A METHOD FOR MECHANICALLY LOADING JOINTS DURING DYNAMIC MAGNETIC RESONANCE IMAGING

摘要

In order to take advantage of the opportunities that dynamic Magnetic Resonance Imaging (d-MRI) offers to the study of in vivo joint mechanics, d-MRI compatible devices capable of producing joint loads replicating dynamic physiological activities are needed (Sheehan et al., 1999). The purpose of this research effort was to design, model and test a device for the expressed purpose of using d-MRI to study precise ankle joint dynamics during loaded pseudo-functional movements. The device adjusts to subject specific anthropometric measurements, allowing for the device's axis of rotation to approximate the ankle's transverse axis. By combining imaging data and the model of the device, the magnitude, direction and point of application of the force applied to the foot were calculated throughout the motion cycle, with an average error of .7 Nm. This allows for comparisons between the externally applied load and internal ankle joint kinematics to be made, which are essential determinants for in vivo estimates of forces within tendon and ligament. The next phase of this work will be to combine this device with fast-Phase Contrast MRI (fast-pc), a previously developed d-MRI technique for the quantification of 3D musculoskeletal motion, in order to create a complete tool for the noninvasive in vivo measurement of joint kinematics during a loaded dynamic functional task in both healthy and impaired ankles.