An Approach to Lumbar Vertebra Biomechanical Analysis Using the Finite Element Modeling Based on CT Images

Lumber disc herniation is one of the most common causes of low back pain. Relevant research indicates that it is generally induced by the degenerated deformation of a disc due to too much labor or spine abnormality. The number and variety of clinical interventions for lumbar disc herniation continue to grow. The lumbar intervertebral disc is a viscoelastic tissue located in the middle of the two intervertebral bodies, which is the largest cartilaginous structure in human body that contributes to flexibility and load support in the spine. They can transfer labor loads, balance body, stabilize spine and absorb vibration[1]. All the functions depend on the intact disc. In pathological cases such as disc herniation caused by excessive load on the spine. The spine will undergo a series of changes in its biomechanical properties. The interbertebral disc consists of endplate, annulus fiber, and nucleus pulposus. The penetration between endplate and the concellous bone will change feebly if the disc bears an abnormal force and thus can affect the nutrient supply of annulus fiber, which results in the degeneration of the disc. Annulus fiber with poor nutrient supply is likely to rupture if there exists a stress concentration on this region. The nucleus pulposus will dissociate from the disc along the ruptured region. At last, the disc extrudes out[2,3]. In order to biomechanically evaluate the treatment options for spine related diseases and gain a better understanding of spinal biomechanical behaviour, there are three types of methodologies available. In vitro biomechanical experimental measurements on spinal components or segments tested in the laboratory have been used extensively to compare different treatment scenarios, but there are inherent limitations in using the specimens[2,4,5]. The limitations include the availability, the range of samples and the representativity of specimens. In vivo measurements can provide true subject-specific information on the spine in its physiological state but are confined by the requirement for limited invasiveness. More recently, in silico testing method has become more prevalent in the biomechanics assessment of the spine. In particular, there has been a rapid rise in the use of finite element analysis for this purpose over the last decade. The finite element analysis is a standard engineering technique generally used in the design of airplanes, machines and bridges. Using a special software, it allows the modeling of complex structures by splitting the structure into numerous simple finite elements, each of which is easy to characterize and