Understanding how Powered Componentry Impacts K2-Level Transfemoral Amputee Gait

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Project Summary Powered prosthetic knee and ankle joints can actively generate torque, potentially enabling safe and efficient performance of more demanding mobility tasks, such as ascending ramps and stairs or performing sit-to-stand transitions, and improving energy efficiency. However, available powered components have been almost exclusively developed for and tested by individuals ambulating at Medicare Functional Classification Level (MFCL) K3-or K4. Individuals designated as K2-level ambulators (i.e., have a more limited ambulation capacity) are typically prescribed a passive prosthesis, but these individuals have been shown to benefit from more advanced microprocessor-controlled knees and may gain additional benefit from powered components. Because available powered components are heavy, we developed lightweight, fully powered knee and ankle components that can be used separately or together and are appropriate for K2-level ambulators. These devices will allow us to evaluate the benefits associated with providing power at the knee, ankle, or knee and ankle, and the tradeoffs associated with the additional weight and control complexity of one or more powered components. Our goal is to determine how powered prosthetic components effect function—in terms of metabolic cost, gait biomechanics, and functional mobility in K2-level ambulators with a unilateral transfemoral amputation, who use a prescribed passive prosthesis. We will recruit 20 individuals, who will participate in three aims, with the expectation that 15 will complete the study. For Aim 1, subjects will be fit first with a fully passive device (Ottobock C-Leg 4 MPK and a Triton 1C60 Foot) and then to our fully powered device (knee-+ ankle prosthesis). They will be trained to use each device before completing the Amputee Mobility Predictor with Prosthesis (AMPPRO) (primary outcome) as well as metabolic and biomechanical assessments, a set of standard outcome measures, and self-report surveys (secondary outcomes). For Aim 2, we will evaluate combinations of powered knee + passive ankle and passive knee + powered ankle, in random order. Subjects will be trained to use each device, and the same primary and secondary outcome measures will be performed to assess functional benefits and the effects of additional weight at the knee or ankle. In Aim 3, we will provide intensive training to enable subjects to independently perform typical activities of daily living and achieve personal mobility goals using the powered knee + ankle device, to determine what level of improvement K2- level ambulators can attain. Subjects will again complete the same primary and secondary outcome measures using the powered device and will repeat these measures using the passive device from Aim 1, to accommodate carryover of training effects from previous Aims. The anticipated outcome is an understanding of how power and the weight of prosthetic components affect function in K2-level ambulators, which will enable optimal selection of components to improve functional mobility in individuals who are designated as limited community ambulators and currently restricted to passive devices.