摘要：目的 利用有限元方法对比采用新型变径螺钉的改良皮质骨轨迹（modified cortical bone trajectory，MCBT）置钉技术与采用骨水泥强化螺钉的传统椎弓根（cement-augmented pedicle screw instrumentation,CAPSI）技术在腰椎中的力学性能。方法 通过获取骨质疏松症病人的CT扫描数据建立完成L4椎体模型中的骨水泥强化椎弓根螺钉置钉与改良皮质骨轨迹置钉。运用有限元方法比较采用不同螺钉的技术分析上、下、左、右四种工况下的稳定性、螺钉轴向抗拔出力与腰椎活动度。 结果 MCBT组螺钉轴向抗拔出力比CAPSI组提高25.3%。MCBT螺钉在的载荷位移比，相对于CAPSI组，在下、左、右两种工况分别提升14.9%，23.2%，19.1%；MCBT组螺钉的载荷位移比，在上工况比CAPSI组略有降低，但差异无显著性意义（P＞0.05）；在前屈与后屈工况下，MCBT组腰椎活动度比CAPSI组分别降低13.3%，2.5%；在左侧弯、右侧弯、轴向旋转工况比CAPSI组分别提升了69.1%，74.6%，118.1%，但差异无显著性意义（P＞0.05）。 结论 MCBT在轴向抗拔出力、螺钉的下、左、右工况、椎体前驱的稳定性略优于CAPSI，在上、左侧弯、右侧弯、轴向旋转工况稳定性略弱于CAPSI。此次研究结果论证了MCBT相比CAPSI有一定的优势，为MCBT在骨质疏松症临床应用提供了前期基础。

Abstract: Objective To compare the mechanical performance of the modified cortical bone trajectory (MCBT) placement technique using a new variable diameter screw with that of the cement-augmented pedicle screw instrumentation (CAPSI) nailing technique in the lumbar spine using a finite element method. The mechanical performance of the cement-augmented pedicle screw instrumentation (CAPSI) technique in the lumbar spine was compared with that of the cement-augmented pedicle screw instrumentation (CAPSI) technique.Merthods Cementau- gmented pedicle screw instrumentation and modified cortical bone track instrumentation in the L4 vertebral body model were established by obtaining CT scan data from osteoporotic patients. The finite element method was used to compare the stability, screw axial pull-out force and lumbar spine mobility under four working conditions: upper, lower, left and right using different screw techniques. Results The axial pull-out force of the screws in the MCBT group was 25.3% higher than that of the CAPSI group; the load-displacement ratios of the screws in the MCBT group were 14.9%, 23.2%, and 19.1% higher than those of the CAPSI group under the lower, left, and right working conditions, respectively; the load-displacement ratios of the screws in the MCBT group were slightly lower than those of the CAPSI group in the upper working conditions, but the differences were not significant (P > 0.05); in the anterior and posterior flexion conditions, the lumbar spine mobility of the MCBT group was reduced by 13.3% and 2.5%, respectively, compared with that of the CAPSI group; in the left lateral bending, right lateral bending, and axial rotational conditions, it was improved by 69.1%, 74.6%, and 118.1%, respectively, compared with that of the CAPSI group, but the difference was not significant (P > 0.05). Conclusion MCBT was slightly better than CAPSI in axial resistance to extraction force, lower, left and right working conditions of screws, and stability of vertebral anterior drive, and slightly weaker than CAPSI in upper, left lateral curvature, right lateral curvature, and axial rotational working conditions.The results of the present study demonstrated that MCBT has certain advantages compared with CAPSI, and it provides a pre-basic foundation for the clinical application of MCBT in osteoporosis.