Intervertebral disc degeneration induced by lumbar instability followed by a maintained standing posture: An in vivo rabbit model

Abstract

Background: Intervertebral disc degeneration (IVDD) is a major clinical cause of low back pain. The ideal animal model should induce a degenerative process and morphological properties similar to those that occur in human IVDD. We established an IVDD model by maintaining rabbits in an upright posture after inducing lumbar instability to better simulate human IVDD. Methods: IVDD was induced in rabbits by severing the supraspinous and interspinous ligaments of the L5-6 and L6-7 segments and maintaining rabbits in an upright position for 12 weeks. After 8 and 12 weeks, X-ray and magnetic resonance imaging (MRI) were analysed. Disc pathological changes at 12 weeks were detected using haematoxylin and eosin staining, safranin-O-fast green staining, and immunohistochemistry. Results: In the model group, L6-7 and L7-S1 segment disc degeneration was aggravated at 12 weeks. MRI analysis showed that at 12 weeks, the L6-7 and L7-S1 intervertebral disc nucleus pulposus (NP) signal intensity was significantly decreased compared with that of the control group. Compared with the control group, the model group had obvious histomorphological degeneration at 12 weeks, and significantly different histological scores. Model group immunohistochemistry results at 12 weeks showed that the NP type II collagen content was decreased and the type I collagen content was increased. Conclusions: An animal model of early lumbar disc degeneration was successfully established by maintaining the rabbit lumbar spine in an upright position for an extended period after inducing lumbar instability. This model will be useful for studying the degenerative process of intervertebral discs under mechanical stimulation.