Development and Preliminary Testing of a Device for the Direct Measurement of Forces and Moments in the Prosthetic Limb of Transfemoral Amputees during Activities of Daily Living

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Abstract
To provide a comprehensive description of the direct measurement of forces and moments applied on the socket of transfemoral amputees during daily living activities. The forces and moments applied on the socket of one female transfemoral amputee were measured with a commercial transducer at a sampling frequency of 200 Hz and recorded at distance using a wireless modem to transmit the data. The subject was asked to walk in a straight line and around a circle as well as to ascend and descend a slope and stairs. The subject was instructed to perform each activity at her natural pace and as she would usually perform it during daily life. The results were based on a high number of gait cycles of the prosthetic leg for each activity. For instance, 62 gait cycles were measured during level walking in a straight line. Ascending a slope produced a larger moment around the mediolateral axis than walking over the entire support phase. In addition, walking around a circle produced a higher moment about the long axis of the socket than walking during the push-off phase of the support. The mean stride frequency while descending a slope was higher than straight level walking. All the other activities presented a slower mean stride frequency than straight level walking. The impulse on the three axes was similar or smaller than walking in a straight line for all of the activities except for walking around a circle on the mediolateral axis, as well as ascending a slope and stairs and walking around a circle on the long axis. An apparatus to directly measure the actual forces and moments applied to the socket of the transfemoral amputees during an unlimited number of steps and a wide range of activities is presented. The apparatus presented here could be used by multidisciplinary teams, including engineers, prosthetists, and physiotherapists, facing the challenge of safely restoring the locomotion of transfemoral amputees fitted with a conventional socket or, in particular, an osseointegrated implant.

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