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目的研究骨质疏松性骨折愈合过程中骨痂生物力学性能与显微三维结构、Ⅰ型胶原面积、骨密度的改变规律及相关性。方法采用双侧卵巢切除术(ovariectomy,OVX)建立大鼠骨质疏松模型(OVX组),假手术组(Sham组)作为对照。两组均于术后10周通过大鼠右后肢胫骨中段截骨建立骨折内固定模型;骨折内固定模型建立后4、6、8、12周进行大鼠右后肢胫骨中段骨密度测定,术后6周及12周进行骨痂生物力学强度、Ⅰ型胶原面积及显微三维结构测定。结果两组中骨密度测量值在骨折内固定术后6周高于术后12周(P<0.05),而生物力学强度、Ⅰ型胶原面积和结构模型参数(structure model index,SMI)值在骨折内固定术后第12周时高于术后6周(P<0.05)。组间比较显示,骨折内固定术后6周与12周时OVX组的SMI值均明显低于Sham组(P<0.05)。结论在骨折愈合过程中,骨矿含量峰值出现时间早于胶原量与生物力学强度峰值出现时间,胶原的累积程度可独立于骨的矿盐沉积程度作为预测骨生物力学强度的一个指标。
OBJECTIVE To study the changes and correlations of biomechanical properties, microscopic three-dimensional structure, type I collagen area, and bone mineral density in osteoporotic fracture healing. Methods The rat model of osteoporosis (OVX) was established by ovariectomy (OVX). Sham group was used as the control. At 10 weeks after operation, the fracture fixation model was established in the middle tibia of the right hindlimb in both groups. The bone mineral density of the middle tibia in the right hindlimb was measured at 4, 6, 8 and 12 weeks after establishment of the fracture fixation model. The biomechanical strength, type I collagen area and microstructure of callus were measured at 6 weeks and 12 weeks. Results The bone mineral density measured in the two groups was significantly higher at 6 weeks postoperatively than at 12 weeks postoperatively (P <0.05), whereas biomechanical strength, type I collagen area, and structure model index (SMI) Fracture fixation was higher at 12 weeks after operation than 6 weeks after operation (P <0.05). Comparisons between groups showed that the SMI values of OVX group were significantly lower than those of Sham group at 6 and 12 weeks after fracture fixation (P <0.05). Conclusions During fracture healing, peak time of bone mineral content occurs earlier than peak time of collagen and biomechanical strength. The accumulation of collagen can be used as an index to predict the biomechanical strength of bone independently of the mineral deposit of bone.