Knee cartilage thickness measurements using MRI: a 4-1/2-month longitudinal study in the meniscectomized guinea pig model of OA

Objective: The aim of this study was to follow, over a 4 1/2-month period, the medial tibia cartilage thickness on a meniscectomy (MNX) guinea pig osteoarthritis (OA) model and to compare with control animals, using three-dimensional high-resolution magnetic resonance imaging (3D HR-MRI). Methods: MRI experimentations were performed in vivo at 7T on guinea pig knee joints. 3D HR-MR images were acquired in 60 controls (SHAM) and 45 osteoarthritic animals (MNX) at four time-points (15, 45, 90 and 135 days) after surgery. Medial tibial cartilage thickness was measured from MRI images using in-house dedicated 3D software followed by a statistical analysis. At each time-point 15 SHAM and 15 MNX animals were sacrificed for histomorphometric assessments. Results: No significant difference of mean cartilage thickness between the groups was found at early stage (D45) using MRI; however, significant differences were found between the groups at D90 (P < 0.001) and D135 (P < 0.001). Histomorphometry data confirmed the pathological status of the animals and was well correlated with MRI at D15 (r= 0.79, P < 0.01), D45 (r = 0.67, P < 0.01), and D135 (r= 0.39, P < 0.05) for SHAM, and at D45 (r= 0.63, P < 0.01), and D135 (r = 0.81, P < 0.01) for MNX. Conclusion: Medial tibial cartilage measurement based on HR-MR images enables the monitoring of longitudinal cartilage thickness changes. This technique showed significant differences between SHAM and MNX as from D90 after surgery. It could be used as a noninvasive and reproducible tool to monitor therapeutic response in this CA model. (c) 2007 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.