May 20 2016 - Testing the Total Knee 2000

14:30
Last Wednesday they took a new plaster cast of my stump. Bradley first measured my stump circumference, and said it is much smaller, and time for a new socket. We are not sure if this will be the final socket, or just another temporary socket on the path to a permanent one.
The constant wearing of a silicone liner, or a sleep shrinker sock gradually reduces the volume of the stump. Some people have a stump that looks like a skin covered bone. My stump varies in volume more than most. That makes it hard to fit snugly inside the socket.

Here is the nylon sleeper sock I wear at night. This is necessary to make the stump small enough to fit in the socket the next morning.

 If I don't wear a liner for a few days, then my bare stump is so large, that it won't even fit in the socket. If I wear a liner and wrap the stump, then the next day my stump is so skinny, it goes right to the bottom of the socket with little touching of the sides. This variance in volume is why I use stump socks. Stump socks  are toeless, fluffy, wool socks that are used to increase the volume of the stump.

Stump socks like these go between the stump liner, and the socket.

A tight, snug fitting socket makes feedback from the prosthetic leg much more sensitive. I can easily "feel" the leg when it hits the ground, and I can "feel" if it is locked before I put weight on the leg. Each layer of stump socks reduces the sensitivity, and makes the leg feel more "sloppy".
Also having layers of wool sock between the leg socket, and my stump makes the alignment of the leg to be less precise. The prosthetic leg is allowed to rotate on the stump more than a tight, snug socket would allow.

I normally wear 3 stump socks now to get a tight fit. I am looking forward to the new socket that should require no socks. Of course needing no socks, also means that a slight swelling of the stump may prevent the stump from being able to fit into the socket. A smaller socket means more control and feedback when everything is working as should, but also means less variance is allowed in the volume of the stump. Socks can add volume, but nothing can reduce the volume except constant wearing of some kind of stump shrinker.

While I was at Bradley's, his next patient arrived, a 5 year old boy. The way this boy was zooming and jumping and climbing left no doubt that this kid was used to his prosthesis. He lost his left leg below the knee about 2 years ago. while I was getting my leg on, he came over, and swung on the parallel bars. He looped his feet and lower leg through his hands, and hung by his knees. Cool to see.

Today I decided to give the Total Knee 2000 a good walk. I walked about 4 km in 1:20. The total knee swings forward much easier than my Mauch knee. It also feels more stable once it is down and locked. The ease and quickness of change from locked to floppy still worries me. But I never stumbled or fell.

This short video shows how easy the Total Knee 2000 locks and unlocks
https://youtu.be/m6Mjxi1Wm9U

One thing I did notice was while walking with my Mauch Knee, I sometimes hear the toe scrape the ground. Just a slight "swish" but enough to warn me that my attention is not all there. Today the Total Knee never did a swish. The fact that it shortens the leg on swing forward is a welcome, noticeable, characteristic.

Maybe tomorrow, I'll try a walk to the mall.
--

May 17 2016 - New (To Me) Knee

17:00
I just spent a few hours with Bradley, my prosthetic guy.
The loaner Mauch knee was swapped for a loaner Total Knee 2000. A totally different concept in prosthetic knees.
My own Mauch Knee is still in Iceland getting repaired.
Tomorrow I will spend many hours with Bradley. I need a new socket. He wants to do completely new measurements as if from scratch. So tonight I will wear the silicone liner, AND in addition, I'll wrap the stump,  so that tomorrow it will be as small as possible.
The current socket is too big. I have to use 3 wool socks between the liner and the socket just to get it to fit. But that means the socket is more "sloppy" and doesn't fit tight.
With this new knee, I can feel the stump banging into the sides of the socket. Like a bell clanger.

The Total Knee 2000 is a polycentric knee. It uses lots of funny mechanical motion to do a few things.
It more mimics the motion of a real knee. The bottom part slides back as the knee bends, just like a real leg. It polycentric design also makes the leg get shorter as it bends. This makes it less likely to catch the toe on something because the leg is shorter while the leg is swinging forward. It also makes it lock much more solidly than the Mauch knee does.
The Mauch Knee uses hydraulics to cause resistance for the knee to unlock. So if it does unlock, it gives a warning of increased resistance in bending. You will still fall, but you have more warning, and you fall slower.
The Total Knee 2000 has like 2 possible states. Locked solid, and floppy.
The lock is much more positive than the Mauch Knee. With any weight on the heel it is locked solid. Very secure. Put weight on the toe, and it is floppy loose. Like no resistance to fold up.

Here is a short video showing the Total Knee 2000 motion.

https://youtu.be/FO_BTNMnJFM

I am actually fibbing a bit. The Total Knee 2000 has a very small hydraulic reservoir than feeds some small orifices, that create slight resistance to motion. I can't feel it, but the book says it is there.
The Total knee also uses colored rubber blocks to create the resistance to breaking loose force when standing with knee locked. This makes it easier or harder to enter floppy mode from locked mode.
The Mauch knee does all that with hydraulics.

Bradley has just been on an Ossur conference. There they told and showed all the newest innovations by the company. The companies newest prosthetic is called the "Pro-Flex". It is an intelligent ankle and foot unit. It allows 27 degrees of movement to the flexing of the ankle. It progressive increases resistance to the flexing to allow the weight to be on the toe, or on the heel. They claim it allows walking up and down slopes.
But it is still VERY expensive. To many zeros on the right of the price.

At the conference were many people from the different medical aids. Ossur showed many statistics regarding above knee amputation co-morbidities. They gave lots of examples and statistics showing that a medical aid paying extra for an active ankle actually saves the medical aid company money. Many above knee amputees soon have problems with the good knee because of the added stress put on the good knee. The Pro-Flex ankle reduces stress on the good knee by up to 70%. They also showed that a knee brace on the good knee saves money in the long run.

I'll know more tomorrow. Now for drugs to stop the PLP.
--