骨折段低频可控微动影响骨痂矿化与力学特性的实验研究

Experimental study on callus calcification and mechanical property of healing bone under low frequency and controlled micromovement

目的探讨自行研制可控性微动外固定器对试验性长骨骨折愈合中骨痂矿化与愈合骨力学特性的影响。方法对45只绵羊行双侧胫骨中段横行截骨,间隙2 mm,用连有微动装置的单边外固定器固定。术后10 d,随机选择一侧肢体进行微动刺激(30 min/d),按不同的微动频率分为0.5 Hz组、1 Hz组和5 Hz组(n=15),幅度为0.25 mm,至第4周末结束;另一侧后肢不作微动,为对照组。分别于术后4、6、9周各处死5只动物,采集标本进行硬组织切片,观察骨痂矿化的程度,并比较9周后愈合骨的成骨速率、骨矿物质密度和力学特性。结果术后4、6周末,各实验组骨痂矿化骨小梁和类骨质的面积大于对照组(P<0.05);术后9周末,各实验组矿化骨小梁的面积迅速增加,类骨质的面积低于对照组(P<0.05)。各实验组成骨速率均快于对照组,且骨矿物质密度和愈合骨的峰值载荷、弯曲刚度高于对照组(P<0.05),以1 Hz组最为显著。结论骨折段早期低频微动能有效促进骨痂类骨质的形成与矿化,缩短骨痂矿化延迟时间,增加愈合骨的矿物质含量,进而加速骨折的愈合,微动频率以1 Hz效果最佳。

Objective To investigate the effects of external fixator with dynamic device under low frequency and controlled micromovement on the callus calcification and mechanical property of healing bone. Methods Forty-five sheep were performed transverse osteotomy with a gap of 2 mm on the mid-shafts of both tibias, and the hind limbs were fixed with unilateral external fixators connected to a controlled micromovement device. Ten days after osteotomy, one hind limb of each sheep was randomly selected for micromovement（30 min/d）. According to different micromovement frequencies, the sheep were randomly divided into 3 groups： 0.5 Hz group, 1 Hz group and 5 Hz group（ n = 15）. The amplitude of micromovement was 0.25 mm and the micromovement stopped by the end of the fourth week postoperation. The other hind limb of each sheep was served as control group without micromovement. Morphometry of callus was done at the end of 4, 6 and 9 weeks after osteotomy. Bone formation velocity, bone mineral density and biomechanical properties were compared at the end of 9 weeks. Results The areas of mineralized bone and osteoid in different miromovement groups were larger than that of control group at the end of 4, 6 weeks postoperation（P 〈0.05）. However, the areas of mineralized bone increased and the areas of osteoid diminished significantly in micromovement groups compared with those of control group at the end of 9 weeks postoperation（P 〈0.05）. Bone formation velocity was faster and bone mineral density, peak loading and bending stiffness were stronger in micromovement groups compared with those of control group （ P 〈 0.05）. Conclusion Low frequency micromovement applied at the early stage of fracture could promote osteoid formation and mineralization, reduce the mineralized lag time and increase the bone mineral content and bending stiffness of the healing bone, promote the bone healing and improve the quality as well. A frequency of 1 Hz is optimal to produce the best results.