Abstract
We investigated the acceleration on the Ilizarov external fixator and the shank. The soft tissue artifact is mostly common phenomena with several motion analysis techniques, such as the optical motion capture and sensor-based measurement system, and it deteriorates the measurement accuracy due to muscle contraction and elasticity of the soft tissue. Fixator’s acceleration represents actual bone motion, hence comparing two acceleration is enable to evaluate the STA quantitatively. Two participants equipping the Ilizarov external fixator were recruited for gait test. Two inertial measurement units (IMUs) were attached; one was on the fixator rigidly, and the other was on the shank. Acquired two accelerations were converted into the common global coordinate system based on the extended Kalman filter. We analyzed correlation coefficients of Pearson’s and Spearman's for each axis, and the root mean square error of accelerations and cross-correlation coefficients between the skin and the fixator. Pearson’s and Spearman's correlation coefficients did not show a high correlation, and cross-correlation result showed a small lag between two accelerations. The results suggested the acceleration sensor on the skin was not affected by the visco-elasticity of soft tissue in terms of frequency response, but the deformation of the surface where the devices were attached on such as muscle contraction adversely affects the measurement result of the acceleration sensor.
