有限元分析腰椎传统椎弓根钉道和改良皮质骨钉道的生物力学性能

目的 通过有限元分析传统椎弓根钉道（traditional trajectory, TT）和改良皮质骨钉道（modified cortical bone trajectory, MCBT）在骨质疏松椎体上的力学性能。方法 建立L4椎体三维模型，在椎体两侧分别模拟置入椎弓根螺钉（pedicle screw，PS）（直径6.0 mm，长45 mm）和MCBT螺钉（直径4.5 mm，长40 mm）。比较螺钉在两种钉道上、下、左、右4种工况下载荷位移比和螺钉抗拔出力，评价在骨质疏松条件下螺钉和椎体之间的稳定性。结果 MCBT螺钉抗拔出力比PS提高13.1%。MCBT螺钉在上、下、左工况下载荷位移比相比PS分别提高57.1%、32.3%、31.6%，MCBT螺钉在右工况下载荷位移比虽高于PS，但不具有统计学差异。在轴向旋转和侧屈工况下，MCBT组椎体载荷位移比明显高于TT组；在前屈工况下，MCBT组椎体载荷位移比低于TT组；在后伸工况下，MCBT组椎体载荷位移比虽高于TT组，但不具有统计学差异。结论 MCBT在抗拔出力、螺钉稳定性、椎体轴向旋转和侧屈的稳定性优于TT，但在椎体前屈和后伸稳定性弱于TT。研究结果论证了MCBT在骨质疏松条件下的优越性，为MCBT的临床应用奠定前期基础。

Finite Element Analysis on Biomechanical Properties of Traditional Trajectory and Modified Cortical Bone Trajectory

Objective To study mechanical properties of traditional trajectory (TT) and modified cortical bone trajectory (MCBT) on osteoporotic vertebrae through finite element analysis. Methods The three-dimensional model of L4 segment was established, and pedicle screw (PS) (diameter 6.0 mm, length 45 mm) and MCBT screw (diameter 4.5 mm, length 40 mm) were placed on both sides of the lumbar spine. The pull-out strength and the load-displacement ratio of screws in two different screw trajectories under up, down, left, right working conditions were analyzed, and the stability between the screw and vertebral body under osteoporotic conditions was evaluated. Results Compared with TT, the pull-out strength of MCBT screw was increased by 13.1%. Compared with PS, the load-displacement ratio of MCBT screw under up, down and left working conditions was increased by 57.2%, 32.4%, and 31.6%. Under right working condition, although the load-displacement ratio of MCBT screw was higher than that of PS, no statistical difference was found. The load-displacement ratio of vertebral body in MCBT group under lateral bending and axial rotation was significantly higher than that in TT group. The load-displacement ratio of vertebral body in MCBT group under flexion was lower than that in TT group. Although the load-displacement ratio of vertebral body in MCBT group under extension was higher that that in TT group, no statistical difference was found. Conclusions MCBT is superior to TT in pull-out strength, screw stability and vertebral body stability under lateral bending and axial rotation, but its vertebral body stability under flexion and extension was weaker than that of TT. The research findings demonstrate the superiority of MCBT under osteoporotic conditions and lay the foundation for clinical application of MCBT.