可注射磷酸钙骨水泥对不同骨质椎弓根螺钉的强化作用

目的评价不同骨质疏松程度条件下,可注射性磷酸钙骨水泥对椎弓根螺钉稳定性强化作用,为其应用于合并有骨质疏松症的患者脊柱手术提供力学理论基础。方法采用新鲜尸体脊柱标本,根据骨密度检测结果,按临床诊断标准分成骨质正常、骨量减少、骨质疏松和重度骨质疏松四个水平;然后,每个骨密度水平,分直接置入椎弓根螺钉（对照组）和用可注射性磷酸钙骨水泥强化钉道后置入椎弓根螺钉（钉道强化组）,各12枚,进行螺钉轴向拔出实验,测定最大拔出力、刚度和能量吸收值三项指标,进行组间的对比分析。结果骨密度水平从正常下降到重度疏松程度,最大拔出力、刚度、能量吸收值均随之下降,同种置钉方法组间存在显著性差异（P〈0.05）。骨质疏松条件下钉道强化组最大拔出力、刚度、能量吸收值与骨量减少条件下对照组的比较,两者无显著性差异（P〉0.05）;但是,重度骨质疏松条件下钉道强化组的最大拔出力、刚度、能量吸收值均显著性低于骨量减少条件下对照组的（P〈0.05）。结论可注射性磷酸钙骨水泥强化钉道后可以提高椎弓根螺钉的稳定性,尤其是骨质疏松条件下经钉道强化后可以达到需要固定强度。

Biomechanical Evaluation of the Augmentation of the Injectable Calcium Phosphate Cement on the Fixation Strength of Pedicle Screws at Different BMD Levels

Objective To evaluate the augmentation of the injectable calcium phosphate cement on the fixation strength of pedicle screws at different BMD Levels,further to provide theoretical evidence for the clinical application of the injectable calcium phosphate cement to augment the pedicle screw in patient with osteoporosis.Methods Fresh human cadaver spines were stratified into four levels：normal,osteopenia,osteoporosis and severe osteoporosis,according to the value of bone mineral density.The vertebrae were bilaterally instrumented pedicle screws by two methods,with（control group）and without the augmentation（augmentation group）of the injectable ccalcium phosphate cement,resulting in 12screws in each group per BMD level.Screw pullout tests were conducted.On the load-stroke curve,the maximum pullout strength,stiffness and energy absorption were determined.The differences between groups were compared.Results With the decline of BMD from normal to severe osteoporosis level,the maximum pullout strength,the stiffness and the absorbed energy of each group were correspondingly decline,significant difference were found between groups of different BMD levels（P0.05）.The pullout strength,the stiffness and the absorbed energy of the augmented group at the osteoporotic level were comparable to those of the control group at the osteopenic level（P0.05）. However,under the severely osteoporotic bone environment,the pullout strength of pedicle screw with whatever placement protocol was significantly lower than that of the control group at the osteopenic level.Conclusion With the augmentation of the injectable calcium phosphate cement,the fixation strength of pedicle screw can be improved,especially under the osteoporotic bone environment.