title: Contrast-Enhanced Micro-Computed Tomography in Evaluation of Spontaneous Repair of Equine Cartilage.
abstract: OBJECTIVE
  Contrast-enhanced computed tomography (CECT) has been introduced for the evaluation of cartilage integrity. Furthermore, CECT enables imaging of the structure and density of subchondral bone. In this laboratory study, we investigate the potential of microCECT to simultaneously image cartilage and subchondral bone for the evaluation of tissue healing.
  
  
  METHODS
  Osteochondral lesions (Ø = 6 mm) were surgically created in equine intercarpal joints (n = 7). After spontaneous healing for 12 months, the horses were sacrificed and osteochondral plugs (Ø = 14 mm), including the repair cartilage and adjacent intact tissue, were harvested. The nonfibrillar and fibrillar moduli and the permeability of cartilage were determined using indentation testing. Contrast agent diffusion into the samples was imaged for 36 hours using high-resolution CT. Results from CECT, mechanical testing, and microscopic analyses were compared and correlated.
  
  
  RESULTS
  The contrast agent diffusion coefficient showed a significant (P < 0.05) difference between the repair and adjacent intact tissue. MicroCECT revealed altered (P < 0.05) bone volume fraction, mineral density, and microstructure of subchondral bone at the repair site. The contrast agent diffusion coefficient correlated with the moduli of the nonfibrillar matrix (R = -0.662, P = 0.010), collagen fibril parallelism index (R = -0.588, P = 0.035), and glycosaminoglycan content (R = -0.503, P = 0.067). The repair cartilage was mechanically and structurally different from adjacent intact tissue (P < 0.05).
  
  
  CONCLUSIONS
  MicroCECT enabled simultaneous quantitative evaluation of subchondral bone and monitoring of cartilage repair, distinguishing quantitatively the repair site from the adjacent intact tissue. As the only technique able to simultaneously image cartilage and determine subchondral bone mineral density and microstructure, CECT has potential clinical value.
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland ; Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland.
authors.forename: K A M
authors.initials: KA
authors.lastname: Kulmala
authors.affiliation: Department of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland.
authors.forename: H J
authors.initials: HJ
authors.lastname: Pulkkinen
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland ; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
authors.forename: L
authors.initials: L
authors.lastname: Rieppo
authors.affiliation: Department of Medicine, Institute of Biomedicine, Anatomy, University of Eastern Finland, Kuopio, Finland ; SIB-labs, University of Eastern Finland, Kuopio, Finland.
authors.forename: V
authors.initials: V
authors.lastname: Tiitu
authors.affiliation: Department of Orthopaedics and Traumatology, Helsinki University Central Hospital, Helsinki, Finland ; University of Helsinki, Helsinki, Finland.
authors.forename: I
authors.initials: I
authors.lastname: Kiviranta
authors.affiliation: Department of Equine Sciences, Utrecht University, Utrecht, the Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Brünott
authors.affiliation: Department of Equine Sciences, Utrecht University, Utrecht, the Netherlands.
authors.forename: H
authors.initials: H
authors.lastname: Brommer
authors.affiliation: Department of Equine Sciences, Utrecht University, Utrecht, the Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: van Weeren
authors.affiliation: Section of Veterinary Clinical Studies, School of Agriculture, Food Science & Veterinary Medicine, University College Dublin, Dublin, Ireland.
authors.forename: P A J
authors.initials: PA
authors.lastname: Brama
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: M T
authors.initials: MT
authors.lastname: Mikkola
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: R K
authors.initials: RK
authors.lastname: Korhonen
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
authors.forename: J S
authors.initials: JS
authors.lastname: Jurvelin
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland ; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Töyräs
keywords: cartilage; computed tomography; contrast agent; repair; subchondral bone