Research on positive acceleration induced rabbit lumbar disc degeneration by means of quantized axial loading device

Abstract

Objective To estimate the influence of simulated positive acceleration on rabbit lumbar disc degeneration by means of a controllable axial loading device,and to provide experimental reference for the further study on pilot's lumbar disc degeneration.Methods Twenty four New Zealand white rabbits were randomly divided into 4-week group (n=8),8 week group (n=8) and control group (n =8).A self-designed controllable axial loading device was utilized to impose 40 N compress forces on the discs of the rabbits for 15 s,10 times a day for 4 and 8 weeks in two experimental groups respectively but in control group.Degeneration of the discs was evaluated by disc height index (DHI),magnetic resonance imaging (MRI) scanning results,type Ⅰ and type Ⅱ collagen that got from haematoxylin and eosin (HE) staining,and immunohistochemical staining.Results ① Compared with that of control group and 4-week group,DHI of 8-week group had statistical difference (P＜ 0.01).There was no DHI difference between 4-week group and control group (P＞0.05).②Compared with that of control group and 4 week group,Pfirrmann's system (MRI) of 8 week group showed statistical difference (Z=3.655,3.330,P＜0.01),but the difference between 4-week group and control group (P＞0.05).③Compared with that of control group and 4-week group,Thompson grade of 8-week group showed statistical difference (Z=2.893,2.095,P＜0.05).Thompson grade did not significantly differ between 4-week group and control group (P＞0.05).④Immunohistochemical staining showed that the degeneration of type Ⅱ collagen in 8-week group was more serious.Staining for type Ⅰ collagen showed that the distribution of positive staining increased in nucleus pulposus.Conclusions According to DHI,MRI and pathology results,the lumbar disc of the rabbits in experimental group appear early degeneration,and become more serious as the loading time prolonged.It provides a good experimental reference for the further study of pilot's lumbar disc degeneration. Key words: Rabbit;  Intervertebral disc;  Magnetic resonance imaging;  Acceleration;  Model,animal