• Tristan Maerz, Michael Newton, Abigail A Marek, Michael Planalp, and Kevin Baker.
• Department of Orthopaedic Surgery & MedSport, University of Michigan, 24 Frank Lloyd Wright Dr, Ann Arbor, MI 48106, USA; Department of Orthopaedic Surgery, William Beaumont Hospital, 3811 West 13 Mile Rd, Suite 404, Royal Oak, MI 48073, USA; Department of Orthopaedic Surgery, Oakland University - William Beaumont School of Medicine, 586 Pioneer Dr, Rochester, MI 48309, USA.
• Spine J. 2018 Nov 1; 18 (11): 2091-2101.

Background ContextDegenerative disc disease (DDD) is associated with longitudinal remodeling of paravertebral tissues. Although chronic vertebral changes in advanced stages of DDD are well-studied, very little data exists on acute vertebral bone remodeling at the onset and progression of DDD.PurposeTo longitudinally characterize bony remodeling in a rodent model of disc injury-induced DDD.Study DesignIn vivo animal study involving a rat annulus fibrosus injury model of DDD.MethodsEight female Lewis rats were assigned to intervertebral disc (IVD) injury (Puncture) or sham surgery (Sham). All rats underwent anterior, transperitoneal approach to the lumbar spine, and Puncture rats underwent annulus fibrosus injury at the L3-L4 and L5-L6 IVDs (n = 8 per group). Live micro computed tomography imaging (10-μm voxel size) was performed 1 week before surgery and postoperatively at 2-week intervals up to a 12-week endpoint. Bone morphology and densitometry of the cranial vertebral body and bony endplate were analyzed and reported with respect to the preoperative baseline scan. Sagittal Safranin-O/Fast-Green and Toluidine Blue histology evaluated using the Rutges IVD score and a custom vertebral endplate score.ResultsVertebral trabecular tissue mineral density (TMD), vertebral trabecular spacing, endplate TMD, and endplate apparent bone mineral density were all significantly greater in Puncture compared with Sham at 4 weeks and each subsequent timepoint. Puncture rats exhibited marginally lower endplate total volume. Anterior endplate osteophyte formation and central physeal ossification were observed in Puncture rats. Endpoint histological analysis demonstrated moderate evidence of IVD degeneration, indicating that vertebral bone adaptation occurs in the acute phases of DDD onset and progression.ConclusionsAnnulus injury-induced DDD leads to acute and progressive changes to the morphology and densitometry of bone in the adjacent vertebral bodies and endplates.Copyright © 2018 Elsevier Inc. All rights reserved.

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