摘要
背景:修复椎弓根螺钉固定失效的方法有多种,但效果均不理想。目的:为改善椎弓根螺钉的稳定性,探讨椎弓根融合器(以下均称空心侧孔椎弓根螺钉)置入时添加聚甲基丙烯酸甲酯(PMMA)骨水泥强化椎弓根螺钉固定的生物力学效果。设计:完全随机对照实验研究。地点和对象:实验在华中科技大学同济医学院生物力学实验室和解剖室完成。实验对象为新鲜脊柱尸体(家属自愿贡献)。干预:用8具成人新鲜腰椎骨T11～L4,共48个椎体,随机数字法选择32个椎体,其中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(F-max)实验(对照组)。拔出螺钉后分别向空心和实心螺钉道注入PMMA3～5mL,拧入螺钉,行拔出试验(修复组)。另选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PMMA和拧入螺钉,再行拔出试验(强化组),并观察PMMA的分布范围。另外12个椎体作空心侧孔椎弓根螺钉的周期抗屈实验。10个空心侧孔螺钉和10个实心螺钉分别做3点弯屈(3pBend)试验。主要观察指标:轴向拔出力,位移,最大折弯力。结果:空心侧孔椎弓根螺钉对照组F-max为(855.0±207.5)N,修复组为(1924.4±383.2)N,强化组为(1943.3±535.8)N;实心螺钉对照组拔出力为(829.2±220.9)N;修复组为(1853.5±387.
BACKGROUND:There are several methods to restore the failure of screw fixation at present, but its efficacy is not satisfactory. OBJECTIVE:To evaluate the biomechanical effect of hollow screws with lateral holes augmented with polymethyl methacrylate(PMMA) in strengthening the fixation to improve the stability of the screw. DESIGN:A completely randomized controlled experiment was conducted. SETTING and PARTICIPANTS:The experiment was completed in the Institute of Biomechanics and Anatomy,Tongji Medical College,Huazhong University of Science and Technology. The subjects were fresh adult cadavers(voluntarily provided by the relatives). INTERVENTIONS:A total of 32 fresh thoracolumbar vertebrae(T11-L4) of 8 adult cadavers were randomly employed in this experiment.Solid screws of 6.5 mm in diameter were implanted directly into the pedicle of vertebral arch unilaterally(subgroup A),and hollow screws with lateral holes of equivalent diameter were implanted contralaterally(subgroup B) on 10 fresh thoracolumbar vertebrae(T11-L4).Then the screws of both subgroups were pulled out and axial pullout test(F max) was performed(control group),and 3-5 mL PMMA was injected into the track of every screw.Five minutes later, the solid screws(subgroup C) and the hollow screws(subgroup D) were reimplanted into the initial track respectively. An hour later at room temperature, axial pullout test was employed again(restoration group). Solid screws of 6.5 mm in diameter were implanted into the pedicle of vertebral arch unilaterally(subgroup E), and hollow screws with lateral holes of equivalent diameter were implanted contralaterally(subgroup F) on other 10 fresh thoracolumbar vertebrae. A drilling bit of 3.5 mm in diameter was used to prepare track, then screwed in the pedicle screws after injecting PMMA. An hour later, axial pullout test was employed(reinforcement group),and the distribution of PMMA was observed. Periodical/Cyclic bending resistance test on hollow screws with lateral holes in pedicle of vertebral arch was performed on the rest 12 vertebrae. And three point bending test was made on 10 solid screws and 10 hollow screws with lateral holes, respectively. MAIN OUTCOME MEASURES: Axial Pull out force,displacement,maximum bending force. RESULTS:Axial pullout strength was (829.2±220.9) N in subgroup A, (855.0±207.5) N in subgroup B,(1853.5±387.4) N in subgroup C, (1924.4±383.2) N in subgroup D,(1866.1±431.7) N in subgroup E and (1943.3±535.8) N in subgroup F. No PMMA was found in the spinal canal or on the surface of pedicle of vertebral arch when PMMA was infused into the hollow screws with lateral holes, while PMMA was easily found in the spinal canal or on the surface of the pedicle of vertebral arch in solid screws. The hollow screws with lateral holes infused with PMMA could bear more loadings or induce fewer shifts under the same loadings compared with the controls.The max loading force of the hollow solid screws with lateral holes was (2051.29±69.86) N, the elastic modulus was (23941.8±1467.4) N/mm2 and the energy absorption was (40.1873±1.4693) J. While the max loading force of the solid screws was (2075.01±117.57)N, the elastic modulus was (24991.8 ±1962.3)N/mm2, and the energy absorption was (44.9630±1.8663) J. CONCLUSION:PMMA can increase significantly the stabilization of the screws in pedicle of vertebral arch. And no PMMA was found in the spinal canal or on the surface of pedicle of vertebral arch when PMMA was infused into the hollow screws with lateral holes, which is suitable for the fixation of loosing screw and the repair of the wound when screws are pulled out.
出处
《中国临床康复》
CSCD
2004年第14期2752-2754,F012,共4页
Chinese Journal of Clinical Rehabilitation
