Redistributing the pressure of prosthetic systems

Limb amputation currently affects 1.7 million people in the United States. Approximately half have experienced a below knee amputation. While current prosthetic leg designs provide amputees with increased mobility, these systems have limitations. Many users experience pain and discomfort while using the current prosthetic designs, including the pin lock, elevated vacuum, and suspension sleeve systems. The goal of this work is to develop a below-knee prosthetic system which will reduce the discomfort experienced by the user at the distal end of the residual limb, thus improving quality of life. To examine the source of discomfort, a static and dynamic model of the user's impact force during the gait cycle was developed. Two sources of impact force were investigated, the impact of the residual limb contacting the bottom of the socket, and the impact of heel strike during the gait cycle. Computational results from the static and dynamic model indicate that the impact force due to the residual limb contacting the bottom of the socket is negligible when compared to the impact force generated at heel strike. These results were consistent with both the analysis of measured forces obtained using force plates, and other studies that analyzed the impact forces of trans-tibial amputees during their gait cycle using force plates. Various design concepts have been developed and tested, which focus on the redistribution of forces experienced due to heel strike. Future aspects of this ongoing effort include evaluating and refining the current testing methods, along with conducting more tests to determine whether the new designs reduce pressure and discomfort.