Journal of Biomechanical Engineering

Kong W.Z., Goel V.K., Gilbertson L.G.


A combined approach involving optimization and the finite element technique was used to predict biomechanical parameters in the lumbar spine during static lifting in the sagittal plane. Forces in muscle fascicles of the lumbar region wwere first predicted using an optimization-based force model including the entire lumbar spine. These muscle forces as well as the distributed uppper body weight and the lifted load were then applied to a three-dimensional finite element model of the thoracolumbar spine and rib cage to predict deformation, the intradiskal pressure, strains, stresses and load transfer paths in the spine. The predicted intradiskal pressures in the L3-4 disk at the most deviated from the in vivo measurement by 8.2 percent for the four lifting cases analyszed. The lumbosacral joint flexed, wheile the other lumbar joints extended for all of the four lifting cases studied (rotation of a joint is the relative rotation between its two vertebral bodies). high stresses were predicted in the posterolateral regions of the endplates at the junction of the pedicles and vertebral bodies. High interlaminar shear stresses were found in the posterolateral regions of the lumbar disks. While the facet joints of the upper two lumbar segments did not transmit any load, the facet joints of the lower two lumbar segments experienced significant loads. The ligaments of all lumbar motion segments except the lumbosacral junction provided only marginal moments. The limitation sof the current model posssible improvements are discussed.