Individuals With Transtibial Amputation Using a Prescribed Prosthesis and a Portable Bionic Prosthesis Under Myoelectric Control During a Stepping Activity.

Navigating changes in surface height is a component of daily living, requiring different musculoskeletal demands compared with level-ground walking. Individuals with transtibial amputation commonly adopt a hip-dominant strategy to compensate for the absence of active ankle plantar flexor power. Recent tests of overground walking with a direct control myoelectric bionic prosthesis found that participants exhibited similar prosthesis torques and powers to their passive devices, likely due to persistent motor memory. We tested six individuals with transtibial amputation performing a noncyclic stepping activity simulating a curb with the Open Source Leg prosthesis under direct proportional myoelectric input. We measured step time, prosthetic preference, lower limb muscle activity, kinematics, and kinetics. Similar to the overground walking study, we found participants chose to perform the task with bionic prosthesis mechanics similar to their passive prosthesis. No significant differences were observed in peak prosthetic ankle power (bionic: 1.5 W/kg, passive: 1.3 W/kg, p = .268), despite the bionic prosthesis being capable of generating 2.5 W/kg. This suggests participants chose a less powerful movement strategy that resembled movement dynamics similar to their passive prosthesis. As a result, there were no significant differences in step time (p = .345) or prosthetic ankle work (p = .062) between prostheses. Stepping with the powered prosthesis led to significantly increased intact limb hip work (p = .026) and residual limb quadriceps activity (p = .011). Four of six participants preferred the powered prosthesis. These results align with prior studies, indicating that extended training or visual biofeedback may be required to retrain amputees to increase mechanical power and adjust movement strategies.