Department of Orthopedics, Qilu Hospital, Cheeloo College of Medicine, Shandong University, Jinan, 250012, Shandong, People's Republic of China.
Shandong Provincial Engineering and Technical Center of Light Manipulations & Shandong Provincial Key Laboratory of Optics and Photonic Device, School of Physics and Electronics, Shandong Normal University, Jinan, 250014, People's Republic of China.
Comput Methods Programs Biomed. 2022 May;218:106713. doi: 10.1016/j.cmpb.2022.106713. Epub 2022 Feb 27.
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.
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.
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.
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.
内固定手术目前是治疗腰椎峡部裂最有效的方法，但最佳固定方法仍存在争议。本研究通过三维有限元分析比较了两种腰椎峡部裂内固定方法的生物力学特性，即椎弓根螺钉-U 形棒（PSUSR）内固定系统和椎弓根螺钉-椎体钩（PSVPH）内固定系统，以期为临床提供指导。
通过 CT 图像分割对一位女性患者的 L4-S1 椎体进行了四个有限元模型（A、B、C、D）的重建。（A：完整模型。B：峡部裂模型。C：PSUSR 内固定峡部裂模型。D：PSVPH 内固定峡部裂模型）。通过对四个模型施加 500N 集中力和 10Nm 力矩载荷，模拟了六种生理运动状态。通过比较模型的运动范围（ROM）、最大应力、最大应变和最大位移，评估了两种内固定系统的生物力学优势。
与模型 B 相比，模型 C 的 ROM 降低了 35.7%-57.1%，模型 D 的 ROM 降低了 39.7%-64.8%。模型 C 和模型 D 的最大位移均减小。模型 C 和模型 D 的椎骨和内固定系统的最大应力均大于模型 D。模型 D 使 L5-S1 椎间盘的最大应力和应变减小幅度大于模型 C。模型 D 将关节软骨的应力恢复到模型 A 的正常水平。模型 C 的骨移植物的最大应力和最大位移大于模型 D。
在几种力学比较中，PSVPH 内固定系统的生物力学性能优于 PSUSR 内固定系统。实验结果表明，PSVPH 内固定系统可以有效治疗腰椎峡部裂，同时保留节段活动度，是治疗腰椎峡部裂的首选方法。
