皮质骨轨迹螺钉技术应用于骨质疏松患者腰椎固定的有限元分析

A finite-element analysis on biomechanical performance of lumbar cortical bone trajectory versus traditional trajectory screw fixation in osteoporosis

[目的]通过有限元方法对传统轨迹椎弓根(traditional trajectory,TT)螺钉与椎弓根皮质骨轨迹(cortical bone trajectory,CBT)螺钉固定在骨质疏松椎体上的应用进行生物力学分析。[方法]通过1名骨质疏松症患者(骨密度T值<-0.25 SD)建立L2、3椎体功能单元骨质疏松有限元模型,模拟传统椎弓根螺钉和皮质骨轨迹螺钉两种固定方式进行固定,分别在静载、前屈、后伸、侧屈、旋转五种状态下加载并测量钉道周围骨质的CT值,比较各部件最大应力值、内固定装置稳定性(以椎间活动度表示)及钉道周围骨质CT值的差异。[结果]CBT组在各个状态下椎骨和内固定装置的最大应力值均大于TT组,椎间活动度在静载、前屈、后伸、旋转四个状态下CBT组均小于TT组,侧屈时CBT组大于TT组;CBT组钉道周围骨质的CT值为(192.20±34.85)Hu,TT组为(118.00±15.90)Hu,组间对比差异有统计学意义(P=0.002)。[结论]CBT组屈伸、旋转状态下稳定性大于TT组,侧屈时CBT组稍小于TT组;CBT组钉道周围骨质CT值大于TT组。CBT螺钉技术是骨质疏松患者腰椎内固定的一种优选方式。

[Objective] To evaluate the biomechanical performance of cortical bone trajectory screw versus traditional trajectory screw in osteoporosis by the finite element（FE） assessment. [Methods] A three-dimensional, anatomically detailed finite element models of the L2~L3 functional spinal unit was reconstructed from an osteoporotic patient with T value of bone mineral density less than-2.5 SD, and pedicle screws were placed using the cortical bone trajectory（CBT） and the traditional trajectory（TT）. Firstly, biomechanical performance of the finite element models within different constructs was examined by simulating the motions of flexion, extension, lateral bending and axial rotation. Sencondly, the CT value of bone in bonescrew interface ofthe CBT screw and the TT screw were measured, the two models in terms of maximum stress value, spinal stability（expressed by range of motion, ROM） were compared. [Results] The maximum stress value of internal fixation device of the CBT group was greater than the TT group. The ROMs of the CBT group were less than those of the TT group in static loading,flexion, extension, and axial rotation, whereas ROM of the CBT was greater than that of the TT group in lateral flexion. The CT value of the bone proved（192.20±34.85） Hu in the CBT group, while（118.00±15.90） Hu in the TT group, associated with a statisticaldifferences between the two groups（P=0.002）. [Conclusions] The CBT group demonstrates superior fixation strength to the TT group in flexion and rotation, while the inferiorstrength to the TT group in lateral flexion. The CT value of CBT group is greater than TT group. Therefore, The CBT screw technique is recommended as a choice for lumbar spine fixation in osteoporosis patients.