多聚甲醛固定对大鼠椎骨黏弹性影响的实验研究

目的 观察多聚甲醛固定对大鼠椎骨黏弹性力学性能的影响，从生物力学角度寻找松质骨样品的最佳保存方式。方法 选择8周龄健康雌性SD大鼠20只，手术分离获得完整的腰椎L4和L5共40只，随机平均分为固定组和对照组,固定组置于4%多聚甲醛中固定72 h，对照组置于5 mL EP管内-20 ℃冷冻保存。两组随机各取10只分别行应力松弛和蠕变实验，7 200 s后收集样品并通过显微CT分析其微观结构变化。结果 固定组松弛蠕变曲线相比对照组更加平滑，达到稳态的时间较短，且500 s和7 200 s的松弛蠕变总量明显降低（P＜0.01）。显微CT结果显示松弛蠕变实验会引起骨小梁断裂，且固定组比对照组骨小梁破坏更加严重。结论 多聚甲醛固定法显著降低大鼠椎骨的黏弹性，在力学负荷下更易造成其微观结构破坏，不利于松质骨保存。
Objective To observe the effect of paraformaldehyde fixation on viscoelastic properties of the vertebrae in rats, so as to find the best methods of preserving cancellous bone samples from the perspective of biomechanics. Methods Twenty 8-week-old healthy female Sprague-Dawley rats were selected, and their whole L4 and L5 vertebra were separated by surgery. The total 40 vertebrae were randomly and evenly divided into experimental group and control group. The experimental group was fixed with 4% paraformaldehyde for 72 h, and the control group was transferred to 5 mL EP tube and cryopreserved at -20 ℃. Ten vertebrae were randomly selected from each group for stress relaxation and creep experiments. After 7 200 s, the samples were collected and their micro-structure changes were analyzed by micro-CT. Results The relaxation creep curve of experimental group was smoother than that of control group, the time to reach steady state was shorter, and the total amount of relaxation creep at 500 s and 7 200 s was significantly decreased (P<0.01). Micro-CT results showed that relaxation and creep experiment could cause trabecular rupture, and trabecular damage was more severe in experimental group than that in control group. Conclusions Paraformaldehyde significantly reduce the viscoelasticity of rat vertebrae, and it is more easily to cause microstructure damage under mechanical stimulation, which is detrimental to cancellous bone preservation.