MR imaging of the knee in the sagittal projection: comparison of three-dimensional gradient-echo and spin-echo sequences

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Abstract
Fifty patients with suspected internal derangement of the knee had arthroscopic examinations after MR imaging with both a standard T1-weighted spin-echo (SE) sequence and a three-dimensional (3-D) gradient-echo sequence. This series permitted correlative evaluation of 100 menisci and 50 anterior cruciate ligaments. Meniscal tears were diagnosed when intrameniscal signal communicated with the meniscal surface. Criteria for diagnosing anterior cruciate ligament disruption included absence or discontinuity of the ligament, ligamentous laxity, and hyperflexion of the posterior cruciate ligament. Arthroscopic surgery confirmed the presence of 39 meniscal tears and 11 anterior cruciate ligament tears in this population. The sensitivity and specificity of the SE sequence for the diagnosis of meniscal tears were 77% and 98%, respectively. The 3-D gradient-echo sequence had a sensitivity of 87% and a specificity of 88%. For disruption of the ligament, the SE technique had a sensitivity of 82% and a specificity of 95% and the 3-D technique had a sensitivity of 64% and a specificity of 100%. Although these differences in sensitivity and specificity are not statistically significant at the p less than .05 level, probably because of the small sample size, the results show the relative strengths and weaknesses of the two imaging sequences. These data suggest that because of the complementary results of the two MR techniques, both the SE and the 3-D gradient-echo sequences have a role in the diagnosis of knee injuries.