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目的 探讨模拟失重下雌、雄性大鼠影像学参数预测骨折风险相关性及性别差异的原因.方法 3月龄雌、雄性SD大鼠40只,按性别及是否失重随机分为4组,4周后,双能X线检测L4椎体、股骨BMD,Micro-CT分析骨小梁结构,生物力学测试力学强度.结果 失重4周后,雌性组子宫重量降低47.3％,雄性组精囊重量降低39.5％.失重试验组BMD显著下降,骨体积分数(BV/TV)、骨小梁厚度(Tb.Th)、骨小梁数目(Tb.N)显著降低(P＜0.05),骨小梁间隙(Tb.Sp)显著增加;悬吊组椎体的最大压缩载荷(N)、压缩压力(MPa)、抗弯曲载荷(N)较对照组显著下降.BMD、BV/TV、Tb.Th、Tb.N、Tb.Sp与最大力学强度Fmax相关性系数r,雄性组为0.985、0.995、0.948、0.957、-0.990,雌性组为0.908、0.899、0.873、0.852、-0.76.结论 失重4周后,不同性别大鼠BMD明显降低,激素水平的影响可能是模拟失重雌性大鼠骨丢失更严重原因之一.骨密度与失重后生物力学的相关性可综合有效地预测失重后的骨折风险.“,”Objective Analyze the different changes of bone mineral density(BMD),bone microstructure and mechanical properties of male and female rats under simulated weightlessness to predict relevant relationship and the risk of bone fracture.Methods Forty 3-months SD rats,containing 20 male and 20 female rats,the same gender rats were randomly divided into tail suspended group (TS) and control group.After 4 weeks,general index changes were compared.The BMD of L4 lumbar vertebra and femoral condyle were measured with dual-energy X-ray absorptiometry (DEXA),the microstructure were analyzed with Micro-CT and the biomechanics was tested with biomechanical testing machine.Results After simulated weightlessness,the BMD of L4 and femoral condyle of TS groups were obviously lower than the control groups.And the bone volume fraction (BV/TV),the thickness and number of the osteal trabeculaes (Tb.Th.& Tb.N) of the cancellous bones were so obviously lower (P ＜ 0.05).However,the trabecular separation (Tb.Sp) of the TS group were significantly higher than the control group (P ＜ 0.05).The maximal compressive load strength(N),the maximal compressive stress(MPa) and the maximal antibending load (N) were obviously lower.The correlation coefficient ‘r’ value between Fmax and BMD,BV/TV,Tb.Th,Tb.N,Tb.Sp in male groups is 0.985,0.995,0.948,0.957,-0.990,and in female group is 0.908,0.899,0.873,0.852,-0.76.However,the weight of seminal vesicle and uterus decreased 39.5％ and 47.3％ in male and female TS groups.Conclusions For 4 weeks simulated weightlessness,obvious osteoporosis,destruction of BMD,decrease of the mechanical strength.The gender differences may be relative to the sex hormones.