腰椎棘突间Coflex动态固定的三维有限元分析

目的比较腰椎棘突间Coflex动态固定、单纯减压及坚强固定术后各节段活动度及椎间盘应力,分析Coflex系统的生物力学特点。方法运用三维有限元方法建立正常成人腰骶椎模型,及开窗减压、棘突间Coflex动态固定、椎弓根钉棒坚强固定模型,约束骶骨及髂腰韧带,施加500N预载荷和7.5Nm运动附加力,测量腰椎节段各方向的活动度及椎间盘应力。结果 Coflex固定模型活动度和椎间盘应力分别为,植入节段(L4/5):前屈3.15°,2.571MPa,后伸1.21°,2.109MPa;上位邻近节段(L3/)4:前屈3.46°,2.001MPa,后伸2.75°,3.149Mpa;下位邻近节段(L5S1):前屈3.22°,2.681MPa,后伸2.46°,3.812MP。结论 Coflex动态固定可保留植入节段部分活动度并减低其椎间盘应力,而对相邻节段活动度及椎间盘应力无明显影响。

Finite element analysis of lumbar interspinous dynamic fixation by Coflex

Objective　To perform the biomechanical evaluation of Coflex system by comparing the ranges of intervertebral motion and intervertebral disc stress among dynamic fixation adopting Coflex, decompression by fenestration or pedicle screw system respectively.　Methods　Three-dimensional finite element model of normal adult's lumbosacral vertebrae was established, as well the models of decompression by fenestration, dynamic fixation with Coflex and fixation with pedicle screw system separately. 500N preload and 7.5 Nm bending moment were performed on the models, while, the range of motion (ROM) and intervertebral disc stress (IDS) were measured.　Results　The ROM and IDS of Coflex model were recorded respectively as follows: on the surgical segment (L4/5), flexion (FLE) 3.15, 2.571MPa and extension(EXT) 1.21°, 2.109MPa. On the upper adjacent segment (L3/4): FLE 3.46°, 2.001MPa and EXT 2.75°,3.149MPa. On the lower adjacent segment (L5S1), FLE 3.22°, 2.681MPa and EXT 2.46°, 3.812 MP respectively.　Conclusions　Dynamic fixation with Coflex could keep some ROM and reduce IDS on the surgical segment, and has no significant effects on ROM and IDS of the adjacent segments.