Study of Ankle Rocker Functions for Unilateral Transtibial Amputees During Slope Walking by Using Effective Roll-Over and Moment Arms Analysis
The ankle-foot systems of healthy people are functioned as rockers to advance the body vectors forward under the control of the ankle muscles. Unlike healthy people, the transtibial amputees (TTAs) lose some of the rocker functions due to the lack of active control of the ankle-foot complexes and the limited deformation capacity of the prosthetic feet. This paper aims to investigate the ankle rocker functions of the TTAs walking on inclined surfaces by employing the effective roll-over shapes (ROS) and the effective moment arms of center of pressure (MACOP) analysis. Ten unilateral TTAs and ten age-matched able-bodied (AB) participants were recruited and performed level ground, uphill (+5°) and downhill (–5°) walking on the Computer Assisted Rehabilitation Environment system. Gait data including three-dimensional kinematics and ground reaction forces were recorded. The ROS was calculated by transforming the center of pressure position data from a laboratory based coordinate system to an ankle based coordinate system. The MACOP was derived based on the geometrical relationship of the ROS and the ground reaction force. The ankle rocker functions of the TTAs were significantly defective under slope walking conditions and in comparison with those of the ABs. The main effects of the walking conditions and groups (the TTAs and the ABs) showed significantly difference on the ROSs and the MACOPs during the load response phase and terminal stance phase. The TTAs with prosthetic feet demonstrated significantly insufficient heel rocker function and forefoot rocker function in comparison with those of the ABs. Among all these three walking conditions, the TTAs with prosthetic feet had the worst heel rocker function during uphill walking. The deficits of these functions result in gait abnormality and thus the TTAs have to walk using compensation mechanisms. The design of future prosthetic feet could focus on the improvement of the heel rocker function and the forefoot rocker function. Development of active prosthetic feet could be the most promising solution for the restoration of normal gait for the TTAs.
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Document Type: Research Article
Publication date: February 1, 2018
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