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目的评价新型设计的Y型椎弓根螺钉(Y type pedicle screw,YPS)在骨质疏松人工骨模块(简称“模块”)中的生物力学稳定性。方法将模块随机分成3组(n=20),用手钻垂直钻入模块中,制备直径3.0 mm、深30.0 mm的钉道。分别将YPS、膨胀式椎弓根螺钉(expansive pedicle screw,EPS)、中空骨水泥椎弓根螺钉(bone cement-injectable cannulated pedicle screw,CICPS)打入已制备好钉道的各组模块中。12 h后行X线检查,并在E10000万能材料试验机上分别对YPS组、EPS组、CICPS组进行生物力学稳定测试,记录最大轴向拔出力、最大旋出力和周期抗屈最大载荷。结果 X线片观察示,YPS组主钉和中芯钉均被周围的聚氨酯材料包绕,中芯钉从主螺钉的中下1/3穿出后,与主钉形成15°夹角,插入的中芯钉最低点与主螺钉位于同水平线上;EPS组螺钉尖端明显膨胀,形成爪型结构;CICPS组骨水泥主要分布于螺钉前部,在骨小梁中弥散,形成稳固的“螺钉-骨水泥-骨小梁”复合体。生物力学检测示,YPS、EPS、CICPS组的最大轴向拔出力分别为(98.43±8.26)、(77.41±11.41)、(186.43±23.23)N,最大旋出力矩分别为(1.42±0.33)、(0.96±0.37)、(2.27±0.39)N/m,周期抗屈试验的最大载荷分别为(67.49±3.02)、(66.03±2.88)、(143.48±4.73)N。CICPS组各指标均明显高于YPS组和EPS组,差异有统计学意义(P<0.05);YPS组最大轴向拔出力和最大旋出力矩显著高于EPS组,差异有统计学意义(P<0.05),但YPS组和EPS组间比较最大载荷差异无统计学意义(P>0.05)。结论相比于EPS,YPS能有效提升其在模块中的最大轴向拔出力和最大旋出力,为骨质疏松条件下的螺钉设计和不同固定方式选择提供了新思路。
Objective To evaluate the biomechanical stability of a newly designed Y type pedicle screw (YPS) in osteoporotic artificial bone (“module”). Methods The rats were randomly divided into three groups (n = 20). The drill was vertically drilled into the module with a hand drill to prepare a 3.0 mm diameter and 30.0 mm deep pin. The YPS, expansive pedicle screw (EPS), and bone cement-injectable cannulated pedicle screw (CICPS) were each inserted into each group of modules that had been prepared for pinning. X-ray examination was performed 12 h later. The biomechanical stability tests of YPS group, EPS group and CICPS group were performed respectively on E10000 universal testing machine. The maximum axial pull-out force, maximum screw-out force and maximum cyclic buckling load were recorded. Results X-ray examination showed that the staples of the YPS group and the SMC were all surrounded by the polyurethane material. The SMC nail passed through the middle and bottom 1/3 of the main screw and formed an angle of 15 with the main nail. The lowest point of the center of the nail in the same horizontal line with the main screw; EPS group of screw tip significantly expanded, the formation of claw-shaped structure; CICPS group of bone cement is mainly distributed in the front of the screw, trabecular in the dispersion, the formation of solid - bone cement - trabecular bone "complex. Biomechanical measurements showed that the maximum axial pull-out forces of YPS, EPS and CICPS groups were (98.43 ± 8.26), (77.41 ± 11.41) and (186.43 ± 23.23) N, respectively, and the maximum unscrew torque was (1.42 ± 0.33) , (0.96 ± 0.37) and (2.27 ± 0.39) N / m, respectively. The maximum load of cyclic buckling test were (67.49 ± 3.02), (66.03 ± 2.88) and (143.48 ± 4.73) N, respectively. The indexes of CICPS group were significantly higher than that of YPS group and EPS group (P <0.05). The maximum axial pull-out force and maximum torque of YPS group were significantly higher than those of EPS group (P <0.05) P <0.05). However, there was no significant difference in maximum load between YPS group and EPS group (P> 0.05). Conclusion Compared with EPS, YPS can effectively increase its maximum axial pull-out force and maximum pull-out force in the module, which provides a new idea for screw design and different fixation options in osteoporosis.