THE ABSENT BOW TIE SIGN IN BUCKET-HANDLE TEARS OF THE MENISCI IN THE KNEE

OBJECTIVE. Bucket-handle tears of the menisci are one of the most freq uently missed diagnoses in MR examinations of the knee. This article d escribes the ''absent bow tie sign,'' which can be used to identify bu cket-handle tears on routine MR examinations of the knee. MATERIALS AN D METHODS. The arthroscopic surgical reports (n = 350) from a single o rthopedic surgeon's practice during a 24-month period were examined fo r patients who had a diagnosis of bucket-handle tear and who underwent MR imaging before surgery (n = 32). The MR examinations were retrospe ctively evaluated for the presence of a bow tie sign. The bow tie sign was considered normal when two sagittal images showed the body segmen t (a bow tie appearance). The bow tie sign was considered abnormal, co nsistent with a bucket-handle tear, when only one or no body segment w as seen (the absent bow tie sign), Coronal images were evaluated for a truncated meniscus. Also, each MR examination was scrutinized for a d isplaced fragment and a double posterior cruciate ligament (PCL) sign. RESULTS. Thirty-three bucket-handle tears were found at arthroscopy i n 32 patients, One patient had rears of the medial and lateral menisci . The absent bow tie sign was seen in 32 of the 33 cases (sensitivity, 97%) and correlated with the medial or lateral meniscus that was repo rted torn at arthroscopy. The single false-negative result occurred in a patient with a nondisplaced bucket-handle tear. The findings in 31 contralateral normal menisci were all negative for an absent bow tie s ign (specificity, 100%). A displaced fragment was found in 30 (94%) of 32 cases. The coronal images showed a truncated meniscus in 21 (64%) of 33 cases. A double PCL sign was seen in 10 (30%) of 33 cases. CONCL USION. The absent bow tie sign is an easily applied finding that can b e used with good sensitivity to diagnose bucket-handle tears of the me nisci on MR imaging. This sign has a higher accuracy rate than other f indings common with bucket-handle rears, such as displaced fragments, a truncated appearance of the meniscus on coronal images, and the doub le PCL sign.