Establishment of rabbit models of lumbar disc degeneration using three methods monitored via X-ray: a comparative...

Intervertebral disc degeneration (IDD) is a major cause of chronic lower back pain and associated spinal disorders. Animal models play a crucial role in elucidating the pathophysiological mechanisms underlying IDD and in the development of potential treatments. Various techniques have been used to induce IDD, including annulus fibrosus puncture, nucleus pulposus aspiration (NPA), and chemical injections. However, few studies have explored the use of NPA combined with puncture needle burning (PNB) or anhydrous ethanol injection (AEI) to induce IDD. We compared the efficacy and consistency of three induction methods - NPA, NPA + PNB, and NPA + AEI - in rabbits. The extent of degeneration was assessed using MRI, X-ray, and histological analyses.

Twenty-four male New Zealand white rabbits (weighing 3.5-4.0 kg) were randomly allocated to three groups (n = 8 per group). Degeneration was induced in the L2/3, L3/4, L4/5, and L5/6 intervertebral discs using one of the three methods: NPA, NPA + PNB, or NPA + AEI. The L6/7 discs served as the internal control. Four weeks post-procedure, the degree of disc degeneration was evaluated via MRI and X-ray imaging. Histological assessment was performed using hematoxylin and eosin and safranin O/fast green staining. The severity of degeneration was quantified using the Masuda histological scoring system.

All three methods successfully induced significant IDD, as confirmed by imaging and histological analyses. The NPA + PNB group had the most severe and uniform degeneration, consistently corresponding to Pfirrmann grade IV. The NPA + AEI group had a comparable severity of degeneration but with more inter-segmental variability. In contrast, the NPA-only group had milder degeneration, predominantly within Pfirrmann grades II-III. All experimental groups had significant reductions in terms of intervertebral disc height and nucleus pulposus area, with the most pronounced reductions observed in the NPA + PNB group. MRI indices and histological scores consistently indicated that the NPA + PNB method produced the most severe and reproducible degeneration. Histological staining revealed decreased cellularity, fissures in the annulus fibrosus, and collapse of the cartilage endplate in all intervention groups, with the NPA + PNB group exhibiting the most extensive degeneration.

These findings confirm that NPA, NPA + PNB, and NPA + AEI are effective techniques for inducing IDD in a rabbit model. Among these, the NPA + PNB method represents one of the best options for achieving a reliable, reproducible, and minimally invasive model, producing consistent and severe degeneration with a high degree of standardization. This technique presents a valuable tool for future research investigating the pathogenesis of IDD and evaluating the efficacy of potential therapeutic strategies.