Understanding How Powered Componentry Impacts K2-Level Transfemoral Amputee Gait

Amputation of the lower limb causes profound disability, significantly limiting mobility, independence, and the ability to pursue employment or leisure activities. Nearly 90% of all lower limb amputations in the United States occur in older persons, mostly due to vascular disease, and this population is expected to triple by 2050. After lower limb loss, individuals walk more slowly and more asymmetrically are less stable, and expend more metabolic energy during walking than persons with intact limbs. Even when using state-of-the-art microprocessor-controlled prostheses (typically a microprocessor knee with a passive ankle), persons with transfemoral amputations expend approximately 60% more energy than able-bodied individuals during ambulation. In addition to the physical limitations caused by the amputation, the increased energy requirements affect performance of everyday activities, including getting up out of a chair or off the toilet, or stepping up or down a curb.

Most commercially available prosthetic legs are passive. The movement of a passive prosthetic joint relies on the properties of its mechanical components, such as hydraulic or pneumatic valves or sliding joints, together with compensatory adjustments made by the user. Since these computerized prostheses are passive, the user cannot efficiently negotiate stairs, an incline, or the numerous other functions that require net knee and/or ankle power.

Powered prostheses can actively generate joint torque, allowing easy and efficient performance of more demanding activities, such as ascending stairs and hills. Powered knees and ankles, may allow for better outcomes in both older and younger individuals with transfemoral amputation; this powered componentry may enable more energy efficient walking, allow users to stand up from a seated position with ease, and enable them to walk across more challenging terrains-such as up and down hills, ramps, and stairs-safely and with more normal and symmetric gait kinematics and kinetics.

This study will demonstrate the functional benefits of adding power at an individual joint. This knowledge will be critical for prioritizing future device development and will provide valuable information for clinicians and individuals on selecting appropriate componentry for transfemoral K2 amputees.