T1ρ magnetic resonance imaging quantification of early articular cartilage degeneration in a rabbit model

Osteoarthritis (OA) is a serious problem in the recent aging society, and early diagnosis and intervention of articular cartilage degeneration are very important for the onset of OA. Therefore, development of newer MRI techniques is necessary and expected for detection of early articular cartilage degeneration.

24 rabbits were randomly divided into four equal experimental groups (Group A, B, C, D) to establish articular cartilage models in different grades of early degeneration by injecting papain into the left knee joint cavity. Another 8 rabbits were considered as blank control (Group E), and then randomized into four subgroups (EA, EB, EC, ED). T1ρ and T2-weighted images of the bilateral knee joints were obtained for rabbits by using 3.0 T MRI. Group A, B, C, and D were imaged respectively at 1, 2, 3, and 4 weeks post-operation, and EA, EB, EC, ED underwent the same period imaging. Rabbits were sacrificed after scanning and the femoral condyle cartilage (FCC) was histological examined. T1ρ values of the femoral condyle cartilage were measured and statistically analyzed, and contrasted with the histologic results.

T1ρ values of the left side in experimental groups were significantly higher than the right side (P < 0.05), and which increased gradually with the passage of post-operation time (P < 0.05). Histological examination demonstrated the proteoglycan content of the left side decreased, and indicated the occurrence of early degeneration.

T1ρ MRI can sensitively and quantitatively reflect the change in proteoglycans prior to the morphologic alterations of articular cartilage, and T1ρ value is gradually increased with a decrease in proteoglycan content, therefore that T1ρ could potentially act as a reliable tool to identify early cartilage degeneration.