Intervertebral disc degeneration induced by intradiscal poly(methyl methacrylate) leakage after spine augmentation in an in vivo rabbit model

Although intradiscal cement leakage is a common complication of spine augmentation, the effects of cement leakage into the intervertebral disc (IVD) have not been well investigated. This study aimed to determine the effects of cement leakage on IVD degeneration in rabbits. Poly(methyl methacrylate) (PMMA) particles were injected into lumbar discs of rabbits using 26 G needles. Tissue effects were assessed using disc height, sagittal T2-weighted images, histology and immunohistochemistry. The results showed that stimulation with PMMA particles significantly reduced disc height compared with that in the sham-operation group at 3 weeks after injection. The mean signal intensity of the operated discs showed little to no changes among all groups at 3 weeks post-operation. After 6 weeks, the signal intensity of the PMMA-injected group decreased by 22% compared with that in the sham-operation group. Histological and quantitative immunohistochemical examination indicated phenotypic tissue changes from cartilaginous tissue into fibrotic tissue, with apparent degeneration in the PMMA group. Additionally, more collagen type II-containing tissues, but fewer matrix metalloproteinase-7-positive cells or apoptotic cells, were detected in the sham-operation group. The PMMA particle-induced degeneration rate was slower than that of the degeneration group, whereas the histologic data showed no difference in the progression of degeneration between the two groups. These data suggest that PMMA particles can moderately accelerate disc degeneration compared with the 18 G needle puncture model. In conclusion, intradiscal injection of PMMA particles induced significant IVD degeneration in vivo. Therefore, further study of the adverse effects of PMMA leakage on IVD degeneration is required.