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

SummaryObjectiveRecent developments on high resolution micro computed tomography (μCT) allow imaging of soft tissues in small animal joints. Nevertheless, μCT 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 μCΤ arthrography of rat knee joints ex vivo.DesignIntact tibiofemoral rat joints were injected with the contrast agent at different concentrations and imaged using a μCT at 2.7 μm isotropic voxel size. Cartilage thickness was measured using an automated procedure, validated against histological measurements, and analyzed as a function of μCT image resolution. Changes in hard and soft tissues were also analyzed in tibiofemoral joints 4 weeks after surgical destabilization of the medial meniscus (DMM).ResultsThe 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 μ-arthrography approaches (R2 = 0.90). Four weeks after surgical DMM, the development of osteophytes (Oph) and cartilage ulcerations was recognizable with μCT, as well as a slight increase in trabecular bone porosity, and decrease in trabecular thickness.ConclusionsA 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 μCT

Strength of cancellous bone trabecular tissue from normal, ovariectomized and drug-treated rats over the course of ageing

Hormone therapy (HT) drugs and bisphosphonates prevent osteoporosis by inhibiting osteoclastic bone resorption. However, the effects of osteoporosis and anti-resorptive drugs on the mechanical behavior of the bone tissue constituting individual trabeculae have not yet been quantified. In this study, we test the hypothesis that the mechanical properties of bone trabecular tissue will differ for normal, ovariectomized and drug-treated rat bones over the course of ageing.Microtensile testing is carried on individual trabeculae from tibial bone of ovariectomized (OVX) rats, OVX rats treated with tibolone and placebo-treated controls. The method developed minimizes errors due to misalignment and stress concentrations at the grips. The local mineralization of single trabeculae is compared using micro-CT images calibrated for bone mineral content assessment.Our results indicate that ovariectomy in rats increases the stiffness, yield strength, yield strain and ultimate stress of the mineralized tissue constituting trabecular bone relative to normal; we found significant differences (P < 0.05) at 14, 34 and 54 weeks of treatment. These increases are complemented by a significant increase in the mineral content at the tissue level, although overall bone mineral density and mass are reduced. With drug treatment, the properties remain at, or slightly below, the placebo-treated controls levels for 54 weeks. The higher bone strength in the OVX group may cause the trabecular architecture to adapt as seen during osteopenia/osteoporosis, or alternately it may compensate for loss of trabecular architecture. These findings suggest that, in addition to the effects of osteoporosis and subsequent treatment on bone architecture, there are also more subtle processes ongoing to alter bone strength at the tissue level