Ⅱa型腰骶部移行椎易发相邻节段椎间盘突出症的机制

Mechanism ofⅡa lumbosacral transitional vertebrae resulting in adjacent segmental disc herniation

目的研究Ⅱa型腰骶部移行椎(LSTV)移行节段及相邻节段生理载荷下三维运动特点,探讨Ⅱa型LSTV导致相邻节段发生椎间盘突出的生物力学机制。方法选择在天津市第一中心医院就诊的L_(4)/L_(5)节段椎间盘突出症伴Ⅱa型LSTV患者9例(移行椎组)作为研究对象,同时招募健康志愿者9名作为对照(对照组)。受试者均接受腰椎薄层CT扫描,将扫描数据导入Rhinoceros软件进行L_(3)~S_(1)三维建模,将模型与双X线透视影像系统捕获的不同活动体位下的腰椎双斜位X线透视图像进行匹配,重现生理载荷下腰椎椎体间三维运动状态。利用三维坐标系计算生理载荷下LSTV及相邻节段的三维运动数据。结果在移行节段(L_(5)/S_(1)),移行椎组左右侧曲时沿冠状轴的位移[(0.90±1.32)mm]、沿矢状轴和垂直轴的旋转角度(1.77°±1.19°、1.42°±1.2°)均明显小于对照组[(2.99±2.46)mm、3.90°±2.59°、5.08°±4.16°],差异有统计学意义(P<0.05)。在相邻节段(L_(4)/L_(5)),移行椎组前屈-后伸时沿冠状轴的旋转角度(5.22°±2.45°)大于对照组(2.22°±3.05°),左右旋转时沿冠状轴位移[(1.19±1.45)mm]小于对照组[(3.00±1.50)mm],左右侧曲时沿冠状轴位移[(1.75±1.28)mm]小于对照组[(3.19±1.26)mm],差异均有统计学意义(P<0.05)。在非邻近节段(L_(3)/L_(4)),2组三维运动数据差异无统计学意义(P>0.05)。结论伴LSTV者由于一侧形成假关节限制了腰椎的正常活动,而对相邻节段的运动产生影响,表现为屈伸活动时相邻节段沿冠状轴的运动增加,这可在生物力学机制上初步解释伴Ⅱa型LSTV者其相邻节段椎间盘易突出的临床现象。

Objective To study the three-dimensional motion characteristics of typeⅡa lumbosacral transitional vertebra(LSTV)and its adjacent segments under physiological load,and to explore the biomechanical mechanism of typeⅡa LSTV leading to adjacent segments’intervertebral disc herniation.Methods Nine patients with L_(4)/L_(5) disc herniation and typeⅡa LSTV treated in Tianjin First Central Hospital were selected as the research object(transitional vertebra group),and 9 healthy volunteers were recruited as the control group.All the subjects received thin-layer CT scanning,and the scanning data were imported into Rhinoceros software for L_(3)-S_(1) three-dimensional modeling,the model was matched with different active position images captured by dual fluoroscopic imaging system,and reproducing the three-dimensional motion state of lumbar vertebra under physiological load.The three-dimensional motion data of LSTV and the adjacent segments under physiological load were calculated by three-dimensional coordinate system.Results In the transitional segment(L_(5)/S_(1)),the displacement of the left-right bending along the coronal axis([0.90±1.32]mm),the rotation angles of the left-right bending along the sagittal axis(1.77°±1.19°and 1.42°±1.2°)in the transitional vertebra group were significantly lower than those in the control group([2.99±2.46]mm,3.90±2.59°and 5.08°±4.16°),and the differences were statistically significant(P<0.05).In the adjacent segment(L4/L5),the rotation angle of flexion-extension along the coronal axis(5.22°±2.45°)was higher than that in the control group(2.22°±3.05°),and the displacement of left-right rotation along the coronal axis[(1.19±1.45)mm]was significantly lower than that in the control group([3.00±1.50]mm),and the displacement of left-right bending along the coronal axis[(1.75±1.28)mm]was significantly lower than that in the control group([3.19±1.26]mm),and the differences were statistically significant(P<0.05).In non-adjacent segments(L_(3)/L_(4)),there was no significant difference in three-dimensional motion data between the 2 groups(P>0.05).Conclusions In the patients with LSTV,the normal activity of lumbar spine is limited due to the formation of pseudojoints on one side,which affects the movement of adjacent segments.It is shown that the movement of adjacent segments along the coronal axis increases during flexion and extension.This can preliminarily explain the clinical phenomenon of adjacent segment disc herniation in patients with typeⅡa LSTV in terms of biomechanical mechanism.