SONOGRAPHY IN THE TEARS OF THE KNEE MENISCI Azzoni Roberto, Cabitza Paolo, Parrini Matteo Orthopaedic Dept., State University of Milan – San Donato Milanese (Milan) 30, via Morandi, Italy ( Results: Of the 216 cases in which US was correlated with MRI or CT, 147 (68%) had US images of tears of the knee menisci mainly involving the medial meniscus (102 cases: 69.3%); the remaining 69 (31.9%) were US normal. Ninety-eight cases (66.6%) involved the anterior horn (78 medial and 20 lateral meniscus) and 49 (33.4%) the posterior horn (24 medial and 25 lateral meniscus); 40 (27.2%) were horizontal and 107 vertical (72.8%), including 13 tears of the capsular attachment of the medial meniscus (8.8%). In the remaining 105 cases (33%), we could not visualise the knee menisci for various reasons, including osteoarthritis, articular effusion, technical difficulties, poor patient compliance, difficulties in rotating the tibia, difficulties in interpreting the images of the inner margins of the meniscus, and operator errors; these cases were excluded from the analysis. Ninety-four (63.9%) of the 147 US-diagnosed cases were also examined by means of MRI, which confirmed 50 (53.2%) but not the remaining 44 tears (US false positives: 46.8%). Of the 69 cases with normal US findings, MRI identified tears in 30/41 cases (US false negatives: 73.1%) and confirmed the absence of damage in 11/41 (26.9%). Arthroscopy was performed in 80 of these cases, 50 (62.5%) of which were both MRI- and US-positive, and 30 (37.5%) MRI-positive and US-negative. The tear was confirmed in all cases (US false negative rate: 37.5%). Fifty-three (36%) of the 147 US-diagnosed cases were also examined by CT, which confirmed 26 (49%) and denied 27 tears (US false positive rate: 51%); in 28 cases with normal US findings, CT identified tears in 20 (US false negative rate 71%) and confirmed the US result in eight cases (29%). Arthroscopy was performed in 46 of these cases, and confirmed the tear in the 26 (57%) CT- and US-positive cases, and in 20 (43%) that were CT- positive and US-negative (US false negative rate: 71%). The final US results were therefore 76 true-positives (35.2%), 19 true-negatives (8.8%), 71 false-positives (32.8%) and 50 false-negatives (23.2%), which means that the US diagnoses were correct in 44% of the cases and incorrect in 56%. Both the sensitivity (60%) and specificity (21%) were therefore low. Fifty percent of the positive ultrasound (US) diagnoses (71 cases) were not confirmed by MRI or CT (false positives), and 72% (50 cases) of the negative diagnoses (false negatives). Altogether, the US diagnoses were right in 95 cases (44%) of the cases and wrong in 121 cases (56%), and both sensitivity (60%) and specificity were low 21%. Arthroscopy confirmed all (100%) diagnoses of meniscal tear established with MRI or CT. Fig. 1: US probe position for the study of anterior horn of the medial meniscus; Knee in 45° flexion and under extrarotation-valgus stress Fig. 2: US probe position for the study of the posterior horn of the medial meniscus Fig. 3: Longitudinal US view of normal anterior horn of the medial meniscus Fig. 4: Longitudinal view of horizontal tear of the anterior horn of medial meniscus Fig. 5: Longitudinal US view of a vertical tear of the anterior horn of medial meniscus Tab. I: Diagnostic results obtained using the various techniques (US, MRI, TC, Artroscopy) Aim of the study: To investigate the usefulness of sonography in studying tears of the knee menisci. In this study, we used US to examine 321 consecutive knees of subjects referred to us because of suspected traumatic meniscus tears. In 216 cases, the US diagnoses were compared with MRI, CT or arthroscopic findings in order to assess the indications for, and limitations of US evaluations of tears of the knee menisci. Materials and Methods: In this retrospective study, we used sonography to examine 321 knees diagnosed as having a torn meniscus; 216 were also examined by means of magnetic resonance imaging (MRI) or computed tomography (CT), and 126 underwent arthroscopic meniscectomy. Discussion and Conclusions: There is still considerable controversy concerning the usefulness or otherwise of US in the diagnosis of tears of the knee menisci. Our findings show that CT and particularly MRI contradict the US detection of tears in 32,8% of cases (false positives), and the US finding of a normal meniscus in 23,2% (false negatives), which means that the US diagnoses were incorrect in 56% of cases. As expected, the MRI and CT findings were 100% confirmed by arthroscopy. We do not believe Sonography is sufficiently accurate, sensitive or specific to be used in studying tears of the knee menisci. The limitations of US studies of the knee menisci are due to the impossibility of visualising the meniscal body and partly the posterior horn because of artefacts coming from sound waves reflected from adjacent bone surfaces. Another limitation is the possibility of misinterpreting the difficult to focus the US images of the inner margins of the meniscus. Given that the results of US are correct in only 44% of cases, and that its sensitivity and specificity are no more than 60% and 21%, we believe that it cannot yet be considered a reliable means of diagnosing tears of the knee menisci. Keywords: Sonography, Tears of menisci, Knee, Menisci.