Abstract
<title>Abstract</title> <p> <bold>Purpose</bold> Intervertebral disc fenestration is a prophylactic procedure that reduces canine intervertebral disc extrusion (IVDE) recurrence and compares to human microdiscectomy, but its biological and biomechanical effects are poorly understood. This study describes a preclinical sheep model of lateral lumbar IVD fenestration to model human intervertebral disc degeneration (IVDD) and assess its time-dependent biological and biomechanical effects. <bold>Methods</bold> Fourteen mature ewes underwent L3/4 IVD fenestration via a lateral retroperitoneal approach, evaluated at 6 (n=6) and 30 weeks (n=8). Treatment effects were compared to non-operated controls using radiography, micro-CT, T2 MRI (Pfirrmann scores), non-destructive robotic range of motion (ROM) testing, and histology. <bold>Results</bold> All sheep recovered uneventfully and ambulated normally. Radiographs and micro-CT showed mild-to-moderate reactive osseous changes and endplate sclerosis at fenestrated discs. Compared to adjacent controls, fenestrated discs exhibited a significantly lower mean disc height index (DHI%) at both 6 and 30 weeks (p<0.001). Lateral bending range of motion was significantly reduced at 30 weeks compared to controls and the 6-week cohort (p<0.001). Pfirrmann MRI scores and histological grading scores were significantly higher in operated discs at both timepoints compared to controls (p<0.001), with no significant progression observed between 6 and 30 weeks (p=0.40; p=0.35). <bold>Conclusion</bold> This ovine model of L3/4 fenestration successfully demonstrated time-dependent IVDD supported by imaging, biomechanical, and histological endpoints. The model is highly suitable for preclinical evaluation of treatment strategies for human and canine IVDD </p>