胸腰椎骨折椎弓根钉置入内固定在不同运动状态的有限元分析

Finite element analysis of pedicle screw fixation for thoracolumbar fracture in different motion states

目的对胸腰椎骨折椎弓根钉置入内固定后不同运动状态下的活动度及应力进行有限元分析。方法回顾性分析2018年2—12月甘肃省中医院收治的11例典型胸腰椎骨折患者的病例资料,采用螺旋CT对脊柱T8~L4节段进行扫描并建立有限元模型,随后进行椎弓根钉置入内固定,按内固定方式的不同分为上伤组(后路上位伤椎6钉2棒固定)、右伤组(后路单右侧伤椎5钉2棒固定)、跨伤组(后路横跨伤椎4钉2棒固定)、双伤4钉组(后路双侧伤椎4钉2棒固定)、双伤6钉组(后路双侧伤椎6钉2棒固定)共5组。分析不同内固定方式(4钉固定、6钉固定)及运动状态(前屈、后伸、左右轴向旋转、左右侧向弯曲)下的活动度和应力情况。结果双伤6钉组在不同运动状态下的活动度均最小,具有最好的生物力学稳定度;其次是右伤组;而双伤4钉组在不同运动状态下的活动度均最大,其生物力学稳定度最差。5组内固定模型在不同运动状态时的上位螺钉应力比较差异有显著性(P<0.05),其中前屈状态时应力最大,具有最好的生物力学耐受度;其次为左轴向旋转及右轴向旋转;而右侧向弯曲时应力最小,其生物力学耐受度最差。5组内固定模型在不同运动状态时的上下位螺钉应力比差异均有显著性(P<0.05),其中后伸状态时上下位螺钉应力比最大,其次为右侧向弯曲及右轴向旋转,而左侧向弯曲时上下位螺钉应力比最小。结论在胸腰椎骨折椎弓根钉置入内固定中采用有限元分析,可充分了解各内固定方法在不同运动状态时的活动度及应力状态,有利于确定合适的内固定方案,具有较高的临床价值。

Objective To study pedicle screw internal fixation for thoracolumbar fracture,and to analyze the mobility and stress of each internal fixation model in different motion states by finite element method.Method The data of thoracolumbar fracture patients treated in Gansu Provincial Hospital of Traditional Chinese Medicine from February to December in 2018 were retrospectively analyzed.Spiral CT scanner was used to scan the T8-L4 segments of the spine,and a finite element model was established to simulate the posterior internal fixation operation.The mobility and stress of each internal fixation mode in different motion states(4 nails fixed,6 nails fixed)were analyzed.Result(1)The activity of the double injury group with 6 nails was the smallest in different motion states,so it had the best biomechanical stability;the second was the right injury group;and the double injury group with 4 nails had the greatest activity in different motion states,so it had the worst biomechanical stability.(2)There was a significant difference in the stress of the upper screw in five groups of internal fixation models in different motion states(P<0.05).In the forward bending state,the stress is the largest,so it has the best biomechanical tolerance;secondly,the left and right axis rotation;and the right-side bending has the lowest stress,so it has the worst biomechanical tolerance.(3)The stress ratios of upper and lower screw of five groups of internal fixation models in different motion states were significantly different,with statistical significance(P<0.05).The stress ratio of upper screw and lower screw is the largest in the backward extension state,followed by right lateral bending and right axial rotation,while the stress ratio of upper screw and lower screw is the smallest in the left lateral bending state.Conclusion Finite element analysis in pedicle screw internal fixation for thoracolumbar fracture can fully study the activity and stress state of each internal fixation method in different motion states,which is helpful to determine the suitable internal fixation scheme for clinical use.