Intervertebral Disk Degeneration is not a Direct Cause of Pain Behavior: An Experimental Study Using a Disk Puncture Model in Rats

Abstract

Introduction Low back pain (LBP) is a common symptom in patients with lumbar diseases. But the relationship between lumbar intervertebral disk degeneration and LBPis still a controversial issue. Some animal models were used to discuss this issue in prior studies. A recent study1 suggested that the pain behavior changes might be related to the epidural presence of the oozed nucleus pulposus in the posterior rat disk puncture model. In this study, an anterior rat disk puncture model was applied to exclude the epidural presence of nucleus pulposus, and the objectives of this study were to establish an intervertebral disk degeneration model in rats and to analyze the relationship between disk degeneration and pain behavior changes in this model. Materials and Methods Total 18 male Sprague-Dawley rats with an average bodyweight of 230 g were used in this study. The anterior intervertebral disk annular puncture model was established as follows: the L5/6 lumbar disks were punctured using a 0.4-mm-diameter injection needle under microscope in nine rats; another nine rats receiving same surgery were considered as control group. Magnetic resonance imaging (MRI) of the punctured rats' spine was taken to confirm the degeneration of the disk. Behavioral tests including assessment of motor function, mechanical threshold, and thermal withdrawal latency were performed before and after surgery in both groups. The behavior tests were performed on days 1, 3, 7, 14, 21, 30, and 45 after the surgery. Results MRI results showed visible degeneration in rats at about 3 weeks after disk puncture (Fig. 1A). There was no degenerative change in the control group in all time points. Regarding motor function, both groups exhibited normal gait during the entire observation period. No significant statistical difference was found between the two groups in both mechanical threshold and thermal withdrawal latency tests at different time points (Fig. 1B, C). Conclusion The degenerative lumbar intervertebral disk model in rats was successfully established by anterior disk annulus needle puncture. The degeneration of the lumbar disk caused by anterior puncture could not induce pain behavior change in rats. I confirm having declared any potential conflict of interest for all authors listed on this abstract No Disclosure of Interest None declared Elin Nilsson, Toshio Nakamae, Kjell Olmarker. Pain behavior changes following disc puncture relate to nucleus pulposus rather than to the disc injury per se: an experimental study in rats. The Open Orthopaedics Journal 2011;5:72–77.