Each year, in the United States alone tens of thousands of people have limbs amputated. The amputation can be due to complications from a disease such as diabetes or from a traumatic injury such as a car accident or combat injury. Prosthetic limbs are commonly used to attempt to replace the function of the amputated limb. Artificial limbs have been created that can do many of the things that intact limbs can do. However, a key challenge with these limbs is the design of the interface to the amputee, the prosthetic socket. Particularly for patients with leg amputations, the quality of the socket fit is of critical importance. The tissues on the residual limb were not designed to tolerate the loads associated with supporting the weight of the person. A poor socket fit can result in skin problems such as pressure sores and abrasions. To make matters worse, the residual limb can change shape over the course of a day and over time. Another challenge relating to the interface between the person and the prosthetic limb is that there is no direct sensory feedback from the artificial limb. Our own limbs have numerous sensors that allow us to sense forces, obstacles, and the position of our joints even when we cannot see them. Amputees lack these senses which results in having to rely on vision to do most tasks.

In the proposed work, we will advance prosthetic socket technology in three ways:

1) By developing and testing comfortable socket liners that can measure the quality of fit over time. This could allow fit adjustments as needed and be a valuable research tool.

2) By developing and testing sockets that can automatically adjust their shape to accommodate for volume changes and activity levels of the amputee. This will be done by moving liquid into and out of various bladders embedded in a socket liner.

3) By adding feedback to the socket to provide a sense of force and joint position from the artificial limb. This feedback will be applied on the skin near the residual limb.

The work will involve both engineering design, and laboratory and amputee testing. The early stages of the project will focus on development and validation of the technologies. The latter stages will provide time for testing with amputees to receive feedback about the performance and clinical utility of the devices. We expect that the proposed socket technology will provide additional comfort and functionality to leg amputees, particularly those who desire to live an active lifestyle. Socket fit is currently one of the limiting factors in the usefulness of an artificial limb, and our goal is to reduce that bottleneck. We expect that the technologies will be particularly useful for soldiers with combat injuries as they are typically young, desire to live an active lifestyle, and are often willing to adopt more technologically advanced equipment. The final outcomes of this work will be refined prototypes of a socket sensing liner, a socket that can adjust its shape, and a socket with sensory feedback along with detailed test results that describe the performance and clinical feedback measured in the proposed studies. Finally, we will work closely with our clinical and commercial partners to develop a plan to make the technologies available to military and civilian populations.