Colton Graham and Dr. Mark Colton, Mechanical Engineering Department
Motivation
Due to a civil war in Sierra Leone many have been left with amputated limbs. In order to provide the required prosthetic limbs for victims who have above the knee amputations they need a quality custom fit socket. Custom fit sockets are very expensive so we created a universal socket meant to comfortably fit everyone. This socket is also designed to be affordable and able to be manufactured in Sierra Leone. For a functional socket, it is to be custom fitted, durable, affordable, adjustable and comfortable for the amputee. Due to varying changes to the volume of the residual limb, it must be adjusted for comfort and function. The socket does not hurt the user, and also allows to work with other existing Red Cross prosthetic components. Through interviews, international communication, and observations on the market, the following market requirements were developed:
The socket is comfortable to wear
The socket is adjustable for limb pressure
The socket is customizable
The socket is built from local materials
The socket can withstand a vertical load impact
The socket is affordable
The socket is easily manufacturable
The socket remains attached to the stump during use
The socket is compatible with standard interface hardware
Key Methods
In order to provide a good solution for Sierra Leone, our socket was designed to use materials that are locally found in Sierra Leone and can be manufactured using tools available to those at the clinic in Sierra Leone. A large majority of our desirability goals for achieving a comfortable, customizable, and affordable socket are based on feedback from our contacts in Sierra Leone.
Other information came from local prosthetists and amputees in the U.S. Using the common practices and tools of the prosthetist in a clinic in Sierra Leone, we created a socket for above-knee amputees based on three struts attached to a base plate. The socket interfaces with the residual limb using a silicone liner and provides additional comfort and function with foam padding and adjustable straps and buckles.
Testing on an amputee was critical to get the specific results needed for the market requirements. Tests were done in cooperation with a local volunteer amputee, Jarem Frye, who demonstrated the functionality of the socket and gave feedback on its design. Other key tests were performed on the socket to test durability and customizability, while other tests used numerical models to ensure affordability and comfort.
Key Results
Our socket is made from an aluminum base plate, custom polypropylene struts, EVA foam, and nylon webbing straps. An optional, but recommended, addition is a custom liner made from a bio-compatible silicone rubber. The total cost of materials for our socket is about $39.
We were able to test our design on a local amputee, Jarem Frye, who reported that the socket provided adequate support and function during normal walking. With the straps tightened, it held onto the residual limb and provided a good interface between the socket and the limb. The scope of our project only included the socket and we were unable to obtain a Red Cross prosthetic unit so we created a mock version conical cup system from Red Cross to verify the interface function between our socket and the Red Cross prosthetic unit. The customizability was verified by Jarem through his feedback on comfort and support of the socket.
Conclusions
Based on our results on the Desirability Goals, we determined our socket design will be successfully implemented in Sierra Leone with their current Red Cross prosthetics and functions well on amputees. There is room for improvement on the polypropylene strut to fit and bend at the proper places, but still functions well as it is. The cost of the socket could be improved by further research into alternative solutions for the silicone liner since it is the most expensive component of the socket. The tests validated that our socket design is a customizable, affordable, and adjustable option to the prosthetic sockets found in Sierra Leone and possibly other developing countries.
