腰椎椎弓根在体相对运动轨迹的研究

Range of motion of lumbar pedicle screw entrance point under physiological weight bearing

目的 研究正常受试者在生理载荷下活动时腰椎椎弓根螺钉入钉点的运动范围.方法 招募45～60岁健康志愿者11名,采用双X线透视影像系统（dual fluoroscopic imaging system,DFIS）和MRI相结合技术,在计算机辅助下,从受试者腰椎MRI获取每一节段腰椎三维重建模型,匹配到由DFIS捕获的不同活动体位时腰椎双斜位X线透视图像上,真实重现生理载荷下腰椎椎体间三维运动状态.通过测定模拟椎弓根螺钉入钉点的三维坐标系变化,最终获得生理载荷下腰椎相邻椎弓根在体运动学数据.结果 从仰卧到站立位,腰椎椎弓根入钉点的运动范围：位移主要沿矢状轴和垂直轴移动,其中L2,3位移最大,在矢状轴为（2.44±1.43）mm,在垂直轴为（2.35±1.52）mm;旋转主要围绕冠状轴.腰椎屈伸位椎弓根入钉点的运动范围：在位移方面,L2～L4节段主要沿矢状轴和垂直轴移动,L4,5节段在冠状轴和垂直轴上的移动度相似;旋转方面,L2～L4节段主要绕冠状轴旋转,L4,5节段主要绕冠状轴和垂直轴旋转.腰椎左、右侧屈位椎弓根入钉点的运动范围：在位移方面,L2,3和L3,4主要沿冠状轴位移,L4,5在三个轴的位移近似;在旋转方面,L,3主要绕矢状轴旋转,L3,4主要绕矢状轴和垂直轴旋转,L4,5绕三个轴的旋转度近似.腰椎左、右旋转位椎弓根入钉点的运动范围：在位移方面,L2,3、L3,4和L4,5节段在三个轴方向的位移近似;在旋转方面,L2,3、L3,4和L4,5三个节段主要绕垂直轴旋转.结论 不同节段、不同体位时腰椎椎弓根螺钉入钉点的运动范围也不同,其中L4,5节段的特点是以部分旋转来代替位移.

Objective To measure the range of motion （ROM） of the lumbar pedicle screw entrance point （LPSEP） in vivo during unrestricted motion under physiological weight bearing. Methods Eleven healthy volunteers aged 45-60 years underwent MRI scans in a supine position. Three-dimensional （3D） models of L2_5 were constructed. Next, each volunteer was asked to stand and was positioned in the following sequence： standing, 45~ flexion, maximal extension, maximal left-right twisting, while two orthogonal fluoroscopic images were taken simultaneously at each position. The MRI models were matched to the osseous out- lines of the images from the two orthogonal views to determine the position of the vertebrae in 3D at each position. Coordinate systems were established to study the ROM of the LPSEP. Results The predominant translations were along anteroposterior and craniocaudal axis from supine to standing position （average, 2.44 mm and 2.35 mm）. Rotation of the LPSEP occurred mainly around the mediolateral axis（average, 3,91°）. During flexion-extension movements of the trunk, the predominant translation were along anteroposterior and craniocaudal axis and rotation were around mediolateral axis. During lateral bending and twisting, ROM of LPSEP did not rotate or translate in one dominant direction. Instead, the resulting motion represented a combination of rotation and translation in different directions. There was no significantly difference in translation and rotation between the three axis in L4.ssegment （P〉0.05）. Conclusion The kinematic behaviors of the LPSEP of the upper lumbar spine （L2,3 and L3, 4） are similar which are different from that of the lower lumbar spine （L4, 5）.