Xu Yichi, Meng Haoye, Yin Heyong, Sun Zhen, Peng Jiang, Xu Xiaolong, Guo Quanyi, Xu Wenjing, Yu Xiaoming, Yuan Zhiguo, Xiao Bo, Wang Cheng, Wang Yu, Liu Shuyun, Lu Shibi, Wang Zhaoxu, Wang Aiyuan
Institute of Orthopedics, Chinese PLA General Hospital, Beijing 100853, P.R. China.
Key Laboratory of Musculoskeletal Trauma and War Injuries, Chinese PLA General Hospital, Beijing 100853, P.R. China.
Exp Ther Med. 2018 Jan;15(1):93-102. doi: 10.3892/etm.2017.5389. Epub 2017 Oct 30.
Degradation limits the application of magnesium alloys, and evaluation methods for non-traumatic quantification of implant degradation and bone formation are imperfect. In the present study, a micro-arc-oxidized AZ31 magnesium alloy was used to evaluate the degradation of implants and new bone formation in 60 male New Zealand white rabbits. Degradation was monitored by weighing the implants prior to and following implantation, and by performing micro-computed tomography (CT) scans and histological analysis after 1, 4, 12, 24, 36, and 48 weeks of implantation. The results indicated that the implants underwent slow degradation in the first 4 weeks, with negligible degradation in the first week, followed by significantly increased degradation during weeks 12-24 (P<0.05), and continued degradation until the end of the 48-week experimental period. The magnesium content decreased as the implant degraded (P<0.05); however, the density of the material exhibited almost no change. Micro-CT results also demonstrated that pin volume, pin mineral density, mean 'pin thickness', bone surface/bone volume and trabecular separation decreased over time (P<0.05), and that the pin surface area/pin volume, bone volume fraction, trabecular thickness, trabecular number and tissue mineral density increased over time (P<0.05), indicating that the number of bones and density of new bone increased as magnesium degraded. These results support the positive effect of magnesium on osteogenesis. However, from the maximum inner diameter of the new bone loop and diameter of the pin in the same position, the magnesium alloy was not capable of creating sufficient bridges between the bones and biomaterials when there were preexisting gaps. Histological analyses indicated that there were no inflammatory responses around the implants. The results of the present study indicate that a micro-arc-oxidized AZ31 magnesium alloy is safe and efficiently degraded. Furthermore, the novel bone formation increased as the implant degraded. The findings concluded that micro-CT, which is useful for providing non-traumatic, , quantitative and precise data, has great value for exploring the degradation of implants and novel bone formation.
降解限制了镁合金的应用，且用于非创伤性定量评估植入物降解和骨形成的方法并不完善。在本研究中，使用微弧氧化的AZ31镁合金在60只雄性新西兰白兔体内评估植入物的降解和新骨形成情况。通过在植入前后对植入物称重，并在植入1、4、12、24、36和48周后进行微型计算机断层扫描（CT）和组织学分析来监测降解情况。结果表明，植入物在最初4周内降解缓慢，第1周降解可忽略不计，随后在第12至24周期间降解显著增加（P<0.05），并持续降解直至48周实验期结束。随着植入物降解，镁含量降低（P<0.05）；然而，材料密度几乎没有变化。微型CT结果还表明，针体积、针矿物质密度、平均“针厚度”、骨表面/骨体积和小梁间距随时间减少（P<0.05），而针表面积/针体积、骨体积分数、小梁厚度、小梁数量和组织矿物质密度随时间增加（P<0.05），表明随着镁降解，骨数量和新骨密度增加。这些结果支持了镁对成骨的积极作用。然而，从新骨环的最大内径和同一位置针的直径来看，当存在预先存在的间隙时，镁合金无法在骨与生物材料之间形成足够的桥接。组织学分析表明，植入物周围没有炎症反应。本研究结果表明，微弧氧化的AZ31镁合金安全且降解效率高。此外，随着植入物降解，新骨形成增加。研究结果得出结论，微型CT对于提供非创伤性、定量和精确数据很有用，在探索植入物降解和新骨形成方面具有重要价值。
