My New Leg

Once again, Wayne was kind enough to take photos of the process of making the test socket in between my appointments, to which I’ve added a brief description. I should point that this is an ususual step in the process of getting a prosthesis. Many prosthetists simply make a check socket, work with their patients to make their adjustments with that (as I described in my last post) and then build the final prosthesis. In this case, Wayne is really going the extra mile so I can use a test socket to try out a variety of feet before I select one for a final prosthesis.

The first step is to take the check socket we had used for adjustments and fill it with plaster to create a positive model of my stump that also incorporates the adjustments we made and space at the bottom to insert the lock.

Having removed the plaster positive model from the check socket, the tech uses sand paper to smooth it.

The next step is to align the pyramid adapter, which will be used to attach the foot, with the cast. Here, the tech positions the cast on top of the adapter in a jig…

…and uses a tool to bend the four arms of the pyramid…

…until they wrap around the bottom of the cast. The arms of the pyramid will later be laminated into the bottom of the socket, so they need to fit together reasonably well.

He uses resin to attach the pyramid to the cast, first coating the base and arms…

…and then applying more around the arms for good measure — this will be the most vulnerable stress point when I walk on the test leg.

That pyramid is going nowhere, but it’s a bit messy to pull a socket over, so…

…the tech grinds off the excess resin on the long-armed router.

Now the cast is ready to be laminated. Prosthetic sockets are basically composites of reinforcing materials such as nylon or carbon fiber laminated with epoxy resin, which makes them strong and lightweight. The test socket doesn’t need to be as robust as a final prosthesis, so the tech has laid up cotton and nylon socks over the cast as the reinforcing materials.

Sockets are laminated by pulling resin down over the cast and into the fabric reinforcing materials. Here the tech pulls the laminating bag down over the cast…

…until the cast is completely bagged and ready to be laminated.

The top of the laminating bag is attached to a makeshift funnel into which the resin will be poured. Here, he’s recycling the top of a water bottle.

The tech mixed up the resin, poured it into the funnel, and turned on a vacuum below the cast (not visible in the photo) that pulled the resin down through the snug laminating bag and into the reinforcing material. I’ve seen techs and prosthetists use shoestrings to help guide the descending resin and push it into any hard to reach places on a socket. When the entire socket was permeated with resin, he turned off the vacuum and let the resin set up and harden.

After the resin dried, the tech used a small circular saw to cut the freshly laminated socket out. Here, he is using an air hammer to break the plaster out of the socket.

Here is the socket, with the plaster removed, ready to be finished.

The black lines mark the trimlines, or edges along the top of the socket.

After cutting the trimlines, the tech uses the router to sand the edges smooth…

…and cuts out the laminated fabric from the hole for the lock release button (sorry about the blurry photo).

The pyramid for attaching the foot, however, was covered by the lamination. The tech used a heat gun to warm and soften the plastic resin holding a cap over the pyramid…

…and cut away the plastic until…

…the pyramid is exposed but still anchored in the laminated composite at the bottom of the socket.

The tech sanded away the excess plastic from around the base of the pyramid,…

…screwed the lock into place in the bottom of the socket,…

…and the test socket is finished.

He aligned the socket and pyramid to the pyramid adapter and…

…tightened the hex screws to attach it.

Now the test socket is finished and ready to attach a foot. My next step will be to come into the shop and pick up the test socket and try out a few feet.

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