Objective: To evaluate the effect of a novel micro-arc oxidation (MAO) coated magnesium-zinc-calcium (Mg-Zn-Ca) alloy scaffold/autologous bone particles to repair critical size bone defect (CSD) in rabbit and explore the novel scaffold in vivo corrosion resistance and biocompatibility.
Methods: Seventy-two New Zealand white rabbits were randomly divided into 3 groups ( n=24), group A was uncoated Mg-Zn-Ca alloy scaffold group, group B was 10 μm MAO coated Mg-Zn-Ca alloy scaffold group, and group C was control group with only autologous bone graft. The animals were operated to obtain bilateral ulnar CSD (15 mm in length) models. The bone fragment was removed and minced into small particles and were filled into the scaffolds of groups A and B. Then, the scaffolds or autologous bone particles were replanted into the defects. The animals were sacrificed at 2, 4, 8, and 12 weeks after surgery (6 rabbits each group). The local subcutaneous pneumatosis was observed and recorded. The ulna defect healing was evaluated by X-ray image and Van Gieson staining. The X-ray images were assessed and scored by Lane-Sandhu criteria. The percentage of the lost volume of the scaffold (ΔV) and corrosion rate (CR) were calculated by the Micro-CT. The Mg 2+ and Ca 2+ concentrations were monitored during experiment and the rabbit liver, brain, kidney, and spleen were obtained to process HE staining at 12 weeks after surgery.
Results: The local subcutaneous pneumatosis in group B was less than that in group A at 2, 4, and 8 weeks after surgery, showing significant differences between 2 groups at 2 and 4 weeks after surgery ( P<0.05); and the local subcutaneous pneumatosis was significantly higher in group B than that in group A at 12 weeks after surgery ( P<0.05). The X-ray result showed that the score of group C was significantly higher than those of groups A and B at 4 and 8 weeks after surgery ( P<0.05), and the score of group B was significantly higher than that of group A at 8 weeks ( P<0.05). At 12 weeks after surgery, the scores of groups B and C were significantly higher than that of group A ( P<0.05). Meanwhile, the renew bone moulding of group B was better than that in group A at 12 weeks after surgery. Micro-CT showed that ΔV and CR in group B were significantly lower than those in group A ( P<0.05). Van Gieson staining showed that group B had better biocompatibility and osteanagenesis than group A. The Mg 2+ and Ca 2+ concentrations in serum showed no significant difference between groups during experiments ( P>0.05). And there was no obvious pathological changes in the liver, brain, kidney, and spleen of the 3 groups with HE staining at 12 weeks.
Conclusion: The MAO coated Mg-Zn-Ca alloy scaffold/autologous bone particles could be used to repair CSD effectively. At the same time, 10 μm MAO coating can effectively improve the osteanagenesis, corrosion resistance, and biocompatibility of Mg-Zn-Ca alloy scaffold.
目的: 探讨一种新型微弧氧化（micro-arc oxidation，MAO）涂层镁（Mg）-锌（Zn）-钙（Ca）合金支架/自体颗粒骨修复兔临界性骨缺损（critical size bone defect，CSD）的效果，以及该支架在体内的耐腐蚀性和生物相容性。.
方法: 将 72 只新西兰白兔随机分为 3 组（ n=24），A 组为无涂层 Mg-Zn-Ca 合金支架组；B 组为 10 μm 厚 MAO 涂层 Mg-Zn-Ca 合金支架组；C 组为单纯自体颗粒骨植骨组。所有动物制备双侧尺骨 15 mm 长 CSD 模型，A、B 组将截取的尺骨制成颗粒骨后填充至支架内修复尺骨缺损，C 组采用自体颗粒骨修复。术后 2、4、8、12 周，行大体观察并记录局部皮下积气量；X 线片和 Van Gieson 染色观察骨缺损愈合情况，根据 Lane-Sandhu 标准行 X 线片评分；Micro-CT 扫描观察并计算支架降解丢失体积百分比（ΔV）及降解速度（corrosion rate，CR）；监测实验过程中血清 Mg 2+、Ca 2+ 浓度变化，并于术后 12 周收集肝、脑、肾和脾组织行病理学观察。.
结果: 术后 2、4、8 周 B 组皮下积气量少于 A 组，其中2、4 周两组间比较差异有统计学意义（ P<0.05）；但术后 12 周时 B 组显著多于 A 组（ P<0.05）。术后 4、8 周 C 组 X 线片评分显著高于 A、B 组（ P<0.05），术后 8 周时 B 组显著高于 A 组（ P<0.05）；术后 12 周 B、C 组显著高于 A 组（ P<0.05），但 B、C 组间差异无统计学意义（ P>0.05），同时 B 组骨缺损部位新骨塑形明显优于 A 组。Micro-CT 示术后 4、8 周，B 组 CR 及ΔV 均显著低于 A 组（ P<0.05）。Van Gieson 染色示 B 组较 A 组具有更好的生物相容性和促成骨性；血清离子监测结果显示术后各时间点 3 组血清 Mg 2+、Ca 2+ 浓度比较，差异均无统计学意义（ P>0.05）；术后 12 周，3 组实验动物肝、脑、肾及脾组织 HE 染色均未见明显病理改变。.
结论: 新型 MAO涂层 Mg-Zn-Ca 合金支架/自体颗粒骨能够有效修复 CSD；同时，10 μm 厚 MAO 涂层能有效改良 Mg-Zn-Ca 合金支架的骨修复效果、耐腐蚀性及生物相容性。.
Keywords: Mg alloy scaffold; biocompatibility; corrosion resistance; critical size bone defect; micro-arc oxidation; rabbit.