膨胀式椎弓根螺钉在骨螺钉界面的显微CT评价及组织学分析

Micro-CT evaluation and histological analysis of screw-bone interface of expansile pedicle screw in osteoporotic sheep

目的研究膨胀式椎弓根螺钉(EPS)在骨质疏松绵羊体内的骨-螺钉界面组织学情况。方法在骨质疏松绵羊股骨髁内置入 EPS,分别于术后3、6个月取材。依次进行显微 CT 扫描及三维重建、骨计量学分析及切片组织学观察。结果显微 CT 扫描及三维重建发现 EPS 膨胀段界面的骨小梁比界面外的骨小梁浓密;EPS 非膨胀段界面的骨小梁与界面外的骨小梁无差异。EPS 膨胀段的"感兴趣区"的组织骨密度和骨体积分数、骨表面积体积比、骨小梁厚度、骨小梁间隙等骨小梁的三维参数,优于非膨胀段,差异有统计学意义。切片染色见新生骨小梁长入螺钉的膨胀缝隙中,并延伸至膨胀中心。EPS 骨-螺钉界面的骨小梁与 EPS 直接紧密接触。结论通过显微 CT 评价及组织学分析的方法,证实了 EPS 所形成的骨中有钉、钉中有骨的立体交叉复合结构的优点,说明在骨质疏松的状态下应用其具有强大的稳定性。

Objective To investigate the properties of screw-bone interface of expansive pedicle screw （EPS） in osteoporotic sheep using micro-CT and histology. Methods Six female sheep with bilateral ovariectomy-induced osteoporosis were employed in this experiment and were randomly assigned into 2 groups： A and B. After EPS insertion in each femoral condyles, sheep in group A were bred for 3 months, while those in group B 6 months. Femoral condyles with EPS were 3D-imaged and reconstructed by micro- CT. Histology was evaluated thereafter. Results The trabecular microstructure was denser at the screw-bone interface than in the distant parts in expansive section, especially within spiral marking. In the non- expansive section, however, there was no significant difference between the interface and the distant parts. The regions of interest （ROI） adjacent to EPS were reconstructed and analyzed by micro-CT using the same thresholds. The 3D-parameters generated, including tissue mineral density （TMD） , bone volume fraction （BVF, BV/TV）, bone surface/bone volume （BS/BV） ratio, trabecular thickness （Tb. Th）, and trabecular separation （Tb. Sp） , were significantly better in expansive than in non-expansive sections （P 〈 0. 05 ）. Histologically, newly formed bone trabeculae crawled along the expansive fissures and into the center of EPS. The newly formed bones, as well as the bone at the bone-screw interface, closely contacted the EPS and constructed four compartments. Conclusions Based on micro-CT and histological evaluation, the study suggest that EPS can significantly provide stabilization in osteoporotic cancellous bone.