Comparison of the effects of bilateral posterior dynamic and rigid fixation devices on the loads in the lumbar spine: a finite element analysis

摘要: A bilateral dynamic stabilization device is assumed to alter favorable the movement and load transmission of a spinal segment without intention fusion that segment. Little known about effect posterior fixation on mechanical behavior lumbar spine. Muscle forces were disregarded in few biomechanical studies published. The aim this study was determine how loads are affected by implant compared rigid fixator which does not claim maintain mobility. paired monosegmental inserted at level L3/L4 validated finite element model Both healthy slightly degenerated disc level. Distraction bridged also simulated. For comparison, as well stiffness intersegmental rotation studied. loaded with upper body weight muscle simulate four loading cases standing, 30° flexion, 20° extension, 10° axial rotation. Intersegmental rotations, intradiscal pressure facet joint calculated adjacent above implant. Implant determined. Compared an intact spine, reduces level, decreases for extension With implant, these effects more pronounced. mildly increased strongly reduced extension. After distraction, values markedly only At L2/L3, has minor pressure. However, it increases Posterior implants mostly compression. Forces generally higher than both shear greater 1,000 N/mm similar those device, except after when considerably lower implants. Thus, results demonstrate necessarily reduce un-instrumented