Foot - College Park Trustep

My prosthetist got together with the College Park importer, and managed to let me borrow a Trustep foot. That was very nice of them, and I am grateful.

Most modern prosthetic ankles are also feet, and feet are also ankles. Now days they are just one unit.

Just so you know, I am an LAK (Left Above Knee) amputee, and I use an Ossur 2100 knee. It is the best knee I have tried. I have worn a Genium, a Mauch Knee, and an Ossur 2000 in the past.

I have been using a College Park, Odyssey K2 ankle for about 4 months. The K2 is a hydraulic ankle with adjustment for dorsi-flexion resistance, and plantar-flexion resistance. A small screw is turned for each resistance.
I love that foot. I bought it used off E-bay. But it now leaks hydraulic fluid. I need a new ankle.

Last year, I wore an Ossur Pro-flex for two weeks.

The Pro-flex must be sent to the factory to change the resistance of the flexions. That is a non starter right there. My K2 takes me about 5 seconds to adjust.

The Trustep works in a completely different way, and uses no hydraulics. It uses small rubber bumpers to supply resistance to movement of the ankle. The Trustep utilities 5 rubber bumpers. One resists dorsi-flexion, one does plantar-flexion, one does rotational resistance, and there are 2 others that fit around the main shaft to give some pronation/supition movement.

I was wearing the Odyssey K2, a few days ago, when I arrived at the prosthetist. My prosthetist put the Trustep on, and I walked around a bit. 

Naturally the Trustep and the K2, (actually any ankle) suffer from needing to be aligned exactly with the plane of rotation of the knee. This makes the foot point straight forward instead of a natural angle outward of a few degrees. I don't understand how manufacturers can't get that right.

On many of my walks, I have cambered terrain, so my pylon is marked and easy to change the length of the leg. This made the fact that the Trustep was about a centimeter higher than the K2 easy to adjust for.

I felt like I  was going to fall backwards. We adjusted the pyramid adapter above the knee, to move the foot farther back (in the posterior direction.)  The K2 adjustment had been perfect, therefor the actual pyramid on the Trustep must be at a different angle. After moving the foot posterior, we had to then raise the toe to make the foot flat. We moved the foot posterior until we ran out of adjustment, and then raised the toe until we ran out of adjustment. I still felt like I was falling backwards.

Maybe when I get a softer toe bumper in, it will feel better.

I left the prosthetist with all the tools I hoped I would need to change the bumpers. They also loaned me a complete kit of replacement bumpers.

Once home I walked my local 2.5 km course on the Trustep. It was not pleasant. Associated with the feeling of falling backwards, was the fact that the amount of force needed to break the knee loose was significant. I like a very "easy to break" the knee setting, to reduce the energy needed to walk. This setting now was very energy intensive.

I got home, and put my K2 foot back on so I could walk around while changing the bumpers on the Trustep.

Once in the shed, I got together all the tools required to change the bumpers. A few special tools are needed to replace the bumpers.

I used the compression tool to put pressure on the toe to allow the removal of a steel plate on the bottom of the foot.

Once this plate is removed, the toes will flop and release the toe bumper.
The foot came with a #5 toe bumper, I put in a #3.

The bumps on the bumper signify the stiffness.

 With all the proper tools, replacing the bumpers is not that hard. But for the average client, it would have to be done by the prosthetist. That is a real PITA.
For me, replacing the foot shell is the main problem. On You Tube, College Park has a video showing how to do it. The guy on the video must be a muscle man, and I bet it took many takes before he got it right for the video.
I have sweated and cussed many hours trying to get the foot shell on. The foot shell does not appear to be very robust. In fact when I got mine, it was already torn in the back. I fail to see the engineering requirement for such a high foot shell. If I owned it, I would cut off about 1/2 inch all around the top.

I then reinstalled the metal plate, and reassembled the foot. While putting the foot shell on, I got my finger trapped, and bleed all over the foot shell.
Once all assembled, I replaced the K2 with the Trustep. I then walked my 2.5 km course again. Much better.
I still felt like I was falling backwards, but less. The knee was still hard to break loose. The solution to this is to move the foot to the rear, but I was at maximum the pyramid will allow already.

