The prospective efficacy of stumble recovery responses in a powered knee prosthesis

Introduction: Transfemoral prosthesis users experience heightened fall risk following a trip or stumble when using their conventional, passive prostheses. In a laboratory setting, 54% of all stumble perturbations resulted in a fall for transfemoral prosthesis users using passive prostheses, while able-bodied controls never fell across 190 similar perturbations at a faster walking speed. Shortcomings in the mechanics and control of passive prostheses may contribute to this disparity, including inadequate stance support, poor swing assistance, and the lack of access to certain able-bodied stumble recovery strategies that require positive power at the knee. Methods: In this work, a powered knee prosthesis was used to provide bimodal stumble recovery behaviors, modeled after able-bodied stumble reflexes, while also providing robust stance support and swing assistance. Three transfemoral prosthesis users underwent a series of treadmill-based obstacle perturbations on both the powered prosthesis and their prescribed, passive prosthesis to compare the stumble recovery outcomes between the two classes of prosthesis. Results: Results from this preliminary study indicate that the powered prosthesis eliminated knee buckling, improved trunk control, improved base of support adjustment, and reduced hip circumduction. While improvements were consistent across stumble conditions and metrics for two of the three participants, improvements were less consistent with the third participant. Discussion: Overall, the results suggest that powered stumble recovery-specific behaviors in prosthetic knee prostheses may have promise to improve stumble recovery outcomes for transfemoral prosthesis users.