Disc degeneration in the rabbit: A biochemical and radiological comparison between four disc injury models

Study Design. A biochemical and radiologic comparison of 4 disc injury models to produce disc degeneration in the rabbit was carried out in 2 experiments. Objectives. To develop a reliable animal model of intervertebral disc degeneration. Summary of Background Data. In order to study various interventions for retarding or preventing disc degeneration, a reliable animal model of disc degeneration is needed. Methods. First experiment: 7 New Zealand white rabbits (1 year old, 3.5-4.5 kg body weight) were used to test 4 different disc injury models; intradiscal injection of Camptothecin (an apoptotic agent) using a 23-gauge needle at L2-L3, nucleus aspiration using a 21-gauge needle at L3-L4, 3 anulus punctures using a 21-gauge needle at L4-L5, and 1 anulus puncture using a 18-gauge needle at L5-L6. The L1-L2 level was used as a control. Rabbits were killed 12 weeks later. Lumbar spinal magnetic resonance images were assessed using 4 grades of disc degeneration. The water content of the nucleus was measured. Dimethylmethylene blue (DMMB) assay was used to measure the sulfated-glycosaminoglycan content. Second experiment: the 21-gauge 3-puncture and the 18-gauge 1-puncture models, thought most effective in producing disc degeneration in the first experiment, were again used in a second study. Six rabbits were killed 8 weeks later, the water and sulfated-glycosaminoglycan contents being measured as in the first experiment. Results. In the first experiment, the water content in the aspiration and puncture models was significantly decreased. Only the sulfated-glycosaminoglycan content in the aspiration model showed a significant decrease as compared to the control. Disc heights and magnetic resonance grades documented significant degeneration occurring in the aspiration and puncture models. In the second experiment, the water content showed a significant decrease in the 21-gauge 3-puncture model, whereas neither of the results for the sulfated-glycosaminoglycan-content showed a significant difference as compared to the control data. Conclusion. In the first experiment, the 21-gauge 3-puncture and the 18-gauge 1-puncture models produced the most consistent disc degeneration in the rabbit lumbar spine. When these 2 models were again studied in the second experiment, the 21-gauge 3-puncture technique was superior in producing disc degeneration over a shorter period of time.