STUDY DESIGN: Animal case control study.

PURPOSE: To create a simple, reproducible disc degeneration model for mouse coccygeal vertebrae.

OVERVIEW OF LITERATURE: Back pain due to disc degeneration is probably the most common problem encountered in neurosurgical practice. An easily reproducible animal model for disc degeneration will help in understanding its pathophysiology, and serve as a platform for examining various therapeutic options.

METHODS: A total of 18 mice were divided into injured (n=12) and non-injured (n=6) groups. The disc height index (DHI%) at coccygeal 4-5 level was measured by computed tomography (CT) scan for all mice. Coccygeal 4-5 discs of the injury group were injured using a 32G needle fixed to a novel tool and confirmed by CT. The non-injury group underwent no procedure. DHI% was measured by CT at 2-, 4-, and 6-week post-injury, and all mice tails were sectioned for histopathology grading of disc degeneration at the respective time intervals.

RESULTS: The injured group showed significant variation in DHI% at 2, 4, and 6 weeks, whereas there was no change in the noninjured group. Histopathologic evaluation with Safranin O stain showed a worsening of the disc degeneration score at 2, 4, and 6 weeks in the injured group, but in the non-injured group there was no change. Percutaneous needle injury technique with our novel tool provided 100% accuracy and uniform degeneration.

CONCLUSIONS: A simple, easily reproducible mouse model for disc degeneration was created using a simple, cost-effective, novel tool and technique, its advantage being high precision and user friendly.