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。方法由新疆医科大学解剖实验室提供四具骨质疏松标本（两男两女，平均年龄71岁，骨密度T值<-0.25 SD）。L4椎体经CT扫描后导入Mimics中建立三维模型，在椎体两侧分别模拟置入椎弓根螺钉（Pedicle Screw，PS）（直径6.0mm，长45mm）和MCBT螺钉（直径4.5mm，长40mm），并通过Abaqus进行有限元分析。比较螺钉在两种钉道上、下，左，右四种工况下的载荷位移比和螺钉的抗拔出力，评价在骨质疏松条件下螺钉和椎体之间的稳定性。结果PS抗拔出力(1431.75±35.51)N，MCBT螺钉抗拔出力(1620±81.33)N,提高13.1%（t=-4.242，p=0.005）。MCBT螺钉稳定性相比于PS：在上，下，左工况下载荷位移比分别提高57.2%，32.4%，31.6%（t=-4.948，p=0.014；t=-4.436,p=0.004；t=-2.780，p=0.032），右工况下载荷位移比虽高于PS但不具有统计学差异（t=-1.042，p=0.337）。MCBT组椎体轴向旋转和侧屈载荷位移比明显高于TT组（t=-5.378，p=0.031、t=-3.039，p=0.023），前屈载荷位移比低于PS组（t=0.094，p=0.929），后伸载荷位移比虽高于TT组，但不具有统计学差异（t=-1.051，p=0.334）。结论本实验说明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，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。
Objective Analyze the mechanical performance of TT and MCBT on osteoporotic vertebrae through finite element analysis.Methods Osteoporosis specimens provided by the Anatomy Laboratory of Xinjiang Medical University (T value of bone density <-0.25 SD). The L4 vertebral body was scanned by CT and imported into Mimics to establish a three-dimensional model，and finite element analysis was performed by Abaqus.PS and MCBT were used on both sides of the lumbar spine to simulate the placement of screws. The pull-out strength and the load-displacement ratio under the four working conditions of the upper, down, left and right of the two screws were analyzed and compared to evaluate the stability of the screw . And the load-displacement ratio of the vertebral body in the four working conditions of flexion, extension, axial rotation, and lateral flexion to evaluate the stability of the vertebral body. Results ①Pull-out strength: PS pull-out strength is (1431.75±35.51)N, and MCBT pull-out strength is (1620±81.33)N, which is increased by about 13.1% (t=-4.242, p=0.005).②Screw stability: The load-displacement ratio of the MCBT screw is significantly higher than that of the PS under the three working conditions (upper, down, left), which is increased by about 57.2%, 32.4%, and 31.6%.Under the right working condition, there was no statistical difference between the MCBT and PS (t=-1.042，p=0.337).③Vertebral body stability: The MCBT construct had superior resistance to lateral bending (t=-3.039,p=0.023) and axial rotation (t=-5.378,p=0.031) and inferior resistance to flexion (t=0.094，p=0.929) and extension (t=-1.051,p=0.334). Conclusions This experiment shows that comparing with the TT , the MCBT has greater pullout resistance and screw stability, and the vertebral body stability of the MCBT is better than that of the TT in axial rotation and lateral flexion,which demonstrates the superiority of MCBT under osteoporotic conditions and lays the foundation for the clinical application of MCBT .