MRI findings in injured articular cartilage of the knee correlated with surgical findings.

Background: There is a strong need for quick noninvasive diagnostic technique that can give a valid estimate of the status of the cartilage reliably, discriminating intact cartilage from various grades of impaired cartilage. The goal of this study was to assess the incidence of knee cartilage injuries and compare the accuracy of two-dimension spin echo (2D SE) and fast spin echo (FSE) (conventional MRI), three-dimensional spoiled gradient echo (3D SPGR), three-dimensional fast imaging employing steady state acquisition (3D FIESTA) MR imaging sequences with surgical examination of the articular cartilage.

Methods: One hundred and thirty-eight knees with history of knee trauma received conventional MRI, 3D SPGR and 3D FIESTA MRI examination before surgery, and surgical examination of articular cartilage was used as reference standard. A modified version of the Noyes classification system was applied for the evaluation of the lateral femoral condyle (LFC), medial femoral condyle (MFC), lateral tibial plateau (LTP), medial tibial plateau (MTP), trochlea and patella. The incidence and distributions of different injured grades at different articular surfaces of knee were assessed. A series of assessment indeces of 3D SPGR, 3D FIESTA, and the combination of the conventional MRI and 3D SPGR imaging were calculated.

Results: The incidence of cartilage defects (grade 2 to 4) was 22% (183/828), according to surgical examination. Grade 3 and 4 lesions were absent at the medial tibial plateau. The rates of exact match between the grading results of different MRI procedures and surgical examination were 49% of 3D SPGR, 61% of 3D FIESTA, and 82% of the combination of 3D SPGR and conventional MRI. Also, the combination of 3D SPGR and conventional MR imaging provided the highest sensitivity, specificity, accuracy, positive and negative predictive values, at 71%, 97%, 90%, 90% and 90%, respectively.

Conclusions: For all the articular surfaces of the traumatic knees, about one fifth (22%) were cartilage defects. Both 3D SPGR and 3D FIESTA imaging performed similarly in detecting cartilage lesions of the knee. The increased accuracy in chondral assessment can be achieved by combining 3D SPGR and conventional MRI within a reasonable time.