三维有限元法分析腰椎不同尺寸关节突成形后相关节段的生物力学特征

Three-dimensional finite element analysis of the biomechanics of the posterior segment of lumbar facet arthroplasty with different sizes

背景:腰椎经皮内镜在全国乃至全世界范围内开展的如火如荼,经椎间孔的侧入路是目前腰椎经皮内镜技术最常用的入路之一,但是对于其术后造成相关节段的生物力学影响鲜有报道。目的:通过三维有限元法模拟对比不同尺寸(7.5,10,15 mm)的关节突成形并探究其对腰椎相关节段生物力学的影响。方法:建立L_(3)-L_(5)三维有限元模型并验证其有效性。模拟L_(4/5)腰椎经皮内镜手术中的关节突成形术,以临床上穿刺针与水平面及冠状面的夹角,以L_(5)上关节突基底部作为穿刺靶点,根据穿刺路径分别做直径为7.5,10,15 mm的环锯环切成形,从而获得L_(5)上关节突基底部不同直径成形的三维有限元模型。通过对正常模型、7.5,10,15 mm直径成形有限元模型在6个方向上施加载荷,计算各模型在前屈、后伸、左屈、右屈、左旋、右旋6种状态下操作节段(L_(4/5))及邻近节段(L_(3/4))椎间盘Von Mises应力极值和相关节段的活动度情况,并进行相关对比研究,以明确不同尺寸的关节突成形对腰椎生物力学稳定性的影响。结果与结论:①对操作节段(L_(4/5))的影响:L_(5)上关节突直径15 mm的成形在前屈、后伸、左右侧弯、左右旋转6个工况下的L_(4/5)椎间盘最大应力较直径7.5,10 mm的关节突成形明显增大,其中以前屈、左转、右旋状态下较为明显,分别较正常状态增加110%,95%,97%;L_(5)上关节突直径15 mm的成形在6个工况下的L_(4/5)节段活动度均大于直径7.5,10 mm的关节突成形,分别较正常模型增加8.6%,21.8%,8.9%,17.6%,35.7%,21.4%;②对邻近节段(L_(3/4))的影响:L5上关节突直径15 mm的成形在6个工况下的邻近节段L_(3/4)椎间盘最大应力较直径7.5,10 mm的关节突成形均有所增大,其中以前屈活动最为明显,此状态下L_(3/4)椎间盘最大应力较正常模型增加29.3%;不同尺寸(7.5,10,15 mm)的关节突成形在前屈、后伸、左右侧弯、左右旋转6个工况下邻近节段L_(3/4)的活动度与正常模型相比均增加不明显;③提示直径15 mm较直径7.5,10 mm的关节突成形而言,对操作节段的力学影响明显增大,甚至对邻近节段椎间盘应力产生相应的影响。

BACKGROUND:Percutaneous lumbar endoscopy is in full swing in China and even in the world.Transforaminal lateral approach is one of the most commonly used approaches in percutaneous lumbar endoscopic surgery,but the biomechanical effects of the relevant segments are rarely reported.OBJECTIVE:To investigate the biomechanical effects of different sizes(7.5 mm,10 mm,15 mm)of facet arthroplasty on related segments of lumbar spine by three-dimensional finite element simulation.METHODS:A three-dimensional finite element model of L_(3)-L_(5) was established to verify its effectiveness.The arthroplasty of L_(4/5) lumbar vertebrae in percutaneous endoscopic surgery was simulated.The angle between the needle and the horizontal plane and the coronal plane was taken as the puncture target,and the base of L_(5) superior articular process was taken as the puncture target.According to the puncture path,the circular saw with the diameter of 7.5 mm,10 mm and 15 mm was made respectively,so as to obtain three-dimensional finite element model formed at different diameters of the base of L_(5) superior articular process.The normal model,7.5 mm,10 mm and 15 mm diameter forming finite element models were loaded in six directions to calculate the von Mises stress extremum and range of motion of the operating segments(L_(4/5))and adjacent segments(L_(3/4))of the three models under six states of flexion,extension,left flexion,right flexion,left rotation and right rotation.Relevant comparative studies were conducted to determine the effect of different sizes of facet arthroplasty on the biomechanical stability of lumbar spine.RESULTS AND CONCLUSION:(1)The effect on the operating segment(L_(4/5)):The maximum stress of L_(4/5) disc with 15 mm diameter of L_(5) superior articular process was significantly increased under six working conditions of flexion,extension,left-right lateral bending and left-right rotation compared with that of 7.5 mm and 10 mm diameter of L_(4/5).The maximum stress of L_(4/5) disc with 15 mm diameter of L_(5) superior articular process was increased by 110%,95% and 97% respectively.The range of motion of L_(4/5) segment of L_(5) with 15 mm diameter was greater than that of 7.5 mm and 10 mm diameter,which increased by 8.6%,21.8%,8.9%,17.6%,35.7% and 21.4% respectively.(2)Effect on adjacent segment(L_(3/4)):The maximum stress of adjacent segment L_(3/4) disc with 15 mm diameter of L_(5) superior articular process increased compared with 7.5 mm and 10 mm diameter of L_(5) superior articular process in six working conditions,in which flexion was the most obvious,and the maximum stress of L_(3/4) disc increased by 29.3% compared with normal model.The range of motion of adjacent segment L_(3/4) of different sizes(7.5 mm,10 mm,15 mm)of zygapoplasty in flexion,extension,leftright lateral bending and left-right rotation was not significantly increased compared with normal model.(3)It is concluded that compared with 7.5 mm and 10 mm in diameter,15 mm in diameter has a greater mechanical effect on the operating segment,and even has a corresponding effect on the stress of adjacent segments.