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Two-slice-touch rule reliable when diagnosing meniscal tears

December 07, 2006

The two-slice-touch rule increased the accuracy of diagnosing meniscal tears, according to a study conducted by the Department of Radiology at the University of Wisconsin Medical School and Hospital, in Madison, WI.

The two-slice-touch rule classifies a meniscus as "torn" if there is one MR image with an abnormal finding. The authors of the study reviewed the medical records of 174 patients who had knee MR exams then correlated the MR results with knee arthroscopy to determine accuracy when diagnosing menisci as: "torn", "possibly torn", or "intact."

"This study was undertaken to confirm that using the two-slice-touch rule increased our positive predictive value for diagnosing a meniscal tear, and to determine whether our accuracy using fast-spin echo imaging was comparable to that previously reported," said Arthur A. De Smet, MD, lead author of the study.

The positive predictive value increased from 91% to 94% in meniscal tears and from 83% to 96% for lateral meniscal tears.

"The sports medicine physicians at our institution have expressed how much they value our high positive predictive value for the diagnosis of a meniscal tear when using the two-slice-touch rule," said Dr. De Smet. "Also, by using the category of 'possible tear', we give them 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," he said.

American Roentgen Ray Society