Mechanical Effect of Double-Level Degeneration of Lumbar Spine Discs By Finite Element Method

This study intends to present a biomechanical model of the lumbar spine applying the finite element method in order to evaluate the behavior of the spine with disc degeneration. the high rates of patients suffering from this phenomenon encouraged us to study the effects of disc degeneration on spinal response. in the proposed method, the entire lumbar spine, including the vertebrae l1 to s1, were simulated. degeneration of the disc was also modeled in three different ways, decreasing disc height, changing the mechanical properties of the nucleus, and changing the properties of ligaments and collagen fibers. this degeneration was considered simultaneously for both l4-5 and l5-s1 discs, which is referred to as double-level degeneration in this study. after modeling and applying synthetic loading (bending moments with a follower load), the analysis was performed via abaqus software. the results, including intradiscal pressures and the intervertebral rotation, were also compared with experimental data for further verification. the findings of this study illustrate that double-level disc degeneration reduces intradiscal pressures in l4-5 and l5-s1 discs. however, the intradiscal pressure of a degenerated disc does not change the intradiscal pressure of other adjacent discs. moreover, in extension and axial rotation loading, increasing disc degeneration would lead to an increase in intervertebral motion.