COMPARATIVE-ANALYSIS OF MR-IMAGING AND AR THROSCOPY FOR THE DIAGNOSISOF KNEE MENISCAL LESIONS

Purpose of study The authors evaluated the use of MR-Imaging of the me nisci compared to arthroscopy considered as the gold standard by which ail noninvasive imaging procedures of the knee have to be measured. M aterial and methods In a prospective study, we evaluated the use of MR I in 50 patients with clinically suspected disorders of the meniscus, followed by an arthroscopic examination by an experienced arthroscopis t. MR[ studies were performed after clinical evaluation and were inter preted by an experienced radiologist, who had no knowledge of the clin ical findings. Results The accuracy of the diagnosis from MRI was 78 p er cent for the medial meniscus (sensitivity 79 per cent and specifici ty 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 patie nts 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 ei ther degenerated or term in the horizontal plane. In all 9 menisci the abnormal MR imaging signal was limited to the posterior horns. The po sitive predictive value was 59 per cent and the negative predictive va lue was 94 per cent representing a moderate lever of diagnostic certai nty, 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 Pro blems 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 gra de 3 signal intensity in the anterior horn of the lateral meniscus. Co nclusion A normal MR[ allows to eliminate a meniscal lesion and so the re is no need for a diagnostic arthroscopy. But with a pathologic MR[ there is a risk to establish too often the diagnostic of a meniscal le sion rather then to identify structural modifications as a degeneratio n.