Evaluation of a Powered Ankle-Foot Prosthetic System During Walking

Objective: To determine whether a powered ankle-foot prosthesis improves gait mechanics, physical performance, and user satisfaction after traumatic transtibial amputation. Design: Pre-post. Setting: Gait analysis laboratory. Participants: Young individuals with traumatic transtibial amputation (n=11) and matched controls (n=11). Interventions: Wearing an energy-storing and -returning (ESR) foot and a powered ankle-foot prosthesis. Main Outcome Measures: Gait mechanics, physical performance, and user satisfaction. Results: The powered prosthesis ankle range of motion (ROM) was significantly larger (similar to 30%) than that of the ESR limb. However, both devices demonstrated significantly less ankle ROM than the control and intact limbs. At preswing, the ESR limb generated approximately 40% less peak ankle power than control and intact limbs. In contrast, the powered prosthesis generated significantly greater peak ankle power than control (35%) and ESR (similar to 125%) limbs, resulting in the powered limb absorbing twice the peak knee power observed in the control and intact limbs. The powered prosthesis limb peak hip power generation was approximately 45% greater at preswing than that of the intact limb. Walking velocity increased with the powered prosthesis compared with the ESR limb and was greater than that of the control group. However, physical performance measures were not significantly different between ESR and powered conditions. User satisfaction scores indicated a preference for the powered prosthesis over the ESR limb. Conclusions: Compensatory strategies during gait with the ESR and powered prosthetic devices were similar to those reported in the literature. However, the addition of ankle power and ROM by the powered prosthesis appeared to increase compensatory strategies at proximal joints.