Establishment of animal model of intradiscal bone cement leakage in vertebroplasty

Objective: To establish an animal model of intradiscal bone cement leakage which can mimic the intradiscal bone cement leakage in clinical vertebroplasty in patients. Methods: Eight healthy adult dogs were used for this study. Four lumbar intervertebral discs (from L1/2 to L5/S1) were taken for experiment. The four discs of each dog were randomly divided into group A, B, C and D. In Group A, the fibrous rings of discs were only stabbed by an 18-gauge needle and were injected with nothing. In Groups B, the fibrous rings of discs were stabbed by an 18-gauge needle and were injected with 0.3 ml polymethylmethacrylate (PMMA). In Group C, the discs were only stabbed by a 16-gauge needle and were injected with nothing. In Group D, the discs were stabbed by a 16-gauge needle and were injected with 0.3 ml PMMA. MRI scanning of all discs was performed at 6, 12 and 24 weeks after the injection. MRI indices (MRII) of all discs were calculated. The results were statistically analyzed by using ANOVA and Scheffe test. Results: Intervertebral disc degeneration was not found in group A on MR images. In group C, the stabbed discs exhibited a progressive decrease in MRII, which started at 6 weeks after puncture and were kept going till 24 weeks. A progressive decrease in MRII of the stabbed discs were seen in both group B and group D, which started at 6 weeks after puncture and were kept going till 24 weeks. Scheffe test indicated that no statistically significant difference in the degree of MRII existed between group B and group D at six weeks (P > 0.05), although at 12 and 24 weeks the difference was significant (P < 0.05). At 6, 12 and 24 weeks after the procedure, the differences in MRII between each other among group B, C and D were statistically significant (P < 0.05). Conclusion: Single puncture of the dog,s fibrous ring of disc with an 18-gauge needle will not cause its degeneration. Percutaneous injection of PMMA into disc with an 18-gauge needle can successfully establish intradiscal bone cement leakage model in dogs. This technique is mini-invasive with high success rate. This model is very suitable for the study concerned with the effect of intradiscal bone cement leakage on the physiology, biochemistry, and pathology of intervertebral disc. (authors)