The role of oblique axial MR imaging in the diagnosis of ACL bundle lesions

Objective: This study was done to evaluate the accuracy of oblique axial MR imaging in studying individual ACL bundle lesions. Subjects and methods: This study included forty-one (41) patients; 20 patients with no symptoms or signs of ACL injury and 21 patients in the suspected ACL lesions group. Each patient had a single MRI examination followed by a single indicated arthroscopy. The standard knee protocol (sagittal FSE proton density, coronal FSE T2-fat suppressed, axial FSE T2, sagittal FSE T1 and sagittal STIR) was designated protocol A, while the standard knee protocol plus oblique axial imaging was designated protocol B. Results: The comparative study was done using MRI protocol A versus protocol B for isolated anteromedial and posterolateral bundle as well as for ACL lesions as a whole with comparing these findings with arthroscopy as the gold standard. The addition of oblique axial imaging, increased sensitivity for ACL lesions (as a whole) from 74% to 95% and the accuracy from 76% to 95% while specificity remained similar. The sensitivity, specificity and accuracy of standard MR imaging for the detection of anteromedial bundle lesions were shown to be 80%, 100% and 86%, while that for posterolateral bundle lesions was 78%, 100% and 81% respectively. However, the addition of oblique axial imaging, increased sensitivity for anteromedial bundle lesions to 88% and accuracy to 90% while specificity remained similar. For posterolateral bundle lesions, the sensitivity increased to 89% and accuracy to 90% while specificity remains similar. Conclusion: Compared with standard MR imaging, the addition of oblique axial imaging improves the diagnostic accuracy for detecting lesions of the ACL, including both bundles’ delineation. This imaging plane seems to provide a useful adjunct to standard MR imaging when ACL lesion is suspected