目的观察恒强旋转磁场对骨折愈合过程中骨形态蛋白-2(BMP-2)和血小板源性生长因子(PDGFs)在骨折部位不同时间表达的变化，探讨恒强旋转磁场促进骨折愈合的机制。 方法将80只建立股骨闭合性骨折模型的Sprague Dawley（SD）大鼠按随机数字表法分为磁场干预组和对照组，每组40只。磁场干预组大鼠置于0.4T恒强旋转磁场(浙江康尔医疗器械公司)中，磁体旋转频率6Hz，每日磁场干预1次，每次连续30min，每周6次；对照组未做任何干预处理。分别于骨折后2、3、4和8周四个观察时间点（每个时间点10只大鼠），观察各组大鼠骨折部位BMP-2、PDGF-A和PDGF-B免疫组化染色阳性表达，并采用Nikon显微成像分析仪（Nikon 50i，日本）拍照（图像放大400倍），用生物图像分析处理软件测量阳性染色区域的积分光密度值(IOD)。采用双因素方差分析比较时间、磁场的主效应及二者的交互效应。 结果①不同时间点各组大鼠骨折部位BMP-2阳性表达的IOD值比较，差异有统计学意义（F=21.58，P<0.01），多重比较显示，BMP-2阳性染色区域在骨折后2、3和4周时的IOD值均明显高于骨折后8周（P<0.01），骨折后4周的IOD值亦明显高于骨折后2周（P<0.01）；磁场干预与时间存在有交互作用（F=3.17；P<0.05）。②磁场干预组与对照组大鼠不同时间点间骨折部位的PDGF-A阳性表达IOD比较，差异有统计学意义（F=28.16，P<0.01），多重比较显示，骨折后2周骨折部位PDGF-A的阳性表达的IOD值显著高于骨折后3周（P<0.01)、4周（P<0.01)和8周（P<0.01)，骨折后3周和4周PDGF-A的阳性表达IOD也显著高于骨折后8周(P<0.01)。③磁场干预组骨折部位的PDGF-B阳性表达IOD值明显高于对照组［磁场干预组（57.6±2.1） vs 对照组（50.11±2.22）］，差异有统计学意义（F=5.98，P<0.05）；且不同时间点骨折部位PDGF-B阳性表达IOD值比较，差异亦有统计学意义（F=50.06，P<0.01），多重比较显示，骨折后3周骨折部位PDGF-B阳性表达IOD值显著高于骨折后2周（P<0.05）、4周（P<0.01）和8周（P<0.01），骨折后2周和4周阳性表达IOD值亦显著高于骨折后8周（P<0.01）。 结论恒强旋转磁场可能通过调节骨折部位BMP-2和PDGF-B的表达，促进骨折的修复。 Objective To evaluate the effect rotation constancy static magnetic field(RCSMF) on the expression of bone morphogenetic protein-2 (BMP-2) and platelet-derived growth factors (PDGFs) in fracture healing, and elucidate the possible mechanism of RCSMF promoting fracture healing. Methods A total of 80 rats with femur closed fracture were randomly divided into a magnetic treatment group (M) and a control group (C). The M group was given RCSMF treatment 30 minutes per day, 6 times per week, using 0.4 T 6 Hz magnetic field, while the C group was not given any intervention. Femurs and calluses were subjected to BMP-2, PDGF-A and PDGF-B immunohistochemistry assay at 2, 3, 4 and 8 weeks after the treatment. The integrated optical density (IOD) of positive staining was calculated. Two-factor variance analysis was used to compare the main effect of time, treatment and that of their interaction. Results For both groups, the IOD of immunoreactivity of BMP-2 at 2, 3 and 4 weeks after the treatment was significantly higher than that 8 weeks after the treatment, and the value at four weeks after the intervention was also significantly higher than that at 2 weeks after it. There was a significant interaction effect of time×treatment of BMP-2 (F=3.17, P<0.05). Significant differences were observed in the IOD of positive staining PDGF-A at different time points for both groups: the value at 2 weeks after treatment was significantly higher than that at 3, 4 and 8 weeks after the treatment,
