AZ31镁合金材料植入物在兔股骨髁内的降解：Micro-CT评价

BACKGROUND: Magnesium can be degraded voluntarily in vivo, so a second surgery is avoided. However, its alloys have not been widely used in the clinical orthopedics because there is a lack of accurate and reliable methods to assess its degradation in vivo.OBJECTIVE: To explore the degradation of micro-arc-oxidized AZ31 magnesium alloy in the femoral condyle of rabbits based on micro-CT images and relative data.METHODS: Forty micro-arc-oxidized AZ31 magnesium alloys were implanted into the right femoral condyle of 40 New Zealand rabbits. Then 10 right femoral condyles were removed at 5, 10, 15 and 20 weeks after surgery, respectively, to quantitatively analyze and evaluate the degradation of AZ31 magnesium alloys by micro-CT images and relative data. RESULTS AND CONCLUSION: The surface of AZ31 alloys was corroded progressively with dark color and distorted appearance at 5-20 weeks post implantation. Micro-CT images showed that in the first 5 weeks, the degradation was inactive, and at the 10th week, it turned active; at the 15th week, the corrosion pits were obviously increased in number, and the corrosion area and corrosion speed were enlarged and fastened, respectively. Up to the 20th week, the alloy surfaces were full of corrosion pits besides roughness and discontinuity. Relevant data analysis showed that the volume fraction of magnesium alloy was 98.6%, 97.1% and 86.4% at the 5th, 10th and 20th weeks after implantation, respectively, and it had a significant decrease from the 10th to 15th week and from the 15th to 20th week (P < 0.05). Within 15-20 weeks, the volume fraction of magnesium alloy was decreased by 6.5% that was the maximum volume reduction per unit cycle. With the progress of corrosion, the surface continuously became rough and vague, and its surface area was enlarged; the ratio of surface area to volume continuously increased, and there was a significant difference at 15 and 20 weeks (P < 0.05). Because of the increasing number of corrosion pits, the cross-sectional radius decreased, which was reflected by the trabecular thickness decreasing from 1.00 to 0.87 mm. From the view of the slope of curve, the trabecular thickness decreased most rapidly at 10-15 weeks. The mineral density of magnesium alloy continuously decreased from 649.302 to 356.445 mg/cm3 during the whole experiment period (P < 0.05). In addition, the micro-CT image density decreased from 679.710 to 644.947 mg/cm3, but there was no significant difference. To conclude, the degradation speed is peaked at 10-20 weeks after implantation, and the content of magnesium alloys decrease with degradation, but the magnesium density has no significant change.中国组织工程研究杂志出版内容重点：生物材料；骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性；组织工程

Degradation of AZ31 magnesium alloys in vivo: micro-CT assessment