OSTEOARTHRITIS STAGING - COMPARISON BETWEEN MAGNETIC-RESONANCE-IMAGING, GROSS PATHOLOGY AND HISTOPATHOLOGY IN THE RHESUS MACAQUE

Although osteoarthritis (OA) is the most common cause of articular ske letal disability in humans, assessing progression (staging) with nonin vasive methods remains a major clinical problem. Using the rhesus maca que animal model, the objective of this study was to compare OA stagin g by noninvasive magnetic resonance imaging (MRI) against gross pathol ogy and histopathology. Right knee joints from 18 rhesus macaques were used in this study. Using a four-point ordinal scale for each of the above-mentioned modalities, the lateral and medial femoral condyle and tibial plateau of each knee joint was independently scored for OA sev erity, i.e. normal, mild OA, moderate OA and severe OA. Correlation be tween each staging system was performed using Stuart's Tau-c correlati on coefficient. By our criteria, MRI staging correlated as well with g ross pathology (tau = 0.75) and histopathology (tau = 0.80) as did gro ss pathology with histopathology (tau = 0.78). Our study shows that MR I is a promising noninvasive modality to evaluate the severity of OA. MRI appears to be sensitive for demarcating the presence and extent of focal OA cartilage lesions. However, at this time, while MRI is sensi tive for detecting OA change it cannot distinguish between certain les ions such as superficial cartilage matrix fibrillation and hypertrophy both of which show elevated signal intensity.