Diagnosis of anterior cruciate ligament tear: Value of oblique axial MR image

Abstract

Background: Accurate magnetic resonance (MR) evaluation of anterior cruciate ligament (ACL) injuries can be challenging due to the oblique orientation of its bundles. Oblique axial MR imaging has been proposed to improve visualization of the ACL bundles and may facilitate the detection of ACL bundle tears. Objective: To investigate the diagnostic value of adding oblique axial ACL imaging to the routine knee MRI protocol for detecting ACL tears and differentiating partial ACL tears from complete tears. Materials and Methods: This retrospective study included 144 patients at Siriraj hospital who underwent knee MRI between August 2018 and April 2022 followed by arthroscopy. Protocols A (routine protocol) and B (with additional oblique-axial imaging) were compared for their performance in the detection of ACL tears, differentiation of partial from complete ACL tears and detection of isolated ACL bundle tears. The performances of an inexperienced (reader 1) and an experienced (reader 2) reader were also compared. Results: The specificity and accuracy for the diagnosis of partial ACL tears were significantly higher for protocol B for reader 2, while for reader 1 these values did not reach statistical significance. With protocol B, the specificity and accuracy of reader 2 were significantly superior to those of reader 1. For the detection of isolated ACL bundle tears, the sample cohort of partial tear cases was too small for statistical evaluation. Conclusion: The addition of oblique-axial imaging to routine knee MR imaging improves diagnostic accuracy for detecting partial tears of the ACL. However, the extent of its usefulness may also rely on the reader’s experience.