不同固定方案的腰椎后路椎间融合术生物力学有限元分析

Biomechanical finite element analysis of lumbar posterior interbody fusion for different fixation schemes

腰椎后路椎间融合术结合内固定系统已被广泛用于治疗腰椎滑脱等疾病。不同的内固定方案会使内固定系统和腰椎产生不同的力学响应,其结果会影响到内固定方案的选择。针对腰椎L5-S1骶骨节段轻度滑脱完全复位状态,在1例健康成年人腰椎模型的基础上,设计了3种不同节段的内固定手术方案:A组L5-S1融合固定、B组L4-L5-S1融合固定、C组L5-S1-S2融合固定,并建立相应的有限元模型。固定骶髂关节的耳状面,在L1椎体上表面施加垂直向下400 N的载荷和不同方向的7.5 N·m力矩,模拟脊柱前屈、后伸、侧弯和旋转等生理活动,比较不同方案模型中固定节段的钉棒应力情况、相邻近节段的椎间盘应力情况和各节段活动度的差异。结果表明,相比于A组模型,B组和C组模型的椎弓根螺钉和连接棒最大应力值较大;B组和C组椎间盘的应力最大值的集中区域明显大于A组;A组、B组和C组模型的腰椎活动总量较完整模型均有所减少。实验结果表明,采用A组L5-S1融合固定的方案可以降低内固定系统断裂的发生率,减少邻近节段椎间盘退变的发生率,在完成复位的情况下仍然可以保持一定的腰椎活动度,且A组方案的手术时间短、术中出血量少,是一种更优的内固定方案。

Posterior lumbar interbody fusion combined with internal fixation has been widely used to treat lumbar spondylolisthesis and other diseases.However,different internal fixation schemes cause different mechanical responses of the internal fixation system and the lumbar region itself,which can affect the selection of internal fixation schemes.In this study,an intact finite element model of the L1-S1 was reconstructed by using CT data for a healthy adult.Three different internal fixation surgical schemes were designed,namely L5-S1 fusion fixation(group A),L4-L5-S1 fusion fixation(group B)and L5-S1-S2 fusion fixation(group C).Their corresponding finite element models were established.The auricular surface of the sacroiliac joint was fixed,and a vertical downward load of 400 N and a moment of 7.5 N·m in different directions were applied to the upper surface of the L1 vertebral body.By simulating physiological activities such as flexion,extension,lateral bending and rotation of the spine,the stress of nails and rods in the fixed segment,the stress of intervertebral discs in adjacent segments and the difference in mobility of each segment were compared for the different groups.The results show that the maximum stress of the pedicle screw and the connecting rod for groups B and C is larger than for group A.The maximum stress concentration areas of the intervertebral discs in groups B and C were significantly larger than that for group A.The total amount of lumbar motion in groups A,B and C was lower than that in the complete model.The results show that the L5-S1 fusion fixation(group A)can reduce the incidence of internal fixation system fracture and the incidence of intervertebral disc degeneration in adjacent segments whilst still maintaining a certain degree of lumbar mobility after the reduction.This study shows that L5-S1 fusion fixation(group A)is a better internal fixation scheme with shorter operation time and less intraoperative bleeding.