骨圈对椎弓根钉系统负载影响的三维有限元分析

目的：探讨单枚人体皮质骨圈(allograft fusion cage，AFC)斜植融合术中椎弓根钉系统受力分布，并对临床常见断钉原理进行分析，为临床应用提供理论依据。方法：采用二三维有限元方法(finite element method，FEM)，对放置及不放置AFC的脊柱Steffee钢板固定效果进行评估。结果：未放置AFC时Steffee钢板所受最大应力约为放置AFC状态下的4．8倍；椎弓根钉与螺帽交界处所受应力为最大，尤其上位螺钉与靠近椎体侧螺帽交界处是应力值最大点，未放置AFC时椎弓根钉最大应力点约为放置AFC状态下的5．0倍。结论：螺钉与钢板交界区是容易发生断钉的区域，尤其上位螺钉与靠近椎体侧螺帽交界处是最易断钉的部位；椎弓根钉系统放置AFC会明显增强融合节段稳定性，减少断钉等并发症。

Three dimensional finite element analysis of spinal pedicle grew internal fixation system on the stability of spine after implanting the AFC into intervertebral space

Objective: To evaluate the influence of spinal pedicle screw internal fixation system on the stability of spine after implanting the AFC into intervertebral space and provide theoretical data for clinical application. Methods: Three dimensional finite element analysis was applied to explore the internal fixational effect of spinal pedicle screw internal fixation system on the stability of spine with or without implanting AFC into intervertebral space. Results: The greatest stress received by the plate without AFC was 4.8 times than with AFC. The juncture between screw and the screw cap, especially between upper screw and the screw cap nearing to the body of vertebra received the greatest stress, which was about 5 times than that with AFC. Conclusions: It seems that the junctional zone between nail and the plate is more likely to be broken, especially at the part where the upper screw meet with the screw cap nearing to the body of vertebra. Putting AFC in the plate-screw system can improve the stability of the segment significantly, as well as cut down the complications of nail breaking.