Step-to-step transition work during level and inclined walking using passive and powered ankle-foot prostheses

Abstract

Background: Individuals with leg amputations who use passive prostheses have greater metabolic demands than nonamputees likely due to limited net positive work compared to a biological ankle. New powered ankle-foot prostheses can perform net positive mechanical work to aid push-off capabilities, which may reduce metabolic demands. Objectives: Compare step-to-step transition work and metabolic demand during level and inclined walking using passive and powered ankle-foot prostheses. Study Design: Repeated measures. Methods: Six individuals with transtibial amputation and six able-bodied controls walked at a standardized speed across level ground and up a 5° incline. Calculated measures included mechanical work during step-to-step transitions from the trailing prosthetic to leading intact limb, steady state metabolic rate, and ankle joint kinetics and kinematics. Results: The powered prosthesis generated 63% greater trailing limb step-to-step transition work than the passive during level walking only (p = 0.004). Metabolic rate was lower with the powered prosthesis during level (p = 0.006) but not inclined walking (p = 0.281). The powered prosthesis increased ankle power compared to the passive, to the extent that power was normalized to controls during inclined walking and greater than controls during level walking. Conclusion: The powered prosthesis improved ankle power, metabolic rate, and step-to-step transition work on level ground, with few negative consequences on inclines. These results may be used to guide the development and use of actively powered prosthetic devices in high-functioning individuals.