As a test, I put on my K2, moved the foot forward, and lowered the toe, and lengthened the pylon by a centimeter. I then walked 2.5 km. What a difference. Very nice. Minimal effort to break the knee loose, and much smoother.
The Trustep seems to have three separate motions. When the heel strikes, the rear bumper compresses, then the foot goes flat, then the front bumper compresses as the toe takes weight. The K2 seems to have a single flow motion, from heel to toe.

Back to the shed. I decided to try a softer rear bumper, and go from a #3 to a #2 on the front bumper.
I removed the foot shell, used the compression device to allow me to remove the steel plate, then swapped the #3 for a #2 front bumper, used the compression tool to re install the steel plate. Then used the pin extraction tool and remover the top part of the ankle to get access to the rear bumper. I didn't do anything with the shaft bumpers or the rotational bumper. I removed the "M" rear bumper, and put in a "S" rear bumper. Then lubed everything, and put loctite on the screw.
It took me over an hour to get the foot shell on. Maybe my problem with the foot shell is because I am 67 years old. At one point my hand slipped and I caught my left hand between something, and it tore of a piece of my left hand. Again lots of blood.

I walked another 2.5 km.  I have walked 10 km testing this foot today. I am sore and tired. The softer bumpers are now too soft. With weight off the prosthetic leg, it feels to long, and with weight on it, it is too short.
The shock absorption, and rotational buffing need to be much stiffer. Resistance to dorsi-flexion and plantar-flexion need to be less stiff, to allow easier walking. Unfortunately, these two features are counter to each other in the Trustep. The same bumpers supply both shock absorption and flexion resistances.
The K2 has the toe in dorsi-flexion during swing forward, but the Trustep does not do that because the bumpers center the ankle once the foot leaves the ground. I twice caught the toe and stumbled during this walk.

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Next day..
Today I did the whole bumper changing procedure again, and replaced the toe bumper back to a #3, and put the "M" bumper back in the rear.
As I was putting it together, I noticed where the toe unit is scrapping on the ankle unit. I think I could hear it while walking. There seemed to be a scraping/rubbing sound.

I checked, and everything seems correct and the screws are all tight. I don't know why this is happening.
After an hour trying to get the foot shell on I quit. My shoulder is very sore, and both hands hurt. I'll stay on the K2 for the rest of today.

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Next day...
I got the foot shell on. It took about 10 minutes and it went on my 5th try. My shoulder and hands are very sore. Now I will swap my K2 for the Trustep, and go for a walk.

I just walked 2.5 km in 33:45. That is fast for me. On a Trustep with a #3 front bumper, and a "M" rear bumper.

Maybe I just need more time on this foot before I can judge it. It doesn't feel right, but it is not slowing me down any.
Also maybe once it is set up correctly, there may be no further maintenance needed until the rubbers wear out.
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Conclusions: After 14 days and 18 kilometers of walking, here are some of my thoughts on the Trustep.
I like Collage Park. They have many videos to explain adjustments and workings of their feet. Ossur wouldn't even tell me the kind of oil used in their knees.
Once set up properly, this foot should be maintenance free. To get it set up properly may require more man hours than a prosthetist is willing to spend.
Special tools are required to change the bumpers. This means even a minor adjustment will require a trip to the prosthetist.
The foot shell is not designed very well. It seems fragile, and goes up too high, making it difficult to put on.
The shock absorption adjustment should be separate from the ankle flexion resistance adjustment.
Patients moving from a fixed foot like the Ossur Variflex to the Trustep will think the Trustep is fantastic. They will love the greater flexibility and freedom to transverse uneven terrain. I don't think anybody going from a higher quality ankle (like the K2 or K3) to the Trustep will be as happy.

For now, I will stay with my old, leaky, bought off E-bay, College Park Odyssey K2.