My New Leg

Now that Wayne had made a check socket for me, it was time to go back to the shop and do the fitting.

The check socket fitting is one of the most important points in getting a new prosthesis and is kind of fun. As I mentioned in my first post, the socket is the most crucial part of a prosthesis because it is the interface between the amputee’s body and the foot. Prosthetic feet are sexy and get a lot of media coverage, but the socket is where the rubber meets the road. I’ve walked on all sorts of feet from around the world and, while I find some preferable to others, pretty much anything will allow you to walk from point A to point B. The same cannot be said for sockets, though. If they don’t fit well or hurt, the simple act of walking is unpleasant and discouraging.

One of the reasons I think check socket fittings are fun is that you get to see if it works: it’s exciting to take a prototype of a new leg for a spin. Also, the point of the check socket fitting is to work with your prosthetist to resolve any problems with the fit, so it’s essentially a game of how closely you can pay attention to your body and communicate how it feels to another person. This is tricky and can be very frustrating for many amputees, particularly recent ones, but I’ve always enjoyed the challenge of it.

My photographer friend Dara and I arrived at the shop and were shown into a fitting room. Wayne came in and handed me the socket so I could take a look while he went back to the workrooms to get the feet he had ordered for me to try out.

Here I am, admiring the finished check socket. The foam insert is in the bottom of the socket. The white plastic piece with the blue button is the lock for holding in the silicone liner sleeve. The pyramid adapter is attached to the socket with a foam resin and will be used to attach the foot. Check sockets aren’t meant to be be super sturdy or cosmetically attractive, just to provide a safe way to check the fit.

Wayne told me about a new foot, the PerfectStride II, from a company called BioQuest. The foot sounds fantastic and has a very unusual design. I got excited as I read their pamphlet, but it turns out I don’t have enough clearance–it’s too tall to fit under me.

First, he removed my Renegade foot from my current prosthesis and attached it to the pyramid adapter on the check socket. Then I put on the check socket and stepped into it.

After I walked around the fitting room in the new socket for a few minutes, we paused to pinpoint a couple tight spots. Prosthetists use flat strips of plastic-coated metal to check for tight spots. Here, Wayne pokes the strip down to where I complained of too much pressure on the medial (inside) and lateral (outside) sides at the bottom of the socket.

Wayne used a long-arm router with a grinding attachment to grind down the plastic at a tight spot around my knee and then a buffer attachment to polish the area. Finally, he used an air hose to blow out the dust before returning to the fitting room.

I stepped into the leg again and Wayne poked around in the socket some more, trying to ferret out a persistent tight spot on the inside of my knee.

Then I walked in the parallel bars so Wayne could watch me walk and do a bit of gait analysis. Parallel bars are particularly useful for recent or older amputees who may have trouble balancing when learning to walk.

Wayne measured my clearance — the height between the bottom of the socket and the floor — so he could confirm which feet to order. Different prosthetic feet have different clearance heights.

We still hadn’t quite nailed the tight spot at the bottom, so I try to describe it for Wayne. It felt as thought the socket tapered at the bottom and squeezed the end of my stump. Wayne suggested that I might be sinking too far down into the socket and feeling the pressure on the bottom.

Wayne offered me the strip and had me poke around to locate the tight area at the bottom of the socket. When I found it, he marked it with a Sharpie pen.

There are different ways to modify or change the shape of the check socket during the fitting. The most common method is to use a heat gun (basically, a very hot blowdryer) to warm and soften the polyethylene socket and then deform the plastic as needed to adjust the fit. The drawback is that it’s not very exact. You can’t adjust the fit of the socket while wearing it because hot plastic on your stump would be A Bad Thing. The prosthetist has to heat up the plastic, deform it, and then cool it down.

Wayne used a different technique with me. The socket was a bit loose in the back, which allowed my stump to settle too far into the socket. So the idea was to inject quick drying silicone into the back of the socket, while I was wearing it, to fill in this loose area. First, he brought the socket back to the workroom and drilled a series of holes in the back of it.

Then we covered my silicone liner with a plastic bag so the injected liquid silicone wouldn’t stick to it, and tried to put the check socket back on. The plastic bag made it difficult, so we had to use baby powder to get the socket back on.

Wayne inserted cartridges of silicone and catalyst into the injection syringe and starts the flow. You can see them mixing as they flow through the tip of the syringe.

Wayne had drilled one of the holes large enough to fit the end of the syringe and inject the silicone into the socket. The other holes were smaller and allowed air to escape (and some of the silicone to dribble out). As he injected the silicone, it felt like firm jelly pressing against the back of my stump — a strange sensation — and the fit of the socket changed immediately and became more snug.

After waiting a couple minutes for the silicone to set up, I walked in the parallel bars to see if the fit had improved. Indeed, I wasn’t sinking so far into the socket, which took the pressure off the bottom of my stump. But we found the plastic bag had ripped and the silicone had leaked through it and stuck to my silicone liner. When we doffed, or took off, the leg, the silicone he had injected fell apart and we had to start the process over.

This time, Wayne used plastic wrap instead of a plastic bag to protect my silicone liner from the injected silicone. The wrap was stickier than the bag, so we used lotion to lubricate the plastic wrap. He worried that the lotion might prevent the silicone from setting up properly, but that turned out not to be a problem.

He injected the silicone again and I stood still for a few minutes to give it a chance to set up, and then trotted through the parallel bars a couple more times to see if the adjustment felt as good as last time.

This time, the plastic wrap worked and the injected silicone stayed in place when we removed the socket. We had made our last adjustment and the socket fit comfortably: we were done! Here, Wayne shows us the check socket. He wrapped the tape around to prevent the silicone from leaking out and the green scribbles mark the tight spots we identified and ground out earlier.

The next step will be for Wayne to make a test socket, based on the finalized check socket, so I can take it home and road test some feet with it.