Kinematic and biomimetic assessment of a hydraulic ankle/foot in level ground and camber walking

Abstract

Improved walking comfort has been linked with better bio-mimicking of the prosthetic ankle. This study investigated if a hydraulic ankle/foot can provide enough motion in both the sagittal and frontal planes during level and camber walking and if the hydraulic ankle/foot better mimics the biological ankle moment pattern compared with a fixed ankle/foot device. Five active male unilateral trans-femoral amputees performed level ground walking at normal and fast speeds and 2.5° camber walking in both directions using their own prostheses fitted with an “Echelon” hydraulic ankle/foot and an “Esprit” fixed ankle/foot. Ankle angles and the Trend Symmetry Index of the ankle moments were compared between prostheses and walking conditions. Significant differences between prostheses were found in the stance plantarflexion and dorsiflexion peaks with a greater range of motion being reached with the Echelon foot. The Echelon foot also showed significantly improved bio-mimicry of the ankle resistance moment in all walking conditions, either compared with the intact side of the same subject or with the “normal” mean curve from non-amputees. During camber walking, both types of ankle/foot devices showed similar changes in the frontal plane ankle angles. Results from a questionnaire showed the subjects were more satisfied with Echelon foot.

The Influence of Hydraulic Ankles and Microprocessor-Control on the Biomechanics of Trans-Tibial Amputees During Quiet Standing on a 5° Slope

“…However, when walking or standing on uneven or sloped surfaces, the relative position of the body's COM to the lower limb joints changes and thus the alignment of a prosthesis may become sub-optimal. [15][16][17][18] Part of the problem may be the prosthetic device. In conventional, energy-storing-and-return (ESR) feet that have a fixed attachment to the distal end of the prosthetic pylon, plantarflexion and dorsiflexion of the foot are achieved through deformation of the foot keel, which is often constructed of elastic elements and structures.…”

A biomechanical assessment of hydraulic ankle-foot devices with and without micro-processor control during slope ambulation in trans-femoral amputees

“…Most gait studies were carried out with TTAs and tests have been performed on level ground [ 8 , 9 , 11 ], slopes [ 12 , 14 ] and general outdoor walking conditions (including slopes and stairs) [ 7 ]. Two studies involved TFAs and both level ground and cross-slope walking were investigated [ 11 , 13 ]. It has been reported that the hydraulic ankle enables increased walking speed [ 9 , 11 ], a smoother transfer of plantar centre of pressure [ 8 , 11 ], a higher bio-mimicry of ankle resistance [ 13 ], and decreased peak internal stresses on the stump [ 7 ].…”

“…Two studies involved TFAs and both level ground and cross-slope walking were investigated [ 11 , 13 ]. It has been reported that the hydraulic ankle enables increased walking speed [ 9 , 11 ], a smoother transfer of plantar centre of pressure [ 8 , 11 ], a higher bio-mimicry of ankle resistance [ 13 ], and decreased peak internal stresses on the stump [ 7 ]. However, other research reported no significant differences in the torque at the distal end of the socket in TTAs during slope ambulation when using hydraulic ankle-foot devices compared with other ankle-foot designs [ 14 ].…”

“…Therefore the quantified similarity between prosthetic ankle moment and biological ankle moment can be used to assess the prosthetic ankle-foot device. However, probably due to the lack of an appropriate quantification method, so far there has only been one study that has tried to use Trend Symmetry Index (TSI) to assess different types of prosthetic ankle-foot devices [ 13 ].…”

“…The first aim of this research was to investigate changes in kinematic and kinetic data of a hydraulic ankle in ascending and descending a 5-degree slope in TFAs in comparison to a rigid ankle. Based on the findings in a previous study [ 13 ], it was hypothesised that the hydraulic ankle would provide a better biomimetic ankle moment (more similar to the biological ankle moment pattern) and a greater ROM in slope walking compared with the rigid ankle. The second aim was to investigate the effects of a micro-processor controlled hydraulic ankle that allows customised adjustments in the adaption to uphill and downhill slope walking.…”