Fig. 3
Analysis of the soft tissue artifacts. (a) A schematic representation of the coordinate transformation between the laboratory coordinate system (Lcs), the fluoroscopy coordinate system (Fcs), and the bone coordinate system (Bcs). (b) Based on the marker position in Bcs during the calibration trial (green) and the position during the motion task (red), the marker displacement at frame t (i.e., Et: the soft tissue artifact at the marker level) is obtained by calculating the coordinate difference