STUDY DESIGN: An in-vivo experiment. OBJECTIVES: To compare the results of various methodologies for an annulotomy, and evaluate the relationship between the degenerative change and the volume of an extruded nucleus according to the various methodologies.
SUMMARY OF LITERATURE REVIEW: Many authors have reported that the traditional annulotomy technique is an open annulotomy.
MATERIAL AND METHODS: 16 female white New Zealand rabbits, each weighing about 4-4.5 kg, were used. A retroperitoneal approach, using a paravertebral incision, was used. Using a number 11 blade, a 21G needle and a number 15 blade, transverse stab incisions, or puncture wounds, were made into the L3-4, L4-5 and L5-6 disc through the antero-ateral annulus. At all the experimental levels, a complete annulotomy, which confirms the leakage of nucleus pulposus after an annulotomy, was used. To check the extruded nucleus volume after each annulotomy, the gross findings and histological findings of 10 disc samples from each level were analyzed. Radiological methods were used simple lumbar x-ray and MRI. From simple x-rays, the change in the disc height was measured with NIH image software, and the degeneration grade was classified using MRI.
RESULTS: The gross and histological findings showed the most advanced degeneration in the number 15 blade annulotomy group (L5-6 level), with the simple radiographs showing a fast decrease in the disc height. From the MRI findings, early degenerative findings were observed 2 months after the annulotomy in the number 11 and 15 blades groups. The largest extruded nucleus volume was observed in the number 15 blade annulotomy group.
CONCLUSION: In conclusion, the degenerative change in the disc, following an annulotomy, was related to the volume of the extruded nucleus.
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