新型腰椎侧前逆向椎弓根钉固定的有限元分析△

A finite element analysis on a novel lumbar reverse anterolateral pedicle screw fixation

摘要:

［目的］ 应用有限元分析评估新型腰椎侧前逆向椎弓根钉固定的生物力学特性。［方法］ 建立正常人体下腰椎 （L₃~S₁） 有限元模型并验证其有效性，而后建立 L_4/5椎间盘切除笼架置入后 5 种内固定模型：（1） 侧方椎体螺钉固定 （lateral vertebral screw, LVS）；（2） 单侧椎弓根螺钉固定 （unilateral pedicle screw, UPS）；（3） 双侧椎弓根螺钉固定 （bilateral pedicle screw, BPS）；（4） 侧前方逆向椎弓根螺钉钉棒系统 （2 钉）（anterolateral pedicle screw-rod, ALPSR）；（5） 侧前方逆向椎弓根螺钉钉板系统 （4 钉）（anterolateral pedicle screw-plate, ALPSP）。L3椎体的上表面施加 400 N 的轴向预载荷和 7.5 N · m 的扭转力矩，模拟腰椎前屈、后伸、左侧屈、右侧屈、左旋转和右旋转的活动度，以及上终板和笼架的峰值 Von Mises 应力。［结果］本研究建立了健康人的下腰椎有限元模型，并验证其有效性。与完整组比较，ALPSP 模型在前屈及左右侧屈控制最佳；而 BPS 模型在后伸和左右旋转控制最佳，ALPSP 模型次之。前屈及左右侧屈的条件下，ALPSP 上终板压力峰值最小。后伸及左右旋转条件下，BPS 上终板压力峰值最小，ALPSP 次之。笼架应力也呈现相应的变化趋势，ALPSP 与 BPS 模型相当。［结论］ALPSP 能够提供良好的生物力学稳定性，具有 BPS 相似的生物力学性能，明显优于 LVS 和 UPS。

Abstract:

[Objective] To evaluate the biomechanical properties of a novel lumbar reverse anterolateral pedicle screw fixation by the fi- nite element analysis. [Methods] A finite element model of normal human lower lumbar spine (L₃~S₁) was established with its effectiveness verified. Subsequently, five internal fixation models were established after L_4/5 discectomy and cage placement, including (1) lateral verte- bral screw fixation (LVS) ; (2) unilateral pedicle screw (UPS) ; (3) bilateral pedicle screw (BPS) ; (4) anterolateral pedicle screw-rod (ALP- SR) and (5) anterolateral pedicle screw-plate (ALPSP) . As axial preload of 400 N with a torsional torque of 7.5 N · m were applied to the upper surface of the L3 vertebral body in conditions of lumbar flexion, extension, left bending, right bending, left rotation and right rotation, the range of motion (ROM) , Von Mises stresses on the upper endplate and cage were measured. [Results] The finite element model of the lower lumbar spine (L₃~S₁) was established and verified successfully. Compared with the intact model, the ALPSP model got the best restric- tion of forward flexion and lateral bending, while the BPS model got the best restriction of backward extension and lateral rotation, followed by the ALPSP model. The pressure peak Von Mises stress on the upper endplate in the ALPSP model was the lowest under forward flexion and left and right bending, whereas which was the lowest in BPS under backward extension and lateral rotation, followed by the ALPSP mod- el. The stress on the cage also presented a corresponding trend, with the ALPSP model corresponding to the BPS model. [Conclusion] The novel lumbar reverse anterolateral pedicle screw fixation, ALPSP, provides good biomechanical stability and has similar biomechanical properties to BPS, which is significantly superior to LVS and UPS.