Comparison of two internal fixation systems in lumbar spondylolysis by finite element methods.

Abstract

BACKGROUND AND PURPOSE:

Internal fixation surgeries are currently the most effective treatments for lumbar spondylolysis, but the optimal fixation method is still on debate. This study was designed to compare the biomechanical characteristics of two fixation methods for lumbar spondylolysis, the pedicle screw-U shape rod (PSUSR) internal fixation system, and the pedicle screw-vertebral plate hook (PSVPH) internal fixation system, through three-dimensional finite element analysis, expecting to provide clinical guidance.

METHODS:

Four finite element models (A, B, C, D) of L4-S1 vertebral body of a female patient were reconstructed by CT image segmentation. (A: intact model. B: spondylolysis model. C: spondylolysis model with PSUSR internal fixation. D: spondylolysis model with PSVPH internal fixation). Six physiological motion states were simulated by applying 500N concentrated force and 10Nm moment load to four models. The biomechanical advantages of the two internal fixation systems were evaluated by comparing the range of motion (ROM), maximum stress, maximum strain, and maximum displacement of the models.

RESULTS:

Compared to model B, the ROM decreased by 35.7%-57.1% in model C and 39.7%-64.8% in model D. The maximum displacements of model C and D both decreased. The maximum stresses in both vertebral and the internal fixation system are greater in model C than those in model D. The maximum stress and strain reduction of L5-S1 intervertebral disc in model D was greater than that in model C. Model D restores the articular cartilage stresses to the normal levels of model A. The maximum stress and maximum displacement of the bone graft in model C are greater than those in model D.

CONCLUSIONS:

The PSVPH internal fixation system has better biomechanical properties than PSUSR internal fixation system in several mechanical comparisons. Experimental results suggest that PSVPH internal fixation system can effectively treat lumbar spondylolysis while preserving segmental mobility, and can be the treatment of choice.

• Authors: Le Li, Shuhao Jiang, Junyong Zhao, Mengmeng Zhao, Xin Zhou, Kunpeng Li, Chen Liu, Wencan Zhang, Junfei Chen, Qun Yu, Yuefeng Zhao, Jingjing Wang, Haipeng Si
• Journal: Computer methods and programs in biomedicine (Comput Methods Programs Biomed) Vol. 218 Pg. 106713 (May 2022) ISSN: 1872-7565 [Electronic] Ireland
• PMID: 35272148 (Publication Type: Journal Article)
• Copyright: Copyright © 2022 Elsevier B.V. All rights reserved.

Topics

• Biomechanical Phenomena
• Bone Plates
• Female
• Finite Element Analysis
• Humans
• Lumbar Vertebrae (diagnostic imaging, physiology, surgery)
• Pedicle Screws
• Range of Motion, Articular (physiology)
• Spinal Fusion
• Spondylolysis (diagnostic imaging, surgery)