两种椎弓根螺钉钉道强化技术在骨质疏松绵羊椎体的应用

Application of two different pedicle screw augmentation techniques used for in vitro sheep osteoporotic vertebra model

目的应用绵羊骨质疏松椎体标本比较两种骨水泥强化技术对椎弓根螺钉固定强度的影响。方法经体外脱钙建立绵羊骨质疏松椎体标本40节,完全随机分为A组(单纯螺钉组);B组(低剂量整体强化组);C1组(低剂量局部强化组);C2组(高剂量局部强化组)。骨密度(bone mineral density,BMD)检测;螺旋CT及MicroCT的影像学观察;测试最大轴向拔出力(Fmax)及能量吸收值(E)。结果各组BMD下降约25%～30%(P>0.05),成功建立骨质疏松椎体模型。影像学观察:B组螺钉完全被骨水泥包裹,形成"骨-骨水泥-螺钉"界面;C2组螺钉周围骨水泥呈局部对称分布,形成"骨-螺钉"和"骨-骨水泥-螺钉"的共存界面。B,C1,2组椎体的Fmax及E均显著高于A组(P<0.05);B,C2组椎体的Fmax及E均明显高于C1组(P<0.05);B,C2组椎体间Fmax及E无显著性差异(P>0.05)。结论钉道整体强化及局部强化技术均能显著提高骨质疏松情况下椎弓根螺钉的固定强度;钉道局部强化技术通过提高注射剂量,可以达到与整体强化技术相近的强化效果。

Objective To determine the effects of the two kinds of pedicle screws with cement augmentation used for in vitro sheep osteoporotic vertebra model.Method Forty osteoporosis specimens of lumbar vertebrae demineralized by decalcification solution were complete randomly devided into four groups including Group A（only screw）,Group B（whole trajectory filled with PMMA）,Group C1（partial trajectory filled with PMMA） and Group C2（partial trajectory filled with PMMA）.Osteoporosis specimens from four groups were tested by bone mineral density（BMD） and observed by spiral CT and MicroCT.The maximum force and energy absorption of pedicle screw were tested.Results BMD in each group were averagely declined about 25% ～30%（P 0.05）,so osteoporotic vertebrae model was successfully established.Spiral CT and MicroCT showed that screw of Group B was fully surrounded by PMMA,which constituted screw-PMMA-bone interface,while screw of Group C2 was partially surrounded by PMMA,which constituted partial screw-bone and partial screw-PMMA-bone interface.The axial pull-out test showed that the maximum force（Fmax） and its energy absorption in Group B,C12,were significantly higher than those in Group A（P 0.05）,those in Group B,C2 were higher than those in Group C1（P 0.05）,and those in Group B and Group C2 had no significant difference（P 0.05）.Conclusions Both the whole and partial pedicle screw augmentation can significantly improve the strength of pedicle screw in the context of osteoporosis.The latter not only formed a special whole interface consisting of partial＂screw-bone＂and partialscrew-CSC-bone interface,but produced the strengthening effect equivalent to the former by increasing injection doses of PMMA.