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MRI imaging of displaced meniscal tears: Report of a case highlighting new potential pitfalls of the MRI signs

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      Abstract

      Magnetic resonance imaging (MRI) has been found to be an excellent imaging tool for meniscal injuries. Various MRI signs have been described to detect displaced meniscal injuries, specifically the bucket-handle tears. Although these signs are quite helpful in diagnosing meniscal tears, various pitfalls have also been reported for these signs. Double anterior cruciate ligament (ACL) sign refers to presence of a linear hypointense soft tissue anterior to the ACL, which represented the flipped bucket-handle tear of the meniscus. Disproportional posterior horn and flipped meniscus signs represent asymmetrically thickened horns of the menisci due to overlying displaced meniscal fragments. We report a case wherein MRI of the knee showed tear and displacement of the medial patellofemoral ligament (MPFL) and vastus medialis complex, medial collateral ligament (MCL), and posterior cruciate ligament (PCL) mimicking these signs. To our knowledge, internally displaced MPFL and MCLs have not been described as mimics for displaced meniscal fragments.

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      Medial patellofemoral ligament injury patterns and associated pathology in lateral patella dislocation: an MRI study

      Background Lateral Patella dislocations are common injuries seen in the active and young adult populations. Our study focus was to evaluate medial patellofemoral ligament (MPFL) injury patterns and associated knee pathology using Magnetic Resonance Imaging studies. Methods MRI studies taken at one imaging site between January, 2007 to January, 2008 with the final diagnosis of patella dislocation were screened for this study. Of the 324 cases that were found, 195 patients with lateral patellar dislocation traumatic enough to cause bone bruises on the lateral femoral trochlea and the medial facet of the patella were selected for this study. The MRI images were reviewed by three independent observers for location and type of MPFL injury, osteochondral defects, loose bodies, MCL and meniscus tears. The data was analyzed as a single cohort and by gender. Results This study consisted of 127 males and 68 females; mean age of 23 yrs. Tear of the MPFL at the patellar attachment occurred in 93/195 knees (47%), at the femoral attachment in 50/195 knees (26%), and at both the femoral and patella attachment sites in 26/195 knees (13%). Attenuation of the MPFL without rupture occurred in 26/195 knees (13%). Associated findings included loose bodies in 23/195 (13%), meniscus tears 41/195 (21%), patella avulsion/fracture in 14/195 (7%), medial collateral ligament sprains/tears in 37/195 (19%) and osteochondral lesions in 96/195 knees (49%). Statistical analysis showed females had significantly more associated meniscus tears than the males (27% vs. 17%, p = 0.04). Although not statistically significant, osteochondral lesions were seen more in male patients with acute patella dislocation (52% vs. 42%, p = 0.08). Conclusion Patients who present with lateral patella dislocation with the classic bone bruise pattern seen on MRI will likely rupture the MPFL at the patellar side. Females are more likely to have an associated meniscal tear than males; however, more males have underlying osteochondral lesions. Given the high percentage of associated pathology, we recommend a MRI of the knee in all patients who present with acute patella dislocation.
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        Bucket-handle tears of the medial and lateral menisci of the knee: value of MR imaging in detecting displaced fragments.

        A bucket-handle tear of a meniscus is a longitudinal tear with an attached fragment displaced away from the meniscus. Several MR findings of bucket-handle tears have been reported previously. However, the sensitivity of MR for detecting the displaced fragment is unknown. We determined the sensitivity of MR for detecting a displaced bucket-handle tear and determined how the sensitivity varied with tears of different sizes. We also evaluated whether the three findings of a displaced fragment differed in frequency between medial and lateral tears. We retrospectively evaluated the MR examinations of 39 patients with arthroscopically proven bucket-handle tears for signs of a displaced meniscal fragment. Thirty-two patients had medial meniscal bucket-handle tears, and seven had lateral tears. Two observers evaluated each examination independently, with discrepancies resolved by consensus of a third reader. Each observer evaluated for three findings of a bucket-handle tear: a double posterior cruciate ligament sign, a flipped meniscus sign, or a fragment in the intercondylar notch. A double posterior cruciate ligament sign is present when the meniscal fragment is displaced anterior to the posterior cruciate ligament, resembling two ligaments. A flipped meniscus sign occurs when the fragment is flipped anteriorly so the anterior horn of the meniscus appears to be enlarged. We tested for differences between menisci in the sensitivity for each sign using Pearson's chi-squared test or Fisher's exact test. We compared the sensitivity of MR for identifying fragments when the tear involved one third, two thirds, or the entire meniscus using Spearman's rank correlation. Overall sensitivity for a displaced fragment was only 0.64. When the bucket-handle tear involved the entire meniscus, the displaced fragment could be seen in 84% of the menisci. The double posterior cruciate ligament sign was seen in 53% of the medial and none of the lateral bucket-handle tears (p = .01). The flipped meniscus sign was noted in 44% of medial and 29% of lateral menisci (p = .68), and a fragment was identified in the intercondylar notch in 66% of medial and 43% of lateral menisci (p = .40). MR is sensitive for detecting meniscal fragments in large bucket-handle tears, but is less so in small tears. The flipped meniscus sign and presence of a fragment in the notch were comparably useful findings of a displaced fragment in both medial and lateral menisci. The double posterior cruciate ligament sign was noted only in medial bucket-handle tears.
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          Inferiorly displaced flap tears of the medial meniscus: MR appearance and clinical significance.

          We describe the MR imaging features of medial meniscus flap tears in which the fragment becomes located inferomedial to the tibial plateau and deep in relation to the medial collateral ligament.
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            Author and article information

            Affiliations
            Department of Radiology, Sector 62, Phase VIII, Fortis Hospital, Mohali, Punjab, India
            Author notes
            Correspondence: Dr. Abhishek Prasad, Department of Radiology, Sector 62, Phase VIII, Fortis Hospital, Mohali, Punjab - 160 062, India. E-mail: drabhishekprasad@ 123456gmail.com
            Journal
            Indian J Radiol Imaging
            Indian J Radiol Imaging
            IJRI
            The Indian Journal of Radiology & Imaging
            Medknow Publications & Media Pvt Ltd (India )
            0971-3026
            1998-3808
            Jul-Sep 2014
            : 24
            : 3
            : 291-296
            4126146 IJRI-24-291 10.4103/0971-3026.137056
            Copyright: © Indian Journal of Radiology and Imaging

            This is an open-access article distributed under the terms of the Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unported, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

            Categories
            Musculoskeletal Radiology

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