam rubber donut to put outside liner, under stumpsock.
    I walked a lot inside the office. It's wonderful to be able to stand and walk more than 3 steps without pain!

    I think the complete lack of impact absorption from SACH foot was a large part of my pain. I have not walked on a non-energy storing foot since around 1985, and have forgotten the technique that I used to use for that. Of course, that technique contributed to the extra wear on my original equipment leg!

    I biked outdoors this evening. Only 3 miles. The pin liner is only 16 inches long. I need to try a coolmax sock inside the liner. In 3 miles, I sweated enough that the top 3 inches of liner slid down and bunched up. This may indicate that I need to have the top portion shrunk (that is possible for some liners).

    My old Flex foot is from a prosthesis that had a cosmetic cover on it. The foam filling to make leg shape was a type of foam that looks like that "blow in" insulation you can get for retrofitting wall insulation into homes. This had adhered to Flex foot, and took some work to remove. That is the reason for the delay in using the Flex foot on this limb. I know that foot is heavier, but the leg feels lighter with that installed than it did with the SACH foot!

  6. #6
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    I imposed on my spouse to take a picture of me pedaling on the trainer.
    I colored a bit on the reflections from front and rear bags. biking prosthesis oct3b.JPG

  7. #7
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    May I suggest getting rid of the pin system and go with a sleeve system prosthetic. I used to use the pin socket and I had the same issues, I was never comfortable with it. I always felt like I had to add and add more socks and at the end of the ride or day of walking the bottom of my stump always felt sore and irritated. Yes, its more convenient to have the pin system but its a mess and its not safe for amputees. I recommend you get something different. I use elevated vacuum system for both my walking and riding legs. Riding leg is an electric pump with a sleeve for constant suction and to keep the leg night and tight. On my walking on I use a mechanical pump and it pushes air out every step I walk and keeps the leg nice and tight. I have used this system for over a year now and all the issues I had with the pub system are no longer there and my stump feels amazing at the end of the ride or day of walking….check out this website, this is what I do….

    www.ride2recovery.com

  8. #8
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    I am adjusting better to biking prosthesis these days. I have done a couple of 21 mile rides, and a 33 mile ride.

    The foot shell is a bit loose on the Flex Foot, which makes getting started more challenging. I need to see if the prosthetist can eliminate the movement of the foot shell on the foot. I am starting to wonder if I could manage to walk with a bare flex foot with a cleat mounted on it!

  9. #9
    LBKA punkncat's Avatar
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    Istump- I would have loved to switch away from the pin based systems, but due to the irregular shape of my knee bones I keep losing suction. Works great till your leg is a half step behind you. I have come to the conclusion that the pain and irritation is the trade off for not being on crutches or in a wheelchair.
    One Foot Less

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