A comparison of the biomechanical properties of three different lumbar internal fixation methods in the treatment of lumbosacral spinal tuberculosis: finite element analysis

Abstract

There are various internal fixation methods in treating lumbosacral spinal tuberculosis. The study compared the stability and stress distribution in surrounding tissues/implants, such as discs, endplates and screw-rod internal fixation system, etc. when applying three different lumbar internal fixation methods to treat lumbosacral spinal tuberculosis. A finite element model was constructed and validated. The spinal stability was restored using three methods: a titanium cage with lateral double screw-rod fixation (group 1), autologous bone with posterior double screw-rod fixation (group 2), and a titanium cage with posterior double screw-rod fixation (group 3). For comparison, group 4 represented the intact L3-S1 spine. Finally, a load was applied, and the ranges of motion and Von Mises stresses in the cortical endplates, screw-rod internal fixation system and cortical bone around the screws in the different groups were recorded and analyzed. All six ranges of motion (flexion, extension, left/right lateral bending, left/right rotation) of the surgical segment were substantially lower in groups 1 (0.53° ~ 1.41°), 2 (0.68° ~ 1.54°) and 3 (0.55° ~ 0.64°) than in group 4 (4.48° ~ 10.12°). The maximum stress in the screw-rod internal fixation system was clearly higher in group 2 than in groups 1 and 3 under flexion, left/right lateral bending, and left/right rotation. However, in extension, group 1 had the highest maximum stress in the screw-rod internal fixation system. Group 2 had the lowest peak stresses in the cortical endplates in all directions. The peak stresses in the cortical bone around the screws were higher in group 1 and group 2 than in group 3 in all directions. Thus, titanium cage with posterior double screw-rod fixation has more advantages in immediate reconstruction of lumbosacral spinal stability and prevention of screw loosening.

Stability simulation analysis of targeted puncture in L4/5 intervertebral space for PELD surgery

“…The FEA method, used for simulating biomechanical changes in lumbar vertebrae, is known for its repeatability, low cost, and simplicity. Consequently, it has gained widespread use in biomechanical studies ( Liu et al, 2023 ; Nikkhoo et al, 2023 ). Changes in vertebral mobility and the maximum von Mises stresses have a close relationship with stability ( Khalaf and Nikkhoo, 2021 ; Nikkhoo et al, 2021 ).…”

“…In order to ascertain the relative position of the nucleus pulposus, a ratio of 1.62 was established by comparing the distance from the front edge of the annulus fibrosus to the nucleus pulposus with the distance from the rear edge of the annulus fibrosus to the nucleus pulposus. Furthermore, the thickness of the facet joint cartilage measured less than 1 mm (Zhao et al, 2018;Li et al, 2020;Liu et al, 2023). The element types for cortical bone, cancellous bone, endplates, facet joint cartilage, and annulus fibrosus were C3D4, while the element type for the nucleus pulposus was C3D4H, and for ligaments, it was T3D2 (Supplementary Figure S3).…”