Finding a better way: Simpler, cheaper prosthetics developed by researchers

School of Medicine researchers have developed an easier and less expensive way to make sockets for prosthetic limbs.

The new process may expedite and simplify the procedure for the estimated 400,000 Americans with an amputated limb. It could also be particularly useful in other countries, where land mines are responsible for millions of amputations, most of which occur in areas that do not have the financial or medical resources to fit prosthetics.

“What we’re doing is an entirely different process from the traditional way of making prosthetic sockets,” said principal investigator Jack R. Engsberg, Ph.D., research associate professor of neurological surgery. “We think that eventually our new technique could be taught throughout the world and would be cheaper and easier to implement.”

Engsberg received the Howard R. Thranhardt Lecture Honorarium for this work and recently presented preliminary findings at the National Assembly of the American Orthotic and Prosthetic Association in Reno, Nev.

The most important and difficult part of making a prosthetic limb is the socket, the part of the prosthetic that fits against the stump of the remaining part of the limb. Traditionally, this requires the expertise of a specially trained prosthetist.

A plaster cast of the stump is made and then filled with plaster to create a model. The model is then used to make a socket, which is adjusted to optimize its ability to contour to an individual’s stump and to comfortably bear his or her weight. Sockets typically require several fittings and adjustments, including production of several test sockets before a final product is achieved.

Several approaches to improving this procedure are under investigation, but most are more complicated and expensive than the traditional approach. Engsberg and his team developed a simpler, less expensive alternative using a gel instead of plaster to make the stump mold.

In this process, the stump is placed in a pail with water and alginate powder, and the powder turns into a Jell-o-like substance in about five minutes. The gel contours to the shape of the stump and produces an exact mold. Plaster is still used to fill the mold and create a model of the stump.

To test this alternative, the team made two sockets for each of the 10 leg amputees. One socket was made with the traditional plaster-mold method; the other was made with the alginate gel.

The two processes also differed in a second important way: The traditional method required production of up to three test sockets, whereas the gel sockets did not undergo any adjustments or additional fittings.

Using several measurements of walking performance and quality of life, the team found no differences in the success of the two types of sockets. And, when asked to choose which socket they wanted to keep, five chose the one made with the gel process, four chose the traditional socket and one person chose to keep both.

“Our data suggests that the gel process produces sockets that fit at least as well as those made in the traditional way,” Engsberg said. “In this preliminary study, we’ve shown that it’s possible to make a socket without any modifications, using a process that’s easy enough to be performed by a technician instead of a specialized prosthetist.”