Improving repeatability of setting volume origin and coordinate system for 3D gait analysis

This study investigated the variability arising from replacement of different calibration objects. A new calibration object (L-Frame) was instigated which consisted of four markers screwed into fixed positions in the floor, to ensure consistency between replacements. The variability of a healthy subject's joint moments from replacement of different calibration objects (5 marker wand and L-Frame) was compared to the subject's stride-to-stride repeatability (SSR). Overall the L-Frame calibration object demonstrated the least amount of variation during object replacement for both sagittal and coronal joint moments. In particular for the coronal ankle moment the 5 marker wand positioned at the end of the force-plate alignment had a variability of 81% of SSR, while the L-Frame showed only 3% of SSR. Utilising the L-Frame to set the volume origin and global coordinate system achieved the most consistent results, which is important for assuring reliable measurements during 3-Dimensional Gait Analysis (3DGA). Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.