Finite Element Stress Analysis of a Spinal Segmentby Vijay K. Goel, Univ of Iowa, Iowa City, United States,
Abstract: A large number of factors need to be determined to understand the biomechanics of a surgical procedure about the lumbar spine. Some of these factors are amenable to experimental investigations while knowledge concerning other parameters requires the development of an analytical model of the spine. A three-dimensional, non-linear, finite element model of an intact ligamentous motion segment was developed to predict the stress and strain distributions within the segment, nucleus pressure, loads across the facet joints, etc. in response to axial compression loads. The intact model was appropriately modified to simulate a number of surgical procedures including the use of a pedicle-screw fixation device. The results indicate that the loads across the facets increase and the disc bulge in the posterior region decreases following discectomy, in comparison to the intact model predictions. The use of a rigid fixation device for stabilizing a decompressed segment leads to stress-shielding within the stabilized model as compared to the intact model. This may lead to stress-induced osteopenia. These results, as a complement to the experimental data, help explain the clinical changes in the spine following surgery.
Subject Headings: Finite element method | Stress analysis | Axial loads | Three-dimensional models | Nonlinear finite element analysis | Stress distribution | Stress strain relations | Load distribution
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