ABSTRACT
The intervertebral lumbar spine disc (IVD) is a small oval body that connects between
two vertebrae. Its degeneration causes lower back pain, which causes economic
losses due to treatment and absence from work. Finite element analysis has been
used for understanding the complex degeneration process. However, such studies
assumed the disc to behave linearly in the elastic region under static loading. In this
work, nonlinear FE analysis was used to model the degeneration process as
realistically as possible. This was accomplished using an advanced FE capable of
simulating the flow of bodily fluid through the living tissues of the disc. This allowed
the material properties to change according to time, load and deformation, which
occurs in reality. Furthermore, an innovative approach – DOE – was applied to
analysis the effect of changing fluid permeability of the annulus fibrosus (AF) and
nucleus pulposus (NP), which are the two main parts of the IVD. The analysis
revealed that permeability has a strong effect on the value of deformation of the IVD
under load. In addition, there is even a clear interaction effect between the
permeability of AF and NP on deformation.