持续过度应力作用下兔胫骨生物力学性质的动态实验观察

Dynamic Investigation of Tibial Biomechanical Property Endured Persistent Intensive Stress

为进一步观察持续过度应力作用下兔胫骨生物力学性质的动态变化,本实验以青紫兰兔37只,进行大强度主动跑跳试验,并于不同训练周期采集胫骨标本进行扭转破坏实验。实验发现:(1)兔胫骨生物力学性质表现出明显的周期性;在本实验里该周期约为6周。(2)在每周期的第2～3周胫骨生物力学性质显著变化,抗变形能力降低-扭转刚度急剧下降(69．7％,P<0．01),柔韧系数明显升高(203．2％,P<0．05),破坏扭转角明显增加(102．9％,P<0．05);力学强度下降-破坏扭矩、破坏能量吸收和破坏能量吸收密度显著低于对照(多低于对照50％,甚至仅为其34．5％;P<0．01或P<0．05)。我们有理由认为:在持续应力作用下,骨组织的力学性质有明显的波动,表现出一定的周期性,在本实验中胫骨的力学性质变化周期约为6周;在训练周期的2～3周,胫骨生物力学性质明显下降。

For investigating the changes in continuous biomechanical nature of bone bearing intensive stress in vivo, we adopted the animal model of persistent intensive stress. Thirty-seven rabbits were involved in the experiment; they were randomly divided into control group （5 rabbits） and trained group （32 rabbits）. All animals were forced to jump and run about 300 times everyday in the electric stimulation cage so as to simulate the persistent intensive stress on tibias for different periods. Subsequently, all animals were sacrificed at different times （1-11weeks）, and all tibias of them were collected for biochemical investigation. By torsion destroy test, the experiment showed that the changes of biomechanical nature appeared obviously in a period of 6 weeks or so in the experiment. Furthermore, during the 2nd-3rd week of each period, the biomechanical indexes decreased strikingly; the abilities of deformation resistant dropped, the twisting rigidity decreased （69. 7% lower than control, P〈 0. 01）, the flexible index inereased （203.2% higher than control,P〈0. 05）,the angle of twisting destroy increased （102.9% greater than control, P〈0. 05）. And the tibial mechanical strength declined too; the destroy torsion, energy absorption and energy absorb density decreased （most of them being 50% lower than control, even accounting for 34.5% of control; P〈 0. 05 or P〈 0. 01）. We noticed that the biomechanical properties of bone endured persistent intensive stress presented periodicity and the period of change in bone biomechanical nature covered about 6 weeks in the experiment. Therefore, we have ground to conclude that a weakness period did exist when rabbit tibias endured 2-3 weeks persistent intensive stress, and such weakness did exist at the 2nd-3rd week of each training period.