| Objective: The study simulates human posterior removal of nucleus pulposus, to establish a rabbit model of intervertibral disc degeneration via posterolateral aspirating the nucleus pulposus with needles of defined gauges, analyse its feasibility and advantage, detect and analyse with imageology and pathology, reproduct the objective law of development of disc degeneration process, provide better animal model for the study of disc degeneration, also provide the disc reconstruction experimental basis for the use of methods such as tissue engineering .Methods: The L1/2 and L3/4 lumbar intervertebral discs of 20 Japanese white rabbits were included in the experimental group, the L2/3 discs were included in the control group. After intramuscular anesthesia with Sumianxin and conventional preoperative preparation, they were lied down as left lateral position, separated bluntly along the right posterolateral intermusecular of L1/2 and L3/4 by the right posterolateral approach, exposed transverse foramen and the posterolateral annulus fibrosus in the inverted "A" region, paralleled the endplate and punctured the posterolateral annulus fibrosus using a 21 G needle with 10 ml sterile disposable syringes. The needle was trapped with sterile plastic sleeve as to hold 5 mm length and control 5 mm in depth. Then aspirated back about 10 ml, with 5.0-8.0 mg nucleus pulposus. Layer sutured and incision closed. Animals were randomly divided into 2,4,8,12-week four model groups after regaining consciousness, each with five ,bred separately and conventionally in the cages. Intramuscular injected gentamicin for three days to prevent wound infection. Each of the experimental group and control group discs was scaned with computed radiography(CR) and magnetic resonance imaging (MRI) at 2,4,8,12 weeks after the operation. Then the rabbits were killed respectively, took the L1/2, L3/4 and L2/3 discs for Masson stain, observing histopathology changes of the discs.Results: (1) Imageology analysis from the 2nd week to 12th week, X-ray showed that the intervertebral spaces of the experimental groups were turning narrow, the DHI% was decreasing as the extension of time, the difference of each period of time was significant (P <0.05), and bone density of the cartilage endplate and vertebral marginal was increasing. MRI showed that in the experimental group,the area of nucleus pulposus was reducing, yet the annulus fibrosus was increasing. The MRI T2-weighted signal of the nucleus pulposus was lower and darken. The signal intensity of nucleus pulposus was gradually decreasing. The improved -Thompson classification of MRI gradually biased serious in various stages, the difference was statistically significant (P <0.05). (2) Pathology observation , Masson staining showed that in the control groups the nucleus pulposus forms regularly, it has clear boundaries with annulus fibrosus and many nucleus pulposus cells. The annulus fibrosus arranges neat and dense .In the experimental groups, nucleus pulposus forms fissure, the collagen arranges disorder, the nucleus pulposus cells were decreasing. As time extense, the analogous- cartilage cells were gradually decreasing, the nucleus pulposus turned fibrosis, and the annulus fibrosus layered disorder, distorted and broken gradually. Nishimura pathological grade of the discs was statistically significant in each period of time (P <0.05).Conclusions: (1) The empirical study confirmed the basic characteristics of rabbit's disc degeneration through the imaging analysis and histopathology; (2) Simulate human posterior removal of nucleus pulposus, posterolateral aspirating the nucleus pulposus with needles of defined gauges results in a slowly progressive intervetibral disc degeneration in rabbit model .Tt's a simple model with good repeatability and so the ideal animal model to study etiology and pathophysiology of disc degeneration. It is available for reproducting the objective law of development of disc degeneration process, providing experimental basis for studying disc herniation recurrence and testing reliable, effective treatment for degenerative disc of the new methods such as growth factor therapy, gene therapy, cell therapy and tissue engineering etc.
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