MR Imaging of Anterior Cruciate Ligament Injury: Associated Findings

ABSTRACT

PURPOSE: Authors investigated the associated findings and their value in the diagnosis of anterior cruciate ligament(ACL) injury in MR image. MATERIAL AND METHODS: The knee MR images of 47 patients with ACL injury(complete; 24, partial; 23) and 61 patients with normal ACL confirmed by the knee arthroscopy or operation were reviewed retrospectively. The degree of anterior translocation of tibia and the degree of posterior cruciate ligament(PCL) buckling were evaluated. The prevalence and pattern of associated adjacent bone, ligament and meniscus injuries were studied. RESULTS: The means( +/- 2standard errors) of anterior translocation were different significantly in statistical analysis(p<0.001, student t-test) between injury group(7.51 +/- 1.16mm) and normal group(-0.56 +/- 0.92mm). In the level of 5mm of anterior translocation for the criteria of ACL injury, the sensitivity, specificity, accuracy were 78.7%, 89.5%, 84.3% for each. The means of PCL buckling ratio were also different statistically b. etween injury group(0.23 +/- 0.02) and normal group(0.17 +/- 0.01)(p<0.001). In the level of 0.20 for diagnostic criteria of ACL injury, the sensitivity, specificity, accuracy were 71.4%, 83.6%, 78.4% for each. Thirty one medial meniscus tear(66%), thirteen lateral meniscus tear(28%), ten medial collateral ligament injury(28%), one PCL injury (2%) were associated with ACL injury. The twenty nine bone marrow changes were found in twenty patients {43%) which included acutely injured seven patients. In acute cases, the bone marrow changes were depicted as diffuse or focal high signal intensity lesions in lateral femoral or tibial condyles in contrast to the changes in chronic cases depicted as focal low signal intensity lesions in variable location. Lateral femoral condylar notch depression were found in nine patients(19%) and avulsion fractures of anterior tibial spine in four patients(9%). CONCLUSION: The associated findings with ACL injury (anterior translocation, buckling of PCL, associated bone, ligament and meniscus injuries) are considered to be helpful in the diagnosis of ACL injury on Knee MR images, when the findings of anterior cruciate ligament itself are not confirmative.