经椎间孔内窥镜下腰椎间盘切除术联合非融合弹性棒内固定对手术节段生物力学影响的有限元分析

A finite element analysis of the effect on the biomechanics at the surgical segment of transforaminal endoscopic lumbar discectomy combined with non-fused elastic rod pedicle screw internal fixation

中文关键词:  经椎间孔内窥镜下腰椎间盘切除术  弹性棒内固定  手术节段  有限元分析

英文关键词:Transforaminal endoscopic lumbar discectom  Elastic rod fixation  Surgical segment  Finite element analysis

中文摘要:

  【摘要】 目的：基于三维有限元分析（finite element，FE）评估经椎间孔内窥镜下腰椎间盘切除术（transforaminal endoscopic lumbar discectomy，TELD）联合非融合弹性棒内固定系统（spinal dynamic stabilization system，SDSS）对手术节段生物力学效应的影响。方法：选取1名健康志愿者的腰椎CT薄层扫描数据，应用有限元方法建立L3~S1正常模型（FE）、TELD手术模型和TELD+SDSS手术模型，模拟手术节段为L4/5。通过计算精度（the computational accuracy，ACC）验证模型有效后，采用混合加载方法，在L1椎体顶部施加150N的轴向载荷，并施加逐渐增大的约束力扭矩，通过提取ROM值，以使三个模型分别达到以下活动度（range of motion，ROM）：前屈15°、后伸10°、左右侧弯5°及旋转3°。比较3个模型在上述6个方向工况下L4/5节段的ROM、椎间盘及纤维环后方的峰值应力及纤维环剪切应力。结果：L3~S1节段前屈、后伸、旋转在不同载荷条件下的ROM值与既往体外试验比较，ACC均超过90%，验证模型有效。与FE模型比较，TELD在屈、伸、左右侧弯、旋转工况下L4/5的ROM分别为4.47°、3.3°、1.72°、1.73°、0.94°、0.92°，TELD+SDSS分别为2.15°、1.21°、1.38°、1.43°、0.67°、0.67°，TELD在前屈、后伸工况下升高了5%、7%，TELD+SDSS在各方向工况下降低了19%~61%；TELD在屈、伸、左右侧弯、旋转工况下L4/5的椎间盘峰值应力分别为14.58MPa、15.08MPa、7.92MPa、5.32MPa、0.9MPa、0.65MPa；TELD+SDSS分别为5.35MPa、1.77MPa、3.45MPa、3.42MPa、0.55MPa、0.48MPa，TELD在后伸、侧弯工况下升高了36%、45%，TELD+SDSS在各向工况下降低了27%～84%；TELD在屈、伸、左右侧弯、旋转工况下L4/5纤维环后方峰值应力分别为2.04MPa、2.08MPa、1.44MPa、0.99MPa、0.41MPa、0.29MPa；TELD+SDSS分别为0.54MPa、0.23MPa、0.72MPa、0.7MPa、0.21MPa、0.18MPa，TELD在屈、伸、左右侧弯工况下升高了10%～99%，TELD+SDSS在各向工况下降低了20%～63%；TELD在后伸及左右侧弯工况下纤维环剪切应力分别为0.4MPa、0.32MPa、0.2MPa，升高了17%、76%、85%，TELD+SDSS在各向工况下降低了12%～98%。结论：TELD+SDSS可保留椎间一定的活动度，相比TELD，对腰椎稳定性影响小，可为手术节段提供低压应力环境。

英文摘要:

  【Abstract】 Objectives: To evaluate the biomechanical effects of transforaminal endoscopic lumbar discectomy(TELD) combined with a spinal dynamic stabilization system(SDSS) on the surgical segment using three-dimensional finite element (FE) analysis. Methods: The CT scan data from the lumbar spine of a healthy volunteer was selected. FE methods were employed to construct normal L3-S1 model(FE), as well as L3-S1 TELD and TELD+SDSS surgical models, with the surgical segment simulated at L4/5. After validating the models′ effectiveness through computational accuracy(ACC), a hybrid loading method was applied. An axial load of 150N was applied to the top of the L1 vertebral body, along with gradually increasing constraint torque. Range of motion(ROM) values were extracted to ensure the three models achieved the following ROM: flexion (15°), extension (10°), lateral bending (5°), and rotation (3°). The ROM, peak stress at the intervertebral disc and posterior annulus fibrosus, and shear stress in the annulus fibrosus at the L4/5 segment under these six directional conditions were compared across the three models. Results: The ROM values of L3-S1 segments under different loading conditions in flexion, extension, and rotation were compared with previous in vitro tests, with ACC exceeding 90%, validating the model′s effectiveness. For L4/5 ROM: in TELD model, it was 4.47°(flexion), 3.3°(extension), 1.72°(left bending), 1.73°(right bending), 0.94°(left rotation), and 0.92°(right rotation); In TELD+SDSS model, it was 2.15°, 1.21°, 1.38°, 1.43°, 0.67°, 0.67° respectively. The ROM in TELD model increased by 5% in flexion and 7% in extension, which in TELD+SDSS model reduced by 19-61% in all directions. For L4/5 disc stress: in TELD model, the peak stress was 14.58MPa, 15.08MPa, 7.92MPa, 5.32MPa, 0.9MPa, and 0.65MPa respectively under flexion, extension, left bending, right bending, left rotation, right rotation conditions; In TELD+SDSS model, it was 5.35MPa, 1.77MPa, 3.45MPa, 3.42MPa, 0.55MPa, and 0.48MPa. The peak stress of L4/5 disc in TELD model increased by 36% and 45% in extension and bending, which in TELD+SDSS model reduced by 27-84% in all directions. For posterior annulus stress: the peak stress in TELD model was 2.04MPa, 2.08MPa, 1.44MPa, 0.99MPa, 0.41MPa, and 0.29MPa respectively under flexion, extension, left bending, right bending, left rotation, right rotation conditions; In TELD+SDSS model, it was 0.54MPa, 0.23MPa, 0.72MPa, 0.7MPa, 0.21MPa, and 0.18MPa. The peak stress at posterior annulus in TELD increased by 10-99% in flexion, extension, and lateral bending, while in TELD+SDSS model it reduced by 20-63% in all directions. For annulus shear stress: in TELD model, it was 0.4MPa, 0.32MPa, and 0.2MPa in extension and left and right bending, which increased by 17%, 76%, and 85%, while in TELD+SDSS model, it reduced by 12-98% in all directions. Conclusions: TELD+SDSS retains certain lumbar motion, affecting lumbar stability less compared to TELD, and provides a low-pressure stress environment.