AB0858 MRI Analysis of Knee Joints by T1Rho Mapping in Young and Middle-Aged Cases Without Radiological Osteoarthritis

Background Recently, some studies have reported that medial meniscal posterior horn tears often occur in aged people, and suggested that these tears could be related to the development of knee osteoarthritis (OA). However, limited data concerning this pathogenesis in young and middle-aged cases without radiological OA changes have been reported. T1rho (or T1 relaxation time in rotating frame)-weighted MRI has recently been proposed as a promising alternative biomarker to existing conventional morphological MRI. T1rho values are believed to reflect the condition of the extracellular matrix of articular cartilage, and particularly the proteoglycan concentration. Objectives The purpose of this study was to analyze the interaction between cartilage degradation depicted by T1rho mapping and meniscus injuries in the knees of cases under 50 years old without obvious radiological OA features. Methods This study included 87 subjects under 50 years old with knee pain (mean: 38.3 years old). We added another 10 healthy volunteers to be used as healthy controls (mean: 38.7 years old). Standard standing anteroposterior radiographs of the knee were obtained in all subjects. The Kellgren-Lawrence (KL) grade was determined by three experienced orthopaedic surgeons. MR examinations were performed using a 3.0T MR unit. 3D T1rho-weighted fast field echo imagingwas performed for T1rho quantification. After direct segmentation by referring to the proton density weighted (PDW) images, 12 regions of interest (ROIs) were manually drawn on the T1rho map of a single coronal image slice which showed a mid-body segment of the medial meniscus. Morphological MRI assessment of ligaments, menisci and subchondral bone was performed by sagittal/coronal fat-suppressed T2-weighted imaging and sagittal PDW imaging. Meniscal lesions were graded using a modified Whole Organ Magnetic Resonance Imaging Score (WORMS) of the knee. Results The study revealed that KL grade, the medial meniscus WORMS and the presence/absence of posterior root/horn radial tears in medial meniscus influenced the T1rho values in the medial femorotibial joint. A multivariate analysis corrected for age and the KL grade revealed that abnormal findings in the posterior segment of the medial meniscus independently increased the T1rho values in the ROIs of the medial compartment (P Conclusions Our results demonstrated that morphological factors of the meniscus on normal MR images are useful for estimating the T1rho values in the cartilage. WORMS provides findings that are useful for screening for early-stage OA and pre-OA in routine medical care. Posterior root/horn radial tears in the medial meniscus depicted on routine MRI are particularly important findings associated with cartilage degeneration observed on T1rho relaxation mapping, even in patients under 50 years old without obvious radiological OA. In other words, abnormalities in the posterior segment of the medial meniscus on MR images indicate that degeneration of the medial femorotibial joint is already in progress, even in young patients, and even when plain radiographs show no abnormalities. Therefore, a programme for preventing future OA is needed for these patients. Disclosure of Interest None declared