【摘要】 背景:椎弓根螺钉内固定的可靠性取决于骨-螺钉界面把持力的维持。目的:分析定向灌注椎弓根螺钉强化椎弓根螺钉固定的生物力学效果。设计、时间及地点:对比观察试验,于2007-12在南方医科大学脊柱外科实验室和南方医科大学广东省生物力学重点实验室完成。材料:①标本取自6具新鲜成人尸体,由南方医科大学解剖实验室提供,T12~L5共36个椎体,随机选取30个椎体进行试验。②自行设计的定向灌注椎弓根螺钉由螺钉、螺母、定向灌注钉芯3个部分组成。③天津合成材料研究所生产的注射用III型丙烯酸树脂骨水泥。标本试验机上固定标本使用上海第二医科大学口腔材料厂甲基丙烯酸甲酯粉和单体。④MTS858Bionix材料试验机,拔出速率选用5.0mm/min。方法:对照组10个椎体一侧椎弓根放置直径6.5mm的空心侧孔椎弓根螺钉,另一侧放置实心螺钉,行最大轴向拔出力试验。修复组10个椎体行拔松螺钉后分别向空心和实心螺钉道注入甲基丙烯酸甲酯3~5mL,拧入螺钉,行最大轴向拔出力试验。强化组10个椎体置入空心侧孔螺钉和实心螺钉,用直径3.5mm的钻头分别导孔,注入甲基丙烯酸甲酯和拧入螺钉,再行最大轴向拔出力试验。10个空心侧孔螺钉和10个实心螺钉分别做剪切试验。主要观察指标:①最大轴向拔出力。②强化或修复后有无骨水泥渗漏。③最大剪切力。结果:①空心侧孔椎弓根螺钉对照组拔出力为(798.24±139.86)N,修复组为(1476.21±223.09)N,强化组为(1741.33±317.79)N;实心螺钉对照组拔出力为(904.37±212.03)N,修复组为(1828.42±239.68)N,强化组为(1783.37±250.49)N。对照组与修复组和强化组差别显著(P=0.000),强化组和修复组间差异无显著性意义(P=0.330)。②定向灌注螺钉通过中空部分注入甲基丙烯酸甲酯,未见椎弓根外或椎管内有甲基丙烯酸甲酯溢出。③空心侧孔螺钉和实心螺钉最大剪切力分别为(3981.77±8.06)N和(3994.78±4.40)N。两样本均数统计学上差异无显著性意义。结论:定向灌注椎弓根螺钉注入甲基丙烯酸甲酯可显著增加椎弓根螺钉的稳定性,并能减少甲基丙烯酸甲酯向椎弓根外或椎管内溢出,适用于螺钉松动和拔出的修复固定。更多还原

【Abstract】 BACKGROUND: The validity of pedicle screw system is determined by the maintenance of bone-screw surface support. OBJECTIVE: To evaluate the biomechanical effect of oriented-injection pedicle screws with hollow lateral holes in enhancing the fixation. DESIGN, TIME AND SETTING: The comparative observation was performed at the Guangdong Key Laboratory of Biomechanics, Southern Medical University and Laboratory of Spinal Surgery, Nanfang Hospital in December 2007. MATERIALS: Thirty-six vertebral bodies (T12-L5) were from 6 fresh adult corpses (Laboratory of Anatomy, Southern Medical University), and 30 vertebral bodies were randomly selected; Self-designed oriented-injection pedicle screws were composed of screw, screw nut and oriented-injection nail; type Ⅲ acrylic resin bone cement for injection (Tianjin Synthetic Material Research Institute); the fixation sample was polymethylmethacrylate (PMMA) power and monomer (Dental Material Factory of Shanghai Second Medical University); MTS858 Bionix material testing machine at 5.0 mm/min. METHODS: In control group, one side of 10 vertebral bodies was implanted with hollow screw (6.5 mm in diameter), and solid screw of equivalent diameter was implanted contralaterally. In augmentation group (10 vertebral bodies), 3- 5 mL PMMA was injected into pilot hole before the solid screw implanted, but 3-5 mL PMMA injected through lateral hole after the hollow screw implantation; In restoration group, 3-5 mL PMMA was injected the same way as augmentation group except that screw track had been made in each pedicle by pulling-out screw in advance. Then the screws of each group were pulled out and F-max test was employed. Shearing force test was performed on 10 hollow screws and 10 solid screws. MAIN OUTCOME MEASURES: Maximum pullout force; bone cement leakage after augmentation or restoration; maximum shearing force. RESULTS: For hollow screws, the peak pullout forces were (798.24±139.86) N in control group, (1 476.21±223.09) N in restoration group, and (1 741.33±317.79) N in augmentation group; For solid screws, the peak pullout forces were (904.37±212.03) N in control group, (1 828.42±239.68) N in restoration group and (1 783.37±250.49) N in augmentation group. There were significant differences in control group compared with restoration group and augmentation group (P =0.000), but no differences between restoration group and augmentation group (P =0.330). No PMMA leakage was found in the vertebral canal or on the surface of pedicle of vertebral arch after PMMA was infused through the hollow screws. The maximum shearing forces of the hollow and solid screws were (3 981.77±8.06) N and (3 994.78±4.40) N, respectively. There were no significant differences between them. CONCLUSION: PMMA can significantly enhance the stabilization of the oriented-injection pedicle screws without leakage in vertebral canal or on the surface of pedicle, which is suitable for the fixation of screw mobilization and for the repair of the wound when screws are pulled out.更多还原