同椎体交叉置钉法对椎弓根螺钉的把持力影响

The mechanical effects of cross-pinned on pedicle screws in same vertebral body

目的研究同一椎体双侧椎弓根螺钉以交叉置入时的生物力学稳定性。方法采用骨密度及形态相似的12个椎体,并随机分成对照组与实验组,每组6个椎体。对照组以双侧椎弓根螺钉均平行上终板方式置入;实验组以一侧椎弓根螺钉平行上终板,另一侧螺钉指向下终板并成角20度的方式置入。所有样本双钉尾部刚性连接,采用万能试验机同时拔出双钉。记录最大载荷。结果对照组的平均最大载荷为(2.93±0.14)kN,实验组的平均最大载荷为(3.12±0.10)kN,两者最大载荷具有显著性差异(P<0.05)。结论在两侧椎弓根以20度夹角置入螺钉时提升大约6.5%螺钉把持力,可提升整套椎弓根螺钉系统的力学稳定性。

Objective To study the biomechanical stability of the same vertebral body with cross-pinned pedicle screw. Methods Twelve vertebral bodies with similar bone density and morphology were collected, they were randomly divided into two groups: control group and experimental group, with 6 vertebrae in each group. In the control group, bilateral pedicle screws were placed in parallel with the superior endplate. In the experimental group, one pedicle screw was parallel to the upper endplate, the other pedicle screw points to the lower endplate with an angle of 20 °. All samples were rigidly connected at the end of the double screws. Universal testing machine was used to pull out the double screws at the same time. The maximum load was recorded. Results The average maximum load in the control group was(2.93±0.14)kN, and the average maximum load in the experimental group was(3.12±0.10)kN. The maximum load between two groups had significant difference(P<0.05). Conclusion 20° angle on both sides of the pedicle in the time of screw placement can increase about 6.5% screws holding force, which can improve the mechanical stability of the entire pedicle screw system.