Rat Model of Lumbar Facet Joint Osteoarthritis Associated With Facet-mediated Mechanical Hyperalgesia Induced by Intra-articular Injection of Monosodium Iodoacetate

The relationship between lumbar facet joint (LFJ) osteoarthritis (OA) and back pain remains unclear. An OA model associated with joint pain was successfully induced by monosodium iodoacetate (MIA) in rat knees. We aimed to establish an experimental OA model with facet-mediated mechanical hyperalgesia in the LFJ in rats. Methods: We established a rat experimental model of LFJ OA with facet-mediated mechanical hyperalgesia by injection of MIA into a single facet joint. After injection, changes in the LFJ structure were assessed histologically and mechanical hyperalgesia in the hind paw was determined using the von Frey test. In addition, interleukin-1β and tumor necrosis factor-α levels in the synovium were measured by enzyme-linked immunosorbent assay, and the inhibitory effects of celecoxib and gabapentin on mechanical hyperalgesia were evaluated. Results: Progressive cartilage degeneration and changes in subchondral bone were observed after injection. A biphasic pattern of mechanical hyperalgesia was noted in the hind paw. The concentrations of interleukin-1β and tumor necrosis factor-α were significantly increased only on Days 1 and 3 when compared with controls. Celecoxib was effective only on Day 3 and ineffective on Days 21 and 35, whereas gabapentin kept its inhibitory effect on Days 3, 21 and 35. Conclusion: An experimental LFJ OA model associated with facet-mediated mechanical hyperalgesia can be established by intra-articular injection of MIA. This model might provide a useful tool for further study to ascertain the complex mechanism of facet joint pain.