Biomechanical implications of lumbar intervertebral disc fenestration in rabbits: Comparison of ex vivo and in vivo conditions as an experimental model for chrondrodystrophic dogs with type 1 intervertebral disc disease.

Abstract

OBJECTIVE: To compare the effect of intervertebral disc (IVD) fenestration on L3/4 range of motion (ROM) under ex vivo and in vivo conditions in a rabbit model. STUDY DESIGN: Randomized experimental study. ANIMALS: New Zealand White rabbits (ex vivo: n = 18; in vivo: n = 12). METHODS: L3/4 motion segments were tested in lateral bending (LB), flexion-extension (FE), and axial rotation (AR) across five groups (n = 6 per group): control (C), ex vivo fenestration (EVF), in vivo fenestration with a 6 (IVF6) and 12 week (IVF12) timepoint, and intact/annulotomy/fenestration on the same specimen (IAF). Data are reported as ROM and neutral zone (NZ) and were compared between groups using ANOVA and t-tests. RESULTS: In IAF, fenestration increased ROM in LB, FE, and AR (p = .030) and NZ in FE (p = .010) compared to intact. EVF had greater ROM and NZ than C in all planes (LB, FE: p = .0010; AR: p = .030). IVF6 and IVF12 showed reduced ROM and NZ in LB and FE compared to C (p = .020-.0010) and EVF (p = .0010), with no difference in AR (p = .35). IVF6 and IVF12 did not differ significantly in any plane. Right lateral bending was significantly greater than left in EVF (p = .020), but not in IVF6 (p = .15) or IVF12 (p = .31). CONCLUSION: Fenestration increased spinal motion ex vivo, while in vivo specimens showed reduced ROM over time, consistent with a stabilizing biological response. CLINICAL SIGNIFICANCE: These findings provide a foundation for investigating the biological and biomechanical effects of IVD fenestration in dogs.