THE DIAGNOSTIC VALIDITY OF MAGNETIC-RESONANCE-IMAGING IN ACUTE KNEE INJURIES WITH HEMARTHROSIS - A SINGLE-BLINDED EVALUATION IN 69 PATIENTSUSING HIGH-FIELD MRI BEFORE ARTHROSCOPY

Sixty-nine patients with traumatic knee hemarthrosis were evaluated an average of 3 days after trauma by high field (1.5T) magnetic resonanc e imaging (MRI) using sagittal T1, T2-weighted and coronal 3D-gradient echo images. All knees were arthroscopically examined shortly afterwa rds. The diagnostic validity of MRI for intraarticular pathology was d etermined using arthroscopy as golden standard. All patients had patho logical findings on arthroscopy. The injuries were sports related in 7 7 % of the cases. MRI was highly sensitive (86 %) and specific (92 %) for diagnosis of anterior cruciate ligament tears. Diagnosis of medial meniscal tears showed a 74 % sensitivity and 66 % specificity. MRI de tected lateral meniscal tears in 50 % with an 84 % specificity. As suc h, MRI missed 10 significant meniscus ruptures requiring surgical trea tment. The sensitivity for partial or total medial collateral ligament tears was 56 %, the specificity 93 %. Rupture of the medial retinacul um in cases with patellar dislocation or. significant damage of articu lar cartilage were only detected by MRI in a few cases (27 % and 20 % sensitivity, respectively). MRIs low diagnostic validity for intraarti cular pathology with hemarthrosis may be attributed to the shifting pa ramagnetic properties of the blood remains and catabolic processes in meniscal and chondral tissues during the hemoglobin degradation proces s. Accordingly, MRI, with the technique used, could neither replace ar throscopy in the diagnosis and screening of acute knee injuries, nor s elect patients with need for immediate arthroscopic meniscal surgery.