OBJECTIVE: To validate a method for histological evaluation of disc degeneration in rabbits based on the reliability of interobserver analysis. METHODS: Thirteen New Zealand white rabbits underwent a procedure to induce disc degeneration through direct puncture of three consecutive intervertebral discs (IVD) with an 18G needle under anesthesia. After two months, the complete spine of each rabbit was collected, and further prepared for histologic examination of the intervertebral discs (Experimental and Control), and stained with the hematoxylin-eosin method. Histology slides were evaluated for the occurrence of degeneration by analyzing the following criteria: presence of blood vessel, presence of protrusion of the nucleus pulposus (NP) through the annulus fibrosus (AF), and rupture of the fibers of the AF. RESULTS: After the euthanasia procedures, collection of the spine and histological preparation, 60 viable IVD were obtained for degeneration assessment. Of a total of 60 pieces, 25 pieces were from Experimental IVD and 35 pieces were from Control IVD. The presence of blood vessel was observed in 18 of 25 degenerated IVD with agreement among observers of Kappa = 0.95. The presence of the extrusion of the NP was identified in 19 of 25 experimental IVD with interobserver agreement of Kappa = 0.78. The rupture of the fibers of AF could be identified in 24 of 25 degenerated IVD, with interobserver agreement of Kappa = 0.65. CONCLUSION: This model of histological assessment of experimental IVD degeneration is feasible, with a high degree of interobserver agreement in the identification of disc degeneration.
Intervertebral disc degeneration; Histology; Animal models; Rabbits; Reproducibility of results
