RELEVANCE OF MAGNETIC-RESONANCE-IMAGING - DIAGNOSING THE MENISCUS IN CORRELATION WITH ARTHROSCOPY

Arthroscopy of the menisci is considered the gold standard by which al l noninvasive imaging procedures of the knee are measured. In a prospe ctive study we evaluated the use of MRI in 50 patients in whom a disor der of the meniscus was suspected clinically, this was followed by an arthroscopic examination by an experienced arthroscopist. The MR studi es were performed after clinical evaluation and were interpreted by an experienced radiologist, who had no knowledge of the clinical finding s. The accuracy of the diagnosis from MRI was 78 % for the medial meni scus (sensitivity 79 % and specificity 78 %) and 94 % for the lateral meniscus (sensitivity 50 % and specificity 98 %). The average age of t he patients was 34 years, with a range of 3-73 years. The imaging stud ies revealed 9 false-positive tests and suggested that the meniscus wa s either degenerated or torn in the horizontal plane. In all 9 menisci the abnormal MR imaging signal was limited to the posterior horns. Th e positive predictive value was 59 % and the negative predictive value was 94 %, representing a moderate level of diagnostic certainty both in patients who had a positive result and in those who had a negative result. The high predictive negative value of MRI indicates that a neg ative MRI is quite reliable for meniscal lesions. The problem areas in MR imaging are the popliteus tendon sheath and the transverse ligamen t. This ligament is seen in association with a large branch of the lat eral inferior geniculate artery and may be mistaken for a grade 3 sign al intensity in the anterior horn of the lateral meniscus.