Comparison between arthroscopic findings and 1.5-T and 3-T MRI of oblique coronal and sagittal planes of the knee for evaluation of selective bundle injury of the anterior cruciate ligament.

Abstract

The purpose of this study was to evaluate the diagnostic usefulness of combining oblique sagittal and oblique coronal MRI views of the anterior cruciate ligament (ACL) with traditional orthogonal views for the evaluation of selective-bundle ACL injury and to evaluate whether there is a statistical difference in diagnostic ability between 1.5-T and 3-T MRI. This retrospective study included 114 patients who underwent knee MRI (46 on 1.5 T and 68 on 3 T) and arthroscopy at our institution. Two radiologists evaluated orthogonal views and ACL views on 1.5-T and 3-T MRI in variable combinations. They diagnosed ACL views as normal, entire ligament tear, anteromedial bundle tear, or posterolateral bundle tear. The surgeon then confirmed tears in the anteromedial or posterolateral bundle of the ACL arthroscopically if a selective-bundle tear did exist. The arthroscopically confirmed diagnoses were used as the reference standard. The values were statistically analyzed. Sixty-seven percent of patients showed an ACL tear on arthroscopy, and 33% had a selective bundle tear; of these, 75% were anteromedial bundle tears and 25% were posterolateral bundle tears. On 1.5-T MRI, specificities of each view and combined views were the same (80%). The sensitivities and accuracies of the combined views were higher than the individual views; differences between individual views ranged from 4% to 15%. Reader 1 saw statistically significant differences between the oblique coronal and combined views. Although the performances of reader 2 showed similar results, the p values exceeded the critical value of statistical significance (0.063). On 3-T MRI, differences in specificities between the orthogonal and combined views and between the orthogonal and oblique coronal views were statistically significant (p, 0.016 and 0.008 for readers 1 and 2, respectively). There were no significant differences in the diagnostic performance of 1.5-T and 3-T MRI. The oblique coronal view and the combination of the orthogonal view and both additional ACL views provide better diagnostic information with an improvement in specificity on 3-T MRI compared with orthogonal views alone in the diagnosis of selective-bundle tears. Although diagnostic performance was not improved with the addition of the oblique views over orthogonal views on 1.5-T imaging, diagnostic performance was improved on 3-T MRI. Accuracies for individual imaging planes were not significantly different when comparing 1.5-T and 3-T MRI.