"Floating Meniscus" a specific indicator of Anterior Cruciate Ligament rupture

Abstract

Although Magnetic Resonance (MR) imaging is accurate in diagnosis Anterior Cruciate Ligament (ACL) rupture, in many cases using indirect signs are inevitable for appropriate decision-making. This study aimed to investigate the diagnostic accuracy of complete medial meniscal tear (floating meniscus) in predicting ACL rupture. In a cross-sectional, prospective study, 620 knee MR images were reviewed in Tabriz Sheikholraeis Center from September 2011 to January 2013. Cases with knee degenerative disease, articular infection, intervening fracture(s) and previous constructive surgeries on the knee were excluded. Totally, 110 cases had floating meniscus in their MR images. ACL rupture was reported in 355 cases, including 206 cases with partial and 149 cases with total subtypes. ACL rupture and floating meniscus coexisted in 97.3% of the studied cases. A floating meniscus predicted the presence of a concomitant ACL rupture with sensitivity, specificity, positive predictive value and negative predictive value of 30.1, 98.9, 97.3 and 51.4%, respectively. In conclusion, a complete medial meniscal rupture or floating meniscus is a highly specific indicator of ACL injury in patients with equivocal findings in their MR images. Unlike other suggested indirect signs of ACL rupture, floating meniscus is independent of patient's position during MR imaging.