生物活性玻璃提高骨质疏松绵羊椎弓根螺钉稳定性的体内实验研究

目的:研究生物活性玻璃(Bioactive Glass,BG)在骨质疏松绵羊体内强化椎弓根螺钉固定的力学效果,并观察钉道界面及材料吸收等情况。方法:4只成年雌性小尾寒羊,采用去势联合激素注射方法建立骨质疏松绵羊模型。选择绵羊L2至L5双侧椎弓根,随机化选取一侧直接拧入椎弓根螺钉(空白组),对侧采用BG强化钉道后拧入椎弓根螺钉(实验组)。术后3月随机选取6个椎体(12枚椎弓根螺钉),对螺钉骨质界面行显微CT分析和组织学观察。对剩余10个椎体(20枚椎弓根螺钉)行轴向拔出实验,分析螺钉固定强度。结果:术前绵羊腰椎BMD为0.818±0.0310 g/cm2,建模完成后为1.000±0.0316 g/cm2,BMD平均值下降22.38%,差异有统计学意义(P<0.05)。实验组螺钉骨质界面的Tb.Th、Tb.N组较对照组分别增加143.60%和33.56%,差异有统计学意义(P<0.05)。实验组钉道周围材料绝大部分已经降解吸收,大量新生骨组织紧密包裹螺钉;对照组钉道周围骨量较少,钉骨结合不紧密,实验组螺钉骨质界面结合优于对照组。实验组的最大轴向拔出力为1083.04±86.37N,空白组为871.76±79.03N,前者较后者提高25.26%,差异有统计学意义(P<0.05)。结论:生物活性玻璃能显著改善骨质疏松情况下螺钉骨质界面的骨微观结构,进而提高椎弓根螺钉的把持力。

In Vivo Study of Bioactive Glass in Improvement of Pedicle Screw Fixationin Osteoporosis Sheep

Objective: To investigate the effect of pedicle screw augmentation using bioactive glass (BG) in osteoporosis sheepand observe the absorption of BG and the interface between bone and screw. Methods: Osteoporosis animal models were established byovariectomy combined with methylprednisolone injection in four adult female sheep. L2-L5 unilateral pedicles were randomly selected ineach sheep which were only implanted with pedicle screw and the contralateral pedicles were implant with pedicle screw after theaugmentation with BG. 3 months later, six vertebraes (12 screws) were randomly collected from all samples and the interface betweenscrew and bone was analyzed by MicroCT. The augmentation of the screws were evaluated by Axial pull-out-test. Results: The bonemineral density (BMD) of the lumbar of the sheep decreased by 22.38%, and significant difference was found (P<0,05). The trabecularthickness (Tb. Th) and the trabecular number (Tb. N) of the interface in experiment group increased by 143.60% and 33.56% comparedwith the control group respectively. Significant differences of Tb. Th and Tb. N were found between experiment group and control group(P<0.05). Most of the BG around the screw channel had been degraded and much newly formed bone tissue wrapped the screws tightly inexperiment group. In control group, the bone mass was much lower and the bone-screw junction was defectively tight. The junction ofthe interface between bone and screw in experiment group was better than that in control group. The maximal axial pullout strength inexperiment group increased by 25.26% compared with that in control group (P<0.05). Conclusion: Bioactive glass can significantlyimprove bone microstructure of the interface in osteoporosis condition and increase the hold-strength of the pedicle screw.