MRI of Bucket-Handle Tears of the Meniscus of the Knee

ABSTRACT

PURPOSE: To determine the frequency of the MRI signs of meniscal bucket - handle tears already known as the double PCL sign, the flipped meniscus sign, the absent bow-tie sign, and the fragment-in-notch sign, and to compare the sagittal with the coronal images. MATERIALS AND METHODS: We retrospectively rev i ewed the MR findings of 37 patients in whom an initial interpretation of MR images had suggested meniscal bucke t - handle tears. All underwent subsequent arthroscopic evaluation and in 28, bucke t - handle tears were confirmed. Sagittal double-echo and coronal fat-suppressed double-echo T 2 - weighted images were obtained. Sagittal images were evaluated to determine whether or not signs of bucket-handle tear were evident, and coronal images we r e checked for a torn meniscus with displaced fragment. We also evaluated the MR findings of the nine false positive cases. RESULTS: The prevalence rate of absent bow-tie, double PCL, fragment-in-notch, and flipped meniscus signs was 96.4%, 53.6%, 17.9%, and 10.7%, respective l y. The detection rate for displaced fragment was higher with coronal images (92.9%) than with sagittal images (78.6%). Among the nine false positive cases, a longitudinal tear in the discoid meniscus was most common. A false-positive diagnosis was much more frequent on sagittal than on coronal images. CONCLUSION: The prevalence rate of absent bow-tie sign was very high, but was accompanied by a relatively high rate of misinterpretation. Coronal fat-suppressed T2- weighted images provided more reliable clues for the diagnosis of bucket-handle tears, with a high detection rate of displaced fragment.