Evaluation of Internal Structure of the Articular Cartilage in Terms of ^1H-NMR Relaxation Behavior

点击翻译按钮获取中文摘要

The structural characteristics of articular cartilage were analyzed usnig ^1H-longitudinal (T_1) and transverse (T_2) relaxation times as measured by fast-inversion-recovery and multi-spin-echo magnetic resonance imaging(MRI). Pairs of cartilage-bone plugs from weight bearing and non-weight bearing regions were dissected from 15 medial femoral condyles and were subjected to NMR measurements with and without static loads (0.15-1.0 MPa). The T_1 of the cartilage with no load showed a maximum value just beneath the articular surface and this value decreased gradually towards the deeper zones. The T_2 of the same cartilage showed a maximum value at or just beneath the articular surface which decreased rapidly towards the intermediate zone yet increased again in the deepest zone. The increase of T_2 in the deepest zone was more greatly pronounced in the weight bearing region than in the non-weight bearing region. These layer-dependent differences in the T_1 and T_2 could account for the laminar appearance of the articular cartilage in the MR images. Under static loads, the decrease of T_1 in the transitional zone (from just beneath the articular surface to the intermidiate zone) was significant. Because the T_1 has a positive correlation with the water content, this decrease of T_1 might signify that the largest water loss occurs in the transitional zone. These results suggest that the transitional zone might be attenuating the mechanical stress in the joint, and the expressed water from the cartilage could substantially contribute to the lubrication of the joint.