The Thesis of Prosthesis

Article by CatholicTech Intern Dominic Andres

A paper published this week in Nature Communications gives us a glimpse into the future of prosthetics: comfortable, affordable, and adaptable. A new technology is demonstrated in the paper, a liner for prosthetic sockets which allows for real-time adaptive changes to its material, changes which will keep wearers comfortable and safe.

When we think of prosthetics, the focus is often on the limb itself. However, the socket which connects the prosthetic to the wearer’s residual limb is an integral part of the prosthetic. These sockets are produced by expert craftsmen using techniques that originated in the nineteenth century. Custom-tailored to fit the patient’s residual limb, they need to be extremely well-fitted, so that the patient isn’t injured by the pressures from the socket. Still, even the custom fitting is rarely enough, and most users require liners which fit between the socket and the residual limb, which are often either prohibitively expensive or homemade and minimally effective.

One major difficulty faced by designers in this field is the set of long and short term changes to the shape of the residual limb. Long term changes can come from age, from changing body-fat percentages, and from general health changes. Short term changes primarily come with exercise, when muscles undergo significant changes in size and shape.

Now, on to the new technology. Researchers at the Imperial College, London, saw the above issue, and decided to design a solution for it. They would create a liner which had a new set of properties. It had to be able to change its material properties on command, be thinner than 6mm, so that the wearer will have full control over their new limb, and be possible to mass-produce cheaply, so that it can be universally available.

These are a difficult set of standards to meet, but this new technology seems to do it. There are two components: the tech itself, and the manufacturing process. The new lining consists of two layers of silicon, which are molded together with incredibly small channels between them. Those channels can then be pressurized, which will change the material properties of the now-unified silicon sheet (properties such as hardness, shape, and volume). These changes can also be tailored moment to moment, and can be different across different sections of the lining. The silicon sheets, once shaped into the form of a liner for the prosthetic, fit all of the property requirements the researchers were looking for.

But what about the mass production? The noble goal of the creators of this technology was to help everyone, not just the rich. Thus, in developing the technology, it needed to be not just effective, but also easy to produce. Fortunately, they succeeded in this. The key component of the technology is the micro-channels inside the silicon. The researchers realized that wax paper, similar to the sort used in cooking, can be placed on top of the first silicon sheet before the second is molded to it, and if it’s cut in the right shape, then it’ll create the channels which give the liner its unique properties. Because this production process is relatively simple, it’s very scalable into mass production.

Pre-clinical trials for the technology have been extremely successful, as reported in Nature Communications. A number of amputees were brought in to test it, and wore motion capture software in a comparison test against the current gold-standard of prosthetic liner technologies, so called “passive liners.” In both objective metrics and subjective patient reports, the answer was the same: The new technology was as good as, or better than, the old.

All-in-all, it’s an exciting development, and an excellent illustration of how science can, if done right, advance the lives of everyone. The dual quest of those researchers to both help amputees and do so in a way which is accessible to everyone is admirable. As Christians, we must always remember Christ’s words “Whatever you did for the least of these brothers and sisters, you did for me.” The poor, the sick, the injured, these are the men and women Christ calls us to assist, to help them live out their lives glorifying God. In this case, technology is an excellent means for that.