预应力对犬完整胫骨结构影响的实验研究

Experimental studies of the effects of prestress on in-tact canine bone structure

实验采用３１６Ｌ医用不锈钢制成等长等宽但底面和中央连接部位不同的普通型、凹面型和滑动型三种４孔钢板，并用以固定犬完整中段腔骨。以单纯普通皮质骨。螺丝钉固定作对照组。用静态应变仪测量不同条件下的胫骨应变值，观察不同时期活体骨组织内双硫蓝灌注后血供情况、骨结构改变及ＣＴ片图像分析观察胫骨灰度值的改变。结果发现不同固定方法使骨组织产生的顶应力不同。刚度较大的普通型钢板的预应力及应力遮挡作用最大，其早期皮质骨内缺血不明显，但其骨质疏松却出现较早（１个月）；刚度较小的滑动型钢板的预应力及应力遮挡作用最小，其早期皮质骨内缺血明显，其骨质疏松却出现较晚（３个月）。作者认为在本实验条件下，导致骨结构改变的主要原因是骨内预应力，而应力遮挡作用的影响相对较小，皮质骨内血运障碍并非骨质疏松改变的主要因素。

AbstractThree types of plate made of 316L medical stain-less steel were applied in the experiment.They weredivided into conventional plate,concave plate,slidingplate by their different shapes and functions. Theywere fixed on intact canine tibias and compared withintact canine tibias that were only fixed with conven-tional screws.Stress values were measured with staticstrain instrumennt in different conditions and in vitrotissue that was poured with disulphine blue.CT scan-ning was done in different stages. The experiment re-sults proved that different extents of intraosseous pre-stress were reduced by different plate fixings. Theconventional plate group with high stiffness producedthe greater prestress and stress shielding value andslight circulation disorder in bone tissue in early stage,but the osteoporosity of tibias bone ocurred early(lmonth );conventional plate with low stiffness producedthe less prestress and stress shielding value and severecirculation disorder in bone in early stage, but the os-teoporosity ocurred late( 3 month ).We consider thecause of local osteoporosity of tibias bone after plate fixed were mainly prestress,and stress shielding is secondary in early stage(3 month). The local circula-tion is disorder is not important factor.