Mg-1．5Sr合金在大鼠骨修复过程中降解的实验研究

Degradation of Mg-1.5Sr alloy during bone repair in rats

目的探讨Sr含量为1．5wt％时Mg-Sr合金在体内的降解行为及其对骨生长的促进作用。方法选取12只8周龄SD雄性大鼠，随机分成两组（n=6）：将Mg-1．5Sr合金制成的多孔支架植入到SD大鼠左侧股骨髁作为实验组，对照组左侧股骨髁植入纯Mg支架。术后4、8、12周进行Micro—CT扫描，通过断层图像观察支架降解状况及骨生长情况。重建支架3D模型并比较各时期体积变化，计算支架在体内的降解速率。测量支架周围的骨密度（BMD）、骨体积分数（BV／TV）、骨小梁厚度（Tb．Th）、骨小梁数量（Tb．N），分析骨生长状况。结果术后4、8、12周断层图像显示实验组Mg-1．5Sr支架较对照组纯Mg支架降解更为缓慢，且周围新骨生长面积更大。术后4、8、12周实验组Mg-1．5Sr合金在体内的降解速率平均分别为（0．34±0．04）、（0．28±0．09）、（0．31±0．05）mm／年，显著低于对照组纯Mg支架[（0．51±0．01）、（0．37±0．08）、（0．39±0．06）mm／年]，差异均有统计学意义（P〈0．05）。术后12周实验组的BMD、BV／TV、Tb．Th、Tb．N平均分别为（0．62±0．08）g／mm^3、53％±11％、（298±50）μm、（0．0027±0．0002）个／μm，均显著高于对照组[（0．56±0．08）g／mm^3、48％±8％、（220±40）μm、（0．0023±0．0002）个／μm]，差异有统计学意义（P〈0．05）。结论Mg．1．5Sr合金具有良好的生物相容性，在体内降解速率低且具有良好的成骨性能，是-种具有巨大潜能的骨科内植入材料。

Objective To explore the effect of degrading process of Mg-Sr alloy （containing 1.5 wt% Sr） on bone growth in rats. Methods Twelve male SD rats of 8 weeks old were randomly divided into 2 even groups （ n = 6）. In the experimental group, a stent made of Mg-1.5Sr alloy was put into the left femoral condyle of each rat while a pure Mg stand was used in the control group. The 2 groups were subjected to Micro-CT scanning at 4, 8, and 12 weeks after surgery. Cross-sectional images were generated for clear observation of the degrading process of the stands and the skeletal growth in the rats. Next, 3D models were made to compare changes in stand volume to calculate their degrading rates. The skeletal growth in the rats were also analyzed by measuring a series of indexes, including bone mineral density （BMD）, bone volume fraction （BV/TV）, trabeeular thickness （Tb. Th） and trabeeular number （Tb. N. ）. Results The cross-sectional images at 4, 8 and 12 weeks showed that the Mg-1.5Sr stands degraded more slowly than the pure Mg ones and more new bone grew out around the Mg-1.5St stands than around the pure Mg ones. The degrading rates of Mg-1.5Sr alloy inside the rats at 4, 8 and 12 weeks were respectively 0.34 ±0.04 ram/y, 0. 28 ± 0. 09 mm/y and 0. 31 ± 0.05 ram/y, significantly lower than those of pure Mg （0. 51 ± 0. 01 ram/y, 0. 37 ± 0. 08 mm/y and 0. 39 ± 0. 06 mm/y） （P 〈0.05）. The BMD, BV/TV, Tb. ThandTb. Nat12 weeks in the experimental group （0. 62 ±0.08 g/mm^3, 53% ± 11%, 298 ±50 μm, 0. 0027 ±0. 0002/μm） were significantly greater than those in the control group （0.56 ± 0.08 g/mm^3, 48% ± 8%, 220 ± 40 μm, 0. 0023 ± 0. 0002/μm） （ P 〈 0. 05 ）. Conehmion Mg-1.5Sr alloy may be a promising orthopedic im- plant material with great bioeompatibility due to its relatively low degrading rate and good bone formation performance.