通用型脊柱内固定系统椎弓根螺钉的生物力学测试

Insertion torque and pullout strength of general spine system pedicle screws in human vertebral bodies:an in vitro biomechanical study

目的测试自行设计的通用型脊柱内固定系统(generalspinesystem,GSS)椎弓根螺钉以及SOCON和CCD螺钉置入正常成人椎体标本的最大轴向拔出力及最大旋入力矩,评价GSS螺钉对椎弓根的锚固作用。方法将27个正常成人腰椎椎体标本随机分为3组,每组9个椎体(18侧椎弓根),分别置入GSS、SOCON和CCD椎弓根螺钉,行螺钉拔出试验,测试并记录螺钉的最大旋入力矩和最大轴向拔出力。结果三组螺钉的最大旋入力矩分别为(1.83±0.27)Nm、(2.09±0.51)Nm和(1.66±0.34)Nm,最大轴向拔出力分别为(1131.0±255.4)N、(1034.0±262.3)N和(886.1±152.9)N。GSS螺钉最大轴向拔出力最大,且与CCD螺钉相比差异有非常显著性意义(P<0.01)。结论GSS螺钉具有很强的椎弓根锚固作用。

Objective To measure and compare the insertion torque and pullout strength of newly designed general spine system(GSS) screws with those of SOCON and CCD pedicle screws in normal human cadaver vertebrae, and to evaluate the screw purchase of GSS pedicle screws. Methods Twenty seven lumbar vertebral bodies obtained from 6 fresh normal male cadavers were classified into 3 groups randomly, 18 pedicles per group. GSS, SOCON and CCD pedicle screws were implanted into the pedicles of each group respectively. Pedicle screws were inserted with a torque screwdriver. Each screw was extracted axially from the pedicle at a rate of 5 mm/min until failure using a material testing machine(SWD-10, Changchun, China). Force data were recorded and analyzed using a one way ANOVA. P< 0.05 was considered significant. Results The torques of the GSS, SOCON, and CCD screws were (1.83±0.27) Nm, (2.09±0.51) Nm and (1.66±0.34) Nm respectively. The pullout strengths of the GSS, SOCON and CCD screws were (1 131.0±255.4) N, (1 034.0±262.3) N and (886.1±152.9) N respectively. The maximum axial pullout strength of GSS pedicle screws was greater than that of SOCON and CCD screws. The pullout strength difference was significant between GSS and CCD screws(P< 0.01). Insertion torque was correlated positively with pullout strength in all three types of screws. Conclusion GSS pedicle screws have good purchase ability, better than that of SOCON and CCD pedicle screws.