对角线式椎弓根钉固定生物力学研究

Biomechanics of Diagonal Pedicle Screw Fixation

目的研究对角线式椎弓根钉置入法的生物力学稳定性、有效固定长度、安全性。方法成人防腐脊柱第12胸椎-第5腰椎标本14具,将每具标本的每个椎体左右两侧按随机数字表法分为2组,每组84个椎弓根,人字嵴顶点法为对照组,对角线法为研究组。对角线法方法为进针点选择在固定椎体的上关节突外缘垂直延长线与横突上缘交点,进针方向头尾夹角指向椎体前下方,矢状夹角与对照组相同。椎弓根钉选用大于对角线长度,以总长度减去外露钉头长度即为有效固定长度。MTS机测量最大抗拔出力。检查螺钉有无穿破椎弓根。结果研究组与对照组相比,椎弓根钉固定可增加有效固定长度(5.2±0.16)mm,抗拔出力增加,由(1 011.1±112.6)N至(1 254.2±128.4)N,差异有统计学意义(P<0.05)。未见椎弓根螺钉穿破椎弓根。结论对角线椎弓根钉固定可增加有效固定长度,增加抗拔出力。对角线椎弓根置钉安全。

Objective To study the safety,effective fixation length and biomechanical stability of diagonal pedicle screw fixation.Methods Fourteen spine specimens（T12-L5 segment） were randomly divided into two groups according to different screw insertion points.Lambdoid crest method and diagonal fixation method were used in control group and study group,respectively.In study group,the pedicle screws were inserted from the intersection between the upper edge of transverse process and the vertical extension cord of outer edge of the border of superior articular process to anteroinferior point of vertebrae.The sagittal angle of the pedicle in control group was same to study group.The effective fixation length was measured in both groups.The MTS machine was used to measure the largest anti-pull force and a pedicle tester was used to check whether the pedicle walls had been breached.Results Compared with control group,the effective fixation length in study group increased by 5.2 mm and the anti-pull force increased from（1 011.1±112.6） N to（1 254.2±128.4） N（P0.05）.No pedicle screws were found outside of the pedicle.Conclusion The diagonal pedicle screw fixation is safe and can increase the effective fixation length and biomechanical stability.