High resolution micro arthrography of hard and soft tissues in a murine model

Objective: Recent developments on high resolution micro computed tomography (mu CT) allow imaging of soft tissues in small animal joints. Nevertheless, mu CT images cannot distinguish soft tissues from synovial fluid due to their similar mass density, limiting the 3D assessment of soft tissues volume and thickness. This study aimed to evaluate a lead chromate contrast agent for mu CT arthrography of rat knee joints ex vivo. Design: Intact tibiofemoral rat joints were injected with the contrast agent at different concentrations and imaged using a mu CT at 2.7 mu m isotropic voxel size. Cartilage thickness was measured using an automated procedure, validated against histological measurements, and analyzed as a function of mu CT image resolution. Changes in hard and soft tissues were also analyzed in tibiofemoral joints 4 weeks after surgical destabilization of the medial meniscus (DMM). Results: The contrast agent diffused well throughout the whole knee cavity without penetrating the tissues, therefore providing high contrast at the boundaries between soft tissues and synovial fluid space. Thickness analysis of cartilage demonstrated a high similarity between histology and mu-arthrography approaches (R-2 = 0.90). Four weeks after surgical DMM, the development of osteophytes (Oph) and cartilage ulcerations was recognizable with mu CT, as well as a slight increase in trabecular bone porosity, and decrease in trabecular thickness. Conclusions: A lead chromate-based contrast agent allowed discriminating the synovial fluid from soft tissues of intact knee joints, and thus made possible both qualitative and quantitative assessment of hard and soft tissues in both intact and DMM tibiofemoral joints using high resolution mu CT. (c) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.