A comparison of two ovine lumbar intervertebral disc injury models for the evaluation and development of novel regenerative therapies

Study Design: Large animal research. Objective: Lumbar discectomy is the most commonly performed spinal surgical procedure. We investigated 2 large animal models of lumbar discectomy in order to study the regenerative capacity of mesenchymal stem cells following disc injury. Methods: Twelve adult ewes underwent baseline 3-T magnetic resonance imaging (MRI) followed by lumbar intervertebral disc injury by either drill bit (n = 6) or annulotomy and partial nucleotomy (APN) (n = 6). Necropsies were performed 6 months later. Lumbar spines underwent 3-T and 9.4-T MRI prior to histological, morphological and biochemical analysis. Results: Drill bit-injured (DBI) and APN-injured discs demonstrated increased Pfirrmann grades relative to uninjured controls (