Experimental Annulotomy-induced Degeneration in Rabbit Intervertebral Discs: Comparative Study Between Incomplete and Complete Annulotomy

Abstract

Purpose: To develop an animal disc degeneration model. Materials and Methods: 12 female 8-month-old white New Zealand rabbits, weighing about 4-4.5 kg, were used. A retroperitoneal approach using a paravertebral incision was adopted. Using a number-11 blade, a transverse stab incision was made into the L3-4 and L5-6 disc through the antero-lateral annulus. At L3-4 level, complete annulotomy was performed and incomplete annulotomy at the L5-6 level. In the complete annulotomy group, extrusion of the nucleus after annulotomy was confirmed. Gross and histological findings, and lumbar x-rays and MRIs were analyzed. From simple x-rays, changes in disc heights were measured using NIH image software; degeneration grade was classified using MRI. Results: The gross and histological findings showed progressive degenerative change in both groups, which were more severe in the complete annulotomy group. Simple radiographs showed a progressive decrease in the disc height and osteophyte formation in several samples, which were more severe in the complete annulotomy group. From the MRI findings, early degenerative findings were identified 2 and 3 months after complete and incomplete annulotomy, respectively. Conclusion: In conclusion, the disc degenerative process, following incomplete annulotomy, more resembled the natural course of disc degeneration than complete annulotomy.