Biomechanical Comparison Using 3-D Finite Element Method between Cortical Screw Trajectory Fixation and Pedicle Screw Fixation for Fusion of the Lumbar Degenerative Spine

Abstract

Posterior fusion has been popularized for degenerative and traumatic spine conditions thanks to its convenience and facilities including direct access to the spinous processes, laminae, facets and exposure of spinal canal through posterior approach and neurological decompression while various surgical instruments and implants and techniques have been developed to enhance stability and apply maneuvers easily. As technology for spinal fusion has rapidly evolved in recent years, a new technique of cortical screw trajectory fixation has been reported minimal invasion and further constructs stiffness compared to pedicle screw fixation. Hence, we purposed to find biomechanical properties of cortical screw trajectory fixation and pedicle screw fixation in lumbar spine model and compare them. Biomechanical analysis was conducted using 3-D geometrical and Finite Element Method (FEM) models of fusion of the lumbar spine at the level of L4-L5 treated by cortical screw trajectory fixation and pedicle screw fixation fewer than four types of loads: flexion, extension, axial compression and torsion. The values of stiffness and displacement in the intervertebral disc and facet joints at the L4-L5 level when treated with the cortical screw trajectory fixation were the same or lower compared to the pedicle screw fixation. Cortical screw trajectory fixation provides greater stability than traditional pedicle screw fixation in fusion of the degenerative lumbar spine.