腰椎椎体间旋转中心的在体研究

In-vivo study of rotational characteristic of human lumbar segments

目的测定生理载荷下正中矢状面上腰椎椎体间屈伸运动中心及横断面上腰椎椎体间左右旋转中心，为人工腰椎间盘假体设计的改进提供参考依据。方法招募40-450岁健康志愿者10名，采用双X线透视影像系统（dual fluoroscopic imaging system，DFIS）和MR检查相结合技术，在计算机软件辅助下，从受试者腰椎MRI获取每一节段腰椎三维重建模型，匹配到DFIS捕获的不同活动体位时腰椎双斜位X线透视图像上，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出生理载荷下正中矢状面上腰椎椎体间屈伸运动中心点及横断面上腰椎椎体间左右旋转中心点。结果在矢状面上L2，3 和L3，4的椎体中心点、骨性椎管中心点和棘突尖部运动范围分别为（0．3±0．3）mm、（0．6±0．3）mm；（2．5±1．7）mm、（2．3±1．1）mm；（7．5±3．2）mm、（7.3±3．6）mm。在横断面上L2，3和L2，4的椎体中心点、骨性椎管中心点和棘突尖部运动范围分别为（0．7±0．4）mm、（1．0±0．9）mm；（1．1±1．0）mm、（1．4±1．3）mm；（1．6±0．9）mm、（2．3±1．6）mm。经过线性拟合计算获得正中矢状面上腰椎椎体间（L2,3L3，4）屈伸运动中心位于椎体中轴后方5mm处，横断面上腰椎椎体间左右旋转中心位于椎体前方35．1mm（L2，3）和32．2mm（L3,4）。结论正常人体在生理载荷条件下，正中矢状面上腰椎椎体间（L2,3L3，4）屈伸运动中心在椎体中后1／3部位；而横断面上腰椎椎体间（L2,3L3，4）左右旋转中心在椎体前方约30mm处。

Objective To measure the vertebral rotational centers in sagittal and transverse plane. These data may be quite valuable for the design of artificial disc. Methods Ten healthy volunteers of 40-60 years old were recruited under IRB approval and informed consent. Three-dimension lumbar spine models of L2, L3 and L4 were reconstructed from MR scans. Spine motions were then reproduced using combined dual fluoroscopic imaging system （DFIS） and MR scan technique during flexion-extension and left-right twisting of the body. Based on the geometrical features of the vertebrae, ranges of motion （ROM） of 3 representative locations were measured from anterior to posterior： the vertebral body center, the spinal cord canal center and the spinous process tip. Rotational centers of the vertebral segments were then located by calculating the point of zero ROM. Results Motion patterns： The ROMs of L： with respect to L3 （L2,3） and L3.4 increased proportionally from anterior to posterior locations. During flexion-extension motion, the vertebral body center moved within a range of 0.6 mm, while the spinous process tip moved within 7.5 mm in the sagittal plane. During left-right twisting, the vertebral body center moved within 1.0 mm, while the tip moved within 1.6 mm in the transverse plane. No statistical differences were found in the ROMs between L2,3 and L3,4. Rotational centers： the rotational centers of flexion-extension in sagittal plane for both L2,3 and L3,4 segments were located at posterior one-third of the vertebral body. The rotational centers of both L2,3 and L3,4 segments were located approximately 30 mm anterior to the front edge of the vertebral body. Conclusion The anterior portion of the vertebrae was found to have smaller ROM than the posterior portion. The vertebra rotates with the center of rotation located at approximately the posterior one-third of the vertebral body in sagittal plane. However, the vertebra rotates in transverse plane with respect to a point about 30 mm in front of the vertebra. The data indicated that the different portions of the vertebra have distinct motion characters during different motions.