Chang Chia-Ming, Lai Yu-Shu, Cheng Cheng-Kung
Department of Biomedical Engineering, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei, 112, Taiwan.
Orthopaedic Device Research Center, National Yang-Ming University, No. 155, Sec. 2, Linong Street, Taipei, 112, Taiwan.
Biomed Eng Online. 2017 Aug 15;16(1):105. doi: 10.1186/s12938-017-0392-1.
Currently, cannulated pedicle screws have been widely used in minimal invasive or navigation techniques. However, the stress distribution and the strength of different core diameters of cannulated screw are not clear. This study aimed to investigate the mechanical strength of cannulated screws with different inner core diameter under various lumbar spine movements using finite element analysis.
The results showed that the von-Mises stress of a cannulated screw was larger than that of a solid screw in all loading conditions, especially above 2 mm in cannulated core diameter. In lateral bending, extension, and flexion, the maximum von-Mises stress was found approximate to the proximal thread for all types of screws. In rotation condition, the maximum von-Mises stress was located at the middle of the screw. Additionally, the difference in stiffness of instrumented levels was not significant among four screws under the same loading condition.
Cannulated screws could provide enough stability for the vertebral body fusion comparing to solid screws. The diameter of cannulated core is suggested not to exceed 2.0 mm.
目前，空心椎弓根螺钉已广泛应用于微创或导航技术中。然而，空心螺钉不同芯直径的应力分布和强度尚不清楚。本研究旨在通过有限元分析研究不同内芯直径的空心螺钉在各种腰椎运动下的力学强度。
结果表明，在所有加载条件下，空心螺钉的von-Mises应力均大于实心螺钉，尤其是空心芯直径大于2mm时。在侧弯、伸展和屈曲时，所有类型螺钉的最大von-Mises应力均位于近端螺纹附近。在旋转条件下，最大von-Mises应力位于螺钉中部。此外，在相同加载条件下，四种螺钉在固定节段的刚度差异不显著。
与实心螺钉相比，空心螺钉可为椎体融合提供足够的稳定性。建议空心芯直径不超过2.0mm。
