内固定系统中在螺钉受拔出负载时腰椎的受力分析

通过有限元方法分析比较传统轨迹椎弓根(traditional trajectory,TT)螺钉与皮质骨轨迹椎弓根(cortical bone trajecto-ry,CBT)螺钉固定技术在腰椎椎体应用下的生物力学性能.依据提取的骨质疏松症患者电子计算机断层扫描图(computed tomography,CT)样本建立L1-L5全椎体功能单元骨质疏松人体有限元模型,模拟TT螺钉和CBT螺钉两种固定方式置钉后,以实际值为依据在加载一定旋转拔出力状态下测量比较两种方式钉道周围骨质的应力分布、最大应力值及分析其差异.结果 表明:相同固定方式下CBT组在相同载荷状态中椎骨的应力分布差异明显.不同的钉道带来不同骨密度,直接影响了内固定螺钉在腰椎骨内的力学性能.不同的钉植入角度也对钉的应力分布以及最大应力值产生影响.L1-L5椎体形状不同,大小不同,其力学性能,表现也不相同.得出CBT螺钉技术是骨质疏松患者腰椎内固定方案中的一种优选方式.但针对5段腰椎需要对不同的椎骨采取不同的治疗方案.

Mechanical analysis of lumbar vertebrae in internal fixation under the pulling out load of screw

Objective to compare the biomechanical properties of traditional trajectories (TT) screws and cortical bone trajectories (CBT) screws fixation in lumbar vertebrae by finite element method. The samples were extracted from the computed tomography (CT) data of patients with osteoporosis to establish the finite element model of L1-L5 whole vertebral functional unit osteoporosis. After simulating the two fixation methods of TT screw and CBT screw, the model measured and compared the stress distribution, the maximum stress value and the difference between the two methods. The results show that under the same fixation mode, the stress distribution of CBT group is significantly different in the same load state. Different screw path leads to different bone mineral density, which directly affects the mechanical properties of internal fixation screw in lumbar spine. Different implant angle also affects the stress distribution and the maximum stress value. The mechanical properties and performance of L1-L5 vertebral bodies are different with different shapes and sizes. So, CBT screw technique is an optimal method for lumbar internal fixation in patients with osteoporosis. However, for the five segments of lumbar, we need to take different treatment for different vertebrae.