Lumbar mechanics from ultrasound imaging

Using ultrasound, the feasibility of estimating lumbar mechanics in-vivo was evaluated. In Experiment 1, images were obtained while subjects were seated with the pelvis fixed and pulled on an anchored cable by isometrically contracting trunk muscles at different force levels. Linear regression identified ultrasound measurements which were correlated with trunk force. In Experiment 2, the cable was released and the trunk was rapidly displaced by shortening springs during the isometric contraction. Ultrasound images of the transverse processes of the L1-L2 vertebrae were acquired during this displacement for the purposes of estimating L1 -L2 joint stiffness. Results suggest that ultrasound is more suitable for estimating lumbar mechanics in the coronal plane than the sagittal plane. A linear trend was found between changes in thickness of some muscles and trunk force and with changes in muscle activity. Displacement of the vertebrae during perturbation occurred too quickly to be tracked by conventional ultrasound.