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

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 passiveelastic 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 21 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.

Does Use of a Powered Ankle-foot Prosthesis Restore Whole-body Angular Momentum During Walking at Different Speeds?

“…Passiveelastic prostheses store and return energy but cannot generate force nor produce net positive work [25]. Use of powered ankle-foot prostheses that mimic biological ankle work [8] may allow better regulation of H compared with use of passive-elastic prostheses. We measured and compared H over a wide range of walking speeds on level ground for people with an amputation using passive-elastic and powered prostheses and for nonamputees.…”

“…During this session, a certified prosthetist fit and aligned the powered prosthesis. Then, the stiffness and power delivery of the prosthesis were tuned so that the prosthetic ankle angle at toe-off and net positive mechanical work matched average biological ankle data [16,23] within 2 SDs of the mean over a full range of walking speeds [8] (0.75, 1.00, 1.25, 1.50, and 1.75 m/s). The tuning parameters we saved and subsequently used during the powered prosthesis experimental session.…”

“…1) that has been previously described [1,2,8], which generates net positive prosthetic ankle work during the stance phase of walking and provides normative ankle mechanical power during late stance. The prosthesis uses both passive and motorized elements to emulate biological ankle and foot function (Fig.…”

“…Newly developed powered ankle-foot prostheses (BiOM, Bedford, MA, USA) can provide biomimetic net positive work during the stance phase of walking [1,8]. To our knowledge, the BiOM is the only commercially available ankle-foot prosthesis that provides power and net positive work during the stance phase of walking.…”

“…To our knowledge, the BiOM is the only commercially available ankle-foot prosthesis that provides power and net positive work during the stance phase of walking. Use of this powered prosthesis has enabled people with a transtibial amputation to achieve normative metabolic costs, preferred walking speeds, and step-to-step transition work while walking over level ground across the full range of speeds [8]. However, the effects of the powered prosthesis on H across this range of walking speeds are not yet known.…”