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MR diagnosis of meniscal tears of the knee: analysis of error patterns
Pieter Van Dyck1, Jan Gielen, Jan D'Anvers
1Department of Radiology, University Hospital Antwerp, Edegem, Belgium. pieter.van.dyck@uza.be
Purpose:
Despite high accuracy of magnetic resonance imaging (MRI) for diagnosing meniscal tears, MR findings do not always agree with surgical findings. We performed a blinded, retrospective study to analyze the nature and frequency of errors in the MR diagnosis of meniscal tears.
Materials And Methods:
Medical records of 100 consecutive patients who underwent MR and arthroscopy of the knee at our institution were reviewed. Twelve patients underwent prior meniscal surgery. Twenty-three patients had 27 discrepancies between MR and surgical findings. These were independently reviewed by two additional musculoskeletal radiologists in a double blinded fashion. Original incorrect diagnoses were categorized as either unavoidable, interpretation error or equivocal for meniscal tear.
Results:
MR accuracy was 88% for the medial and 85% for the lateral meniscus. Of 27 incorrect MR diagnoses, 12 (44%) were unavoidable, 10 (37%) equivocal and 5 (19%) interpretation errors. Of the 67 medial meniscal tears, 12 (18%) were missed. Eight (67%) of these 12 were categorized as equivocal, including three postoperative menisci. Of 30 lateral tears, 12 (40%) were missed, 7 (58%) of which were categorized as unavoidable. Of these 12, 11 (92%) showed fraying of the inner edge, which was shaved at arthroscopy (n = 8) or had stable tear treated conservatively (n = 3). There were three false-positive diagnoses, all occuring in the lateral meniscus, two of which were unavoidable and one interpretation error.
Conclusion:
Of all missed lateral meniscal tears, most are unavoidable and related to confusion between what represents fraying and what represents a tear. Unavoidable false-positive diagnoses are infrequent and may be related to incomplete arthroscopic evaluation. Subtle or equivocal findings still make MR diagnosis difficult, even for experienced radiologists.
Insights
Magnetic resonance imaging (MRI) shows high accuracy for meniscal tears, but discrepancies with surgery occur. Most missed lateral meniscal tears are unavoidable, often due to subtle fraying mistaken for tears.
Area of Science:
- Orthopedics
- Radiology
- Sports Medicine
Background:
- Magnetic resonance imaging (MRI) is a key diagnostic tool for knee meniscal tears.
- Despite high accuracy, discrepancies between MRI findings and surgical outcomes are noted.
- Understanding these discrepancies is crucial for improving diagnostic precision.
Purpose of the Study:
- To analyze the nature and frequency of errors in MRI diagnosis of meniscal tears.
- To compare MRI findings with surgical (arthroscopic) findings in a blinded manner.
- To categorize the reasons for diagnostic discrepancies between MRI and surgery.
Main Methods:
- Retrospective review of 100 consecutive knee MRI and arthroscopy cases.
- Independent, double-blinded review of discrepancies by two musculoskeletal radiologists.
- Categorization of incorrect MRI diagnoses into unavoidable, interpretation error, or equivocal.
Main Results:
- Overall MRI accuracy was 88% for medial and 85% for lateral menisci.
- Of 27 discrepancies, 44% were unavoidable, 37% equivocal, and 19% interpretation errors.
- Missed lateral meniscal tears (40%) were often due to fraying mistaken for tears; missed medial tears (18%) were frequently equivocal.
Conclusions:
- Most missed lateral meniscal tears are unavoidable, stemming from difficulty distinguishing fraying from tears.
- Unavoidable false-positive diagnoses are rare, potentially linked to incomplete arthroscopic evaluation.
- Subtle or equivocal findings continue to challenge even experienced radiologists in diagnosing meniscal tears via MRI.