A lumbar disc degeneration model established through an external compressive device for the study of microcirculation changes in bony endplates

OBJECTIVE: To establish a new animal model of intervertebral disc degeneration (IDD) by axial compression on lumbar spine of rabbits and to investigate the changes of microcirculation in bony endplates during the progress of IDD. METHODS: 32 New Zealand white rabbits were equally divided into 4 groups as follows: Control group with no operation and compression, Sham operation group with apparatus placement only, 2-week compression group and 4-week compression group with the devices installed and compressed for their preset duration. All groups of rabbits underwent MRI, histological evaluation, disc height index measurement and Microfil contrast agent perfusions to examine the ratio of endplate microvascular channels. RESULTS: The new animal model of IDD was successfully established after axial compression for 4 weeks. The MRI grades for the 4-week compression group was 4.63 ± 0.52 and significantly different to the sham operation group (P < 0.05). Histologically, decrease of normal NP cells and extracellular matrix and disorganization of the architecture of the annulus fibrosus apparently occurred in 4-week compression group, which was different to the sham operation group (P < 0.05). There was no statistically difference between the 2-week compression and sham operation group no matter in the histology and MRI assessment. The disc height index slowly decreased as the compression duration rose. The ratio of microvascular channel volume within the bony endplate in 2-week and 4-week compression group were both reduced whereas the 4-week compression group obtained significantly less vascularization volume (6.34 ± 1.52 vs. 19.52 ± 4.63, P < 0.05). CONCLUSION: A new model of lumbar IDD was successfully established by axial compression and the volume of microvascular channels in the bony endplate gradually decreased as the grade of IDD increased. This model provides a new choice for etiological studies on IDD and investigation of nutrient supply disturbance.