Biomechanical evaluation of lumbar spondylolysis repair with various fixation options: A finite element analysis

Abstract

Objective: This study was designed to compare the biomechanical properties of lumbar spondylolysis repairs using different fixation methods by using three-dimensional finite element analysis.Methods: Five finite element models (A, B, C, D, and E) of L4-S1 vertebral body were reconstructed by CT images of a male patient (A: intact model; B: spondylolysis model; C: spondylolysis model with intrasegmental direct fixation by Buck screw; D: spondylolysis model with intersegmental indirect fixation by pedicle screw system; E: spondylolysis model with hybrid internal fixation). L5-S1 level was defined as the operative level. After the intact model was verified, six physiological motion states were simulated by applying 500 N concentrated force and 10 Nm torque on the upper surface of L4. The biomechanical properties of the three different internal fixation methods were evaluated by comparing the range of motion (ROM), maximum stress, and maximum displacement.Results: Compared with Model B, the ROM and maximum displacement of Model C, D, and E decreased. The maximum stress on L5/S1 disc in models A, B, and C was much higher than that in Model D and E under extension and lateral bending conditions. Under axial rotation and lateral bending conditions, the maximum stress of interarticular muscle and internal fixation system in Model B and Model C was significantly higher than that in Model D and Model E. In contrast to Model D, the stress in Model E was distributed in two internal fixation systems.Conclusion: In several mechanical comparisons, hybrid fixation had better biomechanical properties than other fixation methods. The experimental results show that hybrid fixation can stabilize the isthmus and reduce intervertebral disc stress, which making it the preferred treatment for lumbar spondylolysis.

Validation and Estimation of Obesity-Induced Intervertebral Disc Degeneration through Subject-Specific Finite Element Modelling of Functional Spinal Units

“…It is important to mention the shortcomings and oversimplifications of the current FE investigation, of which we are well aware. The models that have been presented have the potential to be improved upon, taking into account the effects of muscle forces, variations in the size and location of ligaments and fibers, computer-simulated IVD, facet cartilage, and endplate constructed by MRI data, as well as including material properties of the subject-specific FSU components used in this study [101]. Other limitations include the level of degeneration and factors such as cell nutrition and transport, intense vibration, genetics and smoking that affect the IVD, were not addressed in this investigation [2,3].…”

Biomechanical Evaluation of 2 Endoscopic Spine Surgery Methods for Treating Lumbar Disc Herniation: A Finite Element Study

“…The 3D finite element model incorporated structures, including the L3–S1 vertebral body, articular synovial joints, intervertebral discs, and ligaments. Based on the grayscale of the original CT images [ 22 ], material parameters for cortical and cancellous bone were assigned. Following previous reports in the literature [ 23 , 24 ], we modeled lumbar osteoporosis by reducing the elastic modulus of cortical bone to 67% of the normal model and that of cancellous bone to 34%.…”