Three-Tesla magnetic resonance imaging of the meniscus of the knee: What about equivocal errors?
BACKGROUND
The significance of borderline magnetic resonance (MR) findings that are equivocal for a tear of the knee meniscus remains uncertain. Given their higher signal-to-noise ratio (SNR) and greater spatial resolution, these equivocal meniscal tears could be expected to be less frequent using a 3.0T MR system.


OBJECTIVE
To investigate the prevalence of equivocal meniscal tears using 3.0T MR, and to study their impact on MR accuracy compared with arthroscopy in the detection of meniscal tears.


METHODS
The medical records of 100 patients who underwent 3.0T MR imaging and subsequent arthroscopy of the knee were retrospectively reviewed. Two observers interpreted MR images in consensus, and menisci were diagnosed as torn (abnormality on two or more images), equivocal for a tear (abnormality on one image), or intact, using arthroscopy as the standard of reference. The prevalence of equivocal meniscal tears was assessed, and MR accuracy was calculated as follows: first, considering both torn menisci and equivocal diagnoses as positive for a tear; and second, considering only torn menisci as positive for a tear.


RESULTS
Evidence of meniscal tears on MR images was equivocal in 12 medial (12%) and three lateral (3%) menisci. Of these equivocal MR diagnoses, tears were found at arthroscopy in eight medial and one lateral meniscus. In our study, the specificity and positive predictive value increased for both the medial and lateral meniscus when only menisci with two or more abnormal images were considered to be torn: from 80% and 89% to 91% and 94% for the medial meniscus, and from 91% and 73% to 93% and 78% for the lateral meniscus, respectively.


CONCLUSIONS
Subtle findings that are equivocal for a tear of the knee meniscus still make MR diagnosis difficult, even at 3.0T. We recommend that radiologists should rather be descriptive in reporting subtle or equivocal MR findings, alerting the clinician of possible meniscal tear.
Van Dyck
Pieter
P
Department of Radiology, University Hospital Antwerp and University of Antwerp, Antwerp (Edegem), Belgium. pieter.van.dyck@uza.be
Vanhoenacker
Filip M
FM
Gielen
Jan L
JL
Dossche
Lieven
L
Weyler
Joost
J
Parizel
Paul M
PM
D000293:Adolescent; D000328:Adult; D000368:Aged; D001182:Arthroscopy / Q000379:methods / Q000706:statistics & numerical data; D003937:Diagnosis, Differential; D003951:Diagnostic Errors / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods* / Q000706:statistics & numerical data; D008280:Magnetics; D008297:Male; D008592:Menisci, Tibial / Q000473:pathology*; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D000070600:Tibial Meniscus Injuries; D055815:Young Adult