大鼠胫骨骨折固定术后同侧股骨骨密度和生物力学性能的变化

目的探讨胫骨骨折后大鼠股骨骨密度及股骨生物力学性能变化及其与胫骨骨折愈合状况的关系。方法将40只3月龄雌性SD大鼠随机分为2组:手术组和对照组,每组20只。手术组实行右侧胫骨中段骨折内固定术。手术前和实行手术后第2、4、6、8、10、12周测量右侧股骨骨密度,第6周和第12周分别处死10只手术组和10只对照组大鼠,进行右侧胫骨和股骨生物力学性能的测量。结果术后6周,胫骨骨折的放射学愈合率为50%,机械愈合率为70%;术后12周胫骨骨折的放射学和机械愈合率均为100%。手术组股骨骨密度与对照组相比,术后2、4、6、8周降低(P<0.05),术后10、12周时与对照组差异无统计学意义。术后6周右侧胫骨和股骨的生物力学性能明显低于术后12周(P<0.05)。相关分析显示胫骨愈合情况与力学性能高度相关(P<0.01),胫骨力学性能与股骨骨密度和股骨力学性能高度相关(P<0.001)。结论胫骨骨折早期同侧股骨骨密度及生物力学性能下降,发生了废用性骨质疏松;但晚期随胫骨骨折愈合,股骨的骨密度和生物力学性能恢复正常。

Changes of bone mineral density and biomechanical properties of the femur after ipsilateral tibia fracture and fixation in rats

Objective To investigate the changes of bone mineral density (BMD) and biomechanical properties of the femur after ipsilateral tibia fracture in rats, and its relationship with the tibia fracture union. Methods Forty 3-month-old female SD rats were divided into 2 groups randomly and evenly: the surgery group and the control group. The surgery group received middle shaft fracture and fixation surgery on the right tibia. BMD of the right femur was measured both before the surgery and at 2nd, 4th, 6th, 8th, 10th, 12th week after the surgery, respectively. Ten rats in the surgery group and ten rats in the control group were executed at 6th and 12th week after the surgery, respectively, to test the biomechanical properties of their right tibia and femur. Results The radiological union rate and mechanical union rate of the tibia were 50% and 70%, respectively, at 6th week after the surgery, and those at 12th week after the surgery were both 100%. At 2nd, 4th, 6th, 8th week after the surgery, BMD of the right femur in the surgery group was significantly lower than that in the control group (P<0.05). Compared with the control group, there was no statistical difference in BMD of the right femur at 10th, 12th week after the surgery. Biomechanical properties of the right tibia and femur at 6th week after the surgery showed obviously worse than those at 12th week after the surgery (P<0.05). Analysis showed that the fracture union was highly related with mechanical properties of the tibia (P<0.01), which was also highly related with BMD and mechanical properties of the femur (P<0.001). Conclusions In the early stage of tibia fracture, disuse osteoporosis might occur due to the decrease of BMD and worse mechanical properties in the ipsilateral femur, but as the tibia fracture united, BMD and biomechanical properties of the femur became normal again.