Bionic ankle–foot prosthesis normalizes walking gait for persons with leg amputation

TLDR

Leg prostheses have improved in design but still cannot adapt to varying walking speeds like a biological limb, causing amputees to expend more energy, walk slower, and exhibit abnormal biomechanics. The authors developed a bionic prosthesis that emulates a biological ankle by delivering net positive work across a range of walking velocities during level‑ground walking. Compared with a passive‑elastic prosthesis, the bionic device lowered metabolic cost by 8 %, increased trailing‑leg work by 57 %, reduced leading‑leg work by 10 %, and raised preferred walking speed by 23 %, yielding metabolic, velocity, and biomechanical outcomes indistinguishable from non‑amputees.

Abstract

Over time, leg prostheses have improved in design, but have been incapable of actively adapting to different walking velocities in a manner comparable to a biological limb. People with a leg amputation using such commercially available passive-elastic prostheses require significantly more metabolic energy to walk at the same velocities, prefer to walk slower and have abnormal biomechanics compared with non-amputees. A bionic prosthesis has been developed that emulates the function of a biological ankle during level-ground walking, specifically providing the net positive work required for a range of walking velocities. We compared metabolic energy costs, preferred velocities and biomechanical patterns of seven people with a unilateral transtibial amputation using the bionic prosthesis and using their own passive-elastic prosthesis to those of seven non-amputees during level-ground walking. Compared with using a passive-elastic prosthesis, using the bionic prosthesis decreased metabolic cost by 8 per cent, increased trailing prosthetic leg mechanical work by 57 per cent and decreased the leading biological leg mechanical work by 10 per cent, on average, across walking velocities of 0.75–1.75 m s −1 and increased preferred walking velocity by 23 per cent. Using the bionic prosthesis resulted in metabolic energy costs, preferred walking velocities and biomechanical patterns that were not significantly different from people without an amputation.