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R. Yamamoto1,2, K. Morimura1, T. Shiraishi1
1Yokohama National University, Graduate School of Environment and Information Sciences, Yokohama, Japan, 2Keio University, Department of Rehabilitation Medicine, Tokyo, Japan
Background: Sideways falls are frequently observed in those accidents and often related to hip fracture which has a major risk to be bedridden in elderly individuals. As an intervention for this issue, we are developing a gait support device as an intelligent fall prevention system for community use through the investigation of a control method.
Purpose: The objective of the study is to confirm the influence of plantar height on lateral stability in gait and to present a sideways fall dynamic model at the frontal plane to further understand the mechanics in the moments prior to a sideways fall with and without an insole.
Methods: 1) A dynamic model of sideways fall was developed in the aspect of the changes in the arc radius of the plantar and on the frontal plane.
2) Furthermore, a rigid body experiment model was created and a sideways fall experiment was performed. The time history data of the COM-COP line angle change was measured and compared to the acquired data of the numerical simulation.
3) The behavior of the COP during walking in the stance phase was analysed in two healthy subjects. We obtained the COP data by the gait analysis system and measured walking with and without the lateral insole attached to the plantar under tuberosity of the 5th metatarsal. We measured the maximum lateral displacement point of the COP (mm) and the time period of the heel contact to the maximum lateral displacement point of the COP(s), which were compared between gait with or without the lateral insole.
4) The validity of the dynamic model was verified from the results of 1) and experiment 2) 3).
2) Furthermore, a rigid body experiment model was created and a sideways fall experiment was performed. The time history data of the COM-COP line angle change was measured and compared to the acquired data of the numerical simulation.
3) The behavior of the COP during walking in the stance phase was analysed in two healthy subjects. We obtained the COP data by the gait analysis system and measured walking with and without the lateral insole attached to the plantar under tuberosity of the 5th metatarsal. We measured the maximum lateral displacement point of the COP (mm) and the time period of the heel contact to the maximum lateral displacement point of the COP(s), which were compared between gait with or without the lateral insole.
4) The validity of the dynamic model was verified from the results of 1) and experiment 2) 3).
Results: Regarding the numerical simulation results, falls occurred without the insole. However, they did not occur when the insole was fitted, as it rotated in the opposite direction to the fall. The falling angular velocity of the COM-COP line was slower under all conditions with the insole than without. A phenomenon where the COP fulcrum on the floor shifted to the lateral side to maintain the COM-COP angle in opposition to the fall direction was also observed when an insole was used. Additionally, the COP maximum lateral displacement point was also shifted to the lateral side by 3.6 mm.
Conclusion(s): The correlation between the result of the numerical simulation and the model experiment in the dynamic model and the association with the gait experiment was confirmed. Furthermore, COP being shifted to the lateral side of the plantar when using the insole is considered as the characteristic mechanism in prevention of sideways falls. From the above, it is suggested that there are potential applications as a fall control method through changing of the height of the lateral area of the plantar.
Implications: This study aims to develop an intelligent orthosis for community use in response to the rapidly aging society. To this end, the results therefore have potential to be useful for the clinical presentation of the mechanism of sideways falls and insole therapy in gait control.
Funding, acknowledgements: This work was funded by "YNU Diversity Research Grant" under MEXT "Initiative for Realizing Diversity in the Research Environment."
Keywords: fall prevention, dynamic model, insole therapy
Topic: Innovative technology: robotics
Did this work require ethics approval? No
Institution: Yokohama National University
Committee: Ethics Committee of Yokohama National University
Reason: The subjects were recruited within the laboratory team and were fully informed of the details and consent was obtained.
All authors, affiliations and abstracts have been published as submitted.
