Role of low-field magnetic resonance imaging in the detection of floating meniscus sign as consequence of sport-related trauma. (Ruolo della RMN a basso campo nel riconoscimento dal segno del menisco galleggiante in seguito a trauma sportivo)

Aim. To assess the role of magnetic resonance (MR) imaging performed with a low-field scanner in the detection of float- ing meniscus sign as a consequence of sports-related trauma. Methods. Retrospective review of 2436 MR knee examinations executed, in 18 months, using a low-field scanner of 0.2T, was performed by three musculoskeletal radiologists of varying experience. Diagnostic criteria to define the presence of a complete floating meniscus were as codified in the literature. If the thickness of the fluid signal band between the meniscus and tibial plateau was comprised in the range ≥3 mm and ≤5 mm the floating meniscus was defined as par- tial. Patients with the sign were called to learn what treatment had been performed; in those submitted to surgery the surgical chart was evaluated. Results. Floating meniscus was detected in 8/2436 cases (0.25%), 5 complete, arthroscopically confirmed, and 3 par- tial; in 5/8 cases the lateral meniscus was involved. Associated lesions were observed, ligamentous in 7/8 cases and meniscal in 2/8 cases; a bone bruise of varied exten- sion was identified in 3/8 cases. Conclusion. Floating meniscus sign could be detected at MR imaging although performed using a low-field scanner. Its presence should be carefully identified, especially in severe traumatic events, as it has some important prognostic implications.