Effect of pedicle-screw fixation on the biomechanics of the lumbar spine: A Case Study finite element analysis

The pedicle-screw fixation is widely used for the surgical treatment of degenerative lumbar disease. The biomechanical effects of the fusion on the vertebral bodies have not still been investigated in detail. In this study, we intended to calculate the stress and strain of the vertebral bodies and intervertebral discs of the lumbar spine after posterior pedicle-screw fixation (PPSF). A three-dimensional (۳D) patient-specific finite element (FE) model of the human L۱ to L۵ spine was established based on the computed tomography (CT)/magnetic resonance imaging (MRI) images. A preload along with a sinusoidal load, were applied to the proximal end (L۱). The distal end (L۵) was fixed in all directions. The highest stress and strain were observed in the intervertebral disc of L۴-L۵ and L۱-L۲. The stress and strain of the unilateral pedicle-screw were higher than the bilateral ones. The results suggested that the unilateral pedicle-screw provides greater stability comparing to bilateral fixation in posterior bending position. The results have implications not only for understanding the stress and strain of the vertebral bodies and intervertebral discs but also, they give comprehensive information to the biomechanical and medical experts concerning the stability of the spine in the posterior bending position.

Keywords:

Pedicle-screw fixation , Lumbar spine , Posterior fixation , Von Mises Stress , Finite element analys