Objective: A preliminary study was done to prospectively compare fat-suppressed three-dimensional spoiled gradient-echo (3D SPGR) MR imaging with standard MR imaging for detection of defects in the hyaline cartilage of the knee, using arthroscopy as the reference standard.
Subjects and methods: We studied 43 consecutive patients referred by two orthopedic surgeons for MR imaging of the knee. Twelve had arthroscopic correlation; they formed the basis of our study. Hyaline cartilage was imaged with a fat-suppressed 3D SPGR sequence with previously determined optimal imaging parameters. Our standard MR imaging study consisted of two-dimensional coronal T1-weighted spin-echo, sagittal dual-echo T2-weighted spin-echo, and axial multiplanar gradient-echo sequences. With arthroscopy as the reference standard, sensitivity and specificity of fat-suppressed 3D SPGR and standard MR images for detecting cartilage tears were determined by articular surface (eight surfaces in each patient: medial and lateral patellar facets, trochlear facets, femoral condyles, and tibial plateaus). Statistically significant differences in sensitivity and specificity were determined.
Results: Arthroscopy showed 15 cartilage defects in seven patients. The fat-suppressed 3D SPGR images had higher sensitivity (93%) than the standard MR images (53%, p = .03). Specificity was 94% for the fat-suppressed 3D SPGR images compared with 93% for the standard MR images (p > .05). The five false-positive articular surfaces on fat-suppressed 3D SPGR images were from focal signal change within the substance of the cartilage without a contour defect. Smoothly contoured thinning and loss of the trilaminar appearance of the hyaline cartilage at the lateral femoral notch was shown in all subjects and was considered a normal finding.
Conclusion: Fat-suppressed 3D SPGR imaging is more sensitive than standard MR imaging for the detection of abnormalities of the hyaline cartilage in the knee. Routine use of this technique may strengthen the role of MR imaging for noninvasive evaluation of internal derangements of the knee.