Poroelastic Finite Element Modeling of a Lumbar Spine Motion Segment and Validation in Different Motions for Clinical Studies

About 80% of the population will experience back pain in their lifetime; however, although many patients have low back pain associated with disc degeneration, the exact course of degeneration is still unclear. The disc degeneration disorder has affected one-third of the worldchr('39')s young population. During degeneration, the disc undergoes morphological and biochemical changes, which in turn alter the tissue hydration, permeability, and ultimately the load-bearing capacity of the disc. Therefore, the finite element model, designed to study the relationship between frequent loading and disk degeneration, must be able to analyze the complex loading in the in-vivo conditions. The aim of this study was to construct and update models of finite element components with the prolastic properties so that different quasi-static loads could be investigated by presenting a personalized model in different individuals and applied in clinical studies to simulate the daily biomechanical behavior for accurate diagnosis and treatment.

This study simulated three different modes of finite element modeling, including axial symmetry method, parametric model and precision model with poroelastic mechanical properties and its results were compared with experimental in-vivo experiments.

To validate the constructed models, the results of three different quasi-static creep experiments were performed, including short-term creep, long-term creep and creep under regular daily activities, the results of which predicted changes. The results predicted height changes, axial displacement of the spine and the intradiscal pressure of the nucleus.

All the proposed results indicated that the models presented in quasi-statistic behavior predicted acceptable results and have sufficient validity to be examined in other quasi-statistic experiments. Therefore, it is possible to take a step forward in examining the results of clinical activities in determining the process of intervertebral disc degeneration.