内镜辅助下髓核摘除术后纤维环缝合对腰椎生物力学影响的有限元分析

Finite element analysis of biomechanical effect of annulus fibrosus suture on the lumbar spine after microendoscopic discectomy

中文关键词:  纤维环缝合  有限元分析  生物力学

英文关键词:Annulus fibrosus suture  Finite element analysis  Biomechanics

中文摘要:

  【摘要】 目的：建立内镜辅助下髓核摘除术后纤维环切口未缝合和纤维环切口缝合的有限元模型，分析髓核摘除术后是否缝合纤维环对腰椎生物力学影响。方法：招募1名健康男性青年志愿者，27岁，经腰椎CT检查排除脊柱畸形、肿瘤等骨病，将L4/5节段的CT扫描结果输入三维重建软件Mimics中提取腰椎轮廓，应用Geomagic、Solidworks和Workbench软件模型实体化处理，建立正常L4/5模型、L4/5髓核摘除术后纤维环切口未缝合模型（纤维环未缝合模型）和L4/5髓核摘除术后纤维环切口缝合模型（纤维环缝合模型）。测量模型椎间活动度、小关节Von-Mises应力、纤维环Von-Mises应力，与既往发表的研究比较验证。验证后，三种模型固定L5椎体下端，在L4椎体上端施加500N轴向载荷，在前屈、后伸、左右侧屈、左右旋转6种情况下分别施加7.5N·m的弯矩载荷，测量并分析不同载荷下三种模型的L4/5间隙椎体活动度、小关节及纤维环Von-Mises应力等生物力学特性。结果：建立的三种有限元模型，6种运动状态下的数据与既往文献报道的数据比较无明显偏差，验证模型有效。应力云图结果显示各运动状态下高应力区存在于椎间盘纤维环未缝合缺损处及周边小关节突部位。与正常模型比较，纤维环缝合模型的椎间活动度分别为8.6802°、8.596°、4.8514°、5.0249°、2.2474°、1.9092°,纤维环未缝合模型分别为8.7475°、8.9453°、5.6441°、5.2546°、2.5886°、1.9487°, 纤维环缝合模型活动度较正常模型增加了9％、19％、44％、38％、50％、40％；与纤维环未缝合模型比较，分别降低了1％、4％、14％、4％、13％、2％。纤维环缝合模型在六种运动工况下的纤维环Von-Mises应力与正常模型比较，分别升高2％、65％、21％、32％、51％、38％，与纤维环未缝合模型比较，分别降低8％、48％、52％、10％、37％、48％。纤维环缝合模型小关节Von-Mises应力值为12.109MPa、8.3601MPa、13.998MPa、12.969MPa、10.219MPa、10.074MPa，纤维环未缝合模型分别为13.399MPa、9.6094MPa、18.175MPa、17.967MPa、12.409MPa、11.6384MPa，纤维环缝合模型小关节Von-Mises应力值较正常模型增加了5％、10％、32％、17％、31％、34％；与纤维环未缝合模型比较，分别降低了9％、13％、22％、27％、17％、13％。结论：在构建的L4/5三种有限元模型中，纤维环缝合模型椎间活动度、小关节及纤维环Von-Mises应力均优于纤维环未缝合模型，有利于提高椎体间稳定性。

英文摘要:

  【Abstract】 Objective: To investigate the effects of annulus fibrosus(AF) suture or not on the lumbar biomechanics following microendoscopic discectomy(MED) through establishing finite element models(FEMs) of unsutured AF incision and sutured AF incision. Methods: A 27-year-old healthy young adult male volunteer was recruited and underwent lumbar CT to exclude spinal deformities, tumors, and other osseous pathologies. CT images of the L4/L5 segment were imported into the software Mimics for three-dimensional reconstruction and contour extraction. The resulting model was further processed using Geomagic, SolidWorks, and Workbench for solid modeling. An intact L4/5 segment model, an L4/5 model with an unsutured AF incision following MED(unsutured AF model), and an L4/5 model with a sutured AF incision following MED(sutured AF model) were established. Intervertebral range of motion(ROM), Von-Mises stress on the facet joints, and Von-Mises stress on the AF of the models were measured, and model validity was verified by comparison with previously published studies. After validation, the inferior end of the L5 vertebral body in all the three models was fixed. An axial load of 500N was applied to the superior end of the L4 vertebral body, and a bending moment of 7.5N·m was separately applied under six physiological loading conditions(flexion, extension, left/right lateral bending, and left/right axial rotation). The biomechanical properties of the three models at the L4/5 level, including intervertebral ROM and Von-Mises stress in facet joints, and Von-Mises stress on the AF were compared under different loading conditions. Results: No significant discrepancies were noted when data obtained under these six motion conditions were compared with the findings from prior literature, thus validating the models. Stress nephogram results revealed that under each motion condition, high-stress areas were located at the unsutured defect of the intervertebral disc AF and the surrounding facet joint processes. Compared with the intact model, the intervertebral ROM of the sutured AF model was 8.6802°, 8.596°, 4.8514°, 5.0249°, 2.2474°, and 1.9092°, respectively, under the six motions, while that of the unsutured AF model was 8.7475°, 8.9453°, 5.6441°, 5.2546°, 2.5886°, and 1.9487°, respectively. The ROM of the sutured AF model was 9%, 19%, 44%, 38%, 50%, and 40% higher than that of the intact model; Compared with the unsutured AF model, it was reduced by 1%, 4%, 14%, 4%, 13%, and 2% respectively. For Von Mises stress on the AF under the six motion conditions, the stress of the sutured AF model was 2%, 65%, 21%, 32%, 51%, and 38% higher than that of the intact model, but 8%, 48%, 52%, 10%, 37%, and 48% lower than that of the unsutured AF model respectively. For Von-Mises stress in facet joints, the stress values of the sutured AF model were 12.109MPa, 8.3601MPa, 13.998MPa, 12.969MPa, 10.219MPa, and 10.074MPa respectively, while those of the unsutured AF model were 13.399MPa, 9.6094MPa, 18.175MPa, 17.967MPa, 12.409MPa, and 11.6384MPa respectively. The stress values of Von-Mises stress in facet joints of the sutured AF model was 5%, 10%, 32%, 17%, 31%, and 34% higher than that of the intact model; Compared with the unsutured AF model, it was decreased by 9%, 13%, 22%, 27%, 17%, and 13% respectively. Conclusions: Among the three constructed L4/5 FEMs, the sutured AF model exhibits more favorable intervertebral ROM, and Von-Mises stress of facet joints and AF compared with the unsutured AF model. This indicates that AF suture contributes to enhancing intervertebral stability.