Review on the progress in development of finite element models for functional spinal units: Focus on lumbar and lumbosacral levels

Functional spinal unit (FSU) has been of major interest in research related to the human spine as it is the simplest entity of spine that is believed to provide vital information useful in analyzing the biomechanics of the spine. In-vitro experiments and in-vivo tests are implemented for this purpose, but due to many restraints in using them, the use of an alternate approach such as Finite Element Analysis (FEA) seems preferential. FEA offers an edge in evaluating significant parameters that may or may not be possible through experiments. The finite element analysis of FSU's has evolved to handle complexity with the increase in computing capacity and advancement in the software packages. This paper reviews the progress in the development of finite element analysis of FSU's and also focuses on the application of FEA to analyse the lumbar (L1-L5) and lumbosacral (L5-S1) levels of the spine where spinal disorders are more prevalent.