中文摘要：

目的通过显微CT技术比较骨质疏松绵羊腰椎内可膨胀椎弓根螺钉（EPS）与骨水泥强化螺钉（PMMA-PS）的界面情况。方法健康成年雌性绵羊8只,成功建立骨质疏松模型后将每只绵羊的腰椎（L1-L6）随机分为3个不同置钉组（采用相同的方法制备钉道）,普通椎弓根螺钉（CPS）组经钉道向椎体内拧入CPS,PMMA-PS组在拧入CPS之前向钉道内注入骨水泥（PMMA）1.0ml,EPS组经钉道向椎体内拧入EPS。分别于术后6周和12周处死绵羊,对螺钉及周围骨组织进行显微CT扫描,通过三维重建和骨组织计量学方法评价钉道界面情况。结果术后6周和12周时CPS组和EPS组中骨小梁与螺钉直接接触,形成了＂钉-骨＂界面,PMMA-PS组中螺钉被PMMA严密包裹,形成了＂钉-PMMA-骨＂界面。EPS组螺钉的前段胀开形成＂爪状＂结构,挤压并显著改善了周围骨质的质量。从术后6周到12周,CPS组和PMMA-PS组中螺钉周围的骨质质量无明显变化,未见PMMA降解吸收,PMMA-PS组中形成了二次界面。术后12周时EPS膨胀部分周围的骨质条件较术后6周有显著提高,形成了良好的＂钉-骨＂界面。结论在骨质疏松绵羊腰椎内,EPS通过膨胀挤压刺激周围骨质生长,在术后早期显著提高了局部骨质的质量,随着挤压应力的持续存在,局部骨质质量在后期进一步改善,形成了良好的生物性界面,为螺钉的远期稳定提供了良好的骨质基础。

英文摘要：

Objective To compare the changes in interfaces of expandable pedicle screw（EPS） and polymethylmethacrylateenhanced pedicle screw（PMMA-PS） after being used in osteoporotic sheep lumbar vertebrae with micro-CT technique. Methods Six lumbar vertebrae（L1-L6） in each sheep were randomly divided into three different screw-insertion groups（two vertebrae with four pedicles in each group） after reproduction of osteoporosis in sheep. After making the pilot hole using the same method, CPS was inserted through the pilot hole into vertebral body in CPS group, while PMMA（1.0ml） was injected into the pilot hole prior to the insertion of CPS in PMMA-PS group, and EPS was inserted through pedicle into vertebral body in EPS group. All the sheep were sacrificed, and lumbar vertebrae（L1-L6） were harvested respectively at the 6-and 12-week postoperatively. The micro-CT three dimensional reconstruction and histomorphometric analysis were performed to evaluate the interfacial conditions. Results It was clearly demonstrated that interface was formed where the bone trabeculae was directly in contact with the screw to form ＂screw-bone＂ interface in both CPS and EPS groups both 6 weeks and 12 weeks after the operation. The screw was fully surrounded by PMMA and formed ＂screw-PMMA-bone＂ interface in PMMA-PS group. The anterior part of EPS expanded in vertebral body to form a clawlike structure, pressing against the surrounding bone trabeculae, thus significantly improved the local bone quality（amount and density of bone trabeculae）. From 6 weeks to 12 weeks after the operation, there was no visual difference in bone quality around the screw in both CPS and PMMA-PS groups. There was no degradation and absorption of PMMA, and it led to form the second non-biological interface in PMMA-PS group. Nevertheless, bone quality around expanding part of EPS at 12-week post-operation was significantly improved compared with that at 6-week post-operation, thus forming a good ＂screw-bone＂ interface. Conclusions EPS