MR imaging of displaced meniscal tears of the knee. Importance of a "disproportional posterior horn sign".
OBJECTIVE
Meniscal tears associated with displaced fragments are clinically significant. We propose the "disproportional posterior horn sign" as a supportive criterion to identify a posterocentrally displaced meniscal fragment on MR imaging studies. If the meniscal posterior horn in the central portion appears larger than that in the peripheral section, it is considered positive for "disproportional posterior horn sign".


METHODS
MR images obtained in 42 patients with 43 lesions, confirmed to have displaced meniscal tears, were included in this study. The MR images were retrospectively evaluated for the presence of the "disproportional posterior horn sign", as well as the other known signs.


RESULTS
The "disproportional posterior horn sign" was seen in 9 (20.9%) of 43 lesions, including 1 lateral discoid meniscal tear, 5 lateral meniscal tears and 3 medial meniscal tears. Five of them also had other signs of a displaced meniscal fragment. However, the remaining 4 cases only exhibited the "disproportional posterior horn sign". For the other MR signs, the "absent bow tie sign" was detected in 40 (93%) of 43 lesions, the "flipped meniscus sign" in 27 (62.8%) of 43 lesions, the "double posterior cruciate ligament sign" in 17 (39.5%) of 43 lesions and the "notch fragment sign" in 22 (51.2%) of 43 lesions.


CONCLUSIONS
The "disproportional posterior horn sign" is helpful in demonstrating a posterocentrally displaced meniscal fragment, especially when other characteristic signs are unremarkable or absent.
Chen
H C
HC
Department of Radiology, China Medical College Hospital, Taichung, P.R. China.
Hsu
C Y
CY
Shih
T T
TT
Huang
K M
KM
Li
Y W
YW
D000293:Adolescent; D000328:Adult; D001182:Arthroscopy; D002648:Child; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology; D008875:Middle Aged; D012189:Retrospective Studies; D000070600:Tibial Meniscus Injuries