重度骨质疏松人工骨模块中不同剂量聚甲基丙烯酸甲酯强化椎弓根螺钉稳定性的比较

目的比较重度骨质疏松人工骨模块中不同剂量聚甲基丙烯酸甲酯(PMMA)强化椎弓根螺钉的稳定性,分析螺钉稳定性与PMMA剂量间的相关关系。方法将48块重度骨质疏松模块随机分为A~F 6个实验组(n=8),A组不注射PMMA,B~F组分别向钉道内注入1.0、2.0、3.0、4.0、5.0 m L PMMA后,各组拧入椎弓根螺钉,记录最大拧入力矩(T_(max))。待骨水泥硬化后进行X线检查,观察螺钉周围骨水泥的分布情况;随后进行力学实验,测量最大轴向拔出力(Fmax)并观察模块的破坏情况。结果 B~F组螺钉被PMMA严密包绕,B~F组螺钉周围PMMA的范围逐渐增加。与A组相比,B~F组的T_(max)均有显著提高。B组和C组、C组与E组之间T_(max)的差异具有统计学意义(P0.05),其余任何2组的T_(max)之间差异均无统计学意义(P0.05)。与A组相比,B~F组的Fmax均有显著提高。B组和C组、C组和D组、E组和F组的Fmax之间差异均无统计学意义(P0.05),其余任何2组的T_(max)之间差异均有统计学意义(P0.05)。T_(max)、Fmax、PMMA剂量三者之间均存在正相关关系。螺钉拔出后,A~F组模块的破坏程度逐渐增加。结论 PMMA可以显著提高重度骨质疏松人工骨模块中椎弓根螺钉的稳定性,螺钉的稳定性与PMMA剂量存在正相关关系。本研究中注射4 m L PMMA可以作为重度骨质疏松条件下合适的选择。

Biomechanical comparison of stability of pedicle screw augmented with different volumes of polymethylmethacrylate in synthetic severely osteoporotic bone block

Objective To compare stability of pedicle screw augmented with different volumes of polymethylmethacrylate (PMMA) in synthetic severely osteoporotic bone block(SSOBB) and analyze the relationship between screw stability and volume of PMMA. Methods Forty-eight SSOBBs were randomly divided into 6 groups. A pilot hole was prepared in advance using the same method in all the samples. Then, the pilot hole was filled with different volumes of PMMA(0, 1.0, 2.0, 3.0, 4.0 and 5.0 mL) followed by insertion of screw in groups A, B, C, D, E and F, respectively. The maximum insertion torque (T_max) was recorded during the insertion of screw. After solidification of PMMA, X-ray examination and axial pull-out tests were performed in all the groups, and the maximum axial pullout strength(F_max) was measured. Then, the destruction of blocks was observed. Results From group B to group F, screws were wrapped up by the increasing scope of PMMA. T_max in groups B-F was significantly increased compared with that in group A(P<0.05). Except significant differences in T_max between groups B and C, groups C and E(P<0.05), there were no significant differences between any 2 groups among 6 groups(P>0.05). F_max in groups B-F was more significantly increased compared with that in group A(P<0.05). There was no a significant difference in F_max between groups B and C, groups D and E, and groups E and F(P>0.05), but a significant differences in F_max was found between any other 2 groups(P<0.05). There were significant positive correlations among T_max, F_max and the volume of PMMA(P<0.05). The destruction of the block was lightest in group A and most severe in group F, and the destruction of block was gradually increased from groups A to F. Conclusion PMMA can significantly enhance stability of pedicle screw in severely osteoporotic synthetic bone, and there is a positive correlation between the screw stability and volume of PMMA. Injection of 4 mL PMMA in this study can be considered the preferred choice in severe osteoporosis.