Shanghai Biomaterials Research & Testing Center, Shanghai, Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200023, China; Department of Prosthodontics, School of Stomatology, Tongji University, Shanghai Engineering Research Center of Tooth Restoration and Regeneration, Shanghai 200072, China.
Shanghai Biomaterials Research & Testing Center, Shanghai, Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai 200023, China.
Acta Biomater. 2018 Apr 15;71:215-224. doi: 10.1016/j.actbio.2018.02.023. Epub 2018 Mar 17.
Magnesium (Mg) based materials are the focus of research for use as degradable materials in orthopedics and cranio-maxillofacial surgery. However, corrosion rate control and biosecurity are still the key issues that need to be solved prior to their clinical applications. In the present study, as-rolled high-purity magnesium (HP Mg, 99.99 wt%) screws were implanted in rabbit tibiae for up to 52 weeks in order to investigate their long-term in vivo degradation and the local and systemic effects of their degradation products. A series of long-term monitoring were performed at various time points (4w, 12w, 26w and 52w) after implantation using numerous investigations such as micro-CT assay, histomorphometric analysis, local micro-environment testing and biochemical analysis of serum and urine. It was revealed that HP Mg screws had a uniform degradation morphology and a slow degradation rate in vivo during the period of 52 weeks. Their degradation products not only increased the local pH values but also changed the local Mg ions concentration and gas cavity area in the peri-implant tissues in a dynamic manner. More importantly, both the new bone formation and bone-implant contact rate were increased at bone-implant interfaces at 26 weeks and 52 weeks post-implantation. Furthermore, neither abnormal elevation of serum magnesium and urine magnesium level, nor liver and kidney dysfunction were detected during the monitoring period of 26 weeks. All these results of long-term investigation suggest that HP Mg screws possess a slow degradation rate, desirable bone repair capacity and long-term local/systemic biosafety, and consequently may have good potential for application as bone fixation devices.
The corrosion resistance control and biosecurity issues of Mg alloys limited their clinical applications in some extent. Mg purification is another effective way to improve corrosion resistance of Mg-based materials. However, the long-term in vivo degradation of high-purity magnesium (HP Mg) and the local and systemic effects of its degradation products have not been fully investigated yet, which are the key factors to determine the clinical application prospect of HP Mg. Especially the changes in peri-implant microenvironment may greatly influence the local physiological response and bone repair. In this study, the long-term evolution tendency of in vivo degradation behavior of HP Mg screws was discovered from the view of space-time. Furthermore, not only the dynamic changes of local microenvironment and the long-term evolution process of bone repair, but also the dynamic systemic responses were systematically revealed. Conclusions of this study may help us to further understand the long-term in vivo evolution of HP Mg degradation and the local/systemic effects of its degradation products and help to guide the design of biodegradable bone fixation material.
研究作为可降解材料在骨科和颅面外科中应用的镁（Mg）基材料，腐蚀速率控制和生物安全性仍然是其临床应用前需要解决的关键问题。本研究将纯镁（HP Mg，99.99wt%）轧制成螺钉，植入兔胫骨中长达 52 周，以研究其体内长期降解情况以及降解产物的局部和全身影响。在植入后不同时间点（4w、12w、26w 和 52w），通过微 CT 检测、组织形态计量学分析、局部微环境检测和血清及尿液生化分析等一系列长期监测，发现 HP Mg 螺钉在 52 周体内具有均匀的降解形态和缓慢的降解速率。其降解产物不仅动态地增加了局部 pH 值，而且改变了植入组织中局部镁离子浓度和气体腔面积。更重要的是，在植入后 26 周和 52 周时，新骨形成和骨-植入物接触率均增加了。此外，在 26 周的监测期间，未检测到血清镁和尿镁水平异常升高，也未检测到肝肾功能障碍。这些长期研究结果表明，HP Mg 螺钉具有缓慢的降解率、理想的骨修复能力和长期的局部/全身生物安全性，因此可能具有作为骨固定装置的良好应用前景。
