Energy cost of ambulation in trans-tibial amputees using a dynamic-response foot with hydraulic versus rigid ‘ankle’: insights from body centre of mass dynamics

Abstract

BackgroundPrevious research has shown that use of a dynamic-response prosthetic foot (DRF) that incorporates a small passive hydraulic ankle device (hyA-F), provides certain biomechanical benefits over using a DRF that has no ankle mechanism (rigA-F). This study investigated whether use of a hyA-F in unilateral trans-tibial amputees (UTA) additionally provides metabolic energy expenditure savings and increases the symmetry in walking kinematics, compared to rigA-F.MethodsNine active UTA completed treadmill walking trials at zero gradient (at 0.8, 1.0, 1.2, 1.4, and 1.6 of customary walking speed) and for customary walking speed only, at two angles of decline (5° and 10°). The metabolic cost of locomotion was determined using respirometry. To gain insights into the source of any metabolic savings, 3D motion capture was used to determine segment kinematics, allowing body centre of mass dynamics (BCoM), differences in inter-limb symmetry and potential for energy recovery through pendulum-like motion to be quantified for each foot type.ResultsDuring both level and decline walking, use of a hyA-F compared to rigA-F significantly reduced the total mechanical work and increased the interchange between the mechanical energies of the BCoM (recovery index), leading to a significant reduction in the metabolic energy cost of locomotion, and hence an associated increase in locomotor efficiency (p < 0.001). It also increased inter-limb symmetry (medio-lateral and progression axes, particularly when walking on a 10° decline), highlighting the improvements in gait were related to a lessening of the kinematic compensations evident when using the rigA-F.ConclusionsFindings suggest that use of a DRF that incorporates a small passive hydraulic ankle device will deliver improvements in metabolic energy expenditure and kinematics and thus should provide clinically meaningful benefits to UTAs’ everyday locomotion, particularly for those who are able to walk at a range of speeds and over different terrains.

Benefits of a microprocessor-controlled prosthetic foot for ascending and descending slopes

“…Ankle-angle characteristics of prosthetic feet, influenced by carbon keel stiffness and design, have been identified as an important factor for ramp walking [ 5 , 9 , 15 , 28 , 29 ]. In this study, the ankle ROM was increased by approximately 35% for Up (TTA, TFA) and Down (TTA) with the MPF-M compared to ESR feet.…”

Shortcomings of human-in-the-loop optimization of an ankle-foot prosthesis emulator: a case series

“…In this series of case studies, we applied human-in-the-loop optimization to the control of an active ankle-foot prosthesis used by participants with unilateral transtibial amputation. Four different classes of control architecture were tested: (i) a heel stiffness controller that varied the stiffness and damping of the heel of the prosthesis ( figure 1 a ), inspired by the observation that damped articulation of the ankle can reduce energy cost compared with rigid prosthetic ankles [ 33 ]; (ii) a neuromuscular controller that emulated biological components of the muscle-tendon complex and has been previously used to reduce the metabolic cost of walking with an active prosthesis [ 34 ] ( figure 2 a ); (iii) a balance controller that provided ankle inversion/eversion torque based on deviation of the user’s lateral centre of mass velocity and has been previously used to reduce the metabolic cost of walking with a prosthesis emulator [ 25 ] ( figure 3 a ); and (iv) a time-based torque controller with similar control architecture to that used to reduce the metabolic cost of walking with exoskeletons ( figure 4 a ). In addition, both five-parameter and four-parameter controllers were implemented for the time-based torque control architecture, resulting in a total of five different control architectures tested.…”

STEPFORWARD study: a randomised controlled feasibility trial of a self-aligning prosthetic ankle-foot for older patients with vascular-related amputations

“…This requires the user to make compensatory actions at proximal joints (compensations at the hip bilaterally and intact knee of the affected limb) and at the intact ankle to achieve stability with a ‘foot flat’ position when walking on slopes. 6 7 These actions result in greater asymmetry between the two limbs and increase the metabolic requirements of walking. 6 This can make walking more difficult and tiring.…”

“… 6 7 These actions result in greater asymmetry between the two limbs and increase the metabolic requirements of walking. 6 This can make walking more difficult and tiring. Our public involvement members reported that a poorly functioning prosthesis can contribute to sedentary behaviour, pain and more frequent visits to prosthetics centres and other healthcare services, which may lead to disuse and poorer quality of life.…”