Quantifying the Spatial Variation of Lower-Limb Soft Tissue Artefact During Functional Activity Using MR Imaging and X-Ray Fluoroscopy

Non-rigid movement of the soft tissue interface between skin-mounted markers and the underlying bones, also known as soft tissue artifact (STA), poses a major limitation to the non-invasive estimation of joint kinematics using three-dimensional (3D) motion analysis systems. Thorough knowledge of the nature of this non-rigid behavior is essential for development of compensation algorithms to enhance the accuracy of these systems. The studies in the literature aimed at quantifying STA have implemented invasive measurement methods such as bone pins [1] and external fixator devices [2], or have used subjects with pathological conditions [3]. In the present study, we integrated Magnetic Resonance (MR) and X-ray imaging techniques to evaluate the non-rigid behavior of the lower-limb soft tissue of healthy adults for a number of different functional tasks.