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MRI Not So Sensitive for Detecting Lateral Meniscal Tears

October 20, 2009
Written by: , Filed in: Musculoskeletal Radiology
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The objective of a recent study was to identify clinical variables, MRI findings, or arthroscopic findings to help understand the decreased sensitivity for diagnosing lateral meniscal tears.

The study has concluded that peripheral longitudinal tears of the posterior horn lateral meniscus are seen in association with anterior cruciate ligament tears; knowing this pattern may help reduce future misses of this specific kind of tear.

Participants
483 patients were included, and their charts were reviewed.

Methodology
Patient age was recorded, as was spontaneous pain versus trauma-related pain, time interval between onset of pain and MRI, and time interval between MRI and arthroscopy. The arthroscopic size, location, and type of tear were considered, and the MRI was reviewed in retrospect to see if the tear could have been diagnosed initially.

Results
A total of 36 tears were missed. MRI sensitivity was 97% for diagnosing medial meniscal tears and 81% for lateral meniscal tears. Specificity was 88% for lateral and 86% for medial meniscal tears. There were no significant differences in patient age, traumatic versus non-traumatic tears, time interval between onset of symptoms and MRI, and time interval between MRI and arthroscopy of missed lateral meniscal tears.

The sensitivity for diagnosing a lateral meniscal tear varied with tear location, with tears in the posterior horn being detected with the least sensitivity.

MRI was significantly more sensitive when involving more than one third of the meniscus. The sensitivity for 9 missed tears in which the pattern was not specified in the operative notes was 11%. When those tears without a specified tear type were excluded from analysis, there was no significant difference between types of tears.

On retrospective MRI review,10 of 36 missed tears could be identified. All tears were seen on only 2 MRIs. Three additional tears were questionably identifiable. Twenty-three tears could not be seen, even in retrospect, among which were 3 root tears, 6 peripheral longitudinal tears near the popliteal hiatus, and 2 radial tears among others.

Conclusions
There is no clinical variable or intra-articular abnormality that accounts for the decreased MRI sensitivity for lateral meniscal tears. Lateral meniscal tears are more likely to be missed if the tear involves only one third of the meniscus or is in the posterior horn.

Reviewer’s Comments
The study did not identify a cause for the decreased sensitivity in detecting lateral meniscal tears. One finding was that 6 of 36 missed tears had a longitudinal vertical peripheral pattern near the attachment of the meniscofemoral ligaments, perhaps being mistaken for variations in meniscofemoral ligament attachment.

Those tears are unstable and can progress to bucket-handle detachment. All of those tears were associated with anterior cruciate ligament (ACL) tears. Perhaps it is helpful to consider this tear pattern when an ACL tear is encountered.

Author: Cornelia Wenokor, MD

Reference:
De Smet AA, Mukherjee R. Clinical, MRI, and Arthroscopic Findings Associated With Failure to Diagnose a Lateral Meniscal Tear on Knee MRI.
AJR; 2008; 190 (January): 22-26

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One Response to “MRI Not So Sensitive for Detecting Lateral Meniscal Tears”

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