Complete and Partial-Thickness Tears of the Anterior Cruciate Ligament: Differential Features Seen on MRImaging

PURPOSE: To evaluate the differential features of complete and partial-thickness tears of the anteriorcruciate ligament, as seen on magnetic resonance imaging(MRI). MATERIALS AND METHODS: We retrospectvely reviewedMR images of 36 patients with ACL injuries (complete tear 16, incomplete tear 20). In all cases, the presence ofan ACL tear was determined by arthroscopy or surgery. Primary and secondary signs of ACL injury and associatedinjuries were assessed. RESULTS: Ligamentous discontinuity of the ACL was observed in ten complete tears (63 %),but in only four (10%) of those that were partial (p=0.009). In addition, complete tears were more likely to showa low degree of ACL axis, less than 45 degree(11/16 : 2/20, p=0.001). There was, however, no statistically significantdifference between complete and partial tears with regard to signal intensity of ACL, PCL buckling or angle,anterior dis-placement of the tibia, uncovered meniscus sign, deep notch sign, empty notch sign, and associatedinjuries. CONCLUSION: Ligamentous discontinuity and the ACL axis are features which usefully differentiatebetween complete and partial tears of the ACL.

MR Imaging of the Combined Anterior and Posterior Cruciate Ligament Tears: Focussing on the Patterns of Injuries and Associated Findings

PURPOSE: To evaluate the patterns of injuries and frequency of associated findings on MR imaging in patients with both anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) tears; to compare the associated findings, as seen on MR imaging, in cases with both ACL and PCL tears with those with ACL or PCL tears. MATERIALS AND METHODS: Ten patients with combined ACL and PCL tears, 16 with ACL tears and 18 with PCL tears, all confirmed by arthroscopy or open surgery, were involved in this study. To identify the associated knee injuries, MR images were retrospectively evaluated. RESULTS: In ten patients with combined ACL and PCL tears, open surgery led to the identification of six complete ACL tears (60%), four partial ACL tears (40%), eight complete PCL tears (80%) and two partial PCL tears (20%). Injuries associated with these combined tears, and revealed by MR imaging, comprised six medial collateral ligament injuries (60%), six lateral collateral ligament injuries (60%), five medial meniscal injuries (50%), three lateral meniscal injuries (30%), nine bony injuries (90%), two posterior capsular injuries (20%), and three popliteus muscle injuries (30%). The frequency of popliteus muscle injury was significantly different (p<0.05, Fisher's exact test) between the group with both ACL and PCL tears and that with ACL or PCL tears. CONCLUSION: Associated findings in patients with combined ACL and PCL tears are more frequentthan in those with ACL or PCL tears. In cases involving combined ACL and PCL tears, associated findings-as seen on MR images-should thus be carefully examined.