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Using 'two-slice-touch' rule improves meniscus tear diagnosis on MRI
Applying the rule increased the positive predictive value for diagnosing lateral meniscal tears from 83% to 96%.
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Applying what is called the "two-slice-touch" rule when reviewing magnetic resonance imaging studies may increase accuracy for diagnosing meniscal tears, according to a study by researchers in Wisconsin.
The two-slice-touch rule classifies a meniscus as "torn" if abnormalities are detected on at least two MRIs and as "possibly torn" if abnormalities are present on only one MRI, according to the study.
Arthur A. De Smet, MD, and Michael J. Tuite, MD, conducted a retrospective study of 174 patients to determine whether the rule could improve the positive predictive value for diagnosing knee meniscus tears. Diagnostic arthroscopy was used to confirm diagnoses as torn, partially torn or intact.
Both De Smet and Tuite are professors of musculoskeletal imaging in the radiology department at University of Wisconsin Medical School and Hospital, Madison.
The researchers found that applying the two-slice-touch rule increased the positive predictive value for diagnosing medial meniscal tears from 91% to 94% (P=.37), and significantly increased the predictive value for diagnosing lateral meniscal tears, from 83% to 96% (P=.02). The improved diagnostic accuracy was compared against the standard diagnostic criterion, which diagnoses a meniscus as torn based on at least one abnormal MRI, according to the study.
"When using the standard criterion, we had 95% sensitivity and 85% specificity for diagnosing medial meniscal tears and 77% sensitivity and 89% specificity for diagnosing lateral meniscal tears," the authors reported.
"[By] using the category of 'possible tear', we give [physicians] more flexibility in managing these patients than if we diagnosed their menisci as definitely torn. Because these patients have an MRI abnormality on only one image, they often have only a small tear if a tear is present. Therefore, conservative treatment rather than surgical treatment can be used if clinically appropriate," De Smet said in a press release announcing the study results.
For more information:
- De Smet AA, Tuite MJ. Use of the "two-slice-touch" rule for the MRI diagnosis of meniscal tears. AJR Am J Roentgenol. 2006;187:911-914.