[Comparison between magnetic resonance imaging and arthroscopy for the diagnosis of knee meniscal lesions].

Purpose Of Study: The authors evaluated the use of MR-imaging of the menisci compared to arthroscopy considered as the gold standard by which all noninvasive imaging procedures of the knee have to be measured.

Material And Methods: In a prospective study, we evaluated the use of MRI in 50 patients with clinically suspected disorders of the meniscus, followed by an arthroscopic examination by an experienced arthroscopist. MRI studies were performed after clinical evaluation and were interpreted by an experienced radiologist, who had no knowledge of the clinical findings.

Results: The accuracy of the diagnosis from MRI was 78 per cent for the medial meniscus (sensitivity 79 per cent and specificity 78 per cent) and 94 per cent for the lateral meniscus (sensitivity 50 per cent and specificity 98 per cent). The average age of the patients was 34 years, with a range from 3 to 73 years. The imaging studies revealed 9 false positive test and suggested that the meniscus was either degenerated or form in the horizontal plane. In all 9 menisci the abnormal MR imaging signal was limited to the posterior horns. The positive predictive value was 59 per cent and the negative predictive value was 94 per cent representing a moderate level of diagnostic certainty, both in patients who had a positive result and in those who had a negative result. High predictive negative value of MRI indicates that a negative MRI is quite reliable for meniscal lesions.

Discussion: Problems of MR-imaging are the popliteus tendon sheath and the transverse ligament. This ligament is seen in association with a large branch of the lateral inferior geniculate artery, and may be mistaken for a grade 3 signal intensity in the anterior horn of the lateral meniscus.

Conclusion: A normal MRI allows to eliminate a meniscal lesion and so there is no need for a diagnostic arthroscopy. But with a pathologic MRI there is a risk to establish too often the diagnostic of a meniscal lesion rather then to identify structural modifications as a degeneration.