Finite element analysis of the influence of three‐joint spinal complex on the change of the intervertebral disc bulge and height

This study evaluated the changes of height and bulging occurring in individual layers of the annulus fibrosus of the intervertebral disc for 3 load scenarios (axial compression, flexion, and extension). The numerical model of a single motion segment of the thoracic spine was analysed for 2 different configurations, ie, for the model of a physiological segment and a segment with the posterior column removed. In the physiological segment, all annulus fibrosus layers decrease in height regardless of the applied load, bulging outside the intervertebral disc. Removal of the posterior column increases mobility and disrupts the load transfer system, with the lamellae bulging into the intervertebral disc. This study evaluated the changes occurring in individual layers of the annulus fibrosus of the intervertebral disc for different load scenarios. We used a numerical model of a single motion segment of the thoracic spine in 2 configurations, ie, the model of a physiological segment and a segment with the posterior column removed. The performed numerical simulations were used to determine the change in the distribution of displacements in the intervertebral disc, thus establishing the height and the bulging of layers.