title: Three-dimensional characterization of in vivo intervertebral disc degeneration using EPIC-μCT.
abstract: OBJECTIVE
  Small animal models are commonly employed to study progression of and potential treatment techniques for degenerative disc disease (DDD), but assessment using conventional imaging techniques is challenging due to resolution. The objective of this study was to employ equilibrium partitioning of an ionic contrast agent micro computed tomography (EPIC - μCT) to map three-dimensional (3D) degenerative changes in the rabbit intervertebral disc (IVD).
  
  
  METHODS
  In vivo degeneration was induced surgically in 12 New Zealand White rabbits via percutaneous annular puncture and percutaneous nucleotomy. IVDs were harvested after 3 and 6 weeks. EPIC-μCT imaging was performed on fresh, IVDs before and after formalin fixation, and 3D IVD volumes were segmented. IVDs were histologically stained with Safranin-O/Fast-Green and Hematoxylin & Eosin (H&E). EPIC-μCT attenuation and 3D morphological measurements were assessed in healthy and degenerate IVDs and compared to qualitative grading and disc height measurement from histology.
  
  
  RESULTS
  EPIC-μCT caused pronounced contrast enhancement of the IVD. Annular puncture and nucleotomy produced mild and severe degenerative changes, respectively. IVD attenuation following contrast enhancement increased significantly in nucleotomized discs at 3 and 6 weeks. IVD attenuation correlated significantly with histologic score and disc height measurements. Disc height decreased most extensively in the posterior and lateral aspects of the IVD. 3D morphological measurements correlated strongly to IVD attenuation and were more sensitive to degenerative changes than histologic measurements. Formalin fixation reduced the attenuation of IVDs by ∼10%.
  
  
  CONCLUSIONS
  EPIC-μCT is sensitive to in vivo DDD induced by nucleotomy and provides a high resolution 3D method for mapping degenerative changes in rabbit IVDs.
authors.affiliation: Orthopaedic Research Laboratories, Beaumont Health System, 3811 W Thirteen Mile Road, Royal Oak, MI 48073, USA; Department of Surgery, Oakland University - William Beaumont Oakland University School of Medicine, Rochester, MI, USA.
authors.forename: T
authors.initials: T
authors.lastname: Maerz
authors.affiliation: Orthopaedic Research Laboratories, Beaumont Health System, 3811 W Thirteen Mile Road, Royal Oak, MI 48073, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Newton
authors.affiliation: Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kristof
authors.affiliation: Orthopaedic Research Laboratories, Beaumont Health System, 3811 W Thirteen Mile Road, Royal Oak, MI 48073, USA.
authors.forename: O
authors.initials: O
authors.lastname: Motovylyak
authors.affiliation: Department of Surgery, Oakland University - William Beaumont Oakland University School of Medicine, Rochester, MI, USA; Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Fischgrund
authors.affiliation: Department of Surgery, Oakland University - William Beaumont Oakland University School of Medicine, Rochester, MI, USA; Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
authors.forename: D K
authors.initials: DK
authors.lastname: Park
authors.affiliation: Orthopaedic Research Laboratories, Beaumont Health System, 3811 W Thirteen Mile Road, Royal Oak, MI 48073, USA; Department of Surgery, Oakland University - William Beaumont Oakland University School of Medicine, Rochester, MI, USA. Electronic address: kevin.baker@beaumont.edu.
authors.forename: K C
authors.initials: KC
authors.lastname: Baker
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D005260:Female; D021621:Imaging, Three-Dimensional; D007403:Intervertebral Disc / Q000000981:diagnostic imaging*; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging*; D011817:Rabbits; D015203:Reproducibility of Results; D055114:X-Ray Microtomography / Q000379:methods*
keywords: Contrast enhanced microcomputed tomography; Degenerative disc disease; EPIC-μCT; Intervertebral disc