The study used thin inductive distance sensors adhered to the insides of sockets of a small group of transtibial prosthesis users to monitor bodily position and type of activity. Though step activity monitors provide insight into the amount of physical activity prosthesis users conduct, they do not provide information on how they use their prostheses.
There were two sensors at proximal locations and two at distal locations. An in-lab structured protocol and a semi-structured out-of-lab protocol were video recorded, and then participants wore the sensing system for up to seven days. A data processing algorithm was developed to identify sit, seated shift, stand, standing weight-shift, walk, partial doff, and non-use. Sensed distance data from the structured and semi-structured protocols were compared against the video data to characterize accuracy. Bodily positions and activities during take-home testing were tabulated to characterize participants’ use of their prostheses.
Sit and walk detection accuracies were above 95 percent for all four participants tested. Stand detection accuracy was above 90 percent for three participants, and 62.5 percent for one participant. The reduced accuracy may have been due to limited stand data from that participant. Step count was not proportional to active use time (sum of stand, walk, and standing weight-shift times).
The researchers concluded that step count may provide an incomplete picture of prosthesis use. Larger studies should be pursued to investigate how bodily position and type of activity may facilitate clinical decision-making and improve the lives of people with lower limb amputation.
The study, “A novel portable sensor to monitor bodily positions and activities in transtibial prosthesis users” was published in Clinical Biomechanics